Scope and Mechanism of Allylic C−H Amination of Terminal Alkenes by the Palladium/PhI(OPiv)2 Catalyst System: Insights into the Effect of Naphthoquinone
journal contributionposted on 01.09.2010, 00:00 by Guoyin Yin, Yichen Wu, Guosheng Liu
Palladium-catalyzed oxidative amination of unactivated alkyl olefins has been developed to produce linear (E)-allylimides with high regioselectivity. This highly efficient transformation of alkenes has been achieved by enhancing the reoxidation of palladium with the strong oxidant PhI(OPiv)2. The present work also provides the first systematic analysis of the mechanism of the allylic C−H oxidative amination. It has been found that naphthoquinone (NQ) plays a vital role in promoting olefin coordination to the palladium catalyst: in the absence of NQ, the turnover-limiting step is olefin coordination to palladium catalyst; in the presence of NQ, the reaction involves a rapid equilibration to give a nitrogen-coordinated olefin-Pd(NQ) complex that undergoes turnover-limiting allylic C−H bond activation to generate a π-allyl-Pd intermediate. This work provides valuable insights for further studies on the functionalization of unactivated olefins.