HFIP-promoted formal [2π + 2σ] cycloaddition of para-quinone methides with bicyclo[1.1.0]butanes: an approach towards spiro-bicyclo[2.1.1]hexanes

Abstract

A formal [2π + 2σ] cycloaddition of BCBs with p-QMs has been developed using a small amount of HFIP (2 M) as the solvent without an additional catalyst, in which HFIP also served as a H-bond donor and a cationic stabilizer. This protocol enables the rapid construction of spiro-BCHs in good to excellent yields with a broad substrate scope. Easy scale-up synthesis, potential applications in the modification of bioactive products, mild reaction conditions and simple operation are its practical advantages.