A Direct Approach to the Synthesis of 5-Aryl-4-chloropyridazinone: From Microwave Assisted Catalyst Screen to Room Temperature Regio- and Chemoselective Suzuki Arylation

Suzuki coupling of 4,5-dichloropyridazinone with phenylboronic acid yielded the desired 4-chloro-5-phenylpyridazinone along with 4-aryl and 4,5-diaryl derivatives.An extensive microwave-assisted screen led to the identification of Pd(PEt 3 ) 2 Cl 2 as an ideal catalyst with superior rate and selectivity.Further optimizations provided an effective, regioselective and chemoselective arylation method at room temperature.3-(2H)-Pyridazinone is a versatile heterocyclic pharmacophore.Its early derivatives have been commercialized as herbicides and insecticides.Recently, the 3-(2H)-pyridazinone core has been utilized