An Efficient Synthesis of 3H‐Pyrrolo[3,2‐d]pyrimidin‐4(5H)‐one Derivatives via an Iminophosphorane

The iminophosphorane (3), obtained from reaction of ethyl 3-amino-4-cyano-1-phenyl-1H-pyrrole-2-carboxylate (2) with triphenylphosphine, hexachloroethane, and triethylamine, reacted with aromatic isocyanates to give carbodiimides (4). Further reaction of 4 with various amines, phenols, or ROH to give 2,3,5,7-tetrasubstituted 3H-pyrrolo[3,2-d]pyrimidine-4(5H)-ones (6) in satisfactory yields in the presence of catalytic amount of sodium alkoxide or solid potassium carbonate.