Cross-Coupling Reactions of DiazineN-Oxides with Aryl Halides

Significance

A reasonably efficient Pd-catalyzed cross-coupling of diazine N-oxides with aryl­halides to afford aryl diazines is reported. In view of the absence of metalated (B, Zn, Mg, Sn) partners, the process may be formally categorized in the C-H-activation group of reactions. The reaction proceeds with pyrazines, pyrimidines, and pyridazine N-oxides to introduce aryl substituents ortho to the N-oxide function. The scope of hetero­cycle substitutent R¹ received inadequate attention whereas that of R², the aryl halides (bromides, iodides, and even chlorides), has been thoroughly investigated in terms of electron-donating and -withdrawing groups. An interesting catalyst inhibitory effect in the coupling reactions of pyrimidine N-oxides was noted but not elucidated.