CsF-PROMOTED DESILYLATION AND RING-CONTRACTION REACTION OF ELECTRON-DEFICIENT 3-SILYL-2H-CHROMENES TO 2-BENZYLBENZOFURANS

The ring-contraction reaction of electron-deficient 3-silyl-2H-chromenes to 2-benzylbenzofurans under mild conditions was developed. CsF efficiently promoted the reaction at room temperature or 80 degrees C to afford a variety of 2-benzylbenzofurans in good yields. 3-Silyl-2H-chromenes having strong electron-withdrawing groups smoothly afforded the desired products. The reaction is proposed to proceed through an allenyl intermediate or dyotropic rearrangement.