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

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...