1
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Stang M, Mycka RJ, Blum SA. Mechanistic Insight from Lewis-Acid-Dependent Selectivity and Reversible Haloboration, as Harnessed for Boron-Based Electrophilic Cyclization Reactions. J Org Chem 2023; 88:15159-15167. [PMID: 37877549 DOI: 10.1021/acs.joc.3c01653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
Different reaction selectivity occurs with the Lewis acids B-chlorocatecholborane (ClBcat), B-bromocatecholborane (BrBcat), and BBr3, favoring either alkyne haloboration, electrophilic cyclization of a tethered nucleophilic sulfur onto the alkyne, or group transfer of the nucleophile. This reaction selectivity also depends on the chain length of the tethered nucleophile, revealing a subtle interplay of relative kinetics and thermodynamics. In all cases, BBr3 reacts readily with alkynes to form haloborated products; however, this process is reversible, and this reversibility can be harnessed to ultimately access regio- and stereodefined cyclic sulfonium zwitterions via the slower but thermodynamically favored electrophilic cyclization pathway. Reversibility was noted by following the reaction by NMR spectroscopy, and by characterizing the kinetic and thermodynamic products by a combination of 2D NMR spectroscopy and single-crystal X-ray diffraction. The "mixed" reagent bromocatechol borane (BrBcat) displayed reactivity between ClBcat and BBr3, producing bromoboration in some cases and electrophilic cyclization in others. With this enhanced understanding of the reaction dynamics, it becomes possible to use boron Lewis acids in a predictable manner in cases where haloboration is the kinetic product but in which the reversibility of this reaction maintains access to eventual alternative reactivity leading to desired building blocks in organic synthesis.
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Affiliation(s)
- Martin Stang
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Robert J Mycka
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
- Community College of Allegheny County, Pittsburgh, Pennsylvania 15212, United States
| | - Suzanne A Blum
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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2
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Desrosiers V, Knight SM, Fontaine FG. A Metal-Free Approach for the C–H Activation and Transfer Borylation of Electron-Rich Alkenes. ACS Catal 2022. [DOI: 10.1021/acscatal.2c04305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Vincent Desrosiers
- Département de Chimie, Université Laval, 1045 Avenue de la Médecine, Quebec City, Quebec G1 V 0A6, Canada
| | - Samantha M. Knight
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia B3H 4R2, Canada
| | - Frédéric-Georges Fontaine
- Département de Chimie, Université Laval, 1045 Avenue de la Médecine, Quebec City, Quebec G1 V 0A6, Canada
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3
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Gao C, Blum SA. Silyl Radical Cascade Cyclization of 2-Isocyanothioanisole toward 2-Silylbenzothiazoles through Radical Initiator-Inhibitor Symbiosis. J Org Chem 2022; 87:13124-13137. [PMID: 36098507 DOI: 10.1021/acs.joc.2c01605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A demethylative silyl radical cascade cyclization of 2-isocyanothioanisoles toward 2-silylated benzothiazole building blocks has been developed. The development of a "radical initiator-inhibitor symbiosis" system solves the challenge of otherwise dominant methyl radical-triggered side reactions brought about by kinetically unfavored generation of reactive silyl radical species. The products accessed in this protocol are amendable to various downstream functionalization reactions, including the quick construction of a topoisomerase II inhibitor via a Hiyama cross-coupling reaction and of an antiviral agent via a fluoride-/hydroxide-free nucleophilic substitution to acyl chloride.
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Affiliation(s)
- Chao Gao
- Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, United States
| | - Suzanne A Blum
- Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, United States
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4
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Hazra S, Mahato S, Kanti Das K, Panda S. Transition-Metal-Free Heterocyclic Carbon-Boron Bond Formation. Chemistry 2022; 28:e202200556. [PMID: 35438817 DOI: 10.1002/chem.202200556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Indexed: 12/16/2022]
Abstract
Heteroaryl boronic acids and esters are extremely important and valuable intermediates because of their wide application in the synthesis of marketed drugs and bioactive compounds. Over the last couple of decades, the construction of highly important heteroaryl carbon-boron bonds has created huge attention. The transition-metal-free protocols are more green, less sensitive to air and moisture, and also economically advantageous over the transition-metal-based protocols. The transition-metal-free C-H borylation of heteroarenes and C-X (X=halogen) borylation of heteroaryl halides represents an excellent approach for their synthesis. Also, various cyclization and alkyne activation protocols have been recently established for their synthesis. The goal of this review article is to summarize the existing literature and the current state of the art for transition-metal-free synthesis of heteroaryl boronic acid and esters.
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Affiliation(s)
- Subrata Hazra
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Somenath Mahato
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Kanak Kanti Das
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Santanu Panda
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
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5
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Milián A, Fernández-Rodríguez MA, Merino E, Vaquero JJ, García-García P. Metal-Free Temperature-Controlled Regiodivergent Borylative Cyclizations of Enynes: BCl 3 -Promoted Skeletal Rearrangement. Angew Chem Int Ed Engl 2022; 61:e202205651. [PMID: 35510716 PMCID: PMC9401584 DOI: 10.1002/anie.202205651] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Indexed: 12/04/2022]
Abstract
Metal‐free borylative cyclization of biphenyl‐embedded 1,3,5‐trien‐7‐ynes in the presence of simple and inexpensive BCl3 provided synthetically useful borylated building blocks. The outcome of the process depends on the reaction temperature, with borylated phenanthrenes obtained at 60 °C and phenanthrene‐fused borylated cyclobutanes formed at 0 °C. Based on DFT calculations, a mechanism for these novel transformations has been proposed, which involves an uncommon skeletal rearrangement, including migration of a methyl group and alkyne fragmentation, unprecedented in BCl3‐promoted cyclization reactions.
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Affiliation(s)
- Ana Milián
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia, Autovía A-II, Km 33.1, 28805-Alcalá de Henares, Madrid, Spain
| | - Manuel A Fernández-Rodríguez
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia, Autovía A-II, Km 33.1, 28805-Alcalá de Henares, Madrid, Spain
| | - Estíbaliz Merino
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia, Autovía A-II, Km 33.1, 28805-Alcalá de Henares, Madrid, Spain
| | - Juan J Vaquero
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia, Autovía A-II, Km 33.1, 28805-Alcalá de Henares, Madrid, Spain
| | - Patricia García-García
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia, Autovía A-II, Km 33.1, 28805-Alcalá de Henares, Madrid, Spain
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6
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Recent synthetic advances in borylated pyrazoles. Tetrahedron Lett 2022. [DOI: 10.1016/j.tetlet.2022.154008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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7
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Milián A, Fernández‐Rodríguez MA, Merino E, Vaquero JJ, García‐García P. Metal‐Free Temperature‐Controlled Regiodivergent Borylative Cyclizations of Enynes: BCl
3
‐Promoted Skeletal Rearrangement. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205651] [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]
Affiliation(s)
- Ana Milián
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica Instituto de Investigación Química “Andrés M. del Río” (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia Autovía A-II, Km 33.1 28805-Alcalá de Henares Madrid Spain
| | - Manuel A. Fernández‐Rodríguez
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica Instituto de Investigación Química “Andrés M. del Río” (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia Autovía A-II, Km 33.1 28805-Alcalá de Henares Madrid Spain
| | - Estíbaliz Merino
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica Instituto de Investigación Química “Andrés M. del Río” (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia Autovía A-II, Km 33.1 28805-Alcalá de Henares Madrid Spain
| | - Juan J. Vaquero
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica Instituto de Investigación Química “Andrés M. del Río” (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia Autovía A-II, Km 33.1 28805-Alcalá de Henares Madrid Spain
| | - Patricia García‐García
- Universidad de Alcalá (IRYCIS). Departamento de Química Orgánica y Química Inorgánica Instituto de Investigación Química “Andrés M. del Río” (IQAR). Campus Científico-Tecnológico, Facultad de Farmacia Autovía A-II, Km 33.1 28805-Alcalá de Henares Madrid Spain
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8
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Kaplan JA, Issaian A, Stang M, Gorial D, Blum SA. Repurposing π Electrophilic Cyclization/Dealkylation for Group Transfer. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202112351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Joseph A. Kaplan
- Department of Chemistry University of California, Irvine Irvine CA 02697 USA
| | - Adena Issaian
- Department of Chemistry University of California, Irvine Irvine CA 02697 USA
| | - Martin Stang
- Department of Chemistry University of California, Irvine Irvine CA 02697 USA
| | - David Gorial
- Department of Chemistry University of California, Irvine Irvine CA 02697 USA
| | - Suzanne A. Blum
- Department of Chemistry University of California, Irvine Irvine CA 02697 USA
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Kaplan JA, Issaian A, Stang M, Gorial D, Blum SA. Repurposing π Electrophilic Cyclization/Dealkylation for Group Transfer. Angew Chem Int Ed Engl 2021; 60:25776-25780. [PMID: 34585500 DOI: 10.1002/anie.202112351] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Indexed: 01/31/2023]
Abstract
A metal-free regio- and stereocontrolled group-transfer route toward the synthesis of trisubstituted alkenes is described. In this route, an electrophilic heterocyclization is followed by ring-opening group transfer. Specifically, a thioboration reaction transforms readily available alkynyl sulfide precursors into alkenyl boronates and alkenyl sulfides with defined regio- and stereochemistry in one synthetic step using commercially available B-chlorocatecholborane (ClBcat). Mechanistic studies identified the likely pathway as proceeding through zwitterionic rather than haloborated intermediates. The regio- and stereochemistry set in the initial cyclization step is preserved in the final acyclic alkene product, producing alkenes with up to four modifiable substituents with predictable regio- and stereochemistry. Downstream functionalization reactions showcase the versatility of the substitutions of the resulting alkenes. The mechanistic concept maps onto future reaction designs, given the abundance of known electrophiles and nucleophiles for electrophilic heterocyclization/dealkylation sequences.
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Affiliation(s)
- Joseph A Kaplan
- Department of Chemistry, University of California, Irvine, Irvine, CA, 02697, USA
| | - Adena Issaian
- Department of Chemistry, University of California, Irvine, Irvine, CA, 02697, USA
| | - Martin Stang
- Department of Chemistry, University of California, Irvine, Irvine, CA, 02697, USA
| | - David Gorial
- Department of Chemistry, University of California, Irvine, Irvine, CA, 02697, USA
| | - Suzanne A Blum
- Department of Chemistry, University of California, Irvine, Irvine, CA, 02697, USA
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10
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Hong SJ, Yoon CJ, Lim HN, Yeom H. Step‐Economical Route to 2‐Amido‐3‐bromobenzo[
b
]thiophenes
via
Ynamide Formation and Selectfluor‐Mediated Oxidative Bromocyclization. European J Org Chem 2021. [DOI: 10.1002/ejoc.202101093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Su Jeong Hong
- Eco-Friendly New Materials Research Center, Therapeutics&Biotechnology Division Korea Research Institute of Chemical Technology (KRICT) 141 Gajeong-ro, Yuseong-gu Daejeon 34114 Republic of Korea
- Department of Chemistry Hanyang University 222, Wangsimni-ro, Seongdong-gu Seoul 04763 Republic of Korea
| | - Chang Ju Yoon
- Eco-Friendly New Materials Research Center, Therapeutics&Biotechnology Division Korea Research Institute of Chemical Technology (KRICT) 141 Gajeong-ro, Yuseong-gu Daejeon 34114 Republic of Korea
- Department of Chemistry Sungkyunkwan University 2066, Seobu-ro, Jangan-gu, Suwon-si Gyeonggi-do 16419 Republic of Korea
| | - Hee Nam Lim
- Department of Chemistry and Biochemistry Yeungnam University 280 Daehak-Ro, Gyeongsan Gyeongbuk 38541 Republic of Korea
| | - Hyun‐Suk Yeom
- Eco-Friendly New Materials Research Center, Therapeutics&Biotechnology Division Korea Research Institute of Chemical Technology (KRICT) 141 Gajeong-ro, Yuseong-gu Daejeon 34114 Republic of Korea
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11
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Hayes HLD, Wei R, Assante M, Geogheghan KJ, Jin N, Tomasi S, Noonan G, Leach AG, Lloyd-Jones GC. Protodeboronation of (Hetero)Arylboronic Esters: Direct versus Prehydrolytic Pathways and Self-/Auto-Catalysis. J Am Chem Soc 2021; 143:14814-14826. [PMID: 34460235 DOI: 10.1021/jacs.1c06863] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The kinetics and mechanism of the base-catalyzed hydrolysis (ArB(OR)2 → ArB(OH)2) and protodeboronation (ArB(OR)2 → ArH) of a series of boronic esters, encompassing eight different polyols and 10 polyfluoroaryl and heteroaryl moieties, have been investigated by in situ and stopped-flow NMR spectroscopy (19F, 1H, and 11B), pH-rate dependence, isotope entrainment, 2H KIEs, and KS-DFT computations. The study reveals the phenomenological stability of boronic esters under basic aqueous-organic conditions to be highly nuanced. In contrast to common assumption, esterification does not necessarily impart greater stability compared to the corresponding boronic acid. Moreover, hydrolysis of the ester to the boronic acid can be a dominant component of the overall protodeboronation process, augmented by self-, auto-, and oxidative (phenolic) catalysis when the pH is close to the pKa of the boronic acid/ester.
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Affiliation(s)
- Hannah L D Hayes
- EaStChem, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, U.K
| | - Ran Wei
- EaStChem, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, U.K
| | - Michele Assante
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, U.K
| | - Katherine J Geogheghan
- EaStChem, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, U.K
| | - Na Jin
- EaStChem, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, U.K
| | - Simone Tomasi
- Chemical Development, Pharmaceutical Technology and Development, Operations, AstraZeneca, Macclesfield SK10 2NA, U.K
| | - Gary Noonan
- Chemical Development, Pharmaceutical Technology and Development, Operations, AstraZeneca, Macclesfield SK10 2NA, U.K
| | - Andrew G Leach
- School of Health Sciences, Stopford Building, The University of Manchester, Oxford Road, Manchester M13 9PT, U.K
| | - Guy C Lloyd-Jones
- EaStChem, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, U.K
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12
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Gao C, Blum SA. Main-group metalated heterocycles through Lewis acid cyclization. TRENDS IN CHEMISTRY 2021. [DOI: 10.1016/j.trechm.2021.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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