Synthesis of some new azo pyrazolo[1,5-a]pyrimidine-thieno[2,3-b]pyridine derivatives and their application as disperse dyes

The 3-amino-4,6-disubstituted-thieno[2,3-b]pyridines were diazotized and coupled with 3-aminocrotononitrile to give the 3-(2-hydrozone-3-ketimino-butyronitrile)-4,6-disubstituted-thieno[2,3-b]pyridines which can react with 85% excess hydrazine hydrate to afford the corresponding 3-(5-amino-3-methyl-pyrazol-4-yl)-azo-4,6-disubstituted-thieno[2,3-b]pyridines. The 3-(2-methyl-5,7-disubstituted-pyrazolo[1,5-a]pyrimidine-3-yl)azo-4,6-disubstituted-thieno[2,3-b]pyridine dyes were obtained by the cyclocondensation reaction of 3-(5-amino-3-methyl-pyrazol-4-yl)-azo-4,6-disubstituted-thieno[2,3-b]pyridines with the appropriate 1,3-diketones under acidic condition. The dyes were applied to polyester fibers and their spectral characteristics and fastness properties measured.