2,5-Disubstituted Pyrazolo[4,3-c]cinnolin-3-ones

Article abstract of DOI:10.1002/jhet.2744

Complementary strategies to 2,5-disubstituted pyrazolo[4,3-c]cinnolin-3-ones are reported herein, providing late stage substituent introduction at either the 2- or the 5-position. Treating a readily prepared 4-thiocinnoline ester with substituted hydrazines afforded late stage access to the 2-position, while late stage substituent introduction at the 5-position was achieved via two different strategies: alkylation of 4-hydrazonopyrazol-3-ones, followed by a ring-closing intramolecular S_NAr tactic and direct reaction of 5-(2-fluorophenyl)-2,4-dihydro-3H-pyrazol-3-ones with aryl diazonium salts, followed by cyclization. The strategies described herein provide practical and general methods to prepare 2,5-disubstituted pyrazolo[4,3-c]cinnolin-3-ones.