Indirect electrochemical oxidation of piperidin-4-ones mediated by sodium halide-base system

Indirect electrochemical oxidation of 1-N-subsituted piperidin-4-ones in methanol in an undivided cell in the presence of sodium iodide/sodium methoxide system leads to the corresponding alpha-hydroxyketals in 50-80% substance yield (50-65% current yield). 2,2,6,6Tetramethylpiperidin-4-one under the same conditions forms a mixture of methyl 2,2,5,5-tetramethyl-3-pyrrolidinecarboxylate and methyl 2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylate in 70% substance yield (60-70% current yield) via electrochemically induced Favorskii rearrangement. (c) 2006 Elsevier Ltd. All rights reserved.