Action des métaux sur les esters carboxyliques en présence d'hexaméthylphosphortriamide: une méthode simple et efficace de réduction des alcools en alcanes

Abstract

Carboxylic acids, alcohols (R′OH), and alkanes (R′H) are the main products of the reduction of carboxylic esters (RCO2R′) by sodium in hexamethylphosphoric triamide (HMPA). Alkanes are preferentially formed from the carboxylic esters of hindered alcohols. The alkane content, however, is lowered when there is less steric hindrance on the carboxylic group, and increased when tert-butanol is introduced into the reaction mixture. The reduction of esters in HMPA has been compared to the reduction in alkylamines. The alkane is produced mainly by the decomposition of a radical anion intermediate which can be solvated by HMPA. The alcohol is the result of several possible bimolecular nucleophilic reactions; however, unimolecular and bimolecular processes are involved in the production of the carboxylic acid.