Crown ether catalysis of decarboxylation and decarbalkoxylation of β-keto acids and malonates: a synthetic application

Abstract

The effect of 18-crown-6 ether on the decarboxylation rates of the sodium and potassium salts of 3-camphorcarboxylic acid 1 and of 1-carbomethoxy-1-carboxycyclohexane 2 was studied. For 2 the K-18C6 salt reacted ca. 104 times faster than the parent acid. This remarkable difference in reactivity was used in developing a one-pot, two-step procedure for decarbalkoxylation of malonic esters. This procedure was then applied to a range of malonates, β-keto esters, and an α-cyano ester. The effect of 15C5, other cations, and good nucleophiles was also studied.