Gold-catalyzed intermolecular addition of carbonyl compounds to 1,6-enynes: reactivity, scope, and mechanistic aspects.

A full account of a recently discovered gold(I)-catalyzed reaction, a cycloaddition of carbonyl compounds to enynes yielding 2-oxabicyclo[3.1.0]hexanes with four stereogenic centers, is presented. The reaction proceeds with very high diastereoselectivity. The scope of the reaction has been investigated. In addition, experiments and DFT calculations concerning mechanistic aspects were carried out. The reaction course varies with the substitution pattern of the alkene moiety of the starting enyne. Branched olefins led to 2-oxabicyclo[3.1.0]hexanes; terminally substituted olefins proceeded with the incorporation of two carbonyl components to give hexahydrocyclopenta[d][1,3]dioxines.