Catalysis hydroamination

The first example of acid catalysis appeared in a 1934 patent in which it is claimed that surface catalysts, particularly hydrosilicates of large surface area , known at that time under the trade name Tonsil, Franconit, Granisol, etc. lead to a smooth addition of the olefine to the molecule of the primary aromatic amine . Aniline and cyclohexene were reacted over Tonsil at 230-240°C to give, inter alia, the hydroamination product, N-cyclohexylaniline [47]. 

Taube, R. Reaction with Nitrogen Compounds Hydroamination. In Applied Homogeneous Catalysis with Organo-metallic Compounds Comils, B. Herrmann, W. A., Eds. VCH Weinheim, Germany, 1996 pp 507-520. 

The intramolecular hydroamination of substrates 170 is catalyzed by a Pd(0) catalyst which is generated in situ from a Pd(II) precursor and a phosphane. One equivalent of acetic acid has to be added for efficient catalysis this is a hint of a hydropallada-tion mechanism. Meguro and Yamamoto obtained good yields of the vinyltetrahy-dropyrroles or the vinylhexahydropyridines 171 in that way (Scheme 15.53) [109]. 

Laurel Schafer of the University of British Columbia reports (Organic Lett. 2003,5,4733-4736) that terminal alkynes undergo smooth hydroamination with a Ti catalyst. The intermediate imine 4 can be hydrolyzed to the aldehyde 5 or reduced directly to the amine 6. The alkyne to aldehyde conversion has previously been carried out by hydroboration/oxidation (J. Org. Chem. 1996, 61, 3224), hydrosilylation/oxidation (Tetrahedron Lett. 1984,25, 321), or Ru catalysis (J. Am. Chem. Soc. 2001, 123, 11917). There was no previous general procedure for the anti-Markownikov conversion of a terminal alkyne to the amine. 

A high-throughput colorimetric assay was applied to identify catalysts by combining metals (Pd, Rh, Ru, Ir) and various phosphines for the hydroamination of dienes.217 Combinatorial catalysis was successfully used to find active catalysts in the Ru-catalyzed ring-closing metathesis reaction218 and the olefin polymerization by Ni and Pd.219... 

The chiral organolanthanides have been especially designed for asymmetric catalysis. Thus far several enantioselective olefin transformations (hydrogenation, hydroamination/cyclization, hydrosilylation) as well as the polymerization of methyl methacrylate mediated by these chiral organolanthanide metallocenes have been investigated. 

The third part of this chapter reviews previously described catalytic asymmetric reactions that can be promoted by chiral lanthanoid complexes. Transformations such as Diels-Alder reactions, Mukaiyama aldol reactions, several types of reductions, Michael addition reactions, hydrosilylations, and hydroaminations proceed under asymmetric catalysis in the presence of chiral lanthanoid complexes. 

Intramolecular addition of amine N-H bonds to carbon-carbon multiple bonds would afford nitrogen heterocycles. To realize catalytic cyclization of a,co-aminoalkenes or aminoalkynes, various catalytic systems have been developed especially with early transition metals such as titanium, zirconium, lanthanide metals, and actinide metals [ 12], Late-transition-metal catalysis based on Ni, Pd, and Rh has also proved to be efficient [ 12], Recently, the ruthenium-catalyzed intramolecular hydroamination of aminoalkynes 15 was reported to afford 5-7-membered ring products 16 in various yields (Eq. 6) [13]. Among... 

A series of rhodium and platinum compounds have been tested in the hydroamination of norbomene with aniline, as shown in Scheme 9.36.[141] Selectivity and activity were highly dependent on the nature of the ionic liquid, but were always superior to those observed in THF. Solvents with chloride anions led to essentially no catalytic activity, whereas [PF6] or Br afforded some catalysis. Nonetheless, even with the best solvent/catalyst combination, less than 40 turnovers are achieved after 6 days at 140°C. 

The C2-symmetric bisoxazolinate 175 formed complexes with lanthanides for the catalysis of enantioselective intramolecular hydroamination /cyclization <03JA14768>. 

Seyam, Alif M. Stubbert, Bryan D. Jansen, Tryg R., O Donnell, James J., III Stem, Charlotte L. Marks, Tobin J. Organolaiithanlde constrained geometry complexes modified for catalysis nthesis, structure, and amirioalkene hydroamination la... 

To catalyze the direct hydroamination of olefins according to eq. (1) two basic approaches have been employed involving primarily the activation either of the amine or of the olefin. One possible way to activate the amine for catalysis is the transformation to the much stronger nucleophilic amide ion by deprotonation. Thus, the amides of strongly electropositive metals, such as alkali metals, alkaline earth metals, or lanthanides, are able to react with the C-C double bond under... 

As the first transition metal-based homogeneous catalysis of hydroamination, in the early 1970s Coulson from the Du Pont laboratories had described the addition of secondary aliphatic amines to ethylene in the presence of various rhodium compounds [15, 16]. Definite results were reported with RhCl3 3 H2O as pre-catalyst in tetrahydrofuran as solvent under starting ethylene pressures of 5-14 MPa at 180-200 °C for different secondary amines (Table 3). 

Quite stable catalytic reaction solutions were obtained in THF with the starting pressure for ethylene of 6-6.5 MPa at a reaction temperature of 120 °C. Under these conditions and with the ratios piperidine/rhodium of 100 1 and 1000 1 in 36 and 72 h, yields of 70 and 50 % ethylpiperidine were reached, which correspond to TONs of 2 and 7 mol amine/(mol Rh) per h, respectively. Total conversion is also possible if the reaction time is prolonged further. As a side reaction, ethylene dimerization to butene was observed. This indicates the formation of a hydrido rhodium(III) complex in the hydroamination reaction, as formulated in Scheme 3, route (b). Hydrido rhodium(III) complexes are known as catalysts for ethylene dimerization [19], and if the reductive elimination of ethylpiperidine from the hydrido-y9-aminoethyl rhodium(III) complex is the rate-limiting step in the catalytic cycle of hydroamination, a competitive catalysis of the ethylene dimerization seems possible. In the context of these mechanistic considerations, an increase of the catalytic activity for hydroamination requires as much facilitation of the reductive elimination step as possible. 

Abstract This review deals with the synthesis and the catalytic application of noncyclopentadienyl complexes of the rare-earth elements. The main topics of the review are amido metal complexes with chelating bidentate ligands, which show the most similarities to cyclopentadienyl ligands. Benzamidinates and guanidinates will be reviewed in a separate contribution within this book. Beside the synthesis of the complexes, the broad potential of these compounds in homogeneous catalysis is demonstrated. Most of the reviewed catalytic transformations are either C-C multiple bond transformation such as the hydroamination and hydrosilylation or polymerization reaction of polar and nonpolar monomers. In this area, butadiene and isoprene, ethylene, as well as lactides and lactones were mostly used as monomers. 

The bis(amido) complexes 141 and 142 showed no catalytic activity in inter- or intramolecular hydroamination reactions. Because of the low basicity of the Ph2N group, it cannot be protonated by aliphatic amines RNH2 or R2NH. Therefore, the initial step of the catalysis failed and these complexes do not serve as catalysts for inter- or intramolecular hydroamination. 

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