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 ortho urea was achieved via unprecedented Ph3P-I-2 mediated 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 N-1-substituted 2-aminobenzimidazoles as well as fused tetracyclic quinazolinone derivatives in one-pot. P-31{H-1} 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.