1
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Dearomative [2 + 1] Spiroannulation of Bromophenols with Electron-Deficient Alkenes. J Org Chem 2024. [PMID: 38757188 DOI: 10.1021/acs.joc.4c00680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
A base-assisted dearomative [2 + 1] spiroannulation of p/o-bromophenols with activated olefins (methylenemalonates) to construct various cyclopropyl spirocyclohexadienone skeletons is reported. Furthermore, several other halophenols (X = Cl, I) were also tolerated in this process. Control experiments reveal a dearomative Michael addition of phenols at their halogenated positions to methylenemalonates, followed by intramolecular radical-based SRN1 dehalogenative cyclopropanation. However, according to the density functional theory (DFT) calculations, an SN2 dehalogenative cyclopropanation with the same low activation energy barrier should not be excluded. The utility of this method is showcased by gram-scale syntheses and transformations of the dearomatized products.
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2
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Furan Dearomatization: A Route to Diverse Fluoroalkyl/Aryl Triazoles. J Org Chem 2024; 89:4349-4365. [PMID: 38497642 DOI: 10.1021/acs.joc.3c02402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
The 5-fluoroalkyl-1,2,3-triazoles, serving as a pivotal element in medicinal chemistry, hold substantial research significance. In this work, we developed a furan dearomatization reaction for the synthesis of various 5-fluoroalkyl-1,2,3-triazoles, which contains -CF3, -CF2H, -CF2CF3, -CF2CF2CF3, -CF2CO2Et, and -C6F5. This methodology relies on the intermolecular [3 + 2] cycloaddition/furan ring-opening triggered by α-fluoroalkyl furfuryl cation with azides to stereoselectively synthesize a series of (E)-fluoroalkyl enone triazoles. The reaction proceeds without metal participation, exhibits excellent substrate tolerance, and has excellent synthetic utility.
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3
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Carbon quaternization of redox active esters and olefins by decarboxylative coupling. Science 2024; 384:113-118. [PMID: 38574151 DOI: 10.1126/science.adn5619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 02/28/2024] [Indexed: 04/06/2024]
Abstract
The synthesis of quaternary carbons often requires numerous steps and complex conditions or harsh reagents that act on heavily engineered substrates. This is largely a consequence of conventional polar-bond retrosynthetic disconnections that in turn require multiple functional group interconversions, redox manipulations, and protecting group chemistry. Here, we report a simple catalyst and reductant combination that converts two types of feedstock chemicals, carboxylic acids and olefins, into tetrasubstituted carbons through quaternization of radical intermediates. An iron porphyrin catalyst activates each substrate by electron transfer or hydrogen atom transfer, and then combines the fragments using a bimolecular homolytic substitution (SH2) reaction. This cross-coupling reduces the synthetic burden to procure numerous quaternary carbon---containing products from simple chemical feedstocks.
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4
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Regiodivergent Ring-Expansion of Oxindoles to Quinolinones. J Am Chem Soc 2024; 146:4301-4308. [PMID: 38335924 PMCID: PMC10885155 DOI: 10.1021/jacs.3c12119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2024]
Abstract
The development of divergent methods to expedite structure-activity relationship studies is crucial to streamline discovery processes. We developed a rare example of regiodivergent ring expansion to access two regioisomers from a common starting material. To enable this regiodivergence, we identified two distinct reaction conditions for transforming oxindoles into quinolinone isomers. The presented methods proved to be compatible with a variety of functional groups, which enabled the late-stage diversification of bioactive oxindoles as well as facilitated the synthesis of quinolinone drugs and their derivatives.
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5
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Furan ring opening reaction for the synthesis of 2,5-dicarbonyl-3-ene-phosphates. Org Biomol Chem 2023; 21:7219-7223. [PMID: 37642497 DOI: 10.1039/d3ob00933e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Furan ring opening reactions are essential in organic synthesis, enabling the incorporation of diverse functional groups and the construction of complex molecular structures. A highly efficient and practical method for synthesizing 2,5-dicarbonyl-3-ene-phosphates from readily available biomass furan and dialkyl phosphonates is reported. The reaction, catalyzed by FeCl3, demonstrated wide substrate scope and high synthetic efficiency. Gram-scale synthesis was achieved, and a one-pot reaction provided a quick access route to the desired compounds. Additionally, a successful Diels-Alder reaction highlighted the versatility of the methodology.
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6
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Base-Promoted Intramolecular Addition of Vinyl Cyclopropanecarboxamides to Access Conformationally Restricted Aza[3.1.0]bicycles. Molecules 2023; 28:molecules28093691. [PMID: 37175101 PMCID: PMC10179847 DOI: 10.3390/molecules28093691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 04/22/2023] [Accepted: 04/22/2023] [Indexed: 05/15/2023] Open
Abstract
3-Azabicyclo[3.1.0]hexanes are common structural components in natural products and bioactive compounds. Traditionally, the metal-mediated cyclopropanation domino reaction of chain enzymes is the most commonly used strategy for the construction of this type of aza[3.1.0]bicycle derivative. In this study, a base-promoted intramolecular addition of alkenes used to deliver conformationally restricted highly substituted aza[3.1.0]bicycles is reported. This reaction was tailor-made for saturated aza[3.1.0] bicycle-containing fused bicyclic compounds that may be applied in the development of concise and divergent total syntheses of bioactive compounds.
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7
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Recent Advances in the Synthesis of 3,n-Fused Tricyclic Indole Skeletons via Palladium-Catalyzed Domino Reactions. Molecules 2023; 28:molecules28041647. [PMID: 36838635 PMCID: PMC9964631 DOI: 10.3390/molecules28041647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 02/03/2023] [Accepted: 02/05/2023] [Indexed: 02/11/2023] Open
Abstract
3,n-fused (n = 4-7) tricyclic indoles are pervasive motifs, embedded in a variety of biologically active molecules and natural products. Thus, numerous catalytic methods have been developed for the synthesis of these skeletons over the past few decades. In particular, palladium-catalyzed transformations have received much attention in recent years. This review summarizes recent developments in the synthesis of these tricyclic indoles with palladium-catalyzed domino reactions and their applications in the total synthesis of representative natural products.
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8
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Synthesis of 2-Aminofurans and 2-Aminothiophenes through Elemental Sulfur-Promoted Switchable Redox Condensation Reaction of Enaminones with Methylene Nitriles. J Org Chem 2022; 87:15312-15326. [PMID: 36343221 DOI: 10.1021/acs.joc.2c01882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Herein, we report an elemental sulfur-promoted switchable redox condensation reaction that can selectively prepare 2-aminofurans and 2-aminothiophenes from the corresponding enaminones and methylene nitriles, respectively. Mechanistic studies demonstrated that the enaminones, as dual nucleophiles, reacted with nitrile acetate to produce 2-aminofurans via 3,5-annulation under promotion by elemental sulfur. These reactions used readily available starting materials, transition metal-free, eco-friendly procedures, gram-scale syntheses, and wide functional group tolerance. The methodology may be useful for the construction of 2-aminofuran and 2-aminothiophene derivatives with potential biological activity.
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9
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Optical control of the β2-adrenergic receptor with Opto-prop-2: a cis-active azobenzene analog of propranolol. iScience 2022; 25:104882. [PMID: 36060054 PMCID: PMC9436767 DOI: 10.1016/j.isci.2022.104882] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 06/17/2022] [Accepted: 08/02/2022] [Indexed: 11/19/2022] Open
Abstract
In this study, we synthesized and evaluated new photoswitchable ligands for the beta-adrenergic receptors β1-AR and β2-AR, applying an azologization strategy to the first-generation beta-blocker propranolol. The resulting compounds (Opto-prop-1, -2, -3) have good photochemical properties with high levels of light-induced trans-cis isomerization (>94%) and good thermal stability (t1/2 > 10 days) of the resulting cis-isomer in an aqueous buffer. Upon illumination with 360-nm light to PSScis, large differences in binding affinities were observed for photoswitchable compounds at β1-AR as well as β2-AR. Notably, Opto-prop-2 (VUF17062) showed one of the largest optical shifts in binding affinities at the β2-AR (587-fold, cis-active), as recorded so far for photoswitches of G protein-coupled receptors. We finally show the broad utility of Opto-prop-2 as a light-dependent competitive antagonist of the β2-AR as shown with a conformational β2-AR sensor, by the recruitment of downstream effector proteins and functional modulation of isolated adult rat cardiomyocytes. A photoswitchable antagonist of the β2-AR was developed: Opto-prop-2 β2-AR binding affinity of the light-induced cis-Opto-prop-2 is 578-fold stronger Opto-prop-2 allowed dynamic control of β2-AR antagonism Opto-prop-2 allowed light-dependent modulation of cardiomyocyte function
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10
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Dual Roles of Azide: Dearomative Dimerization of Furfuryl Azides. J Org Chem 2022; 87:10185-10198. [PMID: 35864566 DOI: 10.1021/acs.joc.2c01118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A dearomative dimerization of furfuryl azides for the construction of furfuryl triazoles is developed. As a rare leaving group, azide is capable of initiating the generation of a furfuryl cation under the Lewis acid-catalyzed conditions, followed by reacting with the other azide to realize an intermolecular [3 + 2] cycloaddition/furan ring-opening cascade. By extending the reaction time, a fragmentation reaction of resulting furfuryl triazoles occurs to afford 1H-triazoles in high yield. Control studies demonstrated that key furfuryl cations also can be obtained from furfuryl triazoles. Furthermore, a chemoselective cross-cycloaddition can be achieved between furfuryl azides and a benzyl azide.
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11
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The construction of phosphonate triazolyl by copper(II)-catalyzed furan dearomatized [3 + 2] cycloaddition. Org Biomol Chem 2022; 20:6319-6323. [PMID: 35856323 DOI: 10.1039/d2ob01060g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Triazole phosphonates are valuable structural motifs in chemical biology and the subject of growing recent interest. A novel methodology to synthesize triazolyl phosphonates starting from furfuryl phosphonate alcohols and organo-azides was developed. This method involved an intermolecular copper-catalyzed dearomatized [3 + 2] cycloaddition/furan ring-opening cascade reaction. A strategy involving a three-component reaction was realized for quick access to triazole phosphonates.
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12
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Asymmetric Total Synthesis of All Rugulovasine Stereoisomers and Preliminary Evaluation of their Biological Properties. European J Org Chem 2022. [DOI: 10.1002/ejoc.202200315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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13
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Allenamides Playing Domino: A Redox‐Neutral Photocatalytic Synthesis of Functionalized 2‐Aminofurans. Adv Synth Catal 2022. [DOI: 10.1002/adsc.202101015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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14
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Direct photo-induced reductive Heck cyclization of indoles for the efficient preparation of polycyclic indolinyl compounds. Chem Sci 2021; 12:14050-14058. [PMID: 34760188 PMCID: PMC8565399 DOI: 10.1039/d1sc04258k] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 09/16/2021] [Indexed: 12/15/2022] Open
Abstract
The photo-induced cleavage of C(sp2)-Cl bonds is an appealing synthetic tool in organic synthesis, but usually requires the use of high UV light, photocatalysts and/or photosensitizers. Herein is described a direct photo-induced chloroarene activation with UVA/blue LEDs that can be used in the reductive Heck cyclization of indoles and without the use of a photocatalyst or photosensitizer. The indole compounds examined display room-temperature phosphorescence. The photochemical reaction tolerates a panel of functional groups including esters, alcohols, amides, cyano and alkenes (27 examples, 50-88% yields), and can be used to prepare polycyclic compounds and perform the functionalization of natural product analogues in moderate to good yields. Mechanistic experiments, including time-resolved absorption spectroscopy, are supportive of photo-induced electron transfer between the indole substrate and DIPEA, with the formation of radical intermediates in the photo-induced dearomatization reaction.
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15
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Direct Synthesis of CF 2H-Substituted 2-Amidofurans via Copper-Catalyzed Addition of Difluorinated Diazoacetone to Ynamides. Org Lett 2021; 23:5528-5532. [PMID: 34190568 DOI: 10.1021/acs.orglett.1c01876] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The significance of molecules containing difluoromethyl groups is driven by their potential applications in pharmaceutical and agrochemical science. Methods for the incorporation of lightly fluorinated groups such as CF2H have been less well developed. Here we report the use of difluorinated diazoacetone as a practical reagent for the direct synthesis of CF2H-substituted 2-amidofurans through addition to ynamides. These newly designed difluorinated amidofurans were elaborated to create new nitrogen-containing frameworks that would be challenging to obtain otherwise.
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16
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Abstract
Oxidation reactions have been extensively studied in the context of the transformations of biomass-derived furans. However, in contrast to the vast literature on utilizing the stoichiometric oxidants, such as m-CPBA and NBS, catalytic methods for the oxidative furan-recyclizations remain scarcely investigated. Given this, we report a means of manganese-catalyzed oxidations of furan with low loading, achieving the Achmatowicz rearrangement in the presence of hydrogen peroxide as an environmentally benign oxidant under mild conditions with wide functional group compatibility.
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17
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Biosynthesis, total synthesis, and biological profiles of Ergot alkaloids. THE ALKALOIDS: CHEMISTRY AND BIOLOGY 2021; 85:1-112. [DOI: 10.1016/bs.alkal.2020.08.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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18
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19
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Formation of cyclopropa[c]indole system in the Mn-mediated radical addition of cyclohexane-1,3-diones to N-substituted acrylamides. MENDELEEV COMMUNICATIONS 2020. [DOI: 10.1016/j.mencom.2020.11.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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20
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Abstract
Myrocins are a family of antiproliferative antibiotic fungal metabolites possessing a masked electrophilic cyclopropane. Preliminary chemical reactivity studies imputed the bioactivity of these natural products to a DNA cross-linking mechanism, but this hypothesis was not confirmed by studies with native DNA. We recently reported a total synthesis of (-)-myrocin G (4), the putative active form of the metabolite myrocin C (1), that featured a carefully orchestrated tandem fragment coupling-annulation cascade. Herein, we describe the evolution of our synthetic strategy toward 4 and report the series of discoveries that prompted the design of this cascade coupling. Efforts to convert the diosphenol (-)-myrocin G (4) to the corresponding 5-hydroxy-γ-lactone isomer myrocin C (1) are also detailed. We present a preliminary evaluation of the antiproliferative activities of (-)-myrocin G (4) and related structures, as well as DNA cross-linking studies. These studies indicate that myrocins do not cross-link DNA, suggesting an alternative mode of action potentially involving a protein target.
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21
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Ytterbium-Catalyzed Intramolecular [3 + 2] Cycloaddition based on Furan Dearomatization to Construct Fused Triazoles. Org Lett 2020; 22:5176-5181. [DOI: 10.1021/acs.orglett.0c01780] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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22
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Furfuryl Cation Induced Three-Component Reaction to Synthesize Triazole-Substituted Thioesters. European J Org Chem 2020. [DOI: 10.1002/ejoc.202000299] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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23
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Iron-Catalyzed Synthesis of 2-Aminofurans from 2-Haloketones and Tertiary Amines or Enamines. European J Org Chem 2020. [DOI: 10.1002/ejoc.202000293] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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24
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Homoleptic Bis(trimethylsilyl)amides of Yttrium Complexes Catalyzed Hydroboration Reduction of Amides to Amines. Org Lett 2020; 22:1306-1310. [PMID: 32013446 DOI: 10.1021/acs.orglett.9b04606] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Homoleptic lanthanide complex Y[N(TMS)2]3 is an efficient homogeneous catalyst for the hydroboration reduction of secondary amides and tertiary amides to corresponding amines. A series of amides containing different functional groups such as cyano, nitro, and vinyl groups were found to be well-tolerated. This transformation has also been nicely applied to the synthesis of indoles and piribedil. Detailed isotopic labeling experiments, control experiments, and kinetic studies provided cumulative evidence to elucidate the reaction mechanism.
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25
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Abstract
The selective catalytic reduction of amides to value-added amine products is a desirable but challenging transformation.
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26
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Formation of 8-Hydroxyphenanthridines by Microwave-Mediated IMDAF Reactions; Synthesis Directed towards Lycorine Alkaloids. European J Org Chem 2019. [DOI: 10.1002/ejoc.201901000] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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27
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Enantioselective Formal Synthesis of (+)-Cycloclavine and Total Synthesis of (+)-5- epi-Cycloclavine. Org Lett 2019; 21:6603-6607. [PMID: 31411477 DOI: 10.1021/acs.orglett.9b02015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Starting from the commercially available 4-bromoindole, a concise and efficient enantioselective formal synthesis of (+)-cycloclavine (1) in 13 steps with 2.0% overall yield and a total synthesis of (+)-5-epi-cycloclavine (2) in 14 steps with 3.3% overall yield were achieved. Key features of the syntheses include the addition of a Grignard reagent to the C═N/Heck reaction sequence to construct the fused 6-5-6 ring systems, cyclopropanation, an ester aminolysis reaction, and the first example of the construction of a 3-azabicyclo[3,1,0]hexane through an intramolecular [3 + 2] cycloaddition/nitrogen extrusion.
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28
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A Domino Aza-Piancatelli Rearrangement/Intramolecular Diels–Alder Reaction: Stereoselective Synthesis of Octahydro-1H-cyclopenta[cd]isoindole. Org Lett 2019; 21:3822-3827. [DOI: 10.1021/acs.orglett.9b01267] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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29
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Pyridazine N-Oxides as Precursors to 2-Aminofurans: Scope and Limitations in Complexity Building Cascade Reactions. Org Lett 2019; 21:2397-2401. [DOI: 10.1021/acs.orglett.9b00682] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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30
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Isocyanide‐Based Multicomponent Reactions: A Concise Approach to 2‐Amino‐3‐perfluoroalkylfurans Using Methyl Perfluoroalk‐2‐ynoates as Fluorinated Building Blocks. ASIAN J ORG CHEM 2019. [DOI: 10.1002/ajoc.201900010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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31
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32
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Furfuryl Cation Induced Cascade Formal [3 + 2] Cycloaddition/Double Ring-Opening/Chlorination: An Approach to Chlorine-Containing Complex Triazoles. Org Lett 2018; 20:7410-7414. [PMID: 30412412 DOI: 10.1021/acs.orglett.8b03121] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A TiCl4-promoted cascade formal [3 + 2] cycloaddition/double ring-opening/chlorination of 2-furylcyclobutanols with alkyl or aryl azides is described. This highly efficient transformation involves the formation/cleavage of several C-N, C-Cl, C-C, and C-O bonds in a single operation. It enables the quick construction of trisubstituted 1,2,3-triazoles with an ( E)-enone moiety and a 3-chloropropyl unit. The chlorinated products are readily transformed into other structurally diverse analogues.
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33
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34
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35
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A Combination of Furfuryl Cation Induced Three-Component Reactions and Photocatalyst-Free Photoisomerization To Construct Complex Triazoles. Org Lett 2018; 20:4893-4897. [DOI: 10.1021/acs.orglett.8b02035] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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36
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Concise Synthesis of (-)-Cycloclavine and (-)-5- epi-Cycloclavine via Asymmetric C-C Activation. J Am Chem Soc 2018; 140:9652-9658. [PMID: 29976068 DOI: 10.1021/jacs.8b05549] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
To illustrate the synthetic significance of C-C activation methods, here we describe an efficient strategy for the enantioselective total syntheses of (-)-cycloclavine and (-)-5- epi-cycloclavine, which is enabled by an asymmetric Rh-catalyzed "cut-and-sew" transformation between benzocyclobutenones and olefins. Despite the compact structure of cycloclavine with five-fused rings, the total synthesis was accomplished in 10 steps with a 30% overall yield. Key features of the synthesis include (1) a Pd-catalyzed tandem C-N bond coupling/allylic alkylation sequence to construct the nitrogen-tethered benzocyclobutenone, (2) a highly enantioselective Rh-catalyzed carboacylation of alkenes to forge the indoline-fused tricyclic structure, and (3) a diastereoselective cyclopropanation for preparing the tetrasubstituted cyclopropane ring. Notably, an improved catalytic condition has been developed for the nitrogen-tethered cut-and-sew transformation, which uses a low catalyst loading and allows for a broad substrate scope with high enantioselectivity (94-99% e.e.). The C-C activation-based strategy employed here is anticipated to have further implications for syntheses of other natural products that contain complex fused or bridged rings.
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37
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Synthesis of 3,4‐Fused Tricyclic Indoles Using 3‐Alkylidene Indolines as Versatile Precursors. CHEM REC 2018; 19:320-332. [DOI: 10.1002/tcr.201800043] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 06/06/2018] [Indexed: 12/31/2022]
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38
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Silylative Reductive Amination of α,β-Unsaturated Aldehydes: A Convenient Synthetic Route to β-Silylated Secondary Amines. Chemistry 2018; 24:5765-5769. [DOI: 10.1002/chem.201800958] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Indexed: 12/23/2022]
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39
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A Heteroarylamine Library: Indium-Catalyzed Nucleophilic Aromatic Substitution of Alkoxyheteroarenes with Amines. Adv Synth Catal 2018. [DOI: 10.1002/adsc.201701452] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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Indole synthesis by palladium-catalyzed tandem allylic isomerization - furan Diels-Alder reaction. Org Biomol Chem 2018; 15:7093-7096. [PMID: 28813061 DOI: 10.1039/c7ob01654a] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A Pd(0)-catalyzed elimination of an allylic acetate generates a π-allyl complex that is postulated to initiate a novel intramolecular Diels-Alder cycloaddition to a tethered furan (IMDAF). Under the reaction conditions, this convergent, microwave-accelerated cascade process provides substituted indoles in moderate to good yields after Pd-hydride elimination, aromatization by dehydration, and in situ N-Boc cleavage.
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41
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Abstract
We report an expeditious catalytic asymmetric approach to clavine alkaloids via a key Heck cyclization. This reaction sets the formation of vicinal stereocenters with excellent diastereoselectivity. Utilizing the aforementioned strategy, the formal total synthesis of cycloclavine (1) has been achieved via another key late-stage ester-aminolysis of 6.
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Cycloaddition/annulation strategies for the construction of multisubstituted pyrrolidines and their applications in natural product synthesis. Org Chem Front 2018. [DOI: 10.1039/c7qo01077j] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Pyrrolidines are privileged substructures of numerous bioactive natural products and drugs.
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Temperature-modulated diastereoselective transformations of 2-vinylindoles to tetrahydrocarbazoles and tetrahydrocycloheptadiindoles. Org Biomol Chem 2018; 16:2910-2922. [DOI: 10.1039/c8ob00228b] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Fe(OTf)3-catalyzed dimerization of 2-vinylindolesviadiastereoselective [4 + 2] or [4 + 3] cyclization gives rise to tetrahydrocarbazoles at low temperature or tetrahydrocycloheptadiindoles at high temperature.
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Construction of the tetracyclic core of (±)-cycloclavine and 4-amino Uhle's ketone. Org Biomol Chem 2018; 16:3801-3808. [DOI: 10.1039/c7ob03067c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Construction of the tetracyclic core of (±)-cycloclavine and 4-amino Uhle's ketone.
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45
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Preparation of 2-Amino-5-homoallylfurans via Palladium-Catalyzed Tandem Cycloisomerization/Heck-Type Coupling of Homoallenyl Amides with Allyltrialkylsilanes. J Org Chem 2017; 82:11134-11140. [PMID: 28948794 DOI: 10.1021/acs.joc.7b02131] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The direct access to 2-amino-5-homoallylfurans has been realized by a palladium-catalyzed tandem cycloisomerization/Heck-type coupling between homoallenyl amides and allyltrialkylsilanes, using a novel DDQ/MnO2 combination as the efficient oxidant. The reaction exclusively affords γ-allylation products in good to excellent yields with broad substrate scope under exceptionally mild reaction conditions. It represents one of the rare examples of the Pd-catalyzed intermolecular Heck-type coupling of allytrialkylsilanes terminated by β-silyl elimination, thus complementing traditional allylation methods because of the excellent γ-selectivity.
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Catalyst-free Synthesis of 6-Hydroxy Indoles via the Condensation of Carboxymethyl Cyclohexadienones and Amines. J Org Chem 2017; 82:8426-8437. [PMID: 28714691 DOI: 10.1021/acs.joc.7b01136] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An efficient catalyst-free synthesis of 6-hydroxy indoles from carboxymethyl cyclohexadienones and primary amines has been developed. The aza-Michael addition of the in situ formed enamine, generated through the condensation of carboxymethyl unit of the substrates with an external amine, to cyclohexadienone moiety followed by rearomatization reaction to provide such indoles. Anilines, aliphatic amines, α-chiral aliphatic amines, or even ammonia were used as amine counterpart. Some of the cyclohexadienones gave 6-amino indoles instead of 6-hydroxy indoles using the Re2O7 catalyst. Various post methodological transformations were performed to explore the synthetic utility of the synthesized hydroxy indoles.
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Total Synthesis of (−)-Chanoclavine I and an Oxygen-Substituted Ergoline Derivative. J Org Chem 2017; 82:7774-7782. [DOI: 10.1021/acs.joc.7b00573] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Intramolecular Nitrofuran Diels-Alder Reactions: Extremely Substituent-Tolerant Cycloadditions via Asynchronous Transition States. J Org Chem 2017; 82:6656-6670. [PMID: 28574257 DOI: 10.1021/acs.joc.7b00781] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nitrofurans undergo intramolecular Diels-Alder reactions with tethered electron-poor dienophiles more rapidly and in higher yield than non-nitrated furans. Computational studies indicate that increased stabilization of a partial positive charge on the nitro-substituted carbon in both transition state and product is the driving force for these reactions. Frontier molecular orbital energy differences indicate a switch from normal to inverse electron demand upon nitration. There does not appear to be a contribution from any differences in aromatic stabilization energy between furans and nitrofurans. Calculations show that the nitrofuran reactions proceed via a highly asynchronous transition state allowing easier bond formation between two sterically hindered carbons.
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Abstract
Several Gold's reagents were synthesized from cyanuric chloride and N,N-dialkylformamides. These synthetic equivalents of N,N-dimethylformamide dimethyl acetal were used in an optimized and scalable procedure for the regioselective synthesis of a variety of enaminones from ketone starting materials, whose utility was demonstrated by the stereoselective synthesis of Rawal-type dienes.
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Abstract
Covering: 2000 to 2017Ergot alkaloids are among the most important pharmaceuticals and natural toxins. Significant progress has been achieved in recent years on the research of ergot alkaloids. In this review, we re-introduced the history of ergot alkaloids. Meanwhile, we summarized all the natural products and semi-synthetic derivatives of ergot alkaloids. We also briefly described the biosynthesis and semi-synthesis of ergot alkaloid drugs from raw materials obtained by fermentation. Moreover, we reviewed the advances that have been made in the total synthesis of ergot alkaloids since 2000.
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