| Abstract: | Synthesis of 3-substituted 2-pyridinethiols was achieved by thiation of pyridine N-oxides with 4-methoxytoluene-α-thiol in the presence of diethylcarbamoyl chloride followed by cleavage of the resulting sulfides. The ease of substitution was shown to be affected by nucleophilicity of the N-oxide oxygen. Addition of zinc bromide to the reaction, a need for triethylamine, decreased most of the yield for thiation products but the formation of 3-methoxy-2-methoxybenzylthiopyridine was only improved. A plausible mechanism of the substitution, particularly β-thiation to the N-oxide function, is discussed compared with the regiochemistry observed in the reaction with diethoxyphosphoryl chloride instead of diethylcarbamoyl chloride. The debenzylation to pyridinethiol was also found to be dependent on the electron-density in the pyridine ring. |
