N-(tert-Butyldimethylsilyl)imidazole and related heterocycles: 13C nuclear magnetic resonance study and reaction with dimethylsulfoxide

Abstract

N-tert-Butyldimethylsilyl derivatives of imidazole, 2-methylimidazole, 4-methylimidazole, benzimidazole, pyrazole, 1,2,4-triazole, and benzotriazole were prepared from tert-butyldimethylsilyl chloride and the corresponding heterocyclic compound. The products were identified by carbon and proton nmr, mass spectrometry, and elemental analysis. The carbon nmr spectra confirmed the absence of intermolecular silyl exchange at ambient temperature. Silyl exchange did occur at elevated temperatures, 130–160 °C.Reaction of N-tert-butyldimethylsilyl or N-trimethylsilyl heterocycles with dimethylsulfoxide gave N-(methylthio)methyl derivatives of imidazole, 2-methylimidazole, 4-methylimidazole, benzimidazole, pyrazole, and 1,2,4-triazole. The products were characterized by carbon and proton nmr, mass spectrometry, and elemental analysis. A mechanism involving a Pummerer rearrangement is proposed to account for the results.