A thermal decarboxylative Cloke-Wilson rearrangement of dispirocyclopropanes derived from para-quinone methides and bromo-Meldrum's acids: an approach to synthesize spirobutyrolactone para-dienones

An unprecedented approach to synthesize spirobutyrolactonepara-dienones frompara-quinone methides and bromo-Meldrum's acids has been developed. A series of spatially congested dispirocyclopropanes are generated by spirocyclopropanation, and their unique reactivities have been explored for the first time in the thermal decarboxylative Cloke-Wilson rearrangement reaction. A variety of spirobutyrolactones are efficiently producedviathe sequential spirocyclopropanation/rearrangement process in two steps with overall yields from 56 to 88%.