Selective cleavage of tetrahydropyranyl ethers and silyl ethers

Abstract

The tetrahydropyranyl (THP) ethers were cleanly and rapidly cleaved into the corresponding esters with various acid chlorides in the presence of a catalytic amount of zinc chloride in acetonitrile at room temperature. However, THP ethers of tertiary alcohols were converted into tertiary chlorides under the present conditions. Similarly, the t-butyldimethulsilyl ethers, trimethylsilyl ethers, and t-butyldiphenylsilyl ethers were cleanly converted into the corresponding esters under the same conditions. The THP ethers and the t-butyldimethylsilyl ethers, were selectively cleaved in the presence of benzyl ethers, though differentiation between the THP ethers and the t-butyldimethylsilyl ethers could not be accomplished under the present conditions. Furthermore, the reactions of acid chlorides with primary, secondary, and aryl alcohols in the presence of zinc chloride gave the corresponding esters, whereas the reaction with tertiary alcohols failed to give the esters due to the fast solvolytic reactions of alcohols with hydrogen chloride generated from the reaction. This procedure was successfully applied for the preparation of thiol esters.