Efficient Molar-Scale Synthesis of 1-Methyl-5-acylimidazole Triflic Acid Salts

A new process for the molar-scale preparation of 1-methyl-5-acylimidazole triflic acid salts was developed. The new process consists of:  (i) regioselective 3N-tritylation of 5-acylimidazole to give 3-trityl-5-acylimidazoles, (ii) 1N-methylation of 3-trityl-5-acylimidazoles, and (iii) hydrolysis of the resulting quaternary ammonium salts to afford 1-methyl-5-acylimidazole triflic acid salts. This process is highly efficient, affording 1-methyl-5-acylimidazole triflic acid salts in 86−88% overall yield in three steps without chromatographic separation of products.