The development of efficient methods for the synthesis of nitrogen-containing compounds remains an important goal in contemporary catalysis research because of the central role of this class of compounds in biological systems and pharmaceutical applications.[1] The addition of an amine N À H bond to a carbon-carbon multiple bond, so-called hydroamination, [2] is a reaction with great synthetic potential, as it not only reduces the formation of waste owing to its atom economy, but it utilizes also very simple starting materials. The development of novel catalyst systems for hydroamination has seen significant progress in the last two decades, [2,3] but the intermolecular hydroamination of unactivated alkenes with simple amines remains very challenging. [4] Therefore, it is not too surprising that asymmetric hydroamination reactions [5] have been studied predominantly in intramolecular reactions. [6, 7] Intermolecular reactions have been reported only sporadically and all of these studies were limited to the reaction between aniline derivatives and activated alkenes, such as vinyl arenes, [8] 1,3-dienes, [9] and strained bicyclic alkenes.[10] The first enantioselective goldcatalyzed addition of cyclic ureas to unactivated alkenes in up to 78 % ee was reported recently by Widenhoefer and coworkers.[11] Herein we report the stereoselective addition of simple amines to unactivated alkenes utilizing chiral rareearth-metal-based catalysts.Catalyst systems based on rare-earth-metal complexes exhibit high catalytic activity, in particular in intramolecular hydroaminations, [2, 3f] whereas intermolecular hydroaminations are significantly more difficult to achieve as a result of the unfavorable competition between weakly coordinating alkenes and strongly coordinating amines. [4a,b, 6b, 12] We have previously reported on efficient biphenolate and binaphtholate rare-earth-metal catalysts, [6b, 13] which can catalyze the intramolecular hydroamination of aminoalkenes with high activity and up to 95 % ee. Preliminary studies with a corresponding binaphtholate lanthanum complex for the reactions of styrene [6b] and 1,3-cyclohexadiene [14] indicated the potential applicability of these systems in asymmetric intermolecular hydroaminations. As the lanthanum catalyst showed rather low selectivity [14] we decided to utilize the generally more selective yttrium and lutetium catalysts in our study. For the initial catalyst screening we chose the reaction of 1-heptene with benzylamine.

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.

3,3′-Silylated binaphtholate tantalum and niobium complexes were shown to be efficient catalysts for the asymmetric hydroaminoalkylation of N-methylaniline derivatives and N-benzylmethylamine with simple alkenes in enantioselectivities of up to 80% ee. No hydroaminoalkylation was observed with aminoalkenes; rather, exclusive asymmetric hydroamination/cyclization took place in up to 81% ee.

A series of novel C 1 -symmetric aminodiolate rare-earth-metal complexes have been prepared via arene elimination from [Ln(o-C 6 H 4 CH 2 NMe 2 ) 3 ] (Ln = Y, Lu) and the corresponding aminodiol proligand. The NOBIN-derived aminodiolate ligands feature sterically demanding triphenylsilyl and methyldiphenylsilyl ortho substituents on the naphtholate moiety and substituents of varying steric demand ranging from tert-butyl to tris(3,5-xylyl)silyl on the phenolate moiety.Complexes with a triphenylsilyl substituent on the naphtholate moiety displayed good catalytic activity in the hydroamination/ cyclization of aminoalkenes, while complexes with a methyldiphenylsilyl substituent exhibited somewhat lower reactivity. The highest enantioselectivities for fiveand six-membered-ring formation were observed utilizing complex 9c-Lu (R 1 = Ph, R 2 = Me, R 3 = SiPh 3 ) in the cyclization of (2,2-diphenylpent-4-enyl)amine (92% ee, N t = 200 h −1 at 25 °C) and (2,2-diphenylhex-5enyl)amine (73% ee, N t = 20 h −1 at 25 °C). The complexes can be applied in asymmetric intermolecular hydroaminations of 1heptene and 4-phenyl-1-butene with benzylamine with enantioselectivities of up to 40% ee using complex 9b-Y (R 1 = Ph, R 2 = Me, R 3 = SiPh 2 Me). Here the higher catalytic activities are achieved with catalysts having a methyldiphenylsilyl substituent on the naphtholate moiety. Lanthanum aminodiolate catalysts generated in situ from [La{CH(C 6 H 5 )NMe 2 } 3 ] did not exhibit improved catalytic activity in the intermolecular hydroamination in comparison to the corresponding yttrium and lutetium catalysts. The overall catalytic activities of the aminodiolate complexes are somewhat diminished in comparison to previously studied binaphtholate complexes due to the presence of the additional amine donor site in the ligand framework.

Binaphthalenedicarboxamide zirconium complexes exhibit significantly enhanced catalytic activity in aminoalkene hydroamination reactions with respect to substrate scope (substrates without gem-dialkyl activation; cyclization of aminoheptenes), catalyst loading (as low as 0.5 mol %) and reaction temperatures (as low as 70 °C) compared to previous group 4 metal-based hydroamination catalyst systems.