Reactions Ullmann reaction

Electrochemical methods Oxidative chemical potymerizations Yamamoto coupling Colon coupling Grignaid coupling Wurtz-Fitdg reaction Ullmann reaction Curtis coupiing... 

Yaunner et al. (2012) reported synthesis of piperidinyl pyridines by piperidina-tion of halopyridines under microwave irradiation by Buchwald-Hartwig reaction, Ullmann reaction and nucleophilic aromatic substitution (Sj Ar). A comparative study of these methodologies show that the Ullmann reaction was most effective for less reactive halopyridines, while uncatalyzed Sj Ar was sufficient for more reactive ones. Reaction was carried out at 150°C for about half an hour in ethylene glycol. 

Activated copper bronze. Commercial copper bronze does not always give satisfactory yields in the Ullmann reaction, but uniform results can... 

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 ... 

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). 

An example of the use of copper as a catalyst is Acid Blue 25 [6408-78-2] (Cl 62055) in which l-amino-2-sulfonic-4-bromoanthraquinone is condensed with aniline using copper salts (Ullmann reaction) (314). Another example is oxidation to the tria2ole of Direct YeUow 106 [12222-60-5] (Cl 40300) (315,316). 

Aromatic haUdes do not react easily with phenoxide ions to produce diaryl ethers unless the aromatic haUde is substituted with one or more electron-withdrawing groups, eg, nitro or carboxyl groups. The Ullmann reaction uses finely divided copper or copper salts to cataly2e the reaction of phenoxides with aromatic haUdes to give diaryl ethers. 

An excess of guaiacol is essential. Weston and Adkins have found that the phenol, copper, and air form the active catalyst in the Ullmann reaction. 

An aryl methane- or toluenesulfonate ester is stable to reduction with lithium aluminum hydride, to the acidic conditions used for nitration of an aromatic ring (HN03/H0Ac), and to the high temperatures (200-250°) of an Ullmann reaction. Aryl sulfonate esters, formed by reaction of a phenol with a sulfonyl chloride in pyridine or aqueous sodium hydroxide, are cleaved by warming in aqueous sodium hydroxide. ... 

Limited reports on the mechanism of the Greabe-Ullmann reaction have appeared. A diradical intermediate is presumably involved in the thermolysis of the triazole 4. ... 

The extension of the method to the synthesis of y-carboline from 1-y-pyridylbenztriazole (199) and of a 3,4-benz-y-carboline from a l-(4-quinolyl)benztriazole proceeded smoothly. In an alternative approach excellent yields of y-carboline were obtained by heating l-phenylpyrido[3,4-d] -triazole (200) at 320-350°. The synthesis of halogeno-substituted j8- and y-carbolines via the Graebe-Ullmann reaction has been reported. ... 

Traditionally, the synthesis of symmetrical biaryls was routinely accomplished using the Ullmann reaction. Recently, palladium-catalyzed homocoupling of aryl halides has also been demonstrated to rival the utility of the Ullmann coupling. As illustrated in Scheme 21, using Pd(OAc)2 as the... 

Reduction with zinc dust in aqueous sulfuric acid gives 2-methyl-4-aminothiophenol (28) Condensation with 2-chlorobenzoic acid (Ullmann reaction) leads to 29, which can close to but one thiox-anthone (25) on treatment with sulfuric acid. Although this procedure is longer than the original, the yields are good and the sequence is regioselective. ... 

With alcohols or more often with alcoholates (refs. 51 - 56) or phenolates (refs. 57 - 64) the arylethers are formed. Typically, one of the Ullmann reactions is corresponding to the diarylethers synthesis. 

This scheme is selfexplanatory. Important in the formation of PBDD by Ullmann reaction of brominated phenoxy radicals. Influences of added water, air content and other factors on PBDD/F yield and pattern have also been studied in detail (ref. 11). 

Vinylic halides can be coupled to give 1,3-butadienes by treatment with activated copper powder in a reaction analogous to the Ullmann reaction (13-14). " This reaction is stereospecific, with retention of configuration at both carbons. 

The coupling of aryl halides with copper is called the Ullmann reaction. The reaction is of broad scope and has been used to prepare many symmetrical and... 

An asymmetric Ullmann reaction has also been reported." ... 

Stephen reaction Stobbe condensation Ullmann reaction Willgerodt reaction. ... 

Cul, 12mol% of 2,2 -dipyridyl, in lOvol of xylene diglyme (9 1) at 140°C with azeotropic removal of the water as it was formed. The azeotropic removal of water helped alleviate the problem of solids coating the reaction vessel walls, which led to stalling of the reaction. The reaction was complete in less than lOh, typically with 96% assay yield and 92% isolated yield for 49 after aqueous work-up and subsequent crystallization [14b-d]. It was noteworthy that this catalytic system composed of the copper(I) salt with bipyridyl ligand was recently reported to be applicable to a wide range of Ullmann-type ether formations [14d]. 

Although the copper mediated Ullmann reaction is a well known method for biaryl synthesis, drastic conditions in the range of 150-280 °C are required. Zerovalent nickel complexes such as bis(l,5-cyclooctadiene)nickel or tetrakis(triphenylphosphine)nickel have been shown to be acceptable coupling reagents under mild conditions however, the complexes are unstable and not easy to prepare. The method using activated metallic nickel eliminates most of these problems and provides an attractive alternative for carrying out aryl coupling reactions(36,38). 

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