Straightforward Entry toward Highly Substituted 2,3-Dihydrobenz[b]oxepines by Ring Expansion of Benzopyryliums with Donor-Acceptor Diazo Compounds

Thibaut Courant (1) , Morgane Pasco (1) , Thomas Lecourt (1)

1 COBRA - Chimie Organique et Bioorganique : Réactivité et Analyse

Ylide-type reactivity of diazo compounds is exploited in a new way to prepare benzo[b]oxepines thanks to the formation of three chemical bonds and two contiguous and highly substituted stereocenters in a single pot. This cationic reaction cascade first involves addition of a donor–acceptor-substituted diazo compound to a benzopyrylium. Selective 1,2 migration of the endocyclic C–C bond then results in a ring-expansion and generates a second oxocarbenium that is trapped by a nucleophile added sequentially.

Domains: Chemical Sciences

Thibaut Courant, Morgane Pasco, Thomas Lecourt. Straightforward Entry toward Highly Substituted 2,3-Dihydrobenz[b]oxepines by Ring Expansion of Benzopyryliums with Donor-Acceptor Diazo Compounds. Organic Letters, 2018, 20 (9), pp.2757-2761. ⟨10.1021/acs.orglett.8b00984⟩. ⟨hal-02024492⟩