Mono(iminophosphorane) 4 was selectively prepared from the reaction of 3,4-diaminothieno[2,3-b]thiophene 3 with excess triphenylphosphine, C(2)Cl(6), and Et(3)N due to intramolecular double hydrogen bond formation. Mono(iminophosphorane) 4 reacted with aromatic isocyanates to give stable carbodiimides 8, which were further treated with aliphatic secondary or primary amines to give 2-amino substituted thieno[3',2':4,5]thieno[3,2-d]pyrimidin-4(3H)-ones 10 or 12 in the presence of a catalytic amounts of EtO(-)Na(+). However, in the presence of a catalytic amounts of potassium carbonate, the carbo...
