The condensation of N1-benzimidazolyl amidines 1 with tris(dimethy- lamino)phosphine leads to the corresponding [1,2a]Benzimidazolo-1,3,5,2-triazaphosphorines 3 . The N2-phosphoroamidine intermediates 2′ are isolated and yielded the corresponding cyclic compounds 4 upon heating. The oxidation by sulfur of the compounds 3 gives the thiooxide derivatives 4 . The structure of these compounds is unambiguously
The reaction of hexamethylphosphotriamide or methylphosphonic bis(dimethylamide) compounds with amidines derived from N-Benzimidazoyl imidates 1 leads to (1,2a)benzimidazolo-1,3,5,2-tiazaphosphorine-2-oxides (4) over bar in good yields. If the condensation is realized at room temperature, N-phosphonic amidines (3) over bar can be isolated as intermediates. The isolated compounds (2) over bar, (3) over bar, and (4) over bar are identified by spectroscopic methods: IR, H-1, C-13, (31)p, NMR, and M.S.