Copper-catalysts, arylation

Aryl selenides (ArSeAr and ArSeAr ) can be prepared by similar methodology. Symmetrical diaryl selenides were prepared by the reaction of iodobenzene with diphenyl diselenide (PhSeSePh), in the presence of Mg and a copper catalyst. Aryl halides react with tin selenides (ArSeSnR3), with a copper catalyst, to give the diaryl selenide. OS I, 220 III, 86, 239, 667 V, 107, 474 VI, 558, 824. Also see, OS V, 977. 

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 new comparison of the copper and nickel catalysts (Fig. 12) on the arylation of alcohols, using potassium carbonate as base, shows once again the superiority of the nickel catalyst (70 % against 40 % for the copper catalyst). 

In connexion with the arylation of hard nucleophiles, it was interesting to reinvestigate the hydrolysis of arylhalides in presence of copper catalysts, which is in fact the arylation of hydroxide anion and represents an important industrial challenge (eqn. 2). 

This reaction is similar to 13-1 and, like that one, generally requires activated substrates. With unactivated substrates, side reactions predominate, though aryl methyl ethers have been prepared from unactivated chlorides by treatment with MeO in HMPA. This reaction gives better yields than 13-1 and is used more often. A good solvent is liquid ammonia. The compound NaOMe reacted with o- and p-fluoronitrobenzenes 10 times faster in NH3 at — 70°C than in MeOH. Phase-transfer catalysis has also been used. The reaction of 4-iodotoluene and 3,4-dimethylphenol, in the presence of a copper catalyst and cesium carbonate, gave the diaryl ether (Ar—O—Ar ). Alcohols were coupled with aryl halides in the presence of palladium catalysts to give the Ar—O—R ether. Nickel catalysts have also been used. ... 

Tributylstannyl)-3-cyclobutene-1,2-diones and 4-methyl-3-(tributylstan-nyl)-3-cyclobutene-l,2-dione 2-ethylene acetals undergo the palladium/copper-catalyzed cross coupling with acyl halides, and palladium-catalyzed carbon-ylative cross coupling with aryl/heteroaryl iodides [45]. The coupling reaction of alkenyl (phenyl )iodonium triflates is also performed by a palladium/copper catalyst [46],... 

Arylations of amines and nitrogen-containing heterocycles require the presence of a copper catalyst, usually 10% copper(ll) acetate. For example, the reaction of 4-MeC6H4Pb(OAc)3 with the benzimidazole 20 affords the arylation product 21 in 98% yield.39 40 Similarly, the arylation of the amino groups of heteroaromatic compounds 22 and 23 gives rise to the corresponding products 24a and 25 in good to excellent yields (Equations (7)-(9)).41 42... 

Arylation of activated double bonds with diazonium salts in the presence of copper catalysts is known as the Meerwin reaction. The reaction is postulated to either proceed through an organocopper intermediate or through a chlorine atom transfer from chiral CuCl complex to the a-acyl radical intermediate. Brunner and Doyle carried out the addition of mesityldiazonium tetrafluoroborate with methyl acrylate using catalytic amounts of a Cu(I)-bisoxazoline ligand complex and were able to obtain 19.5% ee for the product (data not shown) [79]. Since the mechanism of the Meerwin reaction is unclear, it is difficult to rationalize the low ee s obtained and to plan for further modifications. 

S)-(-)-CITRONELLOL from geraniol. An asymmetrically catalyzed Diels-Alder reaction is used to prepare (1 R)-1,3,4-TRIMETHYL-3-C YCLOHEXENE-1 -CARBOXALDEHYDE with an (acyloxy)borane complex derived from L-(+)-tartaric acid as the catalyst. A high-yield procedure for the rearrangement of epoxides to carbonyl compounds catalyzed by METHYLALUMINUM BIS(4-BROMO-2,6-DI-tert-BUTYLPHENOXIDE) is demonstrated with a preparation of DIPHENYL-ACETALDEHYDE from stilbene oxide. A palladium/copper catalyst system is used to prepare (Z)-2-BROMO-5-(TRIMETHYLSILYL)-2-PENTEN-4-YNOIC ACID ETHYL ESTER. The coupling of vinyl and aryl halides with acetylenes is a powerful carbon-carbon bond-forming reaction, particularly valuable for the construction of such enyne systems. 

Enantioselective conjugate addition [40] has become truly useful with the aid of dialkylzinc, cationic copper catalyst, and a chiral ligand (Eq. 1, see also Chapt. 7) [41]. Magnesium-based reagents have found use in quantitative fivefold arylation of Cgo (Eq. 10.2) [42] and threefold arylation of C70 [43], paving ways to new classes of cyclopentadienyl and indenyl ligands with unusual chemical properties. 

It is well established that metallic copper or copper salts efficiently catalyze N- and O-arylation reaction using pentavalent and trivalent organobismuth compounds [5-9, 24]. The C-arylation reaction of phenols and active methylene compounds using pentavalent organobismuth compounds are usually mediated by a base. However, in some cases, copper catalysts mediate C-arylation using pentavalent organobismuth compounds. 

Scheme 9 showed a convenient way to directly prepare N-arylated dihydrobenzoxazines 148-151 from 2-(2-aminoethoxy)chlorobenzene 147 using a soluble palladium catalyst <2004S2527>. A copper catalyst was used in the cyclization of 279 to give 248 (Equation 25). The reaction was also performed on derivatives with different substituents on the nitrogen and the two aryl rings and the yields range from 30% to 60% <2005JOC1679>. 

The coupling of aryl halides and classical carbon nucleophiles, such as malonates, is also feasible in the presence of a properly selected palladium or copper catalyst. Diethyl malonate and 3-iodopyridine, for example, gave diethyl 2-(3 -pyridyl)malonate in 73% yield (7.84.), The optimal catalyst in this process consisted of copper(I) iodide and 2-hydroxylbiphenyl.106... 

Another series of monomers that was prepared began with the displacement of an unactivated aryl halide with phenate anion in the presence of a copper catalyst [113-115], Figure 46 outlines the basic route followed for the preparation of 114a. The sequence of reactions started with 4-bromobenzocyclobu-tene, 2 which was reacted with the phenate of p-acetamidophenol, 112a in the presence of copper (I) chloride as a catalyst, to afford the ether linked product 113a in a yield of 50-75%. 

The addition of Grignard reagents or organolithiums (alkenyl, alkyl, alkynyl, allyl or aryl) to nitroenamines (281)213 was reported by Severin to afford P-substituted-a-nitroalkenes.214 b Similarly, ketone enolates (sodium or potassium), ester enolates (lithium) and lactone enolates (lithium) react to afford acr-nitroethylidene salts (294) which, on hydrolysis with either silica gel or dilute acid, afford 7-keto-a,(3-unsaturated esters or ketones (295)2l4c-d or acylidene lactones (296).214 Alternatively, the salts (294, X s CH2) can be converted to -y-ketoketones (297) with ascorbic acid and copper catalyst. 

Cross-coupling reactions 5-alkenylboron boron compounds, 9, 208 with alkenylpalladium(II) complexes, 8, 280 5-alkylboron boron, 9, 206 in alkyne C-H activations, 10, 157 5-alkynylboron compounds, 9, 212 5-allylboron compounds, 9, 212 allystannanes, 3, 840 for aryl and alkenyl ethers via copper catalysts, 10, 650 via palladium catalysts, 10, 654 5-arylboron boron compounds, 9, 208 with bis(alkoxide)titanium alkyne complexes, 4, 276 carbonyls and imines, 11, 66 in catalytic C-F activation, 1, 737, 1, 748 for C-C bond formation Cadiot-Chodkiewicz reaction, 11, 19 Hiyama reaction, 11, 23 Kumada-Tamao-Corriu reaction, 11, 20 via Migita-Kosugi-Stille reaction, 11, 12 Negishi coupling, 11, 27 overview, 11, 1-37 via Suzuki-Miyaura reaction, 11, 2 terminal alkyne reactions, 11, 15 for C-H activation, 10, 116-117 for C-N bonds via amination, 10, 706 diborons, 9, 167... 

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. 

The reaction was made catalytic when a suitable oxidant of Cu(i) species was used. In the presence of catalytic amount of copper salt, aryl- (Equation (230)) and alkenylboronic acids (Equation (231)) smoothly reacted with A-nucleophiles, such as imidazoles, at room temperature.1012,1013,1015,1017,1018 TEMPO, pyridine A-oxide, oxygen were effective reoxidants to recycle the copper catalyst. 

The unsubstituted 1,2-dihydroquinolin-2-one 90 afforded good yields of the W-arylation product, but the presence of a methoxy group on the ortho-position relative to the nitrogen atom reduced considerably the yields of the iV-arylation products (Equations (96)—(98)). In the absence of a copper catalyst, the C-3-aryl derivative was the only formed product.115... 

In the presence or absence of a copper catalyst, O-arylation of alcohols and phenols by Ph3Bi(OAc)2 proceeds to give the corresponding aryl ethers.196-198 The monophenylation of m-l,2-cyclopentanediol with Ph3Bi(OAc)2 in the presence of a Cu(n) complex bearing a chiral triamine or diamine ligand affords an a-hydroxy phenyl ether with moderate enantiomeric excesses up to 38% (Equation (127)).199 The copper-catalyzed O-arylation has been success-fully applied to the synthesis of immunosuppressive macrolides. 

Direct synthesis is the reaction of alkyl or aryl chloride and silicon in the presence of a proper catalyst. Mostly, methyl chloride is snbjected to the reaction at 250 350 °C in a flnid bed with fine particles of silicon mixed with a copper catalyst (eqnation 2). ... 

The reactivity of 6-haloimidazol[l,2-a]pyridine 135 towards different azoles can be modulated to give ipso product 136 in the presence of copper(l) catalyst or to yield cine product 137 in the absence of copper catalyst <03JOC5614>. Imidazo[l,2-a]pyrimidine 138 can be arylated at the 3-posltion with aryl bromides in the presence of cesium carbonate with catalytic palladium(II) acetate to give 139 <03OL4835>. 

Pd2(DBA)3/BINAP system (DBA = dibenzylideneacetone BINAP = 2,2-bis(diphenyl-phosphanyl)-l,1-binaphthyl). Best results were obtained using electron-deficient aryl bromides. Aryl chlorides of any type, however, failed to react under these conditions. The aryl-aziridine coupling reaction could also be carried out with arylboronic acids using a copper catalyst (Scheme 55) <2003JOC2045>. 

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