The Mannich reaction of various kinds of 3(2H)-pyridazinone derivatives with 2, 2'-dichlorodiethyl amine was examined, and the N-mustard derivatives were obtained only from maleic hydrazide and 4, 5-dichloro-3(2H)-pyridazinone. Other 3(2H)-pyridazinones gave corresponding N-hydroxymethyl compounds. However, the Mannich reaction with dimethylamine, piperidine, or morpholine yielded the corresponding N-Mannich bases in good yields. Similarly, 4(1H)-pyridazinone gave the N-Mannich base, 1-piperidinomethyl-4(1H)-pyridazinone in 66% yield. The N-Mannich bases derived from 4, 5-dichloro-3(2H)-pyridazinone showed bacteriostatic activities to S. aureus and E. coli.
