Electrophilic Bromolactonization of Cyclopropyl Carboxylic Acids Using Lewis Basic Sulfide Catalyst

A highly facile and efficient electrophilic bromolactonization of cyclopropylcarboxylic acids could be effected by a Lewis basic sulfide catalyst. Mechanistic studies performed revealed that the cyclopropane substrates could undergo radical bromination upon exposure to light, yielding a mixture of regioisomers. In stark contrast, the Lewis basic sulfide catalyst could promote the electrophilic bromolactonization and yield the Markovnikov product exclusively.