Heteropoly acid catalyzed cyclization of nerolidol and farnesol : synthesis of bisabolol.

Abstract

Heteropoly acid H3PW12O40 is an active and environmentally friendly homogeneous catalyst for the synthesis of _-bisabolol, a high-priced and highly demanded ingredient for the fragrance, cosmetic and pharmaceutical industries, starting from more abundant biomass-based sesquiterpenic alcohols. The solvent nature remarkably affects the reaction pathways and product selectivity. In acetone solutions, _-bisabolol can be obtained in 55–60% GC yields from nerolidol and 60–70% GC yields from farnesol at complete substrate conversions, which are probably the best results ever reported for these reactions. _-Bisabolol synthesized by this method contains no farnesol, which is a potentially allergenic compound and should be avoided in the commercially used _-bisabolol. This advantage is especially important because the distillative separation of _-bisabolol and farnesol is a troublesome task. The catalyst shows high turnover numbers and operates under mild nearly ambient conditions.