Two Approaches to the Transformation of (Benzimidazol-2-ylmethyl)triphenylphosphonium Chloride into the Derivatives of Pyrimido[1,6-a]benzimidazole

摘要

The reaction of readily accessible (benzimidazol-2-ylmethyl)triphenylphosphonium chloride with acyl isothiocyanates in the presence of triethylamine, as well as consecutive treatment of the above phosphonium salt first with N,N-dimethylformamide dimethyl acetal and then with phenyl or alkyl isothiocyanate gives two types of phosphorus-containing derivatives of pyrimido[1,6-a]benzimidazole with the thione group in position 3 or 1 of the condensed system. The structure of one of compounds of the first type, 3-thioxo-1-p-tolyl-3,4-dihydropyrimido[1,6-a]benizmidazol-4-ylidenetriphenylphosphorane, was determined by single crystal X-ray diffraction.