Simultaneous Formation and Functionalization of Aryliminophosphoranes Using 1,3-Dihydro-1H-benzimidazol-2-ones as Precursors

An atom- and step-economic synthesis of aryliminophosphoranes bearing orthourea was achieved via unprecedented Ph3P-I2mediated ring-opening of 1,3-dihydro-1H-benzimidazol-2-ones with secondary amines. Tandem aza-Wittig/heterocyclization of the functionalized aryliminophosphoranes upon treatment with isothiocyanates enables a facile access to a single regioisomer of N1-substituted 2-aminobenzimidazoles as well as fused tetracyclic quinazolinone derivatives in one-pot. 31P{1H} NMR studies suggested that the urea C–N bond of benzimidazolone is weakened by N-phosphorylation, leading to aminolysis rather than the expected deoxygenative amination.