Ullman synthesis

Ubichromenol synthesis, 3, 752 Ugi reaction, 5, 830 Uliginosin B, bromo-molecular dimensions, 3, 621 Ullman and Fetvadjian synthesis quinolines, 2, 477 Ullman synthesis acridines, 2, 470-benzacridines, 2, 470 Ultraviolet light absorbers in polymers, 1, 397-398 Ultraviolet spectroscopy heterocyclic compounds reviews, 1, 78... 

Hie reactions of 4-chloropyridines and quinolines 17 with benzotriazoles 18 in a modified Graebe-Ullman synthesis give excellent yields of Y arbolines and their benzo-fused derivatives 20. Excellent yields for preparation of the penultimate benzotriazole precursors 19 are reported as well. In the optimized one-pot conditions, the combined neat substrates are heated with microwave irradiation (MW) for short (7-10 min) durations. The crude 19 is treated with H4P2O7 and irradiated futher (4-6 min). The resultant y-carbolines 20 were methylated to form the quaternary salts. These were tested and found to lack DNA intercalation properties <96JOC5587>. 

As a variation on the base-catalyzed nucleophilic displacement chemistry described, polysulfones and other polyarylethers have been prepared by cuprous chloride-catalyzed polycondensation of aromatic dihydroxy compoimds with aromatic dibromo compounds. The advantage of this route is that it does not require that the aromatic dibromo compoimd be activated by an electron-withdrawing group such as the sulfone group. Details of this polymerization method, known as the Ullman synthesis, have been described (8). 

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. 

In a synthesis of decinine a phenol was protected as a methanesulfonate that was stable during an Ullman coupling reaction and during condensation, catalyzed by calcium hydroxide, of an amine with an aldehyde. Aryl methanesulfonates are cleaved by warm sodium hydroxide solution. " ... 

In general, imines are too reactive to be used to protect carbonyl groups. In a synthesis of juncusol, however, a bromo- and an iodocyclohexylimine of two identical aromatic aldehydes were coupled by an Ullman coupling reaction modi-fied by Ziegler. The imines were cleaved by acidic hydrolysis (aq. oxalic acid, THF, 20°, 1 h, 95% yield). Imines of aromatic aldehydes have also been prepared... 

The Graebe-Ullman carbazole synthesis is normally carried out in sealed tubes and at high temperature. The carbazoles/substituted carbazoles are obtained in general in poor to moderate yields. ... 

The Graebe-Ullman carbazole synthesis has been enmloyed in the preparation of substituted carbolines, as well as indolo[2,3-i] quinolines, which are often difficult to synthesize via other approaches, for example, the Fischer indole process. 

The Ullman reaction has long been known as a method for the synthesis of aromatic ethers by the reaction of a phenol with an aromatic halide in the presence of a copper compound as a catalyst. It is a variation on the nucleophilic substitution reaction since a phenolic salt reacts with the halide. Nonactivated aromatic halides can be used in the synthesis of poly(arylene edier)s, dius providing a way of obtaining structures not available by the conventional nucleophilic route. The ease of halogen displacement was found to be the reverse of that observed for activated nucleophilic substitution reaction, that is, I > Br > Cl F. The polymerizations are conducted in benzophenone with a cuprous chloride-pyridine complex as a catalyst. Bromine compounds are the favored reactants.53,124 127 Poly(arylene ether)s have been prepared by Ullman coupling of bisphenols and... 

Pentafluorophenylcopper is representative of a series of fluori-nated organocopper compounds that are highly soluble in organic solvents, more thermally stable than their hydrocarbon analogs, and useful as synthetic intermediates. " Pentafluorophenylcopper has been used to introduce the pentafluorophenyl groups and as a reagent for an improved Ullman diphenyl ether synthesis. It is... 

Dichlorodibenzo-p-dioxin was prepared from isotopic potassium 2,4-dichlorophenate uniformly labeled with Ullman conditions gave a 20.5% yield. Small amounts of dichlorophenoxy chlorophenol were removed from the product by extraction with sodium hydroxide before purification by fractional sublimation and recrystallization from anisole. Chlorination of 2,7-dichlorodibenzo-p-dioxin in chloroform solution containing trace amounts of FeCls and 12 yielded a mixture of tri-, tetra-, and pentachloro substitution products. Purification by digestion in boiling chloroform, fractional sublimation, and recrystallization from anisole was effective in refining this product to 92% 2,3,7,8-tetrachloro isomer, which also contained 7% of the tri- and 1% of the penta-substituted dibenzo-p-dioxin. Mass spectroscopy was used exclusively to monitor the quality of the products during the synthesis. 

The Ullman reaction, discovered in 1903,2 is the prototype cross-coupling method for the synthesis of aryl ether... 

Even more than [6 + 4] and [8 + 2] cycloaddition reactions, the [2 + 2 + 2] cycloaddition reactions require a very well preorganized orientation of the three multiple bonds with respect to each other. In most cases, this kind of cycloaddition reaction is catalyzed by transition metal complexes which preorientate and activate the reacting multiple bonds111,324. The rarity of thermal [2 + 2 + 2] cycloadditions, which are symmetry allowed and usually strongly exothermic, is due to unfavorable entropic factors. High temperatures are required to induce a reaction, as was demonstrated by Berthelot, who described the synthesis of benzene from acetylene in 1866325, and Ullman, who described the reaction between nor-bomadiene and maleic anhydride in 1958326. As a consequence of the limiting scope of this chapter, this section only describes those reactions in which two of the participating multiple bonds are within the same molecule. 

The procedure described here is by far the most efficient synthesis of terpyridine. Previous preparations include the dehydrogenation of pyridine with ferric chloride, the Ullman reaction of 2-bromopyrid1ne and 2,6-dibromopyridine,5 the action of copper on 2-bromopyridine and 6-bromo-2,2 -... 

In a modified Graebe-Ullman reaction, pyridylbenzotriazole 223 was converted to a-carboline 224 in an efficient manner but in moderate yield (Scheme 38) <20060L415>. Microwave irradiation was the energy source for both a-carboline synthesis and the preparation of 223. The advantages of this procedure are that the starting materials are commercially available and lower reaction times are used resulting in fewer undesirable side products. The style of microwave oven, amount of pyrophosphoric acid, power level, and time were all optimized. 

Ullman reaction conditions have also been used in the synthesis of biflavanoids. Heating of 3-haloflavones in the presence of copper powder provided biflavones in good yield <1993SC1075>. Isoflavone and derivatives, for example 425, can be prepared efficiently by the Suzuki cross-coupling of 3-bromo and 3-iodochromones 424 with arylboronic acids (Scheme 71) <1988BCJ3008, 1989CPB529>. 

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