Cyclization of some terpenic alcohols by phenylselenoetherification reaction

Abstract

Highly substituted tetrahydrofuran (THF)- and tetrahydropyran (THP)-type rings are formed through an acid- or base-catalyzed 5-exo and/or 6-endo cyclization of some natural terpenic alcohols (e.g., linalool, nerolidol, and α-terpineol) by an electrophile-mediated cyclization with PhSeCl and PhSeBr. The side chains of these cyclic ether products can be further transformed easily into a wide range of substrates owing to the versatile functionality of the double bond. Certain regioselectivity was noticed in these reactions. Nerolidol behaves like linalool in the reaction with PhSeX and affords predominantly THF derivatives, whereas α-terpineol affords THPs. Some Lewis bases (triethylamine, pyridine, 2,2′-bipyridine, and quinoline) and Lewis acids (SnCl2 and CoCl2) were used as additives, the presence of which increases the yields from 5-40 % to almost quantitative. © 2013 Springer-Verlag Wien.