Synthesis of Bridged N,O‐Heterocyclic 1,6‐Epoxybenzo[c]azocines via Migration‐Annulation Cascade Reaction of α‐Imino Rhodium Carbenes

Abstract

A rhodium-catalyzed cascade migration-annulation reaction of 1-sulfonyl-1,2,3-triazole has been developed. As the key step, the 1,3-sulfinate migration of α-imino rhodium carbene yielded an extended zwitterion, which was intramolecularly trapped by aldehyde group furnishing bridged N,O-heterocyclic 1,6-epoxybenzo[c]azocine as the [5 + 2] cyclization product. This migration-annulation strategy provides more flexibility for heterocycle synthesis and medium-sized ring construction, especially for the construction of polycycles with complex skeletons.

Copper-Catalyzed Synthesis of Furan-Tethered Benzocyclobutenes via Carbene-Mediated 1,4-Sulfinate Migration-Annulation

“…Sulfinate is a unique migrating group, which transforms into a sulfonyl group. The resulting zwitterion intermediate 8 was well stabilized on the anion part by the sulfonyl group, providing an opportunity to regulate the reactivity, leading to a series of sulfonyl-substituted cyclopropanes, dihydropyrroles, azepanes, and N , O -hetero bridge compounds (Scheme C) . Considering the powerful potential of enynone-derived carbene intermediates and the successful applications of the migration-annulation strategy of carbenes in organic synthesis, we report here a copper-catalyzed intramolecular cascade reaction of enynones 9 , involving a 1,4-sulfinate migration as a pivotal step, leading to the practical synthesis of furan-tethered benzocyclobutenes 12 (Scheme D).…”