Applying an Aza-Wittig Reaction for the Synthesis of Novel Thieno[3',2':5,6] Pyrido[4,3-d]pyrimidinone Derivatives.

A series of new 2-substituted tetrahydrobenzo[4',5']thieno[3',2':5,6]pyrido[4,3-d] pyrimidin-4(3H)-ones 5 has been designed and synthesized via an aza-Wittig reaction. Iminophosphorane 3a or iminophosphorane 3b reacted with 4-Cl-phenyl(or 4-F-phenyl) isocyanate to give carbodiimide 4a or carbodiimide 4b, which were further treated with phenols to cyclize to give compounds 5 in presence of a catalytic amount of K2CO3. The structures of compound 5 have been confirmed by 1H NMR, EI-MS, IR spectroscopy, and elemental analyses. [ABSTRACT FROM AUTHOR]