Emmert Reaction

Abstract

Abstract The formation of pyridylalkyl or pyridyldialkyl carbinols by condensation of pyridine (or its analogues) with aldehydes or ketones in the presence of aluminum or magnesium amalgam is generally known as the Emmert reaction. It is found that other metals with low reduction potentials do not work in this reaction and the metals of high reduction potentials and poor coordinating power do not offer the alkylation product but the pinacols of ketones. The study finds that pyridine might react with dialkyl, diaryl, alkyl aryl, and cyclic ketones, while steric effects from ortho substituent on pyridine might inhibit the reaction between such pyridine and aryl ketones. Although both magnesium and aluminum work for this reaction, there exist some subtle differences between magnesium and aluminum. Other acid derivatives (e.g., N,N dialkylamides and nitriles) are also reported to react with pyridines in lower yields. In general, aromatic esters afford higher yields than aliphatic esters, because the carbanion intermediates can be stabilized via resonance.