Zeolite-Mediated Cyclization of an Epoxide-Containing Polyene

摘要

The utility of zeolites as promoters for the cyclization of an epoxide-containing polyene has been investigated. Reaction of polyene 1 with oven-dried 4 A molecular sieves (type A zeolite) proceeds efficiently to generate bicyclic alcohol 2 in a 90% isolated yield. The reaction is sensitive to a variety of factors, including solvent type, water content, and zeolite acidity. Reactivity is apparently due to the zeolite lattice, since alumina and silica either are unreactive or generate a complex mixture of epoxide ring-opened products. Compared to the aluminum-based Lewis acid Me_2AlCl, the zeolite-promoted cyclization of 1 was a more facile reaction, providing excellent product recovery after filtration. These results indicate that zeolites represent a new class of promoters in biomimetic polyene cyclizations.