Friedel- Crafts beta-Silylvinylations

摘要

The Friedel-Crafts reaction is a fundamental method for converting aromatic C-H bonds to C-C bonds. Although Friedel-Crafts alkylatious and acylations are often used in organic synthesis, the corresponding vinylations have not been successful. Attempts at vinylation using either ethyne or vinyl halides have given polymeric substances and 1,1-diarylethanes, even when the arches are present in large excess. This is due to the instability of the vinylated products under the reaction conditions. Even 2-propenylations gave very low yields, and formed various by-products. Low efficiency in generating the elec-trophilrc species may be another reason why the electrophilic vinylations failed. We report here the Friedel-Crafts (E)-beta-silylvinyiation of aromatic hydrocarbons promoted by GaCl_3 This reaction is a direct C_2-olefrnation of arenes that proceeds via novel organogallium interrnediates.