Wadsworth-Emmons reaction: the unique catalytic reaction by a solid base

Abstract

The near-stoichiometric amount of bases is used both in laboratory and industry in Wadsworth-Emmons (WE) reactions, since the by-product, (EtO)₂P(O)OH, formed in the reaction neutralizes the base into an inert salt. A strategy to design, develop, and evolve the recyclable Mg-Al-hydrotalcite-O ^tBu (HT-O ^tBu) by the interaction of KO tBu with the calcined hydrotalcite that transforms a well-defined stoichiometric WE reaction into a catalytic one in an effort to minimize the quantum of effluents released and reduce the cost of the process is described here. HT-O tBu is found to be an efficient solid base for WE reactions for the simple synthesis of α,β-unsaturated esters and nitriles for the first time. The HT-O ^tBu, composed of various ratios of Mg/Al (i.e., 2, 2.5, and 3) and different contents of ^tBuO- (Mg/Al:3), and their precursors were prepared and well characterized to draw a correlation between structure and reactivity of the hydrotalcites in WE reactions.