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

Abstract

Unsymmetrical 3-arylidene-2-oxindoles are useful pharmacophores for many clinical drugs or intermediates in alkaloids synthesis. An Iridium III -catalyzed sequential CÀH oxidative reaction of 2-indolyl enamides has been established. This protocol utilized a,a-dimethyl benzylhydroperoxide as the oxidant and silver fluoride as a key promoter, to provide a wide range of (Z)-3-arylidene-2oxindole 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 CÀH oxidative transformation, and a 6-membered cationic iridacycle intermediate was proposed to be involved in the catalytic cycle.