Synthesis and solution structure of 3,5-dioxopimelic acid diesters--stable 1,3,5,7-tetracarbonyl derivatives

A variety of 3,5-dioxopimelic acid diesters, stable 1,3,5,7-tetracarbonyl derivatives, were prepared by catalytic condensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with methyl malonyl chloride. The keto-enol tautomerization of these compounds has been investigated by NMR spectroscopy. One keto and up to four enolic tautomers could be detected in chloroform solution and the influence of the substituents on the tautomeric equilibria has been studied.