Copper salts, as catalysts for

More recently, Yamamoto [16] reported a comparative study between different copper salts as catalysts for the reaction of n-butylmagnesium chloride with trun.s-allylic phosphate 108 and showed that CuCN -2LiCl gives the best results for the selectivity in favor of the Sn2 product 110 [Eq. (34) and Table 5]. 

The chemical synthesis uses copper salt as catalyst for the hydration of acrylonitrile and has several disadvantages ... 

Copper-complexes prepared with other type of N-chelating ligands have been also prepared and evaluated as catalysts for the Diels-Alder reaction. Eng-berts et al. [103] studied enantioselective Diels-Alder reaction of 3-phenyl-l-(2-pyridyl)-2-propen-l-one with cyclopentadiene in water (Scheme 39). By using coordinating chiral, commercially available a-amino-adds and their derivatives with copper salts as catalysts, they obtained the desired product with yields generally exceeding 90%. With L-abrine (72 in Scheme 39) as chiral moiety, an enantiomeric excess of 74% could be achieved. Moreover, the catalyst solution was reused with no loss of enantioselectivity. 

Phenols such as 2.6-dimethyIphenol are converted rapidly and in high yield to high molecular weight polymers at room temperature with oxygen in the presence of amine complexes of copper salts as catalyst. Much of the work described in the literature has been performed with copper (I) chloride as catalyst and pyridine as ligand and solvent. Other amines, primary, secondary or tertiary can be used as ligands for the catalyst. Autoxidation of copper (I) chloride in pyridine results in the... 

Carbonates are often formed as by-products even in the synthesis of oxalates or acrylates. The catalytic system for such a synthesis does not require the presence of palladium, however, since it can be achieved by using only copper salts as catalysts. 

Greater preparative importance attaches to oxidative ring opening of cycloalkanols and cycloalkanones, which then afford alkanedioic acids containing an unchanged number of carbon atoms. Thus, for instance, adipic acid is obtained in up to 90% yield from cyclohexanol or cyclohexanone by means of about 60% nitric acid containing vanadium and copper salts as catalyst 125... 

Carbene complexes, generated by the reaction between metal salts and diazo compounds can insert into C-H bonds in a form of CH activation (see Chapter 3 for other CH activation reactions). While early reactions involved the use of copper salts as catalysts (Schemes 8.143 and 8.144), rhodium complexes are now more widely used. In molecules such as cyclohexane, there is no issue of regioselectivity, but this issue is critical for the use of the reaction in synthesis. Both steric and electronic factors influence selectivity. Carbon atoms where a build up of some positive charge can be stabilized are favoured. Hence, allylic positions and positions a- to a heteroatom such as oxygen or nitrogen, are favoured. The reaction at tertiary C-H bonds, rather than primary C-H bonds is also favoured for the same reason, but, in this case, are also disfavoured by steric effects. Reactivity and selectivity are also influenced by both the structure of the catalyst, and the... 

The enantioselective, catalytic, three-component Mannich-acetylene reaction is the most direct and economical way to afford chiral nitrogen-containing building blocks. In this field, a great development has been accomplished in the use of different chiral molecules as ligands for several copper(l) salts as catalyst for the synthesis of chiral propargylamines 39. Thus, the addition of phenylacetylene (22a, = Ph) to... 

In addition to the use of copper salts as catalysts, a variety of discrete organosoluble copper compounds have been generated and used to promote the synthesis of triazoles. An example of this chemistry entailed the use of an Af-heterocyclic carbene as the stabi-lizing/solubilizing ligand for the copper (Scheme 3.108) [113]. lodoalkynes were used as... 

Section B gives some examples of metal-catalyzed cyclopropanations. In Entries 7 and 8, Cu(I) salts are used as catalysts for intermolecular cyclopropanation by ethyl diazoacetate. The exo approach to norbornene is anticipated on steric grounds. In both cases, the Cu(I) salts were used at a rather high ratio to the reactants. Entry 9 illustrates use of Rh2(02CCH3)4 as the catalyst at a much lower ratio. Entry 10 involves ethyl diazopyruvate, with copper acetylacetonate as the catalyst. The stereoselectivity of this reaction was not determined. Entry 11 shows that Pd(02CCH3) is also an active catalyst for cyclopropanation by diazomethane. 

Low molecular weight aromatic ethers have been prepared principally by the condensation of phenolate salts with aromatic halides 82). The Ullmann condensation (81), which employs copper or its salts as catalysts has been used in most cases in the laboratory. Recently a modification of the Ullmann condensation which consists of heating copper (1) oxide, the free phenol, and the aromatic halide in s-collidine has been reported (3). This method is recommended for alkali-sensitive aromatic compounds. In addition, reaction of phenolate salts with copper (1) oxide and the aromatic halide in boiling N,N-dimethyl formamide is described. When the halogen is activated by electronegative groups as in -chloroni-... 

The preparation of the related high molecular weight poly-1.4-phenylene sulfide has been accomplished by heating />-bromothio-phenolate salts in pyridine at 250° C (57). The commercially available polyethersulfones are reported to be prepared by condensation of 4.4 -dichlorodiphenyl sulfone with salts of biphenols in solvents such as dimethylsulfoxide at 150° C. The work of Bacon and Hill would suggest that both of these reactions might be carried out at considerably lower temperatures with copper (I) salts as catalysts. In addition, it has been demonstrated that copper (I) acetylides react quantitatively with aromatic iodides to yield tolanes (15, 77) therefore this reaction should also be the basis for a similar polymer forming reaction. 

Copper (II) salts have been found to be inactive as catalysts for the reaction with the exception of the copper (II) carboxylates which are considerably less reactive. In addition, the polymerization of 2.6-xylenol in pyridine with copper (II) acetate as catalyst appears to terminate before high molecular weight polymers are formed. However, treatment of an amine complex of a copper (II) salt with an equivalent of a strong gives the active catalyst. Similarly, although copper (II) hydroxide in pyridine is inactive as a catalyst, treatment with an equivalent of hydrogen chloride generates the active catalyst. Hence it can be concluded that the active catalyst is a basic salt (XV). 

The cyclopropanation of alkenes, alkynes, and aromatic compounds by carbenoids generated in the metal-catalyzed decomposition of diazo ketones has found widespread use as a method for carbon-carbon bond construction for many years, and intramolecular applications of these reactions have provided a useful cyclization strategy. Historically, copper metal, cuprous chloride, cupric sulfate, and other copper salts were used most commonly as catalysts for such reactions however, the superior catalytic activity of rhodium(ll) acetate dimer has recently become well-established.3 This commercially available rhodium salt exhibits high catalytic activity for the decomposition of diazo ketones even at very low catalyst substrate ratios (< 1%) and is less capricious than the old copper catalysts. We recommend the use of rhodium(ll) acetate dimer in preference to copper catalysts in all diazo ketone decomposition reactions. The present synthesis describes a typical cyclization procedure. 

Dimethyl terephthalate is manufactured from terephthalic acid or directly from p-xylene. Esterification of terephthalic acid with methanol occurs with sulfuric acid as the acid catalyst. Direct oxidation of p-xylcnc with methanol present also produced dimethyl terephthalate copper salts and manganese salt are catalysts for this reaction. The dimethyl terephthalate (boiling point 288°C, melting point 141°C) must be carefully purified via a five-column distillation system. 

Acrylamide with a demand of 200,000 tons year" is one of the most important commodities in the world. It is used for the preparation of coagulators, soil conditioners, stock additives for paper treatment, and in leather and textile industry as a component of synthetic fibers. Conventional chemical synthesis involving hydration of acrylonitrile with the use of copper salts as a catalyst has some disadvantages rate of acrylic acid formation higher than acrylamide, by-products formation and polymerization, and high-energy inputs. To overcome these limits since 1985, the Japanese company Nitto Chemical Industry developed a biocatalyzed process to synthesize... 

---