Iridium‐Catalyzed Regio‐ and Stereoselective C‐H Oxidative Reaction to (Z)‐3‐Arylidene‐2‐oxindole Imides under Neutral Conditions

Abstract

AbstractUnsymmetrical 3‐arylidene‐2‐oxindoles are useful pharmacophores for many clinical drugs or intermediates in alkaloids synthesis. An IridiumIII‐catalyzed sequential C−H oxidative reaction of 2‐indolyl enamides has been established. This protocol utilized α,α‐dimethyl benzylhydroperoxide as the oxidant and silver fluoride as a key promoter, to provide a wide range of (Z)‐3‐arylidene‐2‐oxindole imides in moderate to good yields, together with good regio‐ and stereoselectivity. The silver fluoride was found to function as a base to facilitate the generation of the active Iridium catalyst species. The resulting (Z)‐3‐arylidene‐2‐oxindole imides could be further transformed to various valuable derivatives. Mechanistically, radical‐process was excluded from this C−H oxidative transformation, and a 6‐membered cationic iridacycle intermediate was proposed to be involved in the catalytic cycle.magnified image