Mono- and Difluoromethylation of 3(2 H )-Pyridazinones.

A method for direct N -monofluoromethylation of pyridazinones with S -monofluoromethyl- S -phenyl-2,3,4,5-tetramethylphenylsulfonium triflate is disclosed. A method for the N - and O -difluoromethylated pyridazinones with TMSCF 2 Br as the only promising difluorocarbene precursor is also reported. Substrates with various relevant functional groups, including analogues of Lynparza, are tolerated under both methods.