Copper-Catalyzed Selective Arylation of Oxadiazolones by Diaryliodonium Salts

The direct N-arylation of cyclic amides can be considered a pivotal issue for modern organic chemistry. Here, we report the method for copper-catalyzed N-arylation of diverse oxadiazolones by diaryliodonium salts in mild conditions in high yields (up to 92%) using available CuI as a catalyst. The developed method allows to efficiently utilize both symmetric and unsymmetric diaryliodonium salts bearing auxiliary groups such as 2,4,6-trimethoxyphenyl (TMP). The evaluation of steric effects in aryl moieties to the chemoselectivity of N- and O-arylation of the 1,2,4-oxadiazol-5(4H)-ones exhibited the high potential of mesityl-substituted diaryliodonium salts as a selective arylation reagent. The structural study suggests that steric accessibility of N-atom in 1,2,4-oxadiazol-5(4H)-ones impact to arylation with sterically hindered diaryliodonium salts. The synthetic application of proposed method was also demonstrated on selective arylation of 1,3,4-oxadiazol-2(3H)-ones and 1,2,4-oxadiazole-5-thiol.