Synthesis of novel 6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridazin-3(2H)-one derivatives and their preliminary biological evaluation

Simple and accessible pathways for the synthesis of a series of novel 6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridazin-3(2H)-one derivatives including compounds with a combination of a pyrazolyl-pyridazine moiety with pyrimidine, 1,3,5-triazine and 1,3,4-oxadiazole rings in the same molecules were established. The tautomeric structures of 3-oxopyridazine and 5-thioxo-1,3,4-oxadiazole rings and also the position of their alkylation were shown. At preliminary screening the synthesised compounds showed pronounced plant growth stimulant activity. The most active compounds were selected for deeper studies and further field trials.