A practical method for a facile entry to structurally unique ring-fused dihydroazepine
has been developed using 1-sulfonyl-1,3-dienyltriazole as starting materials. Driven
by ring strain release of cyclopropyl group, a rhodium-catalyzed α-imino carbenoid
formation–cyclopropanation–aza-Cope rearrangement cascade takes place efficiently
in a single operation. Substitution effects on yield and diastereoselectivity are
also explored.
Key words
carbenes - bicyclic compounds - heterocycles - cyclization - rearrangement