Gold-Catalyzed Tandem Dual Heterocyclization of Enynones with 1,3,5-Triazines: Bicyclic Furan Synthesis and Mechanistic Insights

A general and unprecedented
gold-catalyzed tandem dual heterocyclization
reaction of enynones with 1,3,5-triazines has been developed, which
provides bicyclic fused furans in high to excellent yields under mild
reaction conditions. In addition, mechanistic studies indicate that
the reaction goes through a stepwise [3+2+2]-cycloaddition of furanyl
gold intermediate, which is generated from gold-catalyzed cyclization
of enynone, with two molecules of formaldimines derived in situ from
1,3,5-triazine, instead of formal [4+3]-cycloaddition.