Copper Compounds as Catalysts

1-Monosubstituted 1,2,3-triazoles are synthesized in moderate yields from a variety of aliphatic halides (Cl and Br), sodium azide, and propiolic acid by a click cycloaddition/decarboxylation process in DMF at 100 C for 0.5 h, using Cul (0.2 equiv.) and sodium ascorbate (0.4 equiv.) as catalyst and in the presence of CS2CO3 (0.5equiv.) [77]. 

The reaction of aryl/alkyl halides, alkynes, and sodium azide in water may be catalyzed by a heterogeneous copper(l) catalyst, oyster shell powders (OSPs)-CuBr (2.5mol%), and microwave irradiation (480 W and 70 °C). The catalyst could be easily recovered from the reaction mixture by a simple filtration and reused at least eight times without significant loss of its catalytic activity. Chitin and protein molecules on OSP particles surface seem to play important roles in the chelation of the CuBr species [112]. 

2 Copper Complexes with Nitrogen-and Phosphorous-Donating Ligands 

The three-component cycloaddition of benzyl bromide and sodium azide with phenylacetylene in water at room temperature is catalyzed by the water-soluble Cu(I)-NHC complex [(SlPr)CuCl] (0.5 mol%), affording a 98% yield of triazole within 48 h. The catalyst could be recovered by a simple extraction [113]. 

Catalysts systems based on Cu(I) and Cu(II) (1.0 mol% loading) species in combination with benzimidazole salts (1.2 mol%) catalyze the multicomponent reaction of phenylacetylene, benzyl bromide, and sodium azide at room temperature in water [116]. 

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Rapid development of the Cu-mediated reactions has led to several excellent catalytic systems based on different copper compounds as catalyst precursors. Further studies of Cu-catalyzed reactions are expected to focus on the mechanism of catalytic reactions to allow rational catalyst design. 

The use of copper compounds as catalysts for the reaction here described is even more limited than the one of iron compounds. We are aware of only one case in which a copper catalyst was used for the synthesis of a carbamate [194]. Thus a mixture of PhN02 (5.0 mmol), CuCl2 2H20 (0.5 mmol), EtOH (86 mmol) and pyridine (0.1 mmol) was reacted at 180 and 68 atm CO for 4 h, to yield a 76 % conversion, with a 90 % selectivity in ethyl phenylcarbamate. The selectivity achieved is good, but the catalytic ratio is very low (10), indicating a very low activity of copper. 

For the aminolysis of chlorobenzene, 3 moles of ammonia usually are used at an operating temperature of 180 to 200°C and a pressure greater than the vapor pressure of the reactants. This reaction is carried out in the liquid phase with copper compounds as catalysts. 

Ethynylation. Base-catalyzed addition of acetylene to carbonyl compounds to form -yn-ols and -yn-glycols (see Acetylene-DERIVED chemicals) is a general and versatile reaction for the production of many commercially useful products. Finely divided KOH can be used in organic solvents or Hquid ammonia. The latter system is widely used for the production of pharmaceuticals and perfumes. The primary commercial appHcation of ethynylation is in the production of 2-butyne-l,4-diol from acetylene and formaldehyde using supported copper acetyHde as catalyst in an aqueous Hquid-fiHed system. 

Stibonium Ylids and Related Compounds. In contrast to phosphoms and arsenic, only a few antimony yhds have been prepared. Until quite recendy triphenyl stibonium tetraphenylcyclopentadienyUde [15081 -36-4] C H Sb, was the only antimony yUd that had been isolated and adequately characteri2ed (192). A new method, uti1i2ing an organic copper compound as a catalyst, has resulted ia the synthesis of a number of new antimony yhds (193) ... 

The main by-products of the Ullmaim condensation are l-aniinoanthraquinone-2-sulfonic acid and l-amino-4-hydroxyanthraquinone-2-sulfonic acid. The choice of copper catalyst affects the selectivity of these by-products. Generally, metal copper powder or copper(I) salt catalyst has a greater reactivity than copper(Il) salts. However, they are likely to yield the reduced product (l-aniinoanthraquinone-2-sulfonic acid). The reaction mechanism has not been estabUshed. It is very difficult to clarify which oxidation state of copper functions as catalyst, since this reaction involves fast redox equiUbria where anthraquinone derivatives and copper compounds are concerned. Some evidence indicates that the catalyst is probably a copper(I) compound (28,29). 

Chromium compounds as catalysts, 188 Chromium oxide in catalytic converter, 62 Chromium oxide catalysts, 175-184 formation of active component, 176,177 of Cr-C bonds, 177, 178 propagation centers formation of, 175-178 number of, 197, 198 change in, 183, 184 reduction of active component, 177 Clear Air Act of 1970, 59, 62 Cobalt oxide in catalytic converter, 62 Cocatalysts, 138-141, 152-154 Competitive reactions, 37-43 Copper chromite, oxidation of CO over, 86-88... 

Nickel compounds as catalysts, 191 Nickel-copper alloys, 252, 253 atomic hydrogen recombination, 273-279... 

The Ullman reaction has long been known as a method for the synthesis of aromatic ethers by the reaction of a phenol with an aromatic halide in the presence of a copper compound as a catalyst. It is a variation on the nucleophilic substitution reaction since a phenolic salt reacts with the halide. Nonactivated aromatic halides can be used in the synthesis of poly(arylene edier)s, dius providing a way of obtaining structures not available by the conventional nucleophilic route. The ease of halogen displacement was found to be the reverse of that observed for activated nucleophilic substitution reaction, that is, I > Br > Cl F. The polymerizations are conducted in benzophenone with a cuprous chloride-pyridine complex as a catalyst. Bromine compounds are the favored reactants.53,124 127 Poly(arylene ether)s have been prepared by Ullman coupling of bisphenols and... 

The use of chiral organometaUic compounds as catalysts in the enantioselective hydrolysis of saturated oxazolones was reported several years ago and the mechanism of the hydrolysis of 4-benzyl-2-methyl-5(4//)-oxazolone catalyzed by the copper(II) complex of (5)-[(A-benzylprolyl)amino]benzaldoxime has been described. ... 

In the industrial manufacture of important starting compounds such as HteCCH2OH, HCaCCH(CHg)OH, and HOCH CsCCI OH, high pressure techniques are employed using alkali hydroxides or copper acetylide as catalyst. For extensive reviews on the alkynylation processes the reader is referred to the book [8] and review of Ziegenbein [6]. 

Humans have been exposed more and more to metallic contaminants in the environment, mostly from the products of industry. There are three main sources of metals in the environment. The most obvious are the processes of extraction and purification mining, smelting, and refining. Another is the release of metals from fossil fuels (e.g., coal, oil), when these are burned. Cadmium, lead, mercury, nickel, vanadium, chromium, and copper are all present in these fuels, and considerable amounts enter the air or are deposited in ash. The third and most diverse source is the production and use of industrial products containing metals, which is increasing as new applications are found. The modem chemical industry, for example, uses many metals or metal compounds as catalysts metal compounds are used as stabilizers in the production of many plastics, and metals are added to lubricants, which then find their way into the environment.21... 

Reactions of this type have been reported tor reactions of a,a -dibromoketones with iron carbonyl compounds or zinc-copper couple as catalysts (4, 157-158 5, 221-224). 

Acid 20 has been transformed to the acid chloride 21 which has been condensed with Meldrums acid to give, after solvolysis with methanol, the p-keto ester 22. Subsequent treatment with / -tosylazide gave the diazo compound 23 which has been stereoselectively cyclized to 2-carbomethoxy-tricyclo[3.3.0.0]octan-3-one 24 with copper acetylacetonate as catalyst. 

Thus, a TON of more than 1000 was achieved using 0.01 to 0.06 % of the [Cu BSP] coordination compound as catalyst and no further oxidation of the aldehyde products was observed. The oxidation reactions can also be performed in acetonitrile solutions, although the catalyst is much less efficient in this solvent (Table IV). The lower activity of [Cu BDB] may find two explanations (1) steric hindrance generated by the four bulky ter -butyl groups which hinders an easy coordination of the alcoholic substrate to the copper ion (2) absence of a thioether bond which may play a role during the catalytic cycle of GOase. 

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... 

With organozinc compounds in the presence of palladium, nickel or copper compounds as the catalysts, highly selective additions to carbonyl groups or carbon-carbon double bonds proceed. For example, an addition of chalcone (Ph-COCH=CH-Ph) proceeds with dialkylzinc in the presence of a nickel catalyst. The asymmetric addition proceeds by using a nickel catalyst having the chiral ligand as shown in eq. (5.17) [38,43]. 

In examining metallic compounds that serve as supports for Pt and Pd catalysts, the metals and metallic compounds as catalyst support are only limited to a few elements. This is because some metals, such as lead, mercury, cadmium, bismuth, tin, zinc, copper and iron have a toxic effect on the catalyst, whereas light metals and alkaline earth metal compounds are without toxic for catalyst, and they can in some cases enhance the selectivity and activity of the catalysts. 

Hydrolysis of organic compounds usually results in the substitution of a group by a hydroxyl group. In water, the reaction is catalyzed by H, OH, and ions. In moist soils, labile complexes of calcium and copper act as catalysts. Sorption tends to increase a chemical s reactivity to or OH radicals. Mabey and Mill (1978) reviewed the kinetic data for hydrolysis of a variety of organic chemicals in aquatic systems and the chemical characteristics of most fresh-water systems. These data could be used to calculate the persistence (half-life for hydrolysis) of chemicals under natural environmental conditions. 

Ziarati et al. [69] developed the synthesis of compounds with pharmaceutical and biological properties. Thus, 2-aryl-5-methyl-2,3-dihydro-lH-3-pyrazolones (72) were synthesized via a four-component reaction of ethyl acetoac-etate (66), hydrazine (67), aldehyde (69), and p-naphthol (70) in water under ultrasound irradiation with a multiwave ultrasonic generator in the presence of nanoparticles of copper iodide as catalyst, using a simple preparation protocol (Scheme 17). It should be mentioned that the catalyst could be recycled and reused for five times without evidently... 

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