Iridium(III)-Catalyzed Intermolecular Allylic C-H Amidation of Internal Alkenes with Sulfonamides.

The Ir(III)-catalyzed direct allylic C-H amidation of substituted internal alkenes with substituted sulfonamides without having directing group is demonstrated. The present protocol provides substituted allylic amines in a highly atom- and step-economical manner. The reaction was compatible with symmetrical and unsymmetrical internal alkenes as well as substituted sulfonamides. It is interesting to note that, in the reaction of aryl-alkyl alkenes, the amidation selectively takes place at the alkyl-substituted allylic carbon. Meanwhile, the better selectivity was also observed in the unsymmetrical aryl-aryl alkenes having an electron-withdrawing substituent at one of the aryl groups. A possible reaction mechanism involving a π-allyl iridium intermediate was proposed and supported by the deuterium labeling studies. The deuterium labeling study clearly reveals that, in the reaction mechanism, the initial C-H activation step via the deprotonation pathway is reversible and the nucleophile prefers to attack at the more electrophilic carbon of the π-allyl iridium intermediate.