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Asmic Isocyanide [3 + 2] Cascade to Dihydrooxazoles and Dihydroimidazoles
Journal article   Peer reviewed

Asmic Isocyanide [3 + 2] Cascade to Dihydrooxazoles and Dihydroimidazoles

Chepuri V. Suneel Kumar, Caleb W Holyoke, Taylor M Keller and Fraser F Fleming
Journal of organic chemistry, v 85(14), pp 9153-9160
17 Jul 2020
PMID: 32639153

Abstract

The versatile isocyanide building block Asmic, anisyl­sulfanyl­methyl­iso­cyanide, reacts with aldehydes and ketones in a BF3·OEt2-mediated condensation to afford thioimidoyl-substituted 2,5-dihydrooxazoles. The condensation is distinguished from related base and transition-metal-catalyzed [3 + 2] processes in proceeding via the condensation of aldehydes and ketones with 2 equiv of an isocyanide followed by a molecular rearrangement that installs four new bonds. BF3·OEt2 mediates an analogous condensation of Asmic with imines to generate N-substituted dihydroimidazoles. Mechanistically, BF3·OEt2 activates the isocyanide to facilitate deprotonation evolving to a zwitterion that traps π-electrophiles in a formal [3 + 2] process. A second deprotonation–condensation with Asmic initiates a structural rearrangement involving a sulfanyl elimination–addition transposition sequence. The resulting dihydrooxazoles and dihydroimidazoles contain a thioimidate that serves as a diversification point for further elaboration.

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Collaboration types
Domestic collaboration
Web of Science research areas
Chemistry, Organic
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