Allylic lithiation of methylenecyclobutanes

Methylenecyclobutanes undergo a lithiation reaction in the presence of n-BuLi or n-BuLi/KOtBu from −78 °C to room temperature or to 40 °C in THF within 3 h and then quenching with a variety of electrophiles to give the corresponding addition products (alcohols) in moderate to good yields within 2 h. The alcohols can be easily oxidized to the ketones, which can be transformed to the substituted cyclopentenes in the presence of AlCl3 within short reaction time.