Synthesis and Characterization of Newly Fused 1,2-Dihydropyrido[3,4-b], Bridged Oxadiazol-2-yl, 4-Substituted-benzylidene Hydrazide and Arylidene 6-Chloroquinoxaline 1,4-Dioxides

Some simple reactions using commercially available chemicals were used in the preparation of new biologically remarkable quinoxaline 1,4-dioxide derivatives. Several steps performed on 4-chloro-2-nitroaniline resulted in a quinoxaline 1,4-dioxide derivative, which reacted with dimethylformamide dimethylacetal (DMF-DMA) to produce an enamine. Transamination of this enamine with anilines gave the fused 1,2-dihydropyrido[3,4-b] quinoxaline 5,10-dioxide derivatives via an addition-elimination mechanism. Basic condensation reaction of quinoxaline active methyl afforded unexpected decarboxylated arylidene derivatives by using different aromatic aldehydes. Bridged oxadiazol-2-yl derivatives were obtained from the reaction of a hydrazide derivative with carbon disulfide and p-nitrobenzoic acid respectively. Whereas, acidic condensation of that hydrazide with aromatic aldehydes afforded the arylidene hydrazides.