Chemoselective Additions of Chloromethyllithium Carbenoid to Cyclic Enones: A Direct Access to Chloromethyl Allylic Alcohols

Abstract

AbstractChloromethyllithium carbenoid has been chemoselectively added to cyclic enones (5‐, 6‐ and 7‐membered systems, including two natural products) to provide chloromethyl allylic alcohols. Under the optimized reaction conditions neither concomitant (n+1) homologation nor conjugate addition or Simmons–Smith‐like cyclopropanation takes place. The presence of LiBr is estimated to play a dual role, namely as a carbenoid stabilizer and mild Lewis acid activator of the CO group. Notably, the mesomeric effect caused by β‐heteroatom‐containing substituents promotes the attack of the reagent at the most activated position.magnified image