O-Bridged medium sized rings via bicyclic oxonium ylides
Abstract
Fused bicyclic oxonium ylides, generated with catalytic Rh2(OAc)4 from cyclic ethers bearing pendant diazo ketones, undergo a [1,2]- or [2,3]-shift to give O-bridged seven- or eight-membered carbocycles, in several cases with a high degree of stereoselectivity.