MgLa mixed oxides as highly active and selective heterogeneous catalysts for Wadsworth-Emmons reactions

摘要

The Wadsworth-Emmons reaction usually run in a stoichiometric mode with a high ratio base/substrate can be achieved catalytically, minimizing the by-products. Diethyl(cyanomethyl)-phosphonate and triethylphosphonoacetate were reacted with different aldehydes on solid bases in batch conditions at 383 K. MgLa mixed oxide was found to be an efficient solid base for the selective synthesis of alpha-, beta-unsaturated esters and nitriles with greater than 80% yields, and avoiding Knoevenagel condensation and aldolisation even with aliphatic aldehydes. The catalyst could be recycled once with high activity. The effect of substituents on phenyl ring proves that the reaction proceeds via a base catalysed mechanism with a low charge on intermediate species. (C) 2004 Elsevier B.V. All rights reserved.