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Murata R, Shitamichi K, Hiramatsu M, Matsubara S, Uraguchi D, Asano K. trans-Cyclooctenes as Scavengers of Bromine Involved in Catalytic Bromination. Chemistry 2024; 30:e202303399. [PMID: 38117956 DOI: 10.1002/chem.202303399] [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: 10/16/2023] [Indexed: 12/22/2023]
Abstract
Scavengers that capture reactive chemical substances are used to prevent the decomposition of materials. However, in the field of catalysis, the development of scavengers that inhibit background pathways has attracted little attention, although the concept will open up an otherwise inaccessible reaction space. In catalytic bromination, fast non-catalyzed background reactions disturb the catalytic control of the selectivity, even when using N-bromoamide reagents, which have a milder reactivity than bromine (Br2 ). Here, we developed a trans-cyclooctene (TCO) bearing a 2-pyridylethyl group to efficiently retard background reactions by capturing Br2 in bromocyclization using N-bromosuccinimide. The use of less than a stoichiometric amount of the TCO was sufficient to inhibit non-catalyzed reactions, and mechanistic studies using the TCO revealed that in situ-generated Br2 provides non-catalyzed reaction pathways based on a chain mechanism. The TCO is useful as an additive for improving enantioselectivity and regioselectivity in catalytic reactions. Cooperative systems using the TCO with selective catalysts offer an alternative strategy for optimizing catalyst-controlled selectivity during bromination. Moreover, it also served as an indicator of Br2 involved in catalytic reaction pathways; thus, the TCO was useful as a probe for mechanistic investigations into the involvement of Br2 in bromination reactions of interest.
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Affiliation(s)
- Ryuichi Murata
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigaku-katsura, Nishikyo, Kyoto, 615-8510, Japan
| | - Kenta Shitamichi
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigaku-katsura, Nishikyo, Kyoto, 615-8510, Japan
| | - Masatsugu Hiramatsu
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigaku-katsura, Nishikyo, Kyoto, 615-8510, Japan
| | - Seijiro Matsubara
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigaku-katsura, Nishikyo, Kyoto, 615-8510, Japan
| | - Daisuke Uraguchi
- Institute for Catalysis, Hokkaido University, Sapporo, Hokkaido, 001-0021, Japan
- List Sustainable Digital Transformation Catalyst Collaboration Research Platform, Institute for Chemical Reaction Design and Discovery (ICReDD List-PF), Hokkaido University, Sapporo, Hokkaido, 001-0021, Japan
| | - Keisuke Asano
- Institute for Catalysis, Hokkaido University, Sapporo, Hokkaido, 001-0021, Japan
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Li WC, Yang L, Wei ZL, Liao WW. Diastereo- and Enantioselective Synthesis of Functionalized Dihydropyrans via an Organocatalytic Claisen Rearrangement/Oxa-Michael Addition Tandem Sequence. Org Lett 2023; 25:6434-6439. [PMID: 37606692 DOI: 10.1021/acs.orglett.3c02461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
A straightforward diastereo- and enantioselective Claisen rearrangement/oxa-Michael addition tandem sequence with a cinchona squaramide catalyst was described, which afforded a practical and atom-economical approach to access a range of valuable dihydropyrans in good to excellent yields with excellent stereoselectivities. The organo-bifunctional catalyst played a key role in enhancing stereoselectivity in this asymmetric tandem sequence. Moreover, the asymmetric catalytic sequential processes of the hydroalkoxylation/Claisen rearrangement/cyclization sequence and Claisen rearrangement/aza-Michael addition tandem sequence have also been afforded good yields and moderate stereoselectivities.
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Affiliation(s)
- Wen-Cheng Li
- Department of Organic Chemistry, College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
| | - Lei Yang
- Department of Organic Chemistry, College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
| | - Zhong-Lin Wei
- Department of Organic Chemistry, College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
| | - Wei-Wei Liao
- Department of Organic Chemistry, College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. China
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Asano K, Matsubara S. Organocatalytic Access to Tetrasubstituted Chiral Carbons Integrating Functional Groups. CHEM REC 2022:e202200200. [PMID: 36163471 DOI: 10.1002/tcr.202200200] [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: 08/08/2022] [Revised: 09/08/2022] [Indexed: 12/15/2022]
Abstract
Three-dimensional organic structures containing sp3 carbons bearing four non-hydrogen substituents can provide drug-like molecules. Although such complex structures are challenging targets in synthetic organic chemistry, efficient synthetic approaches will open a new chemical space for pharmaceutical candidates. This review provides an account of our recent achievements in developing organocatalytic approaches to attractive molecular platforms based on optically active sp3 carbons integrating four different functional groups. These methodologies include asymmetric cycloetherification and cyanation of multifunctional ketones, both of which take advantage of the mild characteristics of organocatalytic activation. Enzyme-like but non-enzymatic organocatalytic systems can be used to precisely manufacture molecules containing complex chiral structures without substrate specificity problems. In addition, these catalytic systems control not only stereoselectivity but also site-selectivity and do not induce side reactions even from substrates with rich functionality.
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Affiliation(s)
- Keisuke Asano
- Institute for Catalysis, Hokkaido University Sapporo, Hokkaido, 001-0021, Japan
| | - Seijiro Matsubara
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University Kyotodaigaku-Katsura, Nishikyo, Kyoto, 615-8510, Japan
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