Allylation of Aldehydes with Allyl Bromides and Zinc Induced by Pyridinium Perchlorates.

Abstract

The effects of inorganic and organic salts on the allylation of benzaldehyde with unactivated zinc powder and allyl bromide in acetonitrile were examined at room temperature. Although Li+, Na+, Mg2+, and R4N+ perchlorates exerted negligible effects on the allylation, various pyridinium perchlorates except the 2, 6-lutidinium salt promoted the formation of the corresponding homoallylic alcohol from benzaldehyde. In the presence of pyridinium perchlorate, the allylation of aliphatic and aromatic aldehydes with allyl bromide and zinc smoothly proceeded to give the corresponding products in good yields. Hydroxy-, methoxy-, and halogen-substituted aromatic aldehydes were tolerated under the reaction conditions emplyed. In the case of cinnamyl aldehyde, only 1, 2-addition was observed.