Synthesis of N‑Aryl Oxindole Nitrones through a Metal-Free Selective N‑Arylation Process

An efficient selective N-arylation of 3-(hydroxy­imino)­indolin-2-ones with diaryl­iodonium salts to prepare (Z)-N-aryl oxindole nitrones has been achieved under simple base-mediated conditions. The reaction tolerated a variety of diaryliodonium salts with diverse and sensitive functional groups. Studies on the oxime structures revealed that the pyrroline ring and carbonyl group in 3-(hydroxy­imino)­indolin-2-ones played important roles in the selective N-arylation process. The N-aryl oxindole nitrones could be prepared rapidly and easily at the gram scale.