Copper catalyst types

The reaction of tert-alkyl Grignard reagents with carboxylic acid chlorides in the presence of a copper catalyst provides ieri-alkyl ketones in substantially lower yields than those reported here.4,14 The simplicity and mildness of experimental conditions and isolation procedure, the diversity of substrate structural type, and the functional group selectivity of these mixed organocuprate reagents render them very useful for conversion of carboxylic acid chlorides to the corresponding secondary and tertiary alkyl ketones.15... 

Other metal oxide catalysts studied for the SCR-NH3 reaction include iron, copper, chromium and manganese oxides supported on various oxides, introduced into zeolite cavities or added to pillared-type clays. Copper catalysts and copper-nickel catalysts, in particular, show some advantages when NO—N02 mixtures are present in the feed and S02 is absent [31b], such as in the case of nitric acid plant tail emissions. The mechanism of NO reduction over copper- and manganese-based catalysts is different from that over vanadia—titania based catalysts. Scheme 1.1 reports the proposed mechanism of SCR-NH3 over Cu-alumina catalysts [31b],... 

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. 

Similar to the intramolecular insertion into an unactivated C—H bond, the intermolecular version of this reaction meets with greatly improved yields when rhodium carbenes are involved. For the insertion of an alkoxycarbonylcarbene fragment into C—H bonds of acyclic alkanes and cycloalkanes, rhodium(II) perfluorocarb-oxylates 286), rhodium(II) pivalate or some other carboxylates 287,288 and rhodium-(III) porphyrins 287 > proved to be well suited (Tables 19 and 20). In the era of copper catalysts, this reaction type ranked as a quite uncommon process 14), mainly because the yields were low, even in the absence of other functional groups in the substrate which would be more susceptible to carbenoid attack. For example, CuS04(CuCl)-catalyzed decomposition of ethyl diazoacetate in a large excess of cyclohexane was reported to give 24% (15%) of C/H insertion, but 40% (61 %) of the two carbene dimers 289). 

Novel example of this reaction type are given by the copper-catalyzed decomposition of ethyl diazoacetate in the presence of bis(dialkoxyphosphoryl)disulfides 374 350 where P/S insertion sometimes accompanies the S/S insertion, and of bis(dialkoxy-thiophosphoryl)trisulfides 375 351 where desulfurization to give the disulfide derived product occurs during the reaction. Only P/S insertion product was obtained from bis(dialkoxyphosphoryl)trisulfide or -tetrasulfide 376 the copper-catalyst is dispensable in this case351K... 

Table 56 time307 Compositions of Raney copper catalysts as function of acid type and extraction ... 

The reaction of monosubstituted alkynes with iodopyrroles in the presence of palladium and copper catalysts leads to the formation of pyrrolylalkynes (79IZV1661, 80IZV726). The preformed phenylethynylcopper(I) derivative also reacts with the iodopyrroles and it is probable that an Ullmann-type mechanism prevails. 

Carbenoid sources other than those derived from diazo precursors for catalytic cyclopropanation reactions are currently limited. Inter- and intramolecular catalytic cyclopropanation using iodonium ylide have been reported. Simple olefins react with iodonium ylides of the type shown in equations 83 and 84, catalysed by copper catalysts, to give cyclopropane adducts in moderate yield127 128. In contrast to the intermolecular cyclopropanation, intramolecular cyclopropanation using iodonium ylides affords high yields of products (equations 85 and 86). The key intermediate 88 for the 3,5-cyclovitamin D ring A synthon 89 was prepared in 80% yield as a diastereomeric mixture (70 30) via intramolecular cyclopropanation from iodonium ylide 87 (equation 87)1 0. 

A classical example of this type of competitive reaction is the conversion of ethanol by a copper catalyst at about 300°C. The principal product is acetaldehyde but ethylene is also evolved in smaller quantities. If, however, an alumina catalyst is used, ethylene is the preferred product. If, in the above reaction scheme, B is the desired product then the selectivity may be found by comparing the respective rates of formation of B and C. Adopting the slab model for simplicity and remembering that, in the steady state, the rates of formation of B and C must be equal to the flux of B and C at the exterior surface of the particle, assuming that the effective diffusivities of B and C are equal ... 

The Cr A and several other zeolites containing transition metal ions, which may exist in two or more valence states, were also found to be oxidation catalysts. One such system of note is the copper containing Type Y zeolite, the redox chemistry of which was studied in several recent investigations (2, 3.4, 5). These studies established the range of conditions at which copper exists in divalent, monovalent, or zerovalent state and in particular determined the reduction conditions in hydrogen and carbon monoxide atmospheres for a complete conversion of Cu Y to Cu Y but no further to Cu°. The Cu ions in type Y zeolite were reported to be specific adsorption centers for carbon monoxide ( 6), ethylene ( 7), and to catalyze the oxidation of CO (8). In the present work the Cu ions were also found to be specific adsorption centers for oxygen. 

Barbier-type reactions, 9, 433 in catalyzed C-C bond formation, 9, 438 in C-C bond formations, 9, 435 in C-heteroatom bond formations, 9, 440 with copper catalysts, 9, 442 non-catalyzed reactions, 9, 443 miscellaneous reactions, 9, 444 in oxidations, 9, 443 in reduction reactions, 9, 444 Bismuth(V) compounds... 

The preparation of ketones by dehydrogenation of secondary alcohols over zinc and copper catalysts and the decarboxylation condensation of acids over manganous oxide or thoria have been adequately covered by standard reference books on catalysis. However, the more complete but equally serviceable catalytic syntheses involving either an aldol or a Tischenko ester type of condensation have been virtually ignored. 

Highly efficient catalytic asymmetric cyclopropanation can be effected with copper catalysts complexed with ligands of type 2.3 These bis(oxazolines) are prepared by reaction of dimethylmalonyl dichloride with an a-amino alcohol. As in the case of ligands of type 1, particularly high stereoselectivity obtains when R is /-butyl. Cyclopropanation of styrene with ethyl diazoacetate catalyzed by copper complexed with... 

Low yields are obtained with halides of the following types, and a copper catalyst is necessary ... 

The direct transmetallation of alkenyl, acyl, and alkylzirconocenes to a copper catalyst and subsequent conjugate addition is also possible without a detour via another metal like zinc. For example, Wipf and Takahashi182 reported the highly diastereoselective 1,4-addition of in situ-prepared alkylzirconocenes (e.g., 246) to chiral N-acyl oxazolidinone 245 and similar substrates in the presence of BF3 OEt2 and catalytic amount of CuBr-SMe2, giving adducts of the type 247 with moderate to good yield (Equation (13)). 

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