Catalysts copper complexes

Tsuchida, E. Oyaizu, K. Kumaki, Y. Saito, K. Copper Complex Catalyst for Oxidative Polymerization of... 

The dioxygenation of 3-hydroxyflavone using various synthetic model copper complex catalysts has been described by Kaizer, Speier, and co-workers (Scheme 6A), to complement biochemical efforts to understand the mechanism of 2,3-QD (92-95). Chavez and co-workers recently reported CuLCl as a model complex and suggested the importance of the carboxylate group of the enzyme glutamate as a stabilizing group for the bound substrate (Scheme 6B) (96). 

I. Ojima Fundamental Research in Homogeneous Catalysis. (Synthetic Reactions by Copper Complex Catalysts. V. 2, Y. Ishii and M. Tsutsui, Eds.), pp. 275—284. Plenum (1978). 

Polyfluorinated BOX ligand 228 provides a useful copper complex catalyst, which can be recovered easily from the reaction mixture by a fluorous solvent system [159]. Benaglia and coworkers reported that an F-BOX ligand with CuOTf catalyzed the asymmetric cyclopropanation of diazoacetate in a CgFig/CHaCN biphasic mixture the F-BOX ligand was readily separated from products by phase separation and recovered from the reaction mixture (Scheme 1.105). 

A new asymmetric urea-copper complex catalyst that is capable of helical chirality inversion has been developed. The enantioselectivity of the asymmetric conjugate addition of diethyl malonate to trans- -nitrostyrene has been found to depend on the helicity of the catalyst. Either enantiomer of the product can be predetermined by selection of the oxidation state of the copper ion. Facile interconversion between the... 

Piperazinothiazoies (2) were obtained by such a replacement reaction, Cu powder being used as catalyst (25. 26). 2-Piperidinothiazoles are obtained in a similar way (Scheme 2) (27). This catalytic reaction has been postulated in the case of benzene derivatives as a nucleophilic substitution on the copper-complexed halide in which the halogen possesses a positive character by coordination (29). For heterocyclic compounds the coordination probably occurs on the ring nitrogen. 

Acetonitrile also is used as a catalyst and as an ingredient in transition-metal complex catalysts (35,36). There are many uses for it in the photographic industry and for the extraction and refining of copper and by-product ammonium sulfate (37—39). It also is used for dyeing textiles and in coating compositions (40,41). It is an effective stabilizer for chlorinated solvents, particularly in the presence of aluminum, and it has some appflcation in... 

The chemical complex includes the methanol plant, methyl acetate plant, and acetic anhydride plant. The methanol plant uses the Lurgi process for hydrogenation of CO over a copper-based catalyst. The plant is capable of producing 165,000 t/yr of methanol. The methyl acetate plant converts this methanol, purchased methanol, and recovered acetic acid from other Eastman processes into approximately 440,000 t/yr of methyl acetate. 

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

Trilialophenols can be converted to poly(dihaloph.enylene oxide)s by a reaction that resembles radical-initiated displacement polymerization. In one procedure, either a copper or silver complex of the phenol is heated to produce a branched product (50). In another procedure, a catalytic quantity of an oxidizing agent and the dry sodium salt in dimethyl sulfoxide produces linear poly(2,6-dichloro-l,4-polyphenylene oxide) (51). The polymer can also be prepared by direct oxidation with a copper—amine catalyst, although branching in the ortho positions is indicated by chlorine analyses (52). 

Since Evans s initial report, several chiral Lewis acids with copper as the central metal have been reported. Davies et al. and Ghosh et al. independently developed a bis(oxazoline) ligand prepared from aminoindanol, and applied the copper complex of this ligand to the asymmetric Diels-Alder reaction. Davies varied the link between the two oxazolines and found that cyclopropyl is the best connector (see catalyst 26), giving the cycloadduct of acryloyloxazolidinone and cyclopentadiene in high optical purity (98.4% ee) [35] (Scheme 1.45). Ghosh et al., on the other hand, obtained the same cycloadduct in 99% ee by the use of unsubstituted ligand (see catalyst 27) [36] (Scheme 1.46, Table 1.19). 

Phosphino-oxazoline)copper complex 28 was found by Helmchen et al. to be an excellent Diels-Alder catalyst [37] (Scheme 1.47, Table 1.20). The nitrogen atom acts as an electron-donating ligand, whereas phosphorus is a cr-donor-Tt-acceptor ligand. The copper complex of this phosphino-oxazoline ligand is therefore expected to have... 

Several chiral BOX-copper(II) catalysts 27a-c, 28a,b [31h, 38] and chiral BOX-copper(II) substrate/hydrolyzed enone complexes 29a,b [31f 39] have been characterized by X-ray structure analysis (Scheme 4.24). 

The absolute configuration of products obtained in the highly stereoselective cycloaddition reactions with inverse electron-demand catalyzed by the t-Bu-BOX-Cu(II) complex can also be accounted for by a square-planar geometry at the cop-per(II) center. A square-planar intermediate is supported by the X-ray structure of the hydrolyzed enone bound to the chiral BOX-copper(II) catalyst, shown as 29b in Scheme 4.24. 

The cationic aqua complexes prepared from traws-chelating tridentate ligand, R,R-DBFOX/Ph, and various transition metal(II) perchlorates induce absolute enantio-selectivity in the Diels-Alder reactions of cyclopentadiene with 3-alkenoyl-2-oxazoli-dinone dienophiles. Unlike other bisoxazoline type complex catalysts [38, 43-54], the J ,J -DBFOX/Ph complex of Ni(C104)2-6H20, which has an octahedral structure with three aqua ligands, is isolable and can be stored in air for months without loss of catalytic activity. Iron(II), cobalt(II), copper(II), and zinc(II) complexes are similarly active. 

Among the J ,J -DBFOX/Ph-transition(II) metal complex catalysts examined in nitrone cydoadditions, the anhydrous J ,J -DBFOX/Ph complex catalyst prepared from Ni(C104)2 or Fe(C104)2 provided equally excellent results. For example, in the presence of 10 mol% of the anhydrous nickel(II) complex catalyst R,R-DBFOX/Ph-Ni(C104)2, which was prepared in-situ from J ,J -DBFOX/Ph ligand, NiBr2, and 2 equimolar amounts of AgC104 in dichloromethane, the reaction of 3-crotonoyl-2-oxazolidinone with N-benzylidenemethylamine N-oxide at room temperature produced the 3,4-trans-isoxazolidine (63% yield) in near perfect endo selectivity (endo/exo=99 l) and enantioselectivity in favor for the 3S,4J ,5S enantiomer (>99% ee for the endo isomer. Scheme 7.21). The copper(II) perchlorate complex showed no catalytic activity, however, whereas the ytterbium(III) triflate complex led to the formation of racemic cycloadducts. 

We therefore prepared a new chiral ligand, (l ,J )-isopropylidene-2,2 -bis[4-(o-hy-droxybenzyl)oxazoline)], hereafter designated J ,J -BOX/o-HOBn. To our delight, the copper(II) complex catalyst prepared from J ,J -BOX/o-HOBn ligand and Cu(OTf)2 was quite effective (Scheme 7.45). Especially, the reaction of O-benzylhydroxylamine with l-crotonoyl-3-isopropyl-2-imidazolidinone in dichloromethane (0.15 m) at -40°C in the presence of J ,J -BOX/o-HOBn-Cu(OTf)2 (10 mol%) provided the maximum enantioselectivity of 94% ee. 

Jorgensen has recently reported similar enantioselective reactions between N-tosylimines 107 and trimethylsilyldiazomethane (TMSD) catalyzed by chiral Lewis acid complexes (Scheme 1.32) [57, 53]. The cis-aziridine could be obtained in 72% ee with use of a BINAP-copper(i) catalyst, but when a bisoxazoline-copper(i) complex was used the corresponding trans isomer was fonned in 69% ee but with very poor diastereoselectivity. 

Werner s coordination theory, 1, 6 Whewellite structure, 6, 849 Wickmanite structure, 6, 849 Wilkinson s catalyst, 6, 239 Wilson s disease, 5, 721 copper, 6,648 removal, 6,769 copper complexes, 2,959 copper metabolism, 6,766 radiopharmaceutical agents, 6,968 Wolfram s red salt, 5,427 Wurzite... 

Keywords bis(oxazoiine) copper complexes, Lewis-acid catalysts for carbo-cyclic and hefero-Diels-Alder reaction, chiral synthesis... 

The reaction on unactivated halides can also be done with copper halide catalysts (the Hurtley reaction), and with palladium complex catalysts. 

Numerous examples have been pubhshed dealing with the heterogeneization of copper complexes, as immobihzed catalysts for the asymmetric cyclo-propanation of alkenes. Some of them have already been mentioned in the text for a direct comparison with their homogeneous coimterparts. Other reusable catalytic systems have been developed and will be described as follows. 

The use of chiral bis(oxazoline) copper catalysts has also been often reported as an efficient and economic way to perform asymmetric hetero-Diels-Alder reactions of carbonyl compounds and imines with conjugated dienes [81], with the main focus on the application of this methodology towards the preparation of biologically valuable synthons [82]. Only some representative examples are listed below. For example, the copper complex 54 (Scheme 26) has been successfully involved in the catalytic hetero Diels-Alder reaction of a substituted cyclohexadiene with ethyl glyoxylate [83], a key step in the total synthesis of (i )-dihydroactinidiolide (Scheme 30). 

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. 

The reaction used to test these solid catalysts was the aziridination of styrene with AT-tosyliminophenyliodinane (Phi = NTos) (Scheme 10). In most cases, enantioselectivities were low or moderate (up to 60% ee). The loss of enantioselectivity on changing from ligand 11a to ligand 12 was attributed to the fact that ligand 12 is too big for the copper complex to be accommodated into the zeolite supercages. Further studies carried out with hgands 11a and 11b [62] demonstrated that the reaction is more enantioselective with the supported catalyst (82% ee with 11a and 77% ee with 11b) than in solution (54% ee with 11a and 31% ee with 11b). This trend supports the confinement effect of the zeolite structure on the stereoselectivity of the reaction. 

Carbonyl- and imino-ene reactions were also catalyzed by the bis(oxazo-line)-copper complexes of ligands 6a, 6b and 11b supported on zeoHte Y (Scheme 13) [69]. The enantioselectivities obtained with the supported catalysts were similar or better than those obtained in homogeneous phase with the same ligands. Some relevant examples are shown in Table 12. 

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