Transition-metal catalyzed synthesis of #delta#-hydroxy-#gamma#-lactones from bis(trimthylsilyl) ketene acetals and allylic acetates via #gamma#-unsaturated carboxylic acids. Comments on the formation of #alpha#-cyclopropyl carboxylic acids

摘要

Bis(trimethylsilyl)ketene acetals react with allylic acetates in the presence of Pd(0) complexes to give #gamma#-unsaturated carboxylic acids together with #alpha#-cyclopropyl carboxylic acids. The unsaturated acids can be converted catalytically to #delta#-hydroxy-#gamma#-lactones by the H_2O_2/MTO system (methyltrioxorhenium) and to butenolides by Pd(II) catalyzed intramolecular cyclization reactions. The structure of two of these lactones has been established by X-ray analysis. The mechanism of the formation of the cyclopropanic acids will be discussed.