Copper-catalyzed <i>N</i>-arylation of 1,2,4-oxadiazin-5(6<i>H</i>)-ones by diaryliodonium salts

Herein, we developed a new synthetic approach for the preparation of <i>N</i>-arylated 1,2,4-oxadiazin-5(6<i>H</i>)-ones by direct arylation with diaryliodonium salts. The reaction with symmetrical diaryliodonium salts using CuI as a catalyst proceeded in toluene in the presence of DIPEA at 60 °C with the formation of the desired products in isolated yields of 46 to 97% (20 examples). The use of more readily available unsymmetrical diaryliodonium salts required higher reaction temperatures (up to 100 °C) to achieve similar yields. The only limitation observed in reaction was with an <i>ortho</i>-substituted iodonium salt. In all other cases, the developed approach allowed the preparation of a broad range of <i>N</i>-arylated 1,2,4-oxadiazin-5(6<i>H</i>)-ones under mild conditions utilizing a cheap and readily available catalyst.