Pyridazine N-oxide

Coupling partner in Pd-catalyzed direct arylation reactions.

Pyridazine N-oxide was prepared as follows: appropriate diazine (1 eq.) and mCPBA (1 eq.) were dissolved in DCM (0.2 M). The reaction was stirred for 16 hours. PPh3 (0.5 eq.) was then added to reduce any unreacted peracid and the mixture was stirred for a further 4 hours. The volatiles were evaporated under reduced pressure and the residue was purified by silica gel column chromatography to give pyridazine N-oxide.

Purify the oxide by distillation in a vacuum and by sublimation in vacuo. When a solution of the oxide in MeOH is treated with an aqueous solution of CuCl2, the [C4H4N2O]2—CuCl2-2H2O-complex (m 182-183o) is formed from which the oxide can be recovered . [Pollak et al. J Org Chem 35 2478 1970, Klinge et al. Recl Trav Chim, Pays Bas 95 21 1976, Ohsawa et al. Tetrahedron Lett 1979 1978, Koelsch & Gumprecht J Org Chem 23 1605 1958, Beilstein 23 III/IV 890.]