Thermal Decarboxylative Cloke-Wilson Rearrangement of Dispirocyclopropanes Derived from para-Quinone Methides and Bromo-Meldrum's Acids: An Approach to Spirobutyrolactone para-Dienones

An unprecedented approach to synthesize spirobutyrolactone para-dienones from para-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 produced via the sequential spirocyclopropanation/rearrangement process in two steps with overall yields from 56 to 88%.