551
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Bercovici DA, Ogilvie JM, Tsvetkov N, Brewer M. Intramolecular polar [4(⊕)+2] cycloadditions of aryl-1-aza-2-azoniaallene salts: unprecedented reactivity leading to polycyclic protonated azomethine imines. Angew Chem Int Ed Engl 2013; 52:13338-41. [PMID: 24218159 DOI: 10.1002/anie.201306553] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/24/2013] [Indexed: 11/08/2022]
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552
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Borukhova S, Noël T, Metten B, de Vos E, Hessel V. Solvent- and catalyst-free huisgen cycloaddition to rufinamide in flow with a greener, less expensive dipolarophile. CHEMSUSCHEM 2013; 6:2220-5. [PMID: 24115350 DOI: 10.1002/cssc.201300684] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Indexed: 05/24/2023]
Abstract
Give it a flow: A continuous-flow process for the synthesis of a 1,2,3-triazole precursor of Rufinamide has been developed. The protocol involves a solvent- and catalyst-free operation and utilizes reaction temperatures above the melting point of the target product to prevent microreactor clogging, resulting in a decrease of the operating time from hours to minutes.
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553
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Versteegen RM, Rossin R, ten Hoeve W, Janssen HM, Robillard MS. Click to release: instantaneous doxorubicin elimination upon tetrazine ligation. Angew Chem Int Ed Engl 2013; 52:14112-6. [PMID: 24281986 DOI: 10.1002/anie.201305969] [Citation(s) in RCA: 280] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 10/15/2013] [Indexed: 11/11/2022]
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554
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Xu X, Zavalij PY, Doyle MP. Highly enantioselective dearomatizing formal [3+3] cycloaddition reactions of N-acyliminopyridinium ylides with electrophilic enol carbene intermediates. Angew Chem Int Ed Engl 2013; 52:12664-8. [PMID: 24123489 PMCID: PMC3858852 DOI: 10.1002/anie.201305539] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Indexed: 11/09/2022]
Abstract
A effective dearomatizing formal [3+3]-cycloaddition reaction triggered by Rh(II)-catalyzed dinitrogen extrusion of enoldiazoacetates followed by vinylogous addition of metal enolcarbenes to N -acyliminopyridinium ylides that produces highly substituted 1,2,3,6-tetrahydropyridazines in up to 98% ee and in high yield has been developed.
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555
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Fernández I, Bickelhaupt FM. Origin of the "endo rule" in Diels-Alder reactions. J Comput Chem 2013; 35:371-6. [PMID: 24449044 DOI: 10.1002/jcc.23500] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 11/02/2013] [Indexed: 11/09/2022]
Abstract
Detailed density functional theory calculations definitively rationalize the preference for the endo cycloadduct (also known as endo rule) in text-book thermal Diels-Alder reactions involving maleic anhydride and cyclopentadiene or butadiene. This selectivity is mainly caused by an unfavorable steric arrangement in the transition-state region of the exo pathway which translates into a more destabilizing activation strain. In contrast with the widely accepted, orbital-interaction-based explanation for the endo rule, it is found that neither the orbital interactions nor the total interaction between the deformed reactants contributes to the endo selectivity.
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556
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Thakur A, Facer ME, Louie J. Nickel-catalyzed cycloaddition of 1,3-dienes with 3-azetidinones and 3-oxetanones. Angew Chem Int Ed Engl 2013; 52:12161-5. [PMID: 24573793 PMCID: PMC4113093 DOI: 10.1002/anie.201306869] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Indexed: 01/16/2023]
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557
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Montavon TJ, Türkmen YE, Shamsi NA, Miller C, Sumaria CS, Rawal VH, Kozmin SA. [2+2+2] Cycloadditions of siloxy alkynes with 1,2-diazines: from reaction discovery to identification of an antiglycolytic chemotype. Angew Chem Int Ed Engl 2013; 52:13576-9. [PMID: 24346942 DOI: 10.1002/anie.201305711] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/13/2013] [Indexed: 11/10/2022]
Abstract
Cycloaddition uncovered: The title reaction produces novel polycyclic compounds with high efficiency and excellent diastereoselectivity under mild reaction conditions. A small-molecule library, synthesized using this reaction, yielded a novel chemotype which inhibited glycolytic ATP production by blocking glucose uptake in CHO-K1 cells. DMF=N,N-dimethylformamide, Tf=trifluoromethanesulfonyl, TIPS=triisopropylsilyl.
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558
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Johansen TK, Villegas Gómez C, Bak JR, Davis RL, Jørgensen KA. Organocatalytic enantioselective cycloaddition reactions of dienamines with quinones. Chemistry 2013; 19:16518-22. [PMID: 24281799 DOI: 10.1002/chem.201303526] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Indexed: 11/10/2022]
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559
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Cruchter T, Harms K, Meggers E. Strain-promoted azide-alkyne cycloaddition with ruthenium(II)-azido complexes. Chemistry 2013; 19:16682-9. [PMID: 24173767 DOI: 10.1002/chem.201302502] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Indexed: 12/17/2022]
Abstract
The reactivity of an exemplary ruthenium(II)-azido complex towards non-activated, electron-deficient, and towards strain-activated alkynes at room temperature and low millimolar azide and alkyne concentrations has been investigated. Non-activated terminal and internal alkynes failed to react under such conditions, even under copper(I) catalysis conditions. In contrast, as expected, rapid cycloaddition was observed with electron-deficient dimethyl acetylenedicarboxylate (DMAD) as the dipolarophile. Since DMAD and related propargylic esters are excellent Michael acceptors and thus unsuitable for biological applications, we investigated the reactivity of the azido complex towards cycloaddition with derivatives of cyclooctyne (OCT), bicyclo[6.1.0]non-4-yne (BCN), and azadibenzocyclooctyne (ADIBO). While no reaction could be observed in the case of the less strained cyclooctyne OCT, the highly strained cyclooctynes BCN and ADIBO readily reacted with the azido complex, providing the corresponding stable triazolato complexes, which were amenable to purification by conventional silica gel column chromatography. An X-ray crystal structure of an ADIBO cycloadduct was obtained and verified that the formed 1,2,3-triazolato ligand coordinates the metal center through the central N2 atom. Importantly, the determined second-order rate constant for the ADIBO cycloaddition with the azido complex (k2=6.9 × 10(-2) M(-1) s(-1)) is comparable to the rate determined for the ADIBO cycloaddition with organic benzyl azide (k2=4.0 × 10(-1) M(-1) s(-1)). Our results demonstrate that it is possible to transfer the concept of strain-promoted azide-alkyne cycloaddition (SPAAC) from purely organic azides to metal-coordinated azido ligands. The favorable reaction kinetics for the ADIBO-azido-ligand cycloaddition and the well-proven bioorthogonality of strain-activated alkynes should pave the way for applications in living biological systems.
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560
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López F, Mascareñas JL. Gold(I)-catalyzed enantioselective cycloaddition reactions. Beilstein J Org Chem 2013; 9:2250-64. [PMID: 24204438 PMCID: PMC3817474 DOI: 10.3762/bjoc.9.264] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 09/26/2013] [Indexed: 12/20/2022] Open
Abstract
In recent years there have been extraordinary developments of gold(I)-catalyzed enantioselective processes. This includes progress in the area of cycloaddition reactions, which are of particular interest due to their potential for the rapid construction of optically active cyclic products. In this article we will summarize some of the most remarkable examples, emphasizing reaction mechanisms and key intermediates involved in the processes.
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561
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Narayan R, Bauer JO, Strohmann C, Antonchick AP, Waldmann H. Catalytic enantioselective synthesis of functionalized tropanes reveals novel inhibitors of hedgehog signaling. Angew Chem Int Ed Engl 2013; 52:12892-6. [PMID: 24151037 DOI: 10.1002/anie.201307392] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Indexed: 01/06/2023]
Abstract
Dipolar cycloaddition: A highly efficient copper(I)-catalyzed enantioselective [3+2] cycloaddition reaction of 1,3-fused cyclic azomethine ylides and nitroalkenes has been developed. This method provides access to functionalized tropane scaffolds with several quaternary and tertiary stereocenters in a single step under mild reaction conditions.
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562
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Wade PA, Pipic A, Zeller M, Tsetsakos P. Sequential Diels-Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene. Beilstein J Org Chem 2013; 9:2137-46. [PMID: 24204426 PMCID: PMC3817504 DOI: 10.3762/bjoc.9.251] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2013] [Accepted: 09/21/2013] [Indexed: 11/30/2022] Open
Abstract
The tin(IV)-catalyzed reaction of β-nitrostyrene with (E)-3-methyl-1,3-pentadiene in toluene afforded two major nitronic ester cycloadducts in 27% and 29% yield that arise from the reaction at the less substituted diene double bond. Also present were four cycloadducts from the reaction at the higher substituted diene double bond, two of which were the formal cycloadducts of (Z)-3-methyl-1,3-pentadiene. A Friedel–Crafts alkylation product from the reaction of the diene, β-nitrostyrene, and toluene was also obtained in 10% yield. The tin(IV)-catalyzed reaction of β-nitrostyrene with (Z)-3-methyl-1,3-pentadiene in dichloromethane afforded four nitronic ester cycloadducts all derived from the reaction at the higher substituted double bond. One cycloadduct was isolated in 45% yield and two others are formal adducts of the E-isomer of the diene. The product formation in these reactions is consistent with a stepwise mechanism involving a zwitterionic intermediate. The initially isolated nitronic ester cycloadducts underwent tin(IV)-catalyzed interconversion, presumably via zwitterion intermediates. Cycloadducts derived from the reaction at the less substituted double bond of (E)-3-methyl-1,3-pentadiene underwent a [3,3]-sigmatropic rearrangement on heating to afford 4-nitrocyclohexenes. Cycloadducts derived from the reaction at the higher substituted diene double bond of either diene failed to undergo a thermal rearrangement. Rates and success of the rearrangement are consistent with a concerted mechanism possessing a dipolar transition state. An initial assessment of substituent effects on the rearrangement process is presented.
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563
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Izquierdo M, Cerón MR, Alegret N, Metta-Magaña AJ, Rodríguez-Fortea A, Poblet JM, Echegoyen L. Unexpected isomerism in cis-2 bis(pyrrolidino)[60]fullerene diastereomers. Angew Chem Int Ed Engl 2013; 52:12928-31. [PMID: 24132934 DOI: 10.1002/anie.201306957] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 09/02/2013] [Indexed: 11/08/2022]
Abstract
Similar yet different: A one-step regio- and diastereoselective synthesis of three new bis(pyrrolidine)[60]fullerenes, one cis-1 and two unprecedented cis-2 diastereoisomers, is reported. The compounds are easily purified using simple chromatographic techniques, and were fully characterized by spectroscopic techniques and X-ray crystallography. A mechanism for the isomeric conversion observed is proposed.
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564
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Worrell BT, Ellery SP, Fokin VV. Copper(I)-catalyzed cycloaddition of bismuth(III) acetylides with organic azides: synthesis of stable triazole anion equivalents. Angew Chem Int Ed Engl 2013; 52:13037-41. [PMID: 24130150 DOI: 10.1002/anie.201306192] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Indexed: 11/05/2022]
Abstract
Fully loaded: Readily accessible and shelf-stable 1-bismuth(III) acetylides react rapidly and regiospecifically with organic azides in the presence of a copper(I) catalyst. The reaction tolerates many functional groups and gives excellent yields of the previously unreported 5-bismuth triazolides. This uniquely reactive intermediate is functionalized under mild reaction conditions to give fully substituted 1,2,3-triazoles.
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565
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Bachollet S, Terao K, Aida S, Nishiyama Y, Kakiuchi K, Oelgemöller M. Microflow photochemistry: UVC-induced [2 + 2]-photoadditions to furanone in a microcapillary reactor. Beilstein J Org Chem 2013; 9:2015-21. [PMID: 24204412 PMCID: PMC3817530 DOI: 10.3762/bjoc.9.237] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Accepted: 09/10/2013] [Indexed: 11/27/2022] Open
Abstract
[2 + 2]-Cycloadditions of cyclopentene and 2,3-dimethylbut-2-ene to furanone were investigated under continuous-flow conditions. Irradiations were conducted in a FEP-microcapillary module which was placed in a Rayonet chamber photoreactor equipped with low wattage UVC-lamps. Conversion rates and isolated yields were compared to analogue batch reactions in a quartz test tube. In all cases examined, the microcapillary reactor furnished faster conversions and improved product qualities.
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566
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Takayama H, Jia ZJ, Kremer L, Bauer JO, Strohmann C, Ziegler S, Antonchick AP, Waldmann H. Discovery of inhibitors of the Wnt and Hedgehog signaling pathways through the catalytic enantioselective synthesis of an iridoid-inspired compound collection. Angew Chem Int Ed Engl 2013; 52:12404-8. [PMID: 24115579 DOI: 10.1002/anie.201306948] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Indexed: 01/12/2023]
Abstract
Cousins you can count on: An iridoid-inspired compound collection was synthesized efficiently by the resolution of cyclic enones in an asymmetric cycloaddition with azomethine ylides. The collection contained novel potent inhibitors of the Wnt and Hedgehog signaling pathways.
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567
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Abstract
Herein, by using dispersion-corrected density functional theory, we investigated the Diels-Alder chemistry of pristine and defective graphene. Three dienes were considered, namely 2,3-dimethoxy-1,3-butadiene (DMBD), 9-methylanthracene (9MA), and 9,10-dimethylanthracene (910DMA). The dienophiles that were assayed were tetracyanoethylene (TCNE) and maleic anhydride (MA). When pristine graphene acted as the dienophile, we found that the cycloaddition products were 47-63 kcal mol(-1) less stable than the reactants, thus making the reaction very difficult. The presence of Stone-Wales translocations, 585 double vacancies, or 555-777 reconstructed double vacancies did not significantly improve the reactivity because the cycloaddition products were still located at higher energy than the reactants. However, for the addition of 910DMA to single vacancies, the product showed comparable stability to the separated reactants, whereas for unsaturated armchair edges the reaction was extremely favorable. With regards the reactions with dienophiles, for TCNE, the cycloaddition product was metastable. In the case of MA, we observed a reaction product that was less stable than the reactants by 50 kcal mol(-1) . For the reactions between graphene as a diene and the dienophiles, we found that the most-promising defects were single vacancies and unsaturated armchair edges, because the other three defects were much-less reactive. Thus, we conclude that the reactions with these above-mentioned dienes may proceed on pristine or defective sheets with heating, despite being endergonic. The same statement also applies to the dienophile maleic anhydride. However, for TCNE, the reaction is only likely to occur onto single vacancies or unsaturated armchair edges. We conclude that the dienophile character of graphene is slightly stronger than its behavior as a diene.
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568
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Montserrat S, Faustino H, Lledós A, Mascareñas JL, López F, Ujaque G. Mechanistic intricacies of gold-catalyzed intermolecular cycloadditions between allenamides and dienes. Chemistry 2013; 19:15248-60. [PMID: 24114995 DOI: 10.1002/chem.201302330] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Indexed: 11/07/2022]
Abstract
The mechanism of the gold-catalyzed intermolecular cycloaddition between allenamides and 1,3-dienes has been explored by means of a combined experimental and computational approach. The formation of the major [4+2] cycloaddition products can be explained by invoking different pathways, the preferred ones being determined by the nature of the diene (electron neutral vs. electron rich) and the type of the gold catalyst (AuCl vs. [IPrAu](+), IPr=1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene). Therefore, in reactions catalyzed by AuCl, electron-neutral dienes favor a concerted [4+3] cycloaddition followed by a ring contraction event, whereas electron-rich dienes prefer a stepwise cationic pathway to give the same type of formal [4+2] products. On the other hand, the theoretical data suggest that by using a cationic gold catalyst, such as [IPrAuCl]/AgSbF6, the mechanism involves a direct [4+2] cycloaddition between the diene and the gold-activated allenamide. The theoretical data are also consistent with the observed regioselectivity as well as with the high selectivity towards the formation of the enamide products with a Z configuration. Finally, our data also explain the formation of the minor [2+2] products that are obtained in certain cases.
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569
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Wang A, Fang Y, Long L, Song Y, Yu W, Zhao W, Cifuentes MP, Humphrey MG, Zhang C. Facile synthesis and enhanced nonlinear optical properties of porphyrin-functionalized multi-walled carbon nanotubes. Chemistry 2013; 19:14159-70. [PMID: 24038312 DOI: 10.1002/chem.201302477] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Indexed: 11/07/2022]
Abstract
Two multi-walled carbon nanotube (MWCNT)-based nanohybrids, MWCNT-ZnTPP and MWCNT-TPP (TPP=5-[4-{2-(4-formylphenoxy)- ethyloxy}phenyl]-10,15,20-triphenylporphyrin, ZnTPP=5-[4-{(4-formylphenyl)ethynyl}phenyl]-10,15,20-triphenylporphinatozinc(II)), were prepared directly from pristine MWCNTs through 1,3-dipolar cycloaddition reactions. Covalent attachment of the porphyrins to the surfaces of the MWCNTs was confirmed by Fourier transform infrared spectroscopy, ultraviolet/visible absorption, fluorescence, Raman, and X-ray photoelectron spectroscopy, elemental analysis, transmission electron microscopy, and thermogravimetric analysis. Attachment of the porphyrin moieties to the surface of the MWCNTs significantly improves the solubility and ease of processing of these MWCNT-porphyrin composite materials. Z-scan studies reveal that these MWCNT-porphyrin nanohybrids exhibit enhanced nonlinear optical properties under both nanosecond and picosecond laser pulses at λ=532 nm in comparison with free MWCNTs and the free porphyrin chromophores, whereas superior optical limiting performance was displayed by MWCNT-porphyrin composite materials rather than MWCNTs/ZnTPP and MWCNTs/TPP blends, which is consistent with a remarkable accumulation effect as a result of the covalent linkage between the porphyrin and the MWCNTs.
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570
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Stockinger S, Trapp O. Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping. Beilstein J Org Chem 2013; 9:1837-42. [PMID: 24062850 PMCID: PMC3778332 DOI: 10.3762/bjoc.9.214] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 08/14/2013] [Indexed: 01/09/2023] Open
Abstract
A new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels-Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarboxaldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reactants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions.
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571
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Cabrera-Pardo JR, Chai DI, Kozmin SA. Silver-Promoted Benzannulations of Siloxy Alkynes with Pyridinium and Isoquinolinium Salts. Adv Synth Catal 2013; 355:2495-2498. [PMID: 24653670 DOI: 10.1002/adsc.201300443] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We describe the development of efficient benzannulations of siloxy alkynes with pyridinium and isoquinolinium salts. Such reactions are successfully promoted by a stoichiometric amount of silver(I) benzolate under mild reaction conditions. This process proceeds via a formal inverse-electron demand Diels-Alder reaction, followed by fragmentation of the initially produced bicyclic adducts to deliver a range of synthetically useful phenols and naphthols.
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572
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Cludius-Brandt S, Kupracz L, Kirschning A. [3 + 2]- Cycloadditions of nitrile ylides after photoactivion of vinyl azides under flow conditions. Beilstein J Org Chem 2013; 9:1745-50. [PMID: 24062837 PMCID: PMC3778330 DOI: 10.3762/bjoc.9.201] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2013] [Accepted: 07/22/2013] [Indexed: 12/03/2022] Open
Abstract
The photodenitrogenation of vinyl azides to 2H-azirines by using a photoflow reactor is reported and compared with thermal formation of 2H-azirines. Photochemically, the ring of the 2H-azirines was opened to yield the nitrile ylides, which underwent a [3 + 2]-cycloaddition with 1,3-dipolarophiles. When diisopropyl azodicarboxylate serves as the dipolarophile, 1,3,4-triazoles become directly accessible starting from the corresponding vinyl azide.
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573
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Heo YM, Paek SM. Ring expansion of vinylaziridines through the strain-release pericyclic reaction: recent developments and applications. Molecules 2013; 18:9650-62. [PMID: 23941884 PMCID: PMC6269818 DOI: 10.3390/molecules18089650] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 08/01/2013] [Accepted: 08/07/2013] [Indexed: 11/28/2022] Open
Abstract
Recent syntheses of azetidines, pyrrolidines, piperidines and azepines through cycloaddition or sigmatropic rearrangements of vinylaziridines are described. Applications to natural product synthesis and mechanistic investigations are also summarized.
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574
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Parr BT, Davies HML. Rhodium-catalyzed tandem cyclopropanation/Cope rearrangement of 4-alkenyl-1-sulfonyl-1,2,3-triazoles with dienes. Angew Chem Int Ed Engl 2013; 52:10044-7. [PMID: 23913819 DOI: 10.1002/anie.201304310] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2013] [Indexed: 11/09/2022]
Abstract
Take your pick… A practical method for the synthesis of structurally diverse rhodium vinylcarbenes from stable 1-sulfonyl-1,2,3-triazole precursors has been developed. The reaction is general for a broad range of 4-alkenyl triazoles and dienes, enabling the stereoselective synthesis of a variety of polycyclic imines, which are readily converted into amines or aldehydes in a one-pot process.
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575
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de Nanteuil F, Waser J. Synthesis of aminocyclobutanes by iron-catalyzed [2+2] cycloaddition. Angew Chem Int Ed Engl 2013; 52:9009-13. [PMID: 23868610 DOI: 10.1002/anie.201303803] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Indexed: 11/11/2022]
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576
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Yuan W, Wei Y, Shi M. Ruthenium-catalyzed intramolecular [2+2+2] cycloaddition and tandem cross-metathesis of triynes and enediynes. ChemistryOpen 2013; 2:63-8. [PMID: 24551536 PMCID: PMC3646433 DOI: 10.1002/open.201300002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Indexed: 11/09/2022] Open
Abstract
[2+2+2] Cycloadditions can be applied to specifically build up derivatives of benzene and cyclohexadiene and, therefore, have attracted much attention. Herein, we present an intramolecular [2+2+2] cycloaddition of triynes catalyzed by the first-generation Grubbs ruthenium complex (Ru gen-1), which can efficiently afford benzene derivatives in good yields under mild conditions. Moreover, we also report on a novel tandem cross-metathesis transformation of intramolecular enediynes also catalyzed by Ru gen-1, which has not been observed previously in related reports. On the basis of deuterium labeling experiments, a possible reaction mechanism is presented.
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577
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Shu D, Song W, Li X, Tang W. Rhodium- and platinum-catalyzed [4+3] cycloaddition with concomitant indole annulation: synthesis of cyclohepta[b]indoles. Angew Chem Int Ed Engl 2013; 52:3237-40. [PMID: 23401302 PMCID: PMC3690624 DOI: 10.1002/anie.201209266] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Indexed: 11/05/2022]
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578
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Nguyen QNN, Tantillo DJ. Caryolene-forming carbocation rearrangements. Beilstein J Org Chem 2013; 9:323-31. [PMID: 23503674 PMCID: PMC3596059 DOI: 10.3762/bjoc.9.37] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 01/21/2013] [Indexed: 11/23/2022] Open
Abstract
Density functional theory calculations on mechanisms of the formation of caryolene, a putative biosynthetic precursor to caryol-1(11)-en-10-ol, reveal two mechanisms for caryolene formation: one involves a base-catalyzed deprotonation/reprotonation sequence and tertiary carbocation minimum, whereas the other (with a higher energy barrier) involves intramolecular proton transfer and the generation of a secondary carbocation minimum and a hydrogen-bridged minimum. Both mechanisms are predicted to involve concerted suprafacial/suprafacial [2 + 2] cycloadditions, whose asynchronicity allows them to avoid the constraints of orbital symmetry.
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579
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Chandrasoma N, Brown N, Brassfield A, Nerurkar A, Suarez S, Buszek KR. Total Synthesis of (±)-Cis-Trikentrin B via Intermolecular 6,7-Indole Aryne Cycloaddition and Stille Cross-Coupling. Tetrahedron Lett 2013; 54:913-917. [PMID: 25278636 DOI: 10.1016/j.tetlet.2012.11.125] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
An efficient total synthesis of the annulated indole natural product (±)-cis-trikentrin B was accomplished by means of a regioselectively generated 6,7-indole aryne cycloaddition via selective metal-halogen exchange from a 5,6,7-tribromoindole. The unaffected C-5 bromine was subsequently used for a Stille cross-coupling to install the butenyl side chain and complete the synthesis. This strategy provides rapid access into the trikentrins and the related herbindoles, and represents another application of this methodology to natural products total synthesis. The required 5,6,7-indole aryne precursor was prepared using the Leimgruber-Batcho indole synthesis.
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580
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Tigchelaar A, Tam W. Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides. Beilstein J Org Chem 2012; 8:1765-70. [PMID: 23209510 PMCID: PMC3511010 DOI: 10.3762/bjoc.8.201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 08/30/2012] [Indexed: 12/02/2022] Open
Abstract
Iridium-catalyzed intramolecular [4 + 2] cycloadditions of diene-tethered alkynyl halides were investigated by using [IrCl(cod)]2 as catalyst, and dppe was found to be the most suitable phosphine ligand for the reaction. No oxidative insertion of the iridium into the carbon–halide bond was observed, and the reactions proceeded to provide the halogenated cycloadducts in good yield (75–94%). These results are the first examples of cycloadditions of alkynyl halides using an iridium catalyst.
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581
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Knowles JP, Elliott LD, Booker-Milburn KI. Flow photochemistry: Old light through new windows. Beilstein J Org Chem 2012; 8:2025-52. [PMID: 23209538 PMCID: PMC3511038 DOI: 10.3762/bjoc.8.229] [Citation(s) in RCA: 317] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 10/29/2012] [Indexed: 12/23/2022] Open
Abstract
Synthetic photochemistry carried out in classic batch reactors has, for over half a century, proved to be a powerful but under-utilised technique in general organic synthesis. Recent developments in flow photochemistry have the potential to allow this technique to be applied in a more mainstream setting. This review highlights the use of flow reactors in organic photochemistry, allowing a comparison of the various reactor types to be made.
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582
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Trost BM, Morris PJ, Sprague SJ. Palladium-catalyzed diastereo- and enantioselective formal [3 + 2]- cycloadditions of substituted vinylcyclopropanes. J Am Chem Soc 2012; 134:17823-31. [PMID: 23030714 PMCID: PMC3495600 DOI: 10.1021/ja309003x] [Citation(s) in RCA: 149] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe a palladium-catalyzed diastereo- and enantioselective formal [3 + 2]-cycloaddition between substituted vinylcyclopropanes and electron-deficient olefins in the form of azlactone- and Meldrum's acid alkylidenes to give highly substituted cyclopentane products. By modulation of the electronic properties of the vinylcyclopropane and the electron-deficient olefin, high levels of stereoselectivity were obtained. The remote stereoinduction afforded by the catalyst, distal from the chiral pocket generated by the ligand, is proposed to be the result of a new mechanism invoking the Curtin-Hammett principle.
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583
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Lu Z, Yoon TP. Visible light photocatalysis of [2+2] styrene cycloadditions by energy transfer. Angew Chem Int Ed Engl 2012; 51:10329-32. [PMID: 22965321 PMCID: PMC3517039 DOI: 10.1002/anie.201204835] [Citation(s) in RCA: 288] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Indexed: 11/06/2022]
Abstract
Hip to be square: Styrenes participate in [2+2] cycloadditions upon irradiation with visible light in the presence of an iridium(III) polypyridyl complex. In contrast to previous reports of visible light photoredox catalysis, the mechanism of this process involves photosensitization by energy transfer and not electron transfer.
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584
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Xu X, Zavalij PY, Doyle MP. Synthesis of tetrahydropyridazines by a metal-carbene-directed enantioselective vinylogous N-H insertion/Lewis acid-catalyzed diastereoselective Mannich addition. Angew Chem Int Ed Engl 2012; 51:9829-33. [PMID: 22945294 PMCID: PMC3517037 DOI: 10.1002/anie.201203962] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 07/03/2012] [Indexed: 11/10/2022]
Abstract
A versatile cascade of reactions, triggered by Rh(II)-catalyzed diazo decomposition followed by a vinylogous N-H insertion/Lewis acid catalyzed Mannich addition, that produces highly substituted 1,2,3,6-tetrahydropyridazines in up to 97 % ee with high yield and diastereocontrol has been developed.
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585
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Hong AY, Stoltz BM. Enantioselective total synthesis of the reported structures of (-)-9-epi-presilphiperfolan-1-ol and (-)-presilphiperfolan-1-ol: structural confirmation and reassignment and biosynthetic insights. Angew Chem Int Ed Engl 2012; 51:9674-8. [PMID: 22915502 PMCID: PMC3517068 DOI: 10.1002/anie.201205276] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Indexed: 11/10/2022]
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586
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Stolley RM, Duong HA, Thomas DR, Louie J. The discovery of [Ni(NHC)RCN]2 species and their role as cycloaddition catalysts for the formation of pyridines. J Am Chem Soc 2012; 134:15154-62. [PMID: 22917161 PMCID: PMC3480329 DOI: 10.1021/ja3075924] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction of Ni(COD)(2), IPr, and nitrile affords dimeric [Ni(IPr)RCN](2) in high yields. X-ray analysis revealed these species display simultaneous η(1)- and η(2)-nitrile binding modes. These dimers are catalytically competent in the formation of pyridines from the cycloaddition of diynes and nitriles. Kinetic analysis showed the reaction to be first order in [Ni(IPr)RCN](2), zeroth order in added IPr, zeroth order in nitrile, and zeroth order in diyne. Extensive stoichiometric competition studies were performed, and selective incorporation of the exogenous, not dimer bound, nitrile was observed. Post cycloaddition, the dimeric state was found to be largely preserved. Nitrile and ligand exchange experiments were performed and found to be inoperative in the catalytic cycle. These observations suggest a mechanism whereby the catalyst is activated by partial dimer-opening followed by binding of exogenous nitrile and subsequent oxidative heterocoupling.
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587
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Kumar P, Zhang K, Louie J. An expeditious route to eight-membered heterocycles by nickel-catalyzed cycloaddition: low-temperature C(sp)2-C(sp)3 bond cleavage. Angew Chem Int Ed Engl 2012; 51:8602-6. [PMID: 22806996 PMCID: PMC3557805 DOI: 10.1002/anie.201203521] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Indexed: 12/31/2022]
Abstract
A cool break: 3-Azetidinone and a variety of diynes undergo a cycloaddition reaction catalyzed by Ni/IPr to give dihydroazocine compounds (see scheme; IPr=1,3-bis(2,6-diisopropylphenyl)imidazolidene). The reaction involves a challenging C(sp)2-C(sp)3 bond cleavage step, yet, surprisingly, proceeds at low temperature.
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588
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Yang J, Karver MR, Li W, Sahu S, Devaraj NK. Metal-catalyzed one-pot synthesis of tetrazines directly from aliphatic nitriles and hydrazine. Angew Chem Int Ed Engl 2012; 51:5222-5. [PMID: 22511586 PMCID: PMC3434974 DOI: 10.1002/anie.201201117] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Indexed: 11/06/2022]
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589
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Enßle M, Buck S, Werz R, Maas G. Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine. Beilstein J Org Chem 2012; 8:433-40. [PMID: 22509214 PMCID: PMC3326622 DOI: 10.3762/bjoc.8.49] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 03/06/2012] [Indexed: 11/23/2022] Open
Abstract
Methionine, S-benzylcysteine and S-allylcysteine were converted into 2-diazo-3-oxo-4-phthalimidocarboxylic esters 8a-c in three steps. Upon rhodium-catalysed dediazoniation, two intramolecular carbenoid reactions competed, namely the formation of a cyclic sulfonium ylide and that of a six-ring carbonyl ylide. The S-methyl and S-benzyl ylides 12a and b could be isolated, while S-allyl ylide 12c underwent a [2,3]-sigmatropic rearrangement. The short-lived carbonyl ylides derived from methionine and S-benzylcysteine formed head-to-tail dimers by a [3 + 3]-cycloaddition and could be trapped with external dipolarophiles, while the S-allyl derivative 14c yielded the pentacyclic compound 17 by an intramolecular [3 + 2]-cycloaddition reaction.
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590
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Friscourt F, Ledin PA, Mbua NE, Flanagan-Steet HR, Wolfert MA, Steet R, Boons GJ. Polar dibenzocyclooctynes for selective labeling of extracellular glycoconjugates of living cells. J Am Chem Soc 2012; 134:5381-9. [PMID: 22376061 PMCID: PMC3319718 DOI: 10.1021/ja3002666] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Although strain-promoted alkyne-azide cycloadditions (SPAAC) have found wide utility in biological and material sciences, the low polarity and limited water solubility of commonly used cyclooctynes represent a serious shortcoming. To address this problem, an efficient synthetic route has been developed for highly polar sulfated dibenzocyclooctynylamides (S-DIBO) by a Friedel-Crafts alkylation of 1,2-bis(3-methoxyphenyl)ethylamides with trichlorocyclopropenium cation followed by a controlled hydrolysis of the resulting dichlorocyclopropenes to give bis(3-methoxyphenyl)cyclooctacyclopropenones, which were subjected to methoxy group removal of the phenols, O-sulfation, and photochemical unmasking of the cyclopropenone moiety. Accurate rate measurements of the reaction of benzyl azide with various dibenzylcyclooctyne derivatives demonstrated that aromatic substitution and the presence of the amide function had only a marginal impact on the rate constants. Biotinylated S-DIBO 8 was successfully used for labeling azido-containing glycoconjugates of living cells. Furthermore, it was found that the substitution pattern of the dibenzylcyclooctynes influences subcellular location, and in particular it has been shown that DIBO derivative 4 can enter cells, thereby labeling intra- and extracellular azido-modified glycoconjugates, whereas S-DIBO 8 cannot pass the cell membrane and therefore is ideally suited for selective labeling of cell surface molecules. The ability to selectively label cell surface molecules will yield unique opportunities for glycomic analysis and the study of glycoprotein trafficking.
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591
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Karver MR, Weissleder R, Hilderbrand SA. Bioorthogonal reaction pairs enable simultaneous, selective, multi-target imaging. Angew Chem Int Ed Engl 2012; 51:920-2. [PMID: 22162316 PMCID: PMC3304098 DOI: 10.1002/anie.201104389] [Citation(s) in RCA: 185] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 10/27/2011] [Indexed: 01/05/2023]
Abstract
Mutually orthogonal tetrazine–transcyclooctene and azide–cyclooctyne cycloaddition reactions were used simultaneously for the bioorthogonal labeling of two different live cell populations in the same culture. These small-molecule probes show good chemical reactivity and can be readily incorporated into biological systems.
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MESH Headings
- Alkynes/chemistry
- Antibodies, Monoclonal/chemistry
- Antibodies, Monoclonal/pharmacology
- Antibodies, Monoclonal, Humanized/chemistry
- Antibodies, Monoclonal, Humanized/pharmacology
- Azides/chemistry
- Cell Line, Tumor
- Cetuximab
- Coculture Techniques
- Contrast Media/chemistry
- Contrast Media/pharmacology
- ErbB Receptors/chemistry
- ErbB Receptors/metabolism
- Fluorescent Dyes/chemistry
- Humans
- Microscopy, Fluorescence
- Receptor, ErbB-2/chemistry
- Receptor, ErbB-2/metabolism
- Trastuzumab
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592
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Nonn M, Kiss L, Sillanpää R, Fülöp F. Synthesis of highly functionalized β-aminocyclopentanecarboxylate stereoisomers by reductive ring opening reaction of isoxazolines. Beilstein J Org Chem 2012; 8:100-6. [PMID: 22423276 PMCID: PMC3302068 DOI: 10.3762/bjoc.8.10] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Accepted: 12/23/2011] [Indexed: 11/23/2022] Open
Abstract
A rapid and simple procedure was devised for the synthesis of multifunctionalized cyclic β-amino esters and γ-amino alcohols via the 1,3-dipolar cycloaddition of nitrile oxides to β-aminocyclopentenecarboxylates. The opening of the isoxazoline reductive ring to the corresponding highly functionalized 2-aminocyclopentanecarboxylates occurred stereoselectively with good yields.
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593
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Steurer M, Jensen KL, Worgull D, Jørgensen KA. Enantioselective one-pot synthesis of α-amino esters by a phosphine-catalyzed [3+2]- cycloaddition reaction. Chemistry 2012; 18:76-9. [PMID: 22162097 PMCID: PMC3482930 DOI: 10.1002/chem.201103502] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Indexed: 11/17/2022]
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594
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Maity S, Zhu M, Shinabery RS, Zheng N. Intermolecular [3+2] cycloaddition of cyclopropylamines with olefins by visible-light photocatalysis. Angew Chem Int Ed Engl 2012; 51:222-6. [PMID: 22109785 PMCID: PMC3330129 DOI: 10.1002/anie.201106162] [Citation(s) in RCA: 217] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Indexed: 12/23/2022]
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595
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Yang Y, Kuang C, Jin H, Yang Q, Zhang Z. Efficient synthesis of 1,3-diaryl-4-halo-1H-pyrazoles from 3-arylsydnones and 2-aryl-1,1-dihalo-1-alkenes. Beilstein J Org Chem 2011; 7:1656-62. [PMID: 22238544 PMCID: PMC3252870 DOI: 10.3762/bjoc.7.195] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 11/10/2011] [Indexed: 11/23/2022] Open
Abstract
An efficient synthesis of 1,3-diaryl-4-halo-1H-pyrazoles was achieved. The synthesis involves the [3 + 2] dipolar cycloaddition of 3-arylsydnones and 2-aryl-1,1-dihalo-1-alkenes. The process proceeds smoothly in moderate to excellent yields. 1,3-Diaryl-4-halo-1H-pyrazoles are found to be important intermediates that can easily be converted into 1,2,5-triaryl-substituted pyrazoles via Pd-catalyzed C–H bond activation.
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596
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Carpenter RD, Hausner SH, Sutcliffe JL. Copper-Free Click for PET: Rapid 1,3-Dipolar Cycloadditions with a Fluorine-18 Cyclooctyne. ACS Med Chem Lett 2011; 2:885-9. [PMID: 24900276 DOI: 10.1021/ml200187j] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 10/07/2011] [Indexed: 01/06/2023] Open
Abstract
The strain-promoted click 1,3-dipolar cycloaddition reactions involving azides and cyclooctynes for the synthesis of triazoles offer the advantage of being able to be performed in biological settings via copper-free chemistries. While strained reagents conjugated to optical dyes and radiometal conjugates have been reported, cyclooctyne reagents labeled with fluorine-18 ((18)F) and radiochemically evaluated in a copper-free click reaction have yet to be explored. This report describes the conversion of a bifunctional azadibenzocyclooctyne (ADIBO) amine to the (18)F-labeled cyclooctyne 4, the subsequent fast copper-free 1,3-dipolar cycloaddition reaction with alkyl azides at 37 °C (>70% radiochemical conversion in 30 min), and biological evaluations (serum stability of >95% at 2 h). These findings demonstrate the excellent reactivity of the (18)F-labeled cyclooctyne 4 with readily available azides that will allow future work focusing on rapid copper-free in vitro and in vivo click chemistries for PET imaging using (18)F-labeled cyclooctyne derivatives of ADIBO.
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597
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Budin G, Yang KS, Reiner T, Weissleder R. Bioorthogonal probes for polo-like kinase 1 imaging and quantification. Angew Chem Int Ed Engl 2011; 50:9378-81. [PMID: 21948435 PMCID: PMC3187564 DOI: 10.1002/anie.201103273] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 07/13/2011] [Indexed: 11/06/2022]
Abstract
A nuclear protein target, polo-like kinase 1 (PLK1) was imaged using a biocompatible bioorthogonal ligation between a specific drug and a fluorescent dye in live cells. Colocalization of the dye and the protein target was confirmed by antibody staining and by expressing a GFP construct of PLK1. The two-step PLK1 imaging procedure was used to quantify PLK1 expression levels in cancer cell lines of various tissue origins.
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598
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Shu XZ, Huang S, Shu D, Guzei IA, Tang W. Interception of a Rautenstrauch intermediate by alkynes for [5+2] cycloaddition: rhodium-catalyzed cycloisomerization of 3-acyloxy-4-ene-1,9-diynes to bicyclo[5.3.0]decatrienes. Angew Chem Int Ed Engl 2011; 50:8153-6. [PMID: 21748834 PMCID: PMC3399041 DOI: 10.1002/anie.201103136] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Indexed: 11/10/2022]
Abstract
Rholling in the bicycles: a rhodium(I)-catalyzed cycloisomerization for the synthesis of bicyclic compounds containing a cycloheptatriene ring from linear alkenynes (see scheme; cod=1,5-cyclooctadiene) is proposed to proceed through 1,2-acyloxy migration, 6 π electrocyclization, migratory insertion, and reductive elimination. The overall process can be viewed as a novel intramolecular [5+2] cycloaddition with concomitant 1,2-acyloxy migration.
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599
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López F, Mascareñas JL. Recent developments in gold-catalyzed cycloaddition reactions. Beilstein J Org Chem 2011; 7:1075-94. [PMID: 21915211 PMCID: PMC3167873 DOI: 10.3762/bjoc.7.124] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 07/14/2011] [Indexed: 12/04/2022] Open
Abstract
In the last years there have been extraordinary advances in the development of gold-catalyzed cycloaddition processes. In this review we will summarize some of the most remarkable examples, and present the mechanistic rational underlying the transformations.
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600
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Dadiboyena S, Hamme AT. One Pot Spiropyrazoline Synthesis via Intramolecular Cyclization/Methylation. Tetrahedron Lett 2011; 52:2536-2539. [PMID: 21686095 PMCID: PMC3115653 DOI: 10.1016/j.tetlet.2011.03.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Regioisomeric spiropyrazolines were synthesized through a tandem intramolecular cyclization/methylation reaction of a functionalized 5,5-disubstituted pyrazoline in one reaction vessel. The 5,5-pyrazolines were constructed through a 1,3-dipolar cycloaddition reaction of aromatic ring containing nitrile imines and a disubstituted geminal alkene. An evaluation of the relative location of the nucleophilic and electrophilic functional groups on the pyrazoline was performed in order to ascertain the best pyrazoline system for the intramolecular cyclization/methylation reaction. Higher spiropyrazoline isolated yields were realized from pyrazolines with the electrophilic ester located further away from the pyrazoline when compared to pyrazolines with a directly bonded ester.
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