Phosphorylation of 1-alkylmidazoles and 1-alkylbenzimidazoles with phosphorus(III) halides in the presence of bases

Phosphorylation of 1-alkyl substituted imidazoles and benzimidazoles with P(III) halides in pyridine was shown to proceed at the 3-N atom of the heteroaryl ring and was followed by triethylamine-induced migration of the phosphorus group to the 2-C atom. Preparative methods were developed for the synthesis of a range of 2-phosphorylated derivatives of the indicated imidazoles. The latter were found to undergo alkylation either at P(III) or 3-N centers, depending on the alkylating agent.