Cupric carbonyl derivatives

Carbonyl cuprous sulphate.—On decolorizing an aqueous solution of cupric sulphate with carbon monoxide, and evaporating in an atmosphere of this gas, a solid complex salt was obtained by Joannis.12 He ascribed to it the formula (Cu-C0)2S04,H20. The great instability of the product is indicated by its decomposition by water into copper and cupric sulphate. In its constitution this compound resembles the carbonyl derivatives of the copper halides, the proportion of carbon monoxide to copper in its molecule being in the ratio of one molecule to one atom. 

The arylation of alkenes by treatment with a diazonium chloride (or bromide) solution and cupric chloride (or bromide) is called the Meerwein arylation reaction, after its discoverer (Meerwein et al., 1939). Originally, it was discovered using a,P-unsaturated carbonyl compounds, namely coumarin (Scheme 10-43) and cinnamic derivatives (Schemes 10-44 and 10-45). As Scheme 10-45 shows, the Meerwein reac-... 

Copper salts, cupric or cuprous also will catalyze the carbonylation of amines. Piperidine, for example, gives a urea derivative with carbon monoxide, and it, too, is probably a metal amide—carbon monoxide insertion reaction. 

In this section, consideration will be given to the actual processes of acetal- or ketal-formation and not to the more indirect methods by which acetals and ketals of the polyhydric alcohols may be synthesized from compounds (e.g. derivatives of the monosaccharides) containing preformed alkylidene or arylidene groupings. The condensation of a carbonyl compound with a glycol is facilitated by acidic catalysts, and, since the reaction is reversible, by dehydration. The catalysts most frequently employed are concentrated sulfuric, hydrochloric and hydro-bromic acids, gaseous hydrogen chloride, zinc chloride and cupric sulfate others are phosphorus pentoxide, sulfosalicylic acid, and anhydrous sodium sulfate. The formation of benzylidene compounds is promoted less efficiently by phosphorus pentoxide than by either concentrated sulfuric acid or concentrated hydrochloric acid 1" the reaction is assisted by chloro- and nitro-substituents on the aromatic nucleus, but hindered by methyl- and methoxy-groups.18... 

Corey and coworkers have outlined the wide usefulness of N.N-dimethvl hydrazones (DMH) in synthesis.25-9 The parent carbonyl compounds can be regenerated by oxidative hydrolysis via periodate at pH 7 or with the very mild cupric acetate in water-THF. Metallation of these hydrazones selectively occurs at the less alkylated carbon. Alkylation occurred axially in the cyclohexane derivatives studied. Quenching of the metallated DMH s... 

The mechanistic details of these laccase/mediator catalyzed aerobic oxidations are still a matter of conjecture (51-54). However, experiments with a probe alcohol point towards one-electron oxidation of the mediator by the oxidized (cupric) form of the laccase followed by reaction of the oxidized mediator with the substrate, either via electron transfer (ET), e.g., with ABTS, or via hydrogen atom transfer (HAT), e.g., with N-hydroxy compounds which form N-oxy radicals (55). TEMPO and its derivatives form a unique case one-electron oxidation of TEMPO affords the oxoammonium cation which oxidizes the alcohol via a heterolytic pathway (Fig. 6), giving the carbonyl product and the hydroxylamine. The Tl copper center in fungal laccases has a redox potential of ca. 0.8 V vs. NHE. Consequently, fungal laccases can easily oxidize TEMPO to the corresponding oxoammonium cation, since the oxidation potential of the latter, which was first measured by Golubev and co-workers (55,57), is 0.75 V. This was confirmed by EPR measurements, which showed that laccase is reduced in the presence of TEMPO One equivalent of laccase could oxidize at least three equivalents of TEMPO within a few minutes under anaerobic conditions (58). 

Palladous chloride j cupric chloride j sodium chloride p-Acoxycarboxylic acid anhydrides from ethylene derivs. Oxidative carbonylation... 

The increasing use of oximes and hydrazones as intermediates in the regio-selective modification of carbonyl compounds has led to an upsurge of interest in seeking mild, specific methods for regeneration of the carbonyl function from these derivatives. AjV-Dimethylhydrazones are hydrolysed rapidly under cupric ion... 

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