Rh2(II)-Catalyzed Enyne Cycloisomerization toward 6–6–5 Tricycles

Abstract

A dirhodium-catalyzed diastereoselective cycloisomerization of enynes derived from cyclohexadienone-tethered ynals is described. This reaction enables a concise synthetic pathway toward a library of 6–6–5 fused tricyclic frameworks incorporating three consecutive stereogenic centers. This protocol features excellent diastereoselectivities. Mechanistic studies indicate a dirhodium carbene is possibly involved. Trapping this species with external alkenes furnishes structurally intricate fused/spirocyclic adducts bearing five stereocenters with complete diastereoselectivity.