Heteropoly acid catalysts in the valorization of the essential oils : acetoxylation of b-caryophyllene.

Abstract

H3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an active and environmentally friendly catalyst for the liquid-phase conversion of b-caryophyllene (1) to b-caryolanyl acetate (2) in homogeneous and heterogeneous systems. An efficient and clean method for the synthesis of 2, providing amixture containing two stereoisomeric b-caryolanyl acetates 2a and 2b, 2a/2b = 80/20 mol/ mol, with 100% GC yield, has been developed using PW as a homogeneous catalyst under mild reaction conditions. The reaction occurs at 25 8C with a catalyst turnover number of 2000. The catalyst can be recovered without neutralization and reused without loss of activity and selectivity.