Hydrogenations ketones

Dicyclohexylarnine may be selectively generated by reductive alkylation of cyclohexylamine by cyclohexanone (15). Stated batch reaction conditions are specifically 0.05—2.0% Pd or Pt catalyst, which is reusable, pressures of 400—700 kPa (55—100 psi), and temperatures of 75—100°C to give complete reduction in 4 h. Continuous vapor-phase amination selective to dicyclohexylarnine is claimed for cyclohexanone (16) or mixed cyclohexanone plus cyclohexanol (17) feeds. Conditions are 5—15 s contact time of <1 1 ammonia ketone, - 3 1 hydrogen ketone at 260°C over nickel on kieselguhr. With mixed feed the preferred conditions over a mixed copper chromite plus nickel catalyst are 18-s contact time at 250 °C with ammonia alkyl = 0.6 1 and hydrogen alkyl = 1 1. 

The use of chiral ruthenium catalysts can hydrogenate ketones asymmetrically in water. The introduction of surfactants into a water-soluble Ru(II)-catalyzed asymmetric transfer hydrogenation of ketones led to an increase of the catalytic activity and reusability compared to the catalytic systems without surfactants.8 Water-soluble chiral ruthenium complexes with a (i-cyclodextrin unit can catalyze the reduction of aliphatic ketones with high enantiomeric excess and in good-to-excellent yields in the presence of sodium formate (Eq. 8.3).9 The high level of enantioselectivity observed was attributed to the preorganization of the substrates in the hydrophobic cavity of (t-cyclodextrin. 

Casey has suggested that the hydrogenation of alkenes by Shvo s catalyst may proceed by a mechanism involving loss of CO from the Ru-hydride complex, and coordination of the alkene. Insertion of the alkene into the Ru-H bond would give a ruthenium alkyl complex that can be cleaved by H2 to produce the alkane [75], If this is correct, it adds further to the remarkable chemistry of this series of Shvo complexes, if the same complex hydrogenates ketones by an ionic mechanism but hydrogenates alkenes by a conventional insertion pathway. 

Direct comparisons of the diamine system against the parent complex led to the conclusion that the effect of the diamine and KOH/i-PrOH activator decelerate olefin hydrogenation and in turn accelerate carbonyl hydrogenation. In the published report, there were no attempts to optimize turnover numbers or TOF for aldehyde hydrogenation. However, the catalyst has been shown to hydrogenate ketones with a SCR of 10000 at room temperature, which suggests that these catalysts represent the current state of the art in terms of activity and selectivity. 

Surprisingly, there are only a few catalysts known capable of hydrogenating ketones in fully or largely aqueous systems. For example, most of the water-soluble rhodium, mthenium and indium phosphine complexes preferentially hydrogenate the C=C bonds in unsaturated ketones, as does the solvated ion pair formed from aqueous rhodium trichloride and Aliquat-336 [206]. 

Research Focus Preparation of polyurethane coatings consisting of carbonyl-hydrogenaled ketone and aldehyde resins and polyisocyanates. 

Hydromorphone hydrochloride, a hydrogenated ketone of morphine, is a narcotic analgesic. Each 5 mL (1 teaspoon) contains 5 mg of hydromorphone hydrochloride. In addi-... 

As a hydrogenated ketone of morphine, it shares common pharmacologic properties with other opioid analgesics.25 These include the expected changes in the CNS, including increased cerebrospinal fluid pressure, increased biliary pressure, and increased parasympathetic activity. It can also... 

Ketones from alcohol Hydrogen, ketones Ketones Water Ketone-hydrogen separation Stripping is practiced to recover ketones from the solution... 

Homogeneous rhodium(I)-chiral tertiary phosphine catalysts have been used to hydrogenate ketones directly and to hydrosilylate ketones and imines thus accomplishing, after hydrolysis, indirect hydrogenation. 

Alkene isomerization Alkene hydrogenation Ketone hydrogenation Hydrogenation of cyanides Hydrogenation of nitro group Alkyne hydrogenation Aminomethylation Water gas shift reaction... 

Rhodium-chiraphos cations also hydrogenate ketone and epoxide functionalities, albeit with low optical yields, and are, therefore, not synthetically useful. While this rhodium system seems somewhat limited to the preparation of amino acids, other rhodium and ruthenium catalyst precursors are currently available which show enhanced activity and selectivity for a much broader group of hydrogenation substrates. 

Fig. 2. Two intermediates proposed for Pt-cinchona catalyzed hydrogenation of a-keto esters a) a protonated cinchonidine-ketone complex [8] b) a stabilized half-hydrogenated ketone intermediate [3]...

Iridium(I) complexes with Schiff base ligands effectively transfer hydrogenate ketones. Use of optically active ligands allows asymmetric reduction of prochinal ketones to optically active alcohols ... 

Other reactions are alkane formation by hydrogenation, ketone formation (especially with ethylene ), ester formation through hydrogen transfer and formate ester synthesis. An improved catalyst system in which one CO ligand of CoH(CO)4 is substituted with a trialkylphosphine ligand , was disclosed by Shell workers in the early 1960s. With this catalyst, which is more thermally stable than the unsubstituted cobalt carbonyl, reaction proceeds at 140-190 C with 3-7 MPa of CO and Hj. Additionally, mostly linear aldehydes are obtained from linear terminal and internal olefins. This remarkable result arises from the high preference for the terminal addition to an a-olefin, and the isomerization of the olefinic position which occurs simultaneously with hydroformyiation. 

Acetaldehyde, alcohols, alkalis, amines, combustible materials, ethylene, fluorine, hydrogen, ketones (acetone, carbonyls, etc.), metals, sulfur Water... 

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