An Improved and Convenient Procedure for the Synthesis of 1-Substituted Imidazoles

Abstract

1-Protected imidazoles, such as 1-acetyl- and 1-benzoylimidazoles, react with various halides, such as benzyl, allyl, a-keto, and alkyl halides, to give l-protected-3-substituted imidazolium salts in high yields. The resultant imidazolium salts are easily deprotected by treatment with water or alcohols to give the corresponding 1-substituted imidazoles in excellent yields. In this reaction the yields of 1-substituted imidazoles vary with the kinds of halides used and/or with the protecting groups, and the yields increase in the following order: benzyl halides≥allyl halides~α-keto halides>alkyl halides, and acetyl≥ benzoyl>ethoxycarbonyl>diethoxymethyl>>trimethylsilyl>tosyl. © 1983, The Pharmaceutical Society of Japan. All rights reserved.