Reduction Of Cyclohexanone Research Articles

The reaction of iodine with lithium tri-tert-butoxyaluminohydride. A reaction with variable stoichiometry unsuitable for analytical standardization

Solutions of lithium tri-tert-butoxyaluminohydride (LTBA) have been standardized by reduction of cyclohexanone, followed by gas–liquid chromatography (glc) and/or spectral analysis of the extent of reaction. These results are compared with the standard titrimetric analysis of LTBA by iodine, to determine whether the standardizing equation is[Formula: see text]Or[Formula: see text]It is clear that in fact both of these reactions occur, with [5] predominating at low hydride to iodine ratios, and [3] becoming increasingly significant when the hydride and iodine concentrations become comparable. The usual titrimetric method of standardizing LTBA is therefore essentially unusable.

Rules for the quantitative prediction of stereochemistry in the reduction of cyclohexanones by sodium borohydride

A procedure is outlined which allows calculation of the stereoselectivity of reduction of cyclohexanones by sodium borohydride under normal conditions (room temperature, 2-propanol as solvent). The procedure rests on incremental enthalpy values of steric hindrance, coupled with known isokinetic relationships to obtain values of ΔΔG≠;thus it delineates quantitatively the steric factors governing stereoselectivity in these reductions.

The preparation of the soluble ROMgH and ROMg 2H 3 compounds and their unusual stereoselectivity in the reduction of cyclohexanones

The preparation of the soluble ROMgH and ROMg 2H 3 compounds and their unusual stereoselectivity in the reduction of cyclohexanones

Aspects of catalysis. Part III. Soluble iridium-containing catalysts for the reduction of cyclohexanones by propan-2-ol and for the formation of ethers from cyclohexanones (or enol ethers) and alcohols

Transfer of hydrogen from propan-2-ol (containing water) to relatively unhindered cyclohexanones is catalysed by some soluble iridium compounds. Stereoselectivity in the reduction of a substituted cyclohexanon depends on the ligands associated with the iridium. The proportion of axial alcohol from the reduction of cholestan-3-one or 4-t-butylcyclohexanone ranges from 30–23%(piperidine present) to 66–78%(dimethyl sulphoxide present). Preformed iridium–sulphoxide complexes also give the latter degree of stereoselectivity. In the absence of water these complexes catalyse another reaction between cyclohexanones and alcohols, ethers being formed by reductive etherification of the ketones. The reaction favours the production of axial ethers and higher yields of ether can be obtained by starting with the ketone in the form of an enol ether.

Study of promoting effect of amines in reduction of cyclohexanone with 2-propanol, catalyzed by tris(triphenylphosphine)ruthenium (II) bichloride complex

1. Aqueous solutions of triethylamine and piperidine promote the homogeneous reduction of cyclohexanone by 2-propanol in the presence of the RuCl2(PPh3)3 complex. 2. At low concentrations of the indicated amines the initial reduction rate of the ketone correlates satisfactorily with the change in the relative pH* value of the solution. 3. Pyridine and n-amylamine do not promote the process and completely destroy the promoting effect of triethylamine and piperidine. Tribenzylamine and diphenylamine lower five- and 20-fold, respectively.

Stereochemistry of reduction of cyclohexanones with complex metal hydrides

Stereochemistry of reduction of cyclohexanones with complex metal hydrides

An electronic interpretation of the stereochemistry of the reduction of cyclohexanones

An electronic interpretation of the stereochemistry of the reduction of cyclohexanones

Investigation of the homogeneous reaction of hydeogen transfer from 2-pentanol to cyclohexanone, catalyzed by tris (triphenylphosphine)-dichlororuthenium in the presence of alkali

1. Alkali promotes the reduction of cyclohexanone by transfer of hydrogen from 2-pentanol, its hydrogenation by hydrogen and condensation in the presence of the complex tris(triphenylphosphine)dichloro-ruthenium. 2. The degree of hydrogen transfer passes through a maximum at an alkali concentration of 1.64 · 10−3 M (in an atmosphere of argon) and at 4.08 · 10−3 M (in an atmosphere of hydrogen). With increasing alkali concentration, the degree of hydrogenation of the ketone by hydrogen and its condensation increase. 3. When the temperature is increased from 50 to 84°, the rate of transfer of hydrogen increases, while the rate of hydrogenation by hydrogen passes through a maximum at 70°, which is apparently associated with the formation of various intermediate complexes, which catalyze these processes.

Deuterium Isotope Effects in the Reduction of Cyclohexanones. The Concepts of Steric Approach Control and Product Development Control

Definitions for the terms stericapproachcontrol and productdevelopmentcontrol in relation to the degree of bonding in the transition state are put forward. Kinetic deuterium isotope effects in the reduction of a graded series of ketones by NaBH4 and NaBD4 have been measured. These effects are inverse, and show no systematic dependence on the degree of steric hindrance of the ketone. This evidence appears to invalidate the steric approach control – product development control explanation of the axial to equatorial product ratios (1). The primary isotope effect is very small, which is consistent with an early transition state in these reductions, as demanded by other explanations of product ratios, but since several other factors causing small isotope effects may be applicable, the evidence does not constitute proof of an early transition state.The main conclusions of this work have already been published in preliminary form (2).

A Novel Reduction in the Presence of Precipitated Metals. II. The Behavior of Precipitated Metals and Water in Catalytic Reduction

Abstract The ppt-metal-catalyzed reduction, which is performed by refluxing the substrates with water in the presence of ppt-metals, was investigated in detail. The participation of water as a hydrogen donor was demonstrated by the fact that benzaldehyde was reduced to the corresponding deuterated alcohols when heated with D2O in the presence of ppt-Ni. The scope of the reduction was established by the reaction of cyclohexanone with ppt-metals and water. The most preferable H2O/cyclohexanone molar ratio was found to be about 15 : 1. The reaction was accelerated when a 0.25n aqueous solution of sodium chloride was used instead of water. It was found that the order of the abilities of various ppt-metals to decompose water is different from that of the abilities to catalyze the reduction of cyclohexanone. The values of the activation energies for the reduction catalyzed by ppt-Ni and ppt-Ni,Co were found to be 4.0 kcal/mol and 7.5 kcal/mol respectively. From these facts, it was concluded that the ppt-metal-catalyzed reduction consists of two steps: the reaction of water with zinc or zinc compounds to supply a hydrogen source necessary for the hydrogenation, followed by ordinary catalytic hydrogenation.

A Comment on the mechanism of reduction of cyclohexanones by complex hydrides

A Comment on the mechanism of reduction of cyclohexanones by complex hydrides

Stereochemical studies in the trisnorlupane series—II : The stereoselectivity of reduction of a cyclopentanone by complex metal hydrides

The stereoselectivity of the reduction of 4,23,24-trisnor-(5βH)-5(4 → 3)-abeolupan-3-one (I) by complex metal hydrides, under a variety of conditions, is reported. This stereoselectivity is discussed in terms of theories relating to the similar reduction of cyclohexanones.

The rates of reduction of cyclohexanones with lithium Tri-t-Butoxyaluminohydride

The rates of reduction of cyclohexanones with lithium Tri-t-Butoxyaluminohydride

The polarography of cyclohexanone and cyclohex-2-en-1-one

Cyclohex-2-en-1-one gives a total of five polarographic waves, in aqueous buffer solutions, over the pH range 0–14 at 25°. One of the three waves observed in acid solutions is due to an inhibition of the hydrogen discharge, and is also observed for cyclohexanone solutions at these pH′s. The remaining two are a diffusion-controlled one-electron wave and an adsorption prewave to this. The combined wave falls from pH 5 to 8 to be replaced by a second wave at a more negative potential; this is also diffusion-controlled, involving a one-electron reduction. These two waves are related by a protonation process occurring in the diffusion layer but not in the bulk solution. In some tetramethylammonium buffer solutions a further wave can be discerned at very negative potentials, but this is not identical with the cyclohexanone reduction wave which is studied in these solutions.

The reduction of cyclohexanone on skeletal zinc catalyst under pressure

1. A high yield of cyclohexanol is obtained when cyclohexanone is hydrogenated on zinc catalyst under pressure. 2. The main reaction is complicated by the secondary dehydration of the formed cyclohexanol to cyclohexene.