Conjugate Addition of Grignard Reagents to Substituted Isopropylidene Methylenemalonates

Abstract

The conjugate addition of various nucleophilic reagents to unsaturated Knoevenagel-type products derived from Meldrum's acid (the cyclic isopropylidene ester of malonic acid) has been the subject of several investigations¹. In most cases the addition occurs rapidly and the adducts are obtained in high yield. The ease with which these conjugate additions take place can be attributed to the special stability of the carbanionic intermediates. The intermediates formed in these reactions are formally anions of monosubstituted isopropylidene malonates and their low basicity can be attributed to the six-membered ring which holds the two carbonyl groups co-planar causing a high degree of conjugative stabilization¹.