Au-Catalyzed Tandem Cyclization/[1,2]-Alkyl Migration Reaction of Epoxy Alkynes: Synthesis of Spiropyranones.

A novel gold-catalyzed tandem cyclization/[1,2]-alkyl migration process of epoxy alkynes to spiropyranones has been discovered. From this process, the construction of adjacent multiple stereocenters with a new quaternary carbon atom is achieved. The gold-catalyzed domino process is stereospecific with respect to the migrating carbon atom. A type of unusual C-C bond cleavage of epoxide systems has also been discovered, which can lead to the formation of two Z alkenes and a carbonyl functional group in one step with excellent stereoselectivity. Furthermore, this efficient domino process could be achieved in the presence of the simplest and least expensive gold catalyst [NaAuCl(4)]center dot 2H(2)O with a low catalyst loading.