PYRIDAZINE DERIVATIVES AND RELATED-COMPOUNDS .1. SOME REACTIONS WITH 4-CYANO-5,6-DIPHENYL-2,3-DIHYDROPYRIDAZINE-3-ONE

4‐Cyano‐5,6‐diphenyl‐2,3‐dihydropyridazine‐3‐onc 1 reacts with phosphorous oxychloride to give 70% of the corresponding 3‐chloro derivative 2. Treating 2 with anthranilic acid in butanol, 4‐cyano‐2,3‐diphenyl‐10H‐pyridazino[6,1‐b]quinoxaline‐10‐one, 3 was obtained. Compound 1 reacts with phosphorous pentasulphide to give 3‐mercapto derivative 4, which was converted by acrylonitrile to S‐(2‐cyanoethyl)pyridazine derivative 5. Compound 4 reacts with ethyl bromoacetate and with phenacyl bromide gave the corresponding thieno[2,3‐c] pyridazine derivatives 8, 9, Alkylation of 1 with ethyl chloroacetate afforded 3‐0‐carbethoxymethyl derivative 10. Compound 10 reacts with amines (aniline, hydrazine) to give the corresponding amide and acid hydrazide 13, 12 respectively. Hydrolysis of 10 with sodium hydroxide gave the corresponding acid derivative 11. Treating 1 with methyl iodide, 3‐0‐methyl derivative 14 was obtained, which was converted by ammonium acetate/acetic acid to 3‐amino‐4‐cyano‐5,6‐diphenyl pyridazine 15. Compound 1 reacts with methyl magnesium iodide gave 4‐acetyl derivative 16, which was reacted with hydrazine, phenyl hydrazine and with hydroxylamine to give the substituted I H pyrazolo [3,4‐c] pyridazine 17 a,b and isoxazolo [5,4‐c] pyridazine 18 derivatives respectively. Copyright © 1990 The Chemical Society Located in Taipei & Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim, Germany