Copper-catalysed reactions

Terminal alkynes are converted in high yield (70-80%) into 1-iodoalkynes by their copper-catalysed reaction with iodine under phase-transfer catalytic conditions... 

As Ph2S is a better leaving group that Me2S, the diphenylsulfonium salt is expected to be more reactive. Tlie same trend was observed in the just described copper-catalysed reaction of sulfonium ylides with alkenes (see Section 4.4.1). 

Copper catalysed reaction of these two, under pressure, demonstrated potential for explosion when increased beyond low gram scale. Excess nitrile was in use as solvent, and the desired reaction is reported as very exothermic ( 3 kJ/g of reagent mix). 

Similarly to methyl- and ethylchlorosilanes, the process of phenylchlorosi-lane production by the copper-catalysed reaction of chlorobenzene and silicon is very complex. Unlike the processes mentioned, the direct synthesis of phenylchlorosilanes is carried out at higher temperatures (500-650 °C, depending on the activity of contact mass), which is largely due to the high temperature of chlorobenzene dissociation. 

The yield of a subsequent copper-catalysed reaction with 2-cyclohexenone was 81%. 

Rearrangement processes of alkyltitanocene dichlorides that occur under electron impact have been investigated using deuterium labelling. A novel type of zirconium-mediated coupling reaction of alkynes with vinyl bromide to afford 2,3-disubstituted dienes has been reported (see Scheme 105), and an inter-intramolecular reaction sequence has been proposed for the observed formation of vinylcyclohexadienes and/or methylenecycloheptadienes from the copper-catalysed reaction of zirconacyclo-pentadienes with allylic dichlorides. The essential step in these processes appears to be transmetallation of the zirconium-carbon bond of the zirconacyclopentadiene to produce a more reactive copper-carbon bond. New phosphorus heterocycles, e.g. (417), have been constructed by the thermal rearrangement of a [l,4-bis(trimethylsilyl)->/ -cyclooctatetraene]- ,3,5-triphospha-7-hafhanorbomadiene complex (416). 

In contrast to silver-catalysed cumene oxidation, the evidence concerning the mechanism of copper-catalysed reactions favours radical initiation via surface hydroperoxide decomposition. Gorokhovatsky has shown that the rate of ethyl benzene oxidation responds to changes in the amount of copper(ii) oxide catalyst used, in a manner which is characteristic of this mechanism. Allara and Roberts have studied the oxidation of hexadecane over copper catalysts treated in various ways to produce different surface oxide species, Depending on the catalyst surface area and surface oxide species present, a certain critical hydroperoxide concentration was necessary in order to produce a catalytic reaction. At lower hydroperoxide levels, the reaction was inhibited by the oxidized copper surface. XPS surface analysis of the copper catalysts showed a... 

This type of copper-catalysed reaction was also extended to the alkynylation of alkenyldiiodonium salts (48), through reaction with lithium alkynyl cuprates. 

Pyrrole and indole derived reagents also reacted with vinyliodonium subtrates in copper catalysed reactions. 

The mono-O-phenylation reaction of glycols discovered by David and Thieffry presents some characteristic features which are not compatible with the postulated covalent bismuth intermediate. (see section 6.3.2) The reaction is solvent-selective (methylene dichloride under reflux), light-catalysed (no reaction in the dark), and presents an induction period (2 hours in the case of the phenylation of 2,2-dimethylpropan-l,3-diol). Addition of small amounts of copper diacetate had a marked effect on the reaction. The reaction became fast reaction times can be as short as 15 minutes. Moreover, the copper-catalysed reaction is no more solvent selective nor light-catalysed. ... 

When the copper-catalysed reactions (type A and type B) were performed in the cavity of an ESR spectrometer, the presence of phenyl radicals was detected by way of their spin adducts with 2-methyl-2-nitrosopropane and with 2,4,6-tribromonitrosobenzene.98 In view of these observations, Dodonov et al. suggested that a free-radical mechanism was involved in both reaction types, A and B, and explained the formation of the hypervalent copper (HI) intermediate. (Scheme 6.23) The copper (HI) intermediate is formed by two consecutive one-electron oxido-reduction elementary steps. The copper (1) catalytic species is first oxidised to a copper(Il) species which is then oxidised by a phenyl rascal to the active copper (HI) intermediate. This hypervalent species then undergoes a ligand coupling reaction with the substrate, either hydroxylic or an amino derivative. In the type B reaction, the in situ generated phenylcopper (III) diacetate reacts with the substrate to eventually afford the O- or the iV-phenyl derivative. 

The efficiency of the arylation is very dependent upon the basicity of the amines. Electron-poor anilines do not react, while electron-rich anilines give high yields of -arylation products. However, in the case of easily oxidised anilines, oxido-reduction of the aryllead reagent can compete with the 7V-arylation when the steric compression becomes too important. For example, in the case of mesitylamine (101), the copper-catalysed reaction with a variety of substituted phenyllead derivatives led to generally high yields of the diarylamines. 

The copper-catalysed reactions are not so well developed but aryl bromides combine with primary amines catalysed by Cu(I) using the salicylamide ligand 115. Free OH groups are tolerated in either partner the amine or the aryl halide.33... 

The cyclisation of nitrones derived from tryptamines is a similar process and can be carried out enanti-oselectively using a chiral Lewis acid."° A similar enantioselective intermolecular process is the copper-catalysed reaction of indoles with tosyl-imines of aromatic aldehydes. "... 

Indolyl A-Grignards, "" or even better their zinc analogues, undergo reaction predominantly at C-3 with a variety of carbon electrophiles such as aldehydes, ketones and acid halides, or reactive halo-hetero-cycles. Including aluminium chloride in the zinc reactions produces high yields of 3-acyl-indoles. The copper-catalysed reactions of indolyl-A-Grignards with A-t-butoxycarbonyl-aziridines also proceed well at C-3. ... 

Oxidation.— Two copper-catalysed reactions have been described for the degradation of the 22-aldehyde (298) to give a pregnan-20-one (299). Oxygenation of a solution of the aldehyde with the copper(n) acetate-2,2 -bipyridyl complex and diazabicyclo-octane in dimethylformamide gave the 20-ketone in 90% yield. A free-radical mechanism is proposed (Scheme 14). 

Palladium-catalysed reactions (also nickel- and copper-catalysed reactions)... 

Synthesis of dideuteriomethylene hydrocarbons by copper catalysed reaction of Grignard reagents... 

Thus in this case the catalytic reaction involves the anionic -form o f the nitroalkaneI which in general undergoes reactions at the metal centre di-f-ferent than those observed with the nitro derivatives in their neutral -form (3.2.) However it is interesting to point out the similarity between the probable intermediate formed during the deoxygenation reactions o-f nitro compounds by carbon monoxide <3.2.1.), and the intermediate which should lead to the oxime in the copper-catalysed reactions ... 

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