An important intermidiate 2-butyl-4-chloro-5-(4-bromomethyl phenoxy) pyridazinone 3 was first obtained from 4,5-dichloropyridazinone using two different methods. Compounds 4a～4l were synthesized by the reaction of 3 with different oximes. The reaction of 3 with aryl aldehyde oximes afforded exclusively the product 4 under the PTC conditions. However, led to a mixture of 4 and 5 the reaction with aryl ketone oximes. Regioselectivity of the reaction and configuration of the products are discussed.

Key words: PYRIDAZINONE P, BIOACTIVE SUBSTANCE, DOMAIN STRUCTURE, SELECTIVITY, OXIME, PESTICIDES, CONFIGURATION