Amine-rhodium ratio

Certain amines, when linked to TPPTS, form ionic solvents liquid at quite low temperature. Bahrman [34] used these ionic liquids as both ligands and solvents for the Rh catalyst for the hydroformylation of alkenes. In this otherwise interesting approach, however, the ligand/rhodium ratio, which influences the selectivity of the reaction, is difficult to control. 

Hydroaminomethylation of alkenes occurred to give both n- and /. so aliphatic amines catalyzed by [Rh(cod)Cl]2 and [Ir(cod)Cl]2 with TPPTS in aqueous NH3 with CO/H2 in an autoclave. The ratio of n-and /.soprimary amines ranged from 96 4 to 84 16.178 The catalytic hydroaminomethylation of long-chain alkenes with dimethylamine can be catalyzed by a water-soluble rhodium-phosphine complex, RhCl(CO) (Tppts)2 [TPPTS P(m-C6H4S03Na)3], in an aqueous-organic two-phase system in the presence of the cationic surfactant cetyltrimethy-lammonium bromide (CTAB) (Eq. 3.43). The addition of the cationic surfactant CTAB accelerated the reaction due to the micelle effect.179... 

The hydrogenation of para-substituted anilines over rhodium catalysts has been investigated. An antipathetic metal crystallite size effect was observed for the hydrogenation of /Moluidinc suggesting that terrace sites favour the reaction. Limited evidence was found for catalyst deactivation by the product amines. Catalysts with pore diameters less than 13.2 nm showed evidence of diffusion control on the rate of reaction but not the cis trans ratio of the product. 

The application of immobilized heterobimetallic cobalt-rhodium in nanoparticles has also been reported. In the presence of water, CO, and amine, internal acetylenes 119 were converted to 3,4-disubstituted furan-2(5H)-ones 120 and 121 in high yields, in which an amine was necessary for the formation of furanone and a higher CO pressure was required for good yield (Equation (8)). It is important to notice that the catalyst has been easily recovered without loss of activity or formation of hydrogenated side-products. The reaction proceeded in good yield for the symmetric substrates (entries 1 and 2) while it always gave two regioisomers for asymmetric alkyne substrates (entries 3-8). The isomer ratio was dependent on the steric and electronic nature of the substituents. 

Rhodium-catalyzed hydroformylation of -(substituted amino)benzyl-amines (387, X = H2) and -(substituted amino)benzamides (387, R = H, X = O) in the presence of rhodium(II) acetate dimer and triphenylphos-phine in deoxygenated ethyl acetate gave a 7 3 mixture of 1,2,3,4,4 ,5-hexahydro-6//-pyrido[l,2-a]quinazolines (388, X = H2,0) and isomeric 3-methyl-l,2,3,3fl,4,5-hexahydropyrrolo[l,2-a]quinazolines (389, X = H2, O) (94AJC1061). The methyl derivative of benzylamine 387 (R = Me, X = H2) afforded a mixture of diastereoisomers 390 and 391 (X = H2). Their ratio depended on the reaction time. Longer reaction times gave more 391 (X = H2), containing the methyl group in an equatorial position. Compound 390 isomerized into 391 (X = H2), under the aforementioned conditions. The benzamide derivative (387, R = Me, X = O) yielded only one isomer (391, X = O), independent of the reaction period. 

Landre et al. report that hydrogenation of 8 over colloidal rhodium in the presence of phase transfer agents like tertiary amines and ammonium salts at 5 MPa H2 affords the product with cis—syn—cis/cis—anti—cis isomer ratio of 95/5.156 Mono- and dibenzo... 

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. 

Since secondary and tertiary amines are obtained by reaction of a primary and secondary amine with the imine intermediate, selected unsymmetric secondary and tertiary amines can be prepared by substituting an added chosen amine for the reacting amines. The product composition of this reductive condensation over an appropriate catalyst depends on the nitrileiamine ratio, and to a lesser extent on solvent. Platinum, Pd, and rhodium-on-carbon, in alcohol or hydrocarbon solvent with about 100% excess of added amine, give good yields of -butyl-n-pentylamine from hydrogenation of valeronitrile in presence of w-butylamine" ... 

Unsaturated amines, such as 5-amino-l -pentenes, upon hydrocarboxylation give lactams (2-piperidones)34,33. With appropriate substituents, mixtures of diastereomers are formed in up to 87% yield with ratios dependent on the phosphanes used for modification of the rhodium catalyst Rh,(OAc)4. The relative configurations introduced with the substrates are retained. Although chiral phosphanes have been used, no asymmetric induction is reported33. 

In the hydrogenation of optically active azomethines (prepared from chiral a-phenylcthyl-amine and ketones), the effect of reaction parameters, i.e., catalyst dispersion, mass and solvent polarity, on the diastereoselectivity has been studied20. The diastereoselective hydrogenation of several related chiral imines using nonchiral or chiral diphosphane ligands/rhodium has been reported to yield the corresponding amines with diastereomeric ratios up to 99.7 0.3 141. 

Even more active was the in situ catalyst prepared from [Rh(l,5-hexadiene)Cl]2 and PPh3 with a low ratio of P/Rh = 1.2, and the use of a p-xylene/methanol solvent instead of benzene/methanol resulted in a further increase of activity (Table II). Both effects already have been observed 1,4) which shows that these may be characteristic for such rhodium, phosphine, and amine catalyst combinations. 

Nickel nanorods (diameter 12 to 15 nm length, 50 to 100 nm) have been synthesized by a solvothermal decomposition of nickel acetate in the presence of n-octylamine (nickel acetate to w-octylamine molar ratio is 1 300) at 250°C (104). The formation of Ni nanorods is favored by the presence of n-octyl amine it reduces, under solvothermal conditions, the Ni ions to Ni° and also acts as a shape-controlling agent to produce metallic nickel nanorods. In the absence of linear alkyl amines, only NiO nanoparticles are produced. Using a similar approach, in the presence of w-octylamine, nanorods of ruthenium and rhodium metals have been produced starting from corresponding acetyl acetonate precursors, Ru(acac)3 and Rh(acac)3. The metallic nanorods are stable in air because of the amine coating and can be redispersed in hydrocarbon solvents. 

Specific examples of the hydroaminomethylations of olefins with secondary amines are shown in Equations 17.19-17.21. Cyclic and acyclic secondary amines occur in high yield with linear-to-branched ratios exceeding 50 to 1 in most cases when catalyzed by the rhodium complex generated from [Rh(COD)JBF and xantphos. The reaction of pen-tene with piperidine is shown in Equation 17.19. These reactions are also compatible with alcohol (Equation 17.20) and acetal functional groups (Equation 17.21). 

Reactions of internal alkenes can also form terminal amines, and examples of this process are shown in Equation 17.24. These reactions occur in the presence of a rhodium catalyst containing the electron-poor bisphosphine ligand shown in these equations. For example, the reaction of 2-pentene (R = Me in Equation 17.24) with piperidine forms a 4 1 ratio of the linear to branched amines, and the same reaction with a excess of 2-butene (R = H in Equation 17.24) forms a 96 4 ratio of linear to branched products. 

In the presence of a chiral catalyst such as rhodium(II) (5)-/V l,8-naphthanoyl-tert-leucinate dimer, Troc-amino indane was produced with 56% yield and 2.57 1 enantiomeric ratio. In contrast to other methods, no hypervalent iodine reagent (typically used stoichiometrically or in excess and forming iodobenzene as by-product) is required for oxidation of the amine component. However, a slight excess of the aromatic alkane component (5 equiv) must be used to achieve good conversions. The reactivity of rhodium nitrenes generated from 2,2,2-trichloroethyl-/V-tosyloxycarbamate with aliphatic alkanes is similar to the one observed with metal nitrenes obtained from the oxidation of sulfamate with hypervalent iodine reagent. Troc-protected amino cyclohexane and cyclooctane were obtained, respectively, in 73 and 62% yields when 2 equiv of alkanes was used, whereas yields up to 85% were observed with 5 equiv (eq 3). 

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