New pyrazolothienopyrimidines were synthesized. The key intermediate 4-aminothieno[2,3-c]pyrazole5-carbonitrile 1 was converted to the chloroacetyl amino derivative 2 followed by nucleophilic substitution and
Dimorth rearrangement upon treatment with nitrogen nucleophiles to give the pyrimidinones 3a-c. Treatment
of 3a with formaldehyde and with triethyl orthoformate afforded the respective tetracyclic derivatives 4 and 5. Condensation of the amino group in the o-aminocarbonitrile 1 with triethyl orthoformate followed by cycloaddition reaction with hydrazine led to the formation of pyrazolothienopyrimidine 8. Compound 8 was used as a synthetic precursor to heterocyclic compounds comprised of pyrazole, triazole, triazine, and triazepine derivatives.