One-pot anodic lactonization of Fenchone and Menthone and electrosynthesis of a new magnolione analogue

Abstract

The terpenoid cycloalkanones Fenchone and Menthone have been oxidized at a platinumanode under neutral and alkaline electrolyte conditions. When NaClO4 was used as electrolyte, Fenchone (1a) afforded 1-isopropyl-4- methyl-2-oxa-bicyclo[2.2.1]heptan-3-one, and Menthone (1b) provided the stable lactone 6-isobutyl-4- methyl-tetrahydropyran-2-one, both in good yield.When using Na2CO3 as electrolyte, the oxidation of 1a gave the fragrance-analogue 2,2-dimethyl-3-(2-oxopropyl) cyclopentanone in only one-pot. Mechanism proposals are presented.