Copper aryls

A distorted butterfly CU4 unit with Cu-Cu distances less than 240 pm is found for (4-methyl-2-cupriobenzyl)dimethylamine tetramers . Copper aryl complexes stabilized by the amine nitrogen lone pair are prepared from CuBr and the appropriate aryllithium reagent in ether in 40-60% yields... 

Cyclohexylisocyanide insertion in copper-aryl bond gives arylimino derivatives. ... 

Nickel, palladium and copper catalysts can effect a variety of C — C bond-forming reactions P to the ester carbonyl via j8-zinc esters. These include 1,4-addition to a,jS-unsaturated carbonyl compounds (copper), arylation with aryl halides (palladium, nickel), allylation with allyl chloride (copper), and acylation with acyl chlorides (palladium, copper). " ... 

It has been speculated that the mechanism of copper-mediated (stoichiometric in copper) arylations of phenols involves the following elemental steps (i) transmetal-lation of Cu(II) with the arylboronic acid (ii) coordination of the phenol nucleophile to copper(II) and (iii) reductive elimination, slowly via the Cu(II) species or via air oxidation to the Cu(III) species which can be expected to undergo reductive eUmination more rapidly, thereby regenerating a potentially catalyticaUy active copper(I) species (Scheme 4.2). A plausible catalytic mechanism (not illustrating the potential role of substrates as copper ligands) is also shown. 

Gnrski, A. and Liebeskind, L. S. 1993. A new process for the regiocontrolled synthesis of sub-stitnted catechols and other 1,2-dioxygenated aromatics Conjugate addition of vinyl-copper, aryl-copper, and heteroarylcopper reagents to cyclobutenediones followed by thermal rearrangement. J. Am. Chem. Soc. 115 6101-6108. 

Copper-mediated arylation of various nucleophilic groups, including phenols, anilines and thiophenols, with boronic acids has been reported by several groups (Scheme 2.178) As an organometallic species is used as the aryl donor, the copper(II) acts as a net oxidant, and must be used stoichiometrically. Inclusion of an oxidant, such as molecular oxygen as in the Wacker reaction (Section 6.1) can allow a system that is catalytic in copper. Aryl trifluoroborates have also been used as the aryl donor. ... 

Ullman reaction The synthesis of diaryls by the condensation of aromatic halides with themselves or other aromatic halides, with the concomitant removal of halogens by a metal, e.g. copper powder thus bromobenzene gives diphenyl. The reaction may be extended to the preparation of diaryl ethers and diaryl thio-ethers by coupling a metal phenolate with an aryl halide. 

An interesting reaetion, which is particularly valuable for the preparation of diphenyl derivatives, consists in heating copper powder or, better, copper bronze with an aryl halide (Ullmann reaction), for example ... 

The alkyl- or aryl-halogenosilanes are prepared commercially by passing the vapour of an alkyl or an aryl halide over a heated intimate mixture of powdered sihcoii and either copper or silver. 

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). 

The oxidative coupling of toluene using Pd(OAc)2 via />-tolylmercury(II) acetate (428) forms bitolyl[384]. The aryl-aryl coupling proceeds with copper and a catalytic amount of PdCl2 in pyridine[385]. Conjugated dienes are obtained by the coupling of alkenylmercury(II) chlorides[386]. 

Arylation or alkenylation of soft carbon nucleophiles such as malonate is carried out by using a copper catalyst, but it is not a smooth reaction. The reaction of malononitrile, cyanoacetate, and phenylsulfonylacetonitrile with aryl iodide is possible by using a Pd catalyst to give the coupling products. 

A key step in the reaction mechanism appears to be nucleophilic attack on the alkyl halide by the negatively charged copper atom but the details of the mechanism are not well understood Indeed there is probably more than one mechanism by which cuprates react with organic halogen compounds Vinyl halides and aryl halides are known to be very unreactive toward nucleophilic attack yet react with lithium dialkylcuprates... 

Although It IS possible to prepare aryl chlorides and aryl bromides by electrophilic aromatic substitution it is often necessary to prepare these compounds from an aromatic amine The amine is converted to the corresponding diazonmm salt and then treated with copper(I) chloride or copper(I) bromide as appropriate... 

Diazotization of a primary arylamine followed by treatment of the diazo mum salt with copper(l) bromide or copper(l) chloride yields the corre spending aryl bromide or aryl chloride... 

Aromatic perfluoroaLkylation can be effected by fluorinated aUphatics via different techniques. One category features copper-assisted coupling of aryl hahdes with perfluoroalkyl iodides (eg, CF I) (111,112) or difluoromethane derivatives such as CF2Br2 (Burton s reagent) (113,114), as well as electrochemical trifluoromethylation using CF Br with a sacrificial copper anode (115). Extmsion of spacer groups attached to the fluoroalkyl moiety, eg,... 

Decafluorobiphenyl [434-90-2] C F C F (mol wt, 334.1 mp, 68°C bp, 206°C), can be prepared by I Jllmann coupling of bromo- [344-04-7] chloro- [344-07-0] or iodopentafluorobenzene [827-15-6] with copper. This product shows good thermal stabiHty decafluorobiphenyl was recovered unchanged after 1 h below 575°C (270). Decafluorobiphenyl-based derivatives exhibit greater oxidative stabiHty than similar hydrocarbon compounds (271). Therm ally stable poly(fluorinated aryl ether) oligomers prepared from decafluorobiphenyl and bisphenols show low dielectric constant and moisture absorption which are attractive for electronic appHcations (272). 

Similarly, hydantoins can be arylated at N-3. For example, treatment of 5,5-diphenyIhydantoin (4), R = R = Cg (phenytoin), with -tolyUead triacetate in the presence of sodium hydride and a catalytic amount of copper(II) acetate (37) gives compound (7). 

Several types of nitrogen substituents occur in known dye stmetures. The most useful are the acid-substituted alkyl N-substituents such as sulfopropyl, which provide desirable solubiUty and adsorption characteristics for practical cyanine and merocyanine sensitizers. Patents in this area are numerous. Other types of substituents include N-aryl groups, heterocycHc substituents, and complexes of dye bases with metal ions (iridium, platinum, zinc, copper, nickel). Heteroatom substituents directly bonded to nitrogen (N—O, N—NR2, N—OR) provide photochemically reactive dyes. 

Catalysts (eg, copper salts) may help with aryl haUdes of lower activity, but amination of chloroben2ene and l,4-dichloroben2ene is generally not... 

This synthesis is only one example of a wide range of reactions which involve aryl (or alkyl) radical addition to electron-deficient double bonds resulting in reduction.The corresponding oxidative reaction using aryl radicals is the well known Meerwein reaction, which uses copper(II) salts. 

Copper-mediated coupling of the aryl iodide derived from l,3-bis(2-hydroxy-hexafluoroisopropyl)benzene with perfluorooctyl iodide gives the desired compound as a dimethyl sulfoxide (DMSO) complex [166] (equation 143) Even bromoarenes can be coupled [167] (equation 144)... 

Ullman type coupling occurs between aryl halides and trifluoromethyl copper species generated by the action of copper iodide on sodium tnfluoroacetate [168, 169] or on methyl fluorosulfonyldifluoroacetate [170] (equation 145) Similarly the pentafluoroethyl group can be introduced from potassium pentafluoropropion-ate [171] (equation 146)... 

The mtroducuon of a tnfluoromethanethio group into an aromatic nng has a synthetic importance The reaction of tnfluoromethanethio copper with aryl bro mides and iodides provides a convenient route to the synthesis of aryltn fluoromethane sulfides The reaction is not sensitive to the type of substituents or the aromahc nucleus Selectivity can be achieved accordmg to the type of halogen or the aromatic rmg, because iodides react at lower temperatures than bromides, whereas chlondes do not react [f J] (equation 12) (Table 5)... 

Aryl bromides were also perfluoroethylated under these conditions [205] The key to improved yields was the azeotropic removal of water from the sodium perfluoroalkylcarboxylate [205] Partial success was achieved with sodium hepta-fluorobutyrate [204] Related work with halonaphthalene and anthracenes has been reported [206 207] The main limitation of this sodium perfluoroalkylcarboxylate methodology is the need for 2 to 4 equivalents of the salt to achieve reasonable yields A trifluoromethylcopper solution can be prepared by the reaction of bis(tri-fluoromethyl)mercury with copper powder in /V-methylpyrrolidone (NMP) at 140 °C [208] (equation 138) or by the reaction of N-trifluoromethyl-A-nitro-sotnfluoromethane sulfonamide with activated copper in dipolar aprotic solvents [209] This trifluoromethylcopper solution can be used to trifluoromethylate aro matic [209], benzylic [209], and heterocyclic halides [209]... 

Tnfluorometltylation of aryl, alkenyl, and alkyl halides can be accomplished by heating methyl fluorosulfonyldifluoroacetate and the appropriate halide precursor with copper(I) iodide at 60-80 °C in DMF [27 7] (equation 145). Similar trifluoromethylations of aryl, benzyl, and vinyl halides can be carried out with fluorosulfonyldifluoromethyl iodide and copper metal in DMF at 60-80 °C [2 75] (equation 146). 

The copper species formed depends on the solvent, and three different species were detected by F NMR, although the structure of each species was not elucidated [245 This copper reagent undergoes a variety of coupling reactions with aryl, alkenyl, allyl, and acetylenic halides [244, 245 (equation 162)... 

The perfluoroacetylenic copper compounds undergo coupling reactions with aryl iodides and provide a useful synthetic route to the perfluoroalkyl aryl alkynes [147, 255] (equation 170) Coupling of these copper reagents with the 1-iodo-perfluoroalkynes gives the perfluorodiynes [747 255] (equation 171)... 

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