Synthesis and herbicidal activities of 4H-pyrazolo3,4-d1,2,3triazine-4-one with bulky substituents

Through different synthetic routes, 22 novel 4H-pyrazolo3,4-d1,2,3 triazine-4-ones with bulky substituents were synthesized using 1-(substituted) phenyl-5-amino-1H-pyrazole-4-formate or 1-tert-butyl-5-amino-1H-pyrazole-4-carbonyl chloride and 2-methyl-4-propargyl-6-amino-7-fluoro-2H-benzob1,4-oxazine-3(4H)-one as starting materials. Their structures were confirmed by ¹H NMR and HRMS. Preliminary results showed that most of the target compounds displayed herbicidal activities at the dosage of 375 g/hm². The inhibition rates of 4h , 4i and 4j against Amaranthus retroflexus were nearly 100%.