Carbon-oxygen bonds copper,

Carbon-oxygen bonds are formed by the Ullmann reaction (- coupling of aryl halides with copper) which has been varied in alkaloid chemistry to produce diaryl ethers instead of biaryls. This is achieved by the use of CuO in basic media (T. Kametani, 1969 R.W. Dos-kotch, 1971). 

Catalysts suitable specifically for reduction of carbon-oxygen bonds are based on oxides of copper, zinc and chromium Adkins catalysts). The so-called copper chromite (which is not necessarily a stoichiometric compound) is prepared by thermal decomposition of ammonium chromate and copper nitrate [50]. Its activity and stability is improved if barium nitrate is added before the thermal decomposition [57]. Similarly prepared zinc chromite is suitable for reductions of unsaturated acids and esters to unsaturated alcohols [52]. These catalysts are used specifically for reduction of carbonyl- and carboxyl-containing compounds to alcohols. Aldehydes and ketones are reduced at 150-200° and 100-150 atm, whereas esters and acids require temperatures up to 300° and pressures up to 350 atm. Because such conditions require special equipment and because all reductions achievable with copper chromite catalysts can be accomplished by hydrides and complex hydrides the use of Adkins catalyst in the laboratory is very limited. 

Hydrogenation of phthalic anhydride over copper chromite afforded 82.5% yield of the lactone, phthalide, and 9.8% of o-toluic acid resulting from hydrogenolysis of a carbon-oxygen bond [1015]. Homogeneous hydrogenation of a,a-dimethylsuccinic anhydride over tris(triphenylphos-phine)rhodium chloride gave 65% of a,a-dimethyl- and 7% of )S,)S-dimethyl-butyrolactone [1016]. 

Examples of the transition metal catalyzed formation of carbon-heteroatom bonds other than carbon-nitrogen are less abundant. In a recent survey of the copper catalyzed carbon-oxygen bond formation between alcohols and organotrifluroborates the coupling of 3-thienyltrifluoroborate and 2-furfuryl alcohol gave the expected thienyl-furfuryl-ether in good yield (6.83.),113... 

A new synthesis of olefins involves carbon-oxygen bond cleavage in enol phosphates, e.g. (69), with lithium copper reagents. ... 

Deamination via sulphonamide intermediates allows the conversion of the carbon-nitrogen bond into the carbon-oxygen bond. Conditions have been established such that nitrates may be obtained from the deamination of primary amines with dinitrogen tetroxide at low temperature rather than alcohols/ The oxidation of amines to nitriles has been carried out using copper(l) chloride in pyridine under an oxygen atmosphere/ which is a milder reagent than those previously used to perform this transformation. Cleavage of tertiary amines with ethyl chloroformate affords a simple preparation of di- and tri-substituted olefinic synthons (Scheme... 

Mixed oxide methanol synthesis catalysts containing copper are very selective and the selectivity of the conversion of carbon oxides to methanol exceeds 99%. This is simply explained because there is no sphtting of carbon-oxygen bonds when carbon oxides are adsorbed on the copper surface. 

Organomagnesiums frequently prove superior also in other types of reactions. They may facilitate the oxidation of a carbon-metal to a carbon-oxygen bond, secure clean monoaddition of an acetylide to an activated ester (a critical issue in a monensin synthesis X favor in the presence of a copper catalyst 1,4-addition onto a conjugated enone over 1,2-addition, reorient the attack of formaldehyde on a benzylic entitiy from the a- to the or /to-position, and provide diastereoselectivity in nucleophilic additions onto aldehydes. Furthermore organomagnesiums combine under carbon-carbon linking with a variety of organic halides, tosylates, and acetates if the process is mediated by transition elements such as palladium(O) copper(I), nickel(II) or iron(II) Organoalkalis are often less fit to enter such catalytic cycles. 

The copper catalyzed carbon-heteroatom bond forming reactions are also efficient in the introduction of oxygen and phosphorous based substitutents onto the aromatic ring. 3-Iodopyridine was reacted with -butanol in the presence of 10 mol% copper(I) iodide and 20 mol% 1,10-phenantroline... 

The scope of the copper promoted nucleophilic displacement reactions on heterocyclic systems is not limited to nitrogen, oxygen and phosphorous nucleophiles. Buchwald and co-workers demonstrated that the same catalyst system that is efficient in carbon-phosphorous bond formation is also the... 

In phosphine and arsine complexes of the type LM(diketonate) (M = Ag, Au) and CuL2(dike-tonate), t]2 oxygen bonded diketonate ligands occur in the copper(I) and silver(I) derivatives but the gold(I) analogues feature the jj, carbon bonded form.483... 

Oxidative coupling of a terminal alkyne is a particularly easily performed carbon-carbon bond forming reaction, which results in a good yield of the symmetrical diacetylene. A widely used procedure involves the oxidation of the alkyne with air or oxygen in aqueous ammonium chloride in the presence of a copper(i) chloride catalyst (Glaser oxidative coupling). 

This reaction allows aryl carbon-heteroatom bond formation via an oxidative coupling of arylboronic acids, stannanes or siloxanes with N-H or O-H containing compounds in air. Substrates include phenols, amines, anilines, amides, imides, ureas, carbamates, and sulfonamides. The reaction is induced by a stoichiometric amount of copper(II) or a catalytic amount of copper catalyst which is reoxidized by atmospheric oxygen. 

Table I. Carbon-nitrogen (C-N), carbon-oxygen (C=0), and nitrogen-copper (N-Cu) bond-lengths (in A) for Cu5-N(CHO)2...

Fluorovinylcopper reagents are prepared by metathesis reactions, and the corresponding zinc or cadmium species are the most convenient metalated precursors, e.g. formation of 1. Note that attempted insertion of copper metal into the vinyl carbon — halogen bond fails to afford the fluorovinylcopper reagent and instead a dimerization reaction occurs.Fluorovinylcopper reagents exhibit excellent thermal stability in the absence of oxygen or moisture. The thermal... 

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