Microwave-Assisted Mild Conversion of Natural Dihydrotagetone into 5-Isobutyl-3-methyl-4,5-dihydro-2(3H)-furanone, an Analogue of Whisky Lactone

Abstract

A microwave-assisted mild protocol is developed for the synthesis of 5-isobutyl-3-methyl-4,5-dihydro-2(3H)-furanone, an analogue of whisky lactone, from dihydrotagetone, an acyclic monoterpenoid obtained from Tagetes minuta. The methodology involved oxidation of dihydrotagetone in the presence of sodium metaperiodate/potassium permanganate/alumina to give 2,6-dimethyl-4-oxo-heptanoic acid, which upon reduction and subsequent lactonization provided 5-isobutyl-3-methyl-4,5-dihydro-2(3H)-furanone. The reaction is also conducted under conventional conditions and is compared with the microwave method.