A convenient synthesis of (z)‐3‐(α‐alkoxycarbonyl‐α‐cyanomethylene)‐2‐oxo‐1,2,3,4‐tetrahydroquinoxalines and related compounds

(Z)‐3‐(α‐Alkoxycarbonyl‐α‐cyanomethylene)‐2‐oxo‐1,2,3,4‐tetrahydroquinoxalines 3 and (Z)‐3‐(α‐alkoxycarbonyl‐α‐cyanomethylene)‐3,4‐dihydrobenzo[ g ]quinoxalin‐2(1 H )‐ones 5 possessing various alkoxycarbonyl groups were prepared in good yields directly from the reaction of dialkyl ( E )‐2,3‐dicyanobutendioates 1 with o ‐phenylenediamine ( 2 ) or with 2,3‐diaminonaphthalene ( 4 ), respectively. Furthermore, 2,3‐diaminopyridine ( 6 ) and 3,4‐diaminopyridine ( 7 ) were reacted with the diethyl ester 1b to give (Z)‐2‐(α‐cyano‐α‐ethoxycarbonylmethylene)‐1,2‐dihydro‐4 H ‐pyrido[2,3‐ b ]pyrazin‐3‐one ( 8 ) and (Z)‐3‐(α‐cyano‐α‐ethoxycarbonylmethylene)‐3,4‐dihydro‐1 H ‐pyrido[3,4‐ b ]pyrazin‐2‐one ( 9 ), respectively. The structural studies of 3, 5, 8 , and 9 were carried out by nmr experiments in some details.