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.

The reaction of phosphorus(III) halides with imidazo [l,2-a]pyridines i n the presence of bases leads to the formation of 3-phosphorylated imidazo[l,2alpyridines. The reaction proceeds i n high yield and requires no catalysts. In the compounds obtained, in contrast to phosphorylated indolizines, the phosphorus-heterocycle bond is stable and not cleaved by dry hydrogen c h bride, alcohols, or water, Imidazo[l,2-a]pyridines with the phosphinic and phosphinous groups can be alkylated both at the phosphorus and at the nitrogen atom of the heterocycle, the alkylation direction being dependent on the strength of the alkylation reagent used. 0 1995 John Wiley & Sons, Inc. 1042-7 163/95/0504 19-14 Phosphorylated Irnidazo[l,2-a]pyridines 423 M e M e 29c, 33c M e 1 * Q J $ PCNEt5,>3 , Q f J M e Ie PRh II PRk 44, 45 se 46, 47 M e M e PCNEt5,>3 , 29c, 33c M e 1 * Q J $ M e PRh II PR; -44, 45 se

The first representatives of hydrazones laaving trivalent phosphorus at the azomethine carbon atom or the carbon atom vinylogous to it were synthesized by reactions of formaldehyde and crotonaldehyde N,N-dimethylhydrazones with PBr 3 and diphenylchlorophosphine in the presence of organic bases. Some properties of the compounds synthesized were studied.

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