Copper catalysis oxidative coupling

The synthesis of phosphino sulfoximine 97 relied significantly on the successful development of methods pursued in parallel in our group. Whereas palladium-catalyzed cross-couplings between 53 and 98 proceeded in low yield, the copper catalysis with a combination of copper(l) iodide and cesium acetate worked well, affording 99 in up to 83% yield [78]. The resulting phosphine oxides 99 were then reduced to the corresponding phosphines 97 using a mixture of trichlorosilane and triethylamine (Scheme 2.1.1.33). 

BINOL and its derivatives have been utilized as versatile chiral sources for asymmetric catalysis, and efficient catalysts for their syntheses are, ultimately, required in many chemical fields [39-42]. The oxidative coupling of 2-naphthols is a direct synthesis of BINOL derivatives [43, 44], and some transition metals such as copper [45, 46], iron [46, 47] and manganese [48] are known as active metals for the reaction. However, few studies on homogeneous metal complexes have been reported for the asymmetric coupling of 2-naphthols [49-56]. The chiral self-dimerized V dimers on Si02 is the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol. 

Oxidative coupling polymerization provides great utility for the synthesis of high-performance polymers. Oxidative polymerization is also observed in vivo as important biosynthetic processes that, when catalyzed by metalloenzymes, proceed smoothly under an air atmosphere at room temperature. For example, lignin, which composes 30% of wood tissue, is produced by the oxidative polymerization of coniferyl alcohol catalyzed by laccase, an enzyme containing a copper complex as a reactive center. Tyrosine is an a-amino acid and is oxidatively polymerized by tyrosinase (Cu enzyme) to melanin, the black pigment in animals. These reactions proceed efficiently at room temperature in the presence of 02 by means of catalysis by metalloenzymes. Oxidative polymerization is observed in vivo as an important biosynthetic process that proceeds efficiently by oxidases. 

A number of syntheses of di- and polyacetylenes has been reported. 1-Iodo-l-alkynes couple with terminal acetylenes under palladium-copper catalysis to give 1,3-diynes thus y-iodopropargyl alcohol and phenylacetylene afford compound 30. Oxidative coupling of 1 -alkynes to yield symmetrical 1,3-diynes is brought about by air and copper(I) chloride in the presence of N, A -tetramethylethylenediamine (equation Trialkylsilyl sub-... 

Oxidative addition of alkenyl halides, triflates, and other esters to zerovalent palladium compounds has been long known as a viable route to palladium(ii)-alkenyl complexes. Stereospecific coupling reactions involving mono- and (E)- or (Z)-dihalo-alkenes with palladium-copper catalysis under modified Sonogashira conditions are quite versatile and useful. These proceed through oxidative addition of the alkenyl halide via palladium(ii) alkenyl complexes, followed by coupling with a nucleophile (usually an alkynylcopper reagent obtained in situ with co-catalytic copper(i) from terminal alkynes in the presence of, in this case, a base like piperidine instead of diethylamine). ... 

In the same year, Chi et al. developed an enantioselective oxidative coupling of tertiary amines with ahphatic aldehydes by combination of copper catalysis and aminocatalysis (Scheme 2.6) [31]. Both A -Aryl tetrohydroisoquinolines and simple A-Aryl tertiary amines can undergo this enantioselective alkylation reaction. Soon afterwards, organocatalytic enantioselective CDC reaction of ethers with aliphatic aldehydes [32] and Cu-catalyzed asymmetric CDC reaction of iV-carbamoyl tetrahydroisoquinohnes with terminal alkynes [33] were reported. 

Similar transformations are described by Schreiber and Duan (see Scheme 16.5, (2-4)) where N-nucleophiles are coupled under oxidative conditions via copper catalysis. The protocols are applicable to not only sec-ondaiy amines but also cyclic secondaiy amides, primary amides and sulfonamides or via decarbojgrlative coupling with formamides under acidic... 

Somewhat related to cross-coupling reactions, the carbomagnesiation of terminal alkenes was shown to proceed efficiently in the presence of [(IMes)AgCl] and 1,2-dibromoethane, which was used as an oxidant. The hydroboration of terminal alkynes was also achieved using [(NHC)Ag] catalysts, and with higher regioselectivity compared to copper catalysis conditions. 

Intramolecular carbon-nitrogen bond formation may result from the Ullmann coupling of l,3-bis(2-iodoaryl)propan-2-amines catalysed by copper. Using (i )-BINOL, l,l -Bi-2-naphthol, ligands, the enantioselective formation of indolines and 1,2,3,4-tetrahydroquinolines was achieved. Copper catalysis has also been used in the intramolecular formation of imidazobenzimidazole derivatives. The reaction is likely to involve the formation of intermediates, such as (16), which on aerobic oxidation yield the product. There is evidence for an intramolecular 0- -N Smiles rearrangement, as... 

So-called blue multinuclear copper oxidase enzymes, such as laccase and ascorbate oxidase, catalyze the stepwise oxidation of organic substrates (most likely in successive one-electron steps) in tandem with the four-electron reduction of O2 to water, i.e. no oxygen atom(s) from O2 are incorporated into the substrate (Eq. 4) [15]. Catechol oxidase, containing a type 3 center, mediates a two-electron substrate oxidation (o-diphenols to o-chinones), and turnover of two substrate molecules is coupled to the reduction of O2 to water [34,35]. The non-blue copper oxidases, e.g. galactose oxidase and amine oxidases [27,56-59], perform similar oxidation catalysis at a mononuclear type 2 Cu site, but H2O2 is produced from O2 instead of H2O, in a two-electron reduction. 

This section reports a series of examples of application of the cluster model approach to problems in chemisorption and catalysis. The first examples concern rather simple surface science systems such as the interaction of CO on metallic and bimetallic surfaces. The mechanism of H2 dissociation on bimetallic PdCu catalysts is discussed to illustrate the cluster model approach to a simple catalytic system. Next, we show how the cluster model can be used to gain insight into the understanding of promotion in catalysis using the activation of CO2 promoted by alkali metals as a key example. The oxidation of methanol to formaldehyde and the catalytic coupling of prop)me to benzene on copper surfaces constitute examples of more complex catalytic reactions. 

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