The Reactivity of 4-Hydroxy- and 4-Silyloxy-1,5-allenynes with Homogeneous Gold(I) Catalysts

Two new gold(I)-catalyzed cascade reactions of 4-hydroxy- and 4-silyloxy-1,5-allenynes are disclosed, offering access to a variety of mono- and bicyclic, polyunsaturated carbonyl compounds. The diverse reactivity observed for the investigated allenyne system is controlled by the nature of the unsaturated substrate: Allenynes bearing a free hydroxyl group engage in what is likely an oxycyclization/allene-ene carbocyclization cascade, while their silylated analogues are converted through a carbocyclization/pinacol-type rearrangement process.