OLEFIN SYNTHESIS BY VANADIUM(V)-INDUCED OXIDATIVE DECARBOXYLATION DEOXYGENATION OF 3-HYDROXY CARBOXYLIC-ACIDS

Oxidative decarboxylation of 3-hydroxy carboxylic acids can be effected with various V(V) complexes. This process likely yields an intermediate 1,4-metalla diradical. β-Elimination from this intermediate gives olefin and regenerates V(V), likely as VO2C1. Thus, although the overall process involves no net change in oxidation state for vanadium, the decarboxylation process is oxidatively induced. Intramolecular trapping of the intermediate yields glycolate and then C-C cleavage products, and skeletal rearrangement gives ketonic products. Qualitatively, rates for oxidative decarboxylation of the acids and the stereospecificity of formation of olefinic products depend on the electron-withdrawing ability of groups attached to vanadium. Methodology is described for the preparation of tri- and tetrasubstituted olefins in high yield from appropriate 3-hydroxy carboxylic acid precursors. © 1990, American Chemical Society. All rights reserved.