title: Control of the Chemoselectivity of Metal N-Aryl Nitrene Reactivity: C-H Bond Amination versus Electrocyclization.
abstract: A mechanism study to identify the elements that control the chemoselectivity of metal-catalyzed N-atom transfer reactions of styryl azides is presented. Our studies show that the proclivity of the metal N-aryl nitrene to participate in sp3-C-H bond amination or electrocyclization reactions can be controlled by either the substrate or the catalyst. Electrocyclization is favored for mono-β-substituted and sterically noncongested styryl azides, whereas sp3-C-H bond amination through an H-atom abstraction-radical recombination mechanism is preferred when a tertiary allylic reaction center is present. Even when a weakened allylic C-H bond is present, our data suggest that the indole is still formed through an electrocyclization instead of a common allyl radical intermediate. The site selectivity of metal N-aryl nitrenes was found to be controlled by the choice of catalyst: Ir(I)-alkene complexes trigger electrocyclization processes while Fe(III) porphyrin complexes catalyze sp3-C-H bond amination in substrates where Rh2(II) carboxylate catalysts provide both products.
authors.affiliation: Department of Chemistry, University of Illinois at Chicago , 845 West Taylor Street, Chicago, Illinois 60607-7061, United States.
authors.forename: Chen
authors.initials: C
authors.lastname: Kong
authors.affiliation: Department of Chemistry, University of Illinois at Chicago , 845 West Taylor Street, Chicago, Illinois 60607-7061, United States.
authors.forename: Navendu
authors.initials: N
authors.lastname: Jana
authors.affiliation: Department of Chemistry, University of Illinois at Chicago , 845 West Taylor Street, Chicago, Illinois 60607-7061, United States.
authors.forename: Crystalann
authors.initials: C
authors.lastname: Jones
authors.affiliation: Department of Chemistry, University of Illinois at Chicago , 845 West Taylor Street, Chicago, Illinois 60607-7061, United States.|Institute of Next Generation Matter Transformation, College of Chemical Engineering, Huaqiao University , 668 Jimei Boulevard, Xiamen, Fujian 361021, P. R. China.
authors.forename: Tom G
authors.initials: TG
authors.lastname: Driver