title: The mechanism of hydroaminoalkylation catalyzed by group 5 metal binaphtholate complexes.
abstract: The intermolecular hydroaminoalkylation of unactivated alkenes and vinyl arenes with secondary amines occurs readily in the presence of tantalum and niobium binaphtholate catalysts with high regio- and enantioselectivity (up to 98% ee). Mechanistic studies have been conducted in order to determine the kinetic order of the reaction in all reagents and elucidate the rate- and stereodetermining steps. The effects of substrate steric and electronic properties on the overall reaction rate have been evaluated. The reaction is first order in amine and the catalyst, while exhibiting saturation in alkene at high alkene concentration. Unproductive reaction events including reversible amine binding and arene C-H activation have been observed. The formation of the metallaaziridine is a fast reversible nondissociative process and the overall reaction rate is limited either by amide exchange or alkene insertion, as supported by reaction kinetics, kinetic isotope effects, and isotopic labeling studies. These results suggest that the catalytic activity can be enhanced by employing a more electron-deficient ligand backbone.
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, New Jersey 08854-8087, USA.
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Reznichenko
authors.forename: Kai C
authors.initials: KC
authors.lastname: Hultzsch
mesh_terms: D000475:Alkenes / Q000737:chemistry; D000586:Amination; D000588:Amines / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D002384:Catalysis; D002621:Chemistry / Q000379:methods*; D056831:Coordination Complexes; D004583:Electrons; D006859:Hydrogen / Q000737:chemistry; D007554:Isotopes; D007700:Kinetics; D008670:Metals / Q000737:chemistry; D008956:Models, Chemical; D013379:Substrate Specificity
chemical_list: D000475:Alkenes; D000588:Amines; D056831:Coordination Complexes; D007554:Isotopes; D008670:Metals; D002244:Carbon; D006859:Hydrogen