Monosubstituted Oxazoles. 1. Synthesis of 5-Substituted Oxazoles by Directed Alkylation

A general method is presented for synthesis of 2-(methylthio)-5-substituted oxazoles 2. Deprotonation of the readily available 2-(methylthio)oxazole (1) with n-BuLi occurs smoothly in the presence of TMEDA and regiospecifically at C5. The organometallic 1a added rapidly to aldehydes and other electrophiles to provide 5-substituted-2-(methylthio)oxazoles in very good to excellent yields. Reductive removal of the MeS group gave the desired 5-monosubstituted oxazoles 3 in good yield.