Characterization and biological evaluation of some novel pyrazolo[3',4':4,5]thieno[2,3-d]pyrimidin-8-ones synthesized via the Gewald reaction

The synthesis of substituted pyrazolo(3',4':4,5)thieno(2,3-d)pyrimi- din-8-ones (IIIa-j) from 5-amino-3-methyl-1H-thieno(3,2-c)pyrazole-6-carbo- nitrile (II) is described. The key compound II was synthesized from (5-methyl- -2,4-dihydro-3H-pyrazol-3-ylidene)malononitrile I via the Gewald reaction. The synthesis of the title compounds IIIa-j was accomplished by condensation of II with different aromatic aldehydes. The newly synthesized heterocyles were characterized by elemental analysis, IR, 1 H-NMR, 13 C-NMR and mass spectro- scopic investigation. All the newly synthesized compounds were evaluated for antimicrobial activity against a variety of bacterial strains.