A Novel Synthesis of Some 1,4-Phenylene-bis-heterocyclic Carboxamide Derivatives

N,N'-(1,4-phenylene)bis(3-oxo-3-phenylpropanamide) I reacts with DMFDMA in refluxing toluene to afford N,N'-(1,4-phenylene)bis(2-benzoyl-3-(dimethylamino)acrylamide) 2. Compound 2 reacts with a twofold excess of the active methylene reagents 3a-c to afford the pent-2-enediamide derivatives 7 and 8a,b, respectively. Compounds 7 and 8a could be cyclized to afford the same compound N,N'-(1,4-phenylene)bis(5-cyano-6-oxo-2-phenyl-1,6-dihydropyridine-3-carboxamide) 9a while 8b was cyclized to afford the 6-thioxo analogue 9b. Compound 2 reacts with hydrazine derivatives 10a,b in refluxing ethanol/piperidine to afford the hydrazinylacrylamide derivatives 11a,b, which have been cyclized to the corresponding N,N'-(1,4-phenylene)bis(1H-pyrazole-4-carboxamide) derivatives 12a,b, respectively. Compound 2 reacts also with urea derivatives 13a-c in refluxing ethanol/piperidine to afford the N,N( 1,4-phenylene)bis(2 -benzoyl-3-substituted-acrylamide) derivatives 14a-c, which could be cyclized into N,N'-(1,4-phenylene)bis(6-phenyl-1,2-dihydropyrimidine-5-carboxamide)-2-oxo; 2-thioxo or 2-imino derivatives 15a-c, respectively.