Application of bis(iminophosphorane) in heterocyclic synthesis: New entries to symmetrically or unsymmetrically substituted thieno[2,3-d:5,4-d′] dipyrimidine-4,5(3H,6H)-diones

Abstract

The bis(carbodiimides) 4, obtained from bis-aza-Wittig reactions of bis(iminophosphorane) 3 with 2 equiv of aromatic isocyanates, were reacted with secondary amine to give symmetrically substituted 2,7-diaminothieno[2,3-d:5,4- d′]dipyrimidine-4,5(3H,6H)-dione 6 in the presence of a catalytic amount of EtO-Na+. Reactions of 4 with phenols or ROH in the presence of a catalytic amount of potassium carbonate or RO-Na + gave symmetrically substituted 2,7-diaryl(alkyl)-oxythieno[2,3-d:5, 4-d′]dipyrimidine-4,5(3H,6H)-diones 6 in satisfactory yields. However, iminophosphoranes 9 were obtained via reaction of bis(iminophosphorane) 3 with 1 equiv of aromatic isocyanate and subsequent reaction with an amine in the presence of a catalytic amount of EtO-Na+. Further reaction of iminophosphoranes 9 with aromatic isocyanates and various nucleophile generated unsymmetrically substituted thieno[2,3-d:5,4-d′] dipyrimidine-4,5(3H,6H)-diones 12 in good yields.