Alcohol copper catalysts

Oxalic acid produced from syngas can be esteiified (eq. 20) and reduced with hydrogen to form ethylene glycol with recovery of the esterification alcohol (eq. 21). Hydrogenation requires a copper catalyst giving 100% conversion with selectivities to ethylene glycol of 95% (15). 

The Guerbet reaction can be used to obtain higher alcohols 2-propyl-1-heptanol [10042-59-8] from 1-pentanol condensation and 6-methyl-4-nonanol from 2-pentanol (80—83). Condensations with alkah phenolates as the base, instead of copper catalyst, produce lower amounts of carboxyhc acids and requke lower reaction temperatures (82,83). The crossed Guerbet reaction of 1-pentanol with methanol in the presence of sodium methoxide catalyst afforded 2-heptanol in selectivities of about 75% (84). 

Nerol, geraniol, and linalool, known as the rose alcohols, are found widely in nature. Nerol and geraniol have mild, sweet odors reminiscent of rose flowers. They are manufactured by the hydrochlorination of mycene at the conjugated double bonds when a copper catalyst is used (88,89). 

Many anthraquinone reactive and acid dyes are derived from bromamine acid. The bromine atom is replaced with appropriate amines in the presence of copper catalyst in water or water—alcohol mixtures in the presence of acid binding agents such as alkaU metal carbonate, bicarbonate, hydroxide, or acetate (Ullmaim condensation reaction). 

The reaction of alcohols with arylbromides and nickel or copper catalysts, in presence of base, has been investigated comparatively in regard to the influence of the metals, of the ligands, of the base, of the primary or secondary alcohols and of the substituents on the arylbromide. The best conditions, with bipyNiBr2 in presence of KHCO3 at 125°C, afford quantitative yields in the phenylalkyl ethers from the primary alcohols. 

A new comparison of the copper and nickel catalysts (Fig. 12) on the arylation of alcohols, using potassium carbonate as base, shows once again the superiority of the nickel catalyst (70 % against 40 % for the copper catalyst). 

This reaction is similar to 13-1 and, like that one, generally requires activated substrates. With unactivated substrates, side reactions predominate, though aryl methyl ethers have been prepared from unactivated chlorides by treatment with MeO in HMPA. This reaction gives better yields than 13-1 and is used more often. A good solvent is liquid ammonia. The compound NaOMe reacted with o- and p-fluoronitrobenzenes 10 times faster in NH3 at — 70°C than in MeOH. Phase-transfer catalysis has also been used. The reaction of 4-iodotoluene and 3,4-dimethylphenol, in the presence of a copper catalyst and cesium carbonate, gave the diaryl ether (Ar—O—Ar ). Alcohols were coupled with aryl halides in the presence of palladium catalysts to give the Ar—O—R ether. Nickel catalysts have also been used. ... 

The hydrosilylation of carbonyl compounds by EtjSiH catalysed by the copper NHC complexes 65 and 66-67 constitutes a convenient method for the direct synthesis of silyl-protected alcohols (silyl ethers). The catalysts can be generated in situ from the corresponding imidazolium salts, base and CuCl or [Cu(MeCN) ]X", respectively. The catalytic reactions usually occur at room tanperature in THE with very good conversions and exhibit good functional group tolerance. Complex 66, which is more active than 65, allows the reactions to be run under lower silane loadings and is preferred for the hydrosilylation of hindered ketones. The wide scope of application of the copper catalyst [dialkyl-, arylalkyl-ketones, aldehydes (even enoUsable) and esters] is evident from some examples compiled in Table 2.3 [51-53],... 

Copper(II) triflate is quite inefficient in promoting cyclopropanation of allyl alcohol, and the use of f-butyl diazoacetate [164/(165+166) = 97/3%] brought no improvement over ethyl diazoacetate (67/6 %)162). If, however, copper(I) triflate was the catalyst, cyclopropanation with ethyl diazoacetate increased to 30% at the expense of O/H insertion (55%). As has already been discussed in Sect. 2.2.1, competitive coordination-type and carbenoid mechanisms may be involved in cyclopropanation with copper catalysts, and the ability of Cu(I) to coordinate efficiently with olefins may enhance this reaction in the intramolecular competition with O/H insertion. 

L. Ma, D.L. Trimm and M.S. Wainwright Promoted skeletal copper catalysts for methanol synthesis, in Advances of Alcohols Fuels in the World, - Proceedings of the XII International Symposium on Alcohol Fuels, Beijing, China, Tsinghua University Press, 1998, pp. 1-7. 

The first asymmetric procedure consists of the addition of R2Zn to a mixture of aldehyde and enone in the presence of the chiral copper catalyst (Scheme 7.14) [38, 52]. For instance, the tandem addition of Me2Zn and propanal to 2-cyclohexenone in the presence of 1.2 mol% chiral catalyst (S, R, R)-1S gave, after oxidation of the alcohol 51, the diketone 52 in 81% yield and with an ee of 97%. The formation of erythro and threo isomers is due to poor stereocontrol in the aldol step. A variety of trans-2,3-disubstituted cyclohexanones are obtained in this regioselective and enantioselective three-component organozinc reagent coupling. 

Various transition metals have been used in redox processes. For example, tandem sequences of cyclization have been initiated from malonate enolates by electron-transfer-induced oxidation with ferricenium ion Cp2pe+ (51) followed by cyclization and either radical or cationic termination (Scheme 41). ° Titanium, in the form of Cp2TiPh, has been used to initiate reductive radical cyclizations to give y- and 5-cyano esters in a 5- or 6-exo manner, respectively (Scheme 42). The Ti(III) reagent coordinates both to the C=0 and CN groups and cyclization proceeds irreversibly without formation of iminyl radical intermediates.The oxidation of benzylic and allylic alcohols in a two-phase system in the presence of r-butyl hydroperoxide, a copper catalyst, and a phase-transfer catalyst has been examined. The reactions were shown to proceed via a heterolytic mechanism however, the oxidations of related active methylene compounds (without the alcohol functionality) were determined to be free-radical processes. 

The catalytic properties of copper catalysts for CSRM are significantly different from those of other transition metals. Several investigations have been performed on the behavior of group 9-10 transition metals in the conversion of alcohols [120-122]. 

Quite interestingly, propargyl alcohol itself can be applied in the copper-catalyzed protocol. In the absence of copper catalyst, only the metalation (deprotonation) of terminal hydrogen occurs (Scheme 38) °. 

The low-pressure copper catalysts are very selective for the synthesis of methanol. Under industrial conditions on the Cu-Zn0-Al203 catalyst, the selectivity is typically greater than 99%. The impurities formed include hydrocarbons, higher alcohols, ethers, ketones, and esters. These, as well as any water formed, can easily be removed by distillation to give very pure methanol. 

Supported copper catalysts are widely used in industrial chemical processes far the hydrogenation of different compounds. Of great importance are the synthesis of methanol in the presence of CuO/ZnO/Al203 catalyst and hydrogenation of fat oxo-aldehydes to alcohols with mixed copper-chromium oxides. 

The formal hydrogen transfer from the alcoholic function to the enone one, parallels the conventional hydrogenation reaction as both processes are catalyzed by the same copper catalyst. 

In A, a Raney copper catalyst would be able to hydro-dehydrogenate alcoholic functions (-H, +H) on metallic copper sites. About 10 to 15% of the copper would be hydroxylated copper able to catalyze the degradation reactions DOH, RC, RM. These sites would be more reactive than Cu towards Mn + in the oxido-reduction modification of the initial Raney copper, so that, beeing first exchanged, the rates of DOH, RC, RM decrease. 

Copper-catalysts promoted with i) other group VIA or VIIIA metals and ii) alcaline or alcaline earth elements (IA or IIA) are used for selective hydrogenation of various organic compounds (1). Moreover Cu(Co) Zn-Al catalysts were extensively studied for the synthesis of methanol and of light alcohols (2,3). More recently, due to the development of fine chemical processes, detailed studies of copper catalysts were carried out in order to show, like for noble metals, the effect of supports (SMSI), of promoters and of activation-on metal dispersion or reduction, on alloy formation... For example modified copper catalysts are known for their utilization in the dehydrogenation of esters (4-6), in the hydrolysis of nitriles (7), in the selective hydrogenation of nitriles (8), in the amination of alcohols (9)... 

Now the influence of water or ammonia on copper catalysts is being investigated. Previously A. BAIKER and coll, have shown that ammonia could modify the catalytic properties of copper catalysts used in the amination of alcohols (9). These authors noticed the formation of copper nitride after NH3 exposure at a temperature of about 300°C which is the reaction temperature of our study. The first results that we obtained in our study showed that both H2O and NH3 decrease significantly the copper dispersion in unpromoted catalysts and that this modification is less significant when Ca or Mn are added to the Cu-Cr catalyst. We are now studying what are the superfical modifications consecutive to the addition of promoters or/and water and ammonia. 

P-Benzilmoitoxime. The a-oxime is converted into the /J-form by treatment with a solution of hydrogen chloride in benzene (CAUTION) (or ether) at room temperature. From benzene, solvated crystals which melt on rapid heating at about 65 °C are obtained. Removal of benzene of crystallisation in an oven at 50 °C and recrystallisation from carbon disulphide (CAUTION) yields pure /J-benzilmonoxime, m.p. 112°C. The product gives no colour change with aqueous-alcoholic copper acetate solution if it is contaminated with the a-form a greenish colour is produced. (Conversion of the a-form into the / -form may also be effected by boiling in benzene solution in the presence of animal charcoal, which presumably contains adsorbed acidic catalysts.)... 

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