Condensation Copper powder

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. 

A halogen atom directly attached to a benzene ring is usually unreactive, unless it is activated by the nature and position of certain other substituent groups. It has been show n by Ullmann, however, that halogen atoms normally of low reactivity will condense with aromatic amines in the presence of an alkali carbonate (to absorb the hydrogen halide formed) and a trace of copper powder or oxide to act as a catalyst. This reaction, known as the Ullmant Condensation, is frequently used to prepare substituted diphenylamines it is exemplified... 

The experimental conditions for conducting the above reaction in the presence of dimethylformamide as a solvent are as follows. In a 250 ml. three-necked flask, equipped with a reflux condenser and a tantalum wire Hershberg-type stirrer, place 20 g. of o-chloronitrobenzene and 100 ml. of diinethylform-amide (dried over anhydrous calcium sulphate). Heat the solution to reflux and add 20 g. of activated copper bronze in one portion. Heat under reflux for 4 hours, add another 20 g. portion of copper powder, and continue refluxing for a second 4-hour period. Allow to cool, pour the reaction mixture into 2 litres of water, and filter with suction. Extract the solids with three 200 ml. portions of boiling ethanol alternatively, use 300 ml. of ethanol in a Soxhlet apparatus. Isolate the 2 2- dinitrodiphenyl from the alcoholic extracts as described above the 3ueld of product, m.p. 124-125°, is 11 - 5 g. 

In a 1 or 1-5 htre round-bottomed flask prepare a solution of 53-5 g. of o-toluidine in 170 ml. of 48 per cent, hydrobromic acid, cool to 5° by immersion in a bath of ice and salt. Diazotise by the gradual addition of a solution of 36 -5 g. of sodium nitrite in 50 ml. of water stopper the flask after each addition and shake until all red fumes are absorbed. Keep the temperature between 5° and 10°. When the diazotisation is complete, add 2 g. of copper powder or copper bronze, attach a reflux condenser to the flask, and heat very cautiously on a water bath. Immediately evolution of gas occurs, cool the flask in crushed ice unless the... 

The main by-products of the Ullmaim condensation are l-aniinoanthraquinone-2-sulfonic acid and l-amino-4-hydroxyanthraquinone-2-sulfonic acid. The choice of copper catalyst affects the selectivity of these by-products. Generally, metal copper powder or copper(I) salt catalyst has a greater reactivity than copper(Il) salts. However, they are likely to yield the reduced product (l-aniinoanthraquinone-2-sulfonic acid). The reaction mechanism has not been estabUshed. It is very difficult to clarify which oxidation state of copper functions as catalyst, since this reaction involves fast redox equiUbria where anthraquinone derivatives and copper compounds are concerned. Some evidence indicates that the catalyst is probably a copper(I) compound (28,29). 

To the dry salt is added 0.3 g. of copper powder (Note 2), 81 g. (0.51 mole) of bromobenzene, and a few drops of guaiacol (Note 3). The mixture is stirred thoroughly with a glass rod the flask is fitted with an air condenser and heated in a metal bath (Note 4). A reaction becomes evident at a bath temperature of 160-180°, liquefaction occurs, and the color of the mixture changes to red or purple. The temperature is gradually raised to 200° and maintained at 200° for 2 hours. 

Solanidine contains at least three CMe groups, and since it yields dihydrosolanidine, m.p. 219-220°, must contain one ethylenic linkage. When solanidine is heated with copper powder at 160-300°/ll mm., it is converted into solanidone, C27H41ON, m.p. 218°, which yields an oxime, m.p. 228°, and condenses with benzaldehyde or amyl nitrite to give compounds indicating the existence in solanidone of the group —CHj—CO—CH — and therefore in solanidine of —CHjj—CHOH—CHa—... 

In a 2-1. three-neck, round-bottom flask, fitted with a very efficient mechanical stirrer, a 100-cc. separatory funnel and a large air-cooled reflux condenser (Note 1), the upper part of which is bent downwards and attached to a vertical water condenser, are placed t. jS g. (r.04 moles) of ground diphenylamine (Note 2), 204 g. (1 mole) of iodobenzene, 11. of nitrobenzene (Note 3), 138 g. (1 mole) of finely powdered anhydrous potassium carbonate and 5 g. of copper powder (Note 4). 

The phthalide 25, obtainable by condensation of 4,4 -bisdimethyl-aminobenzophenone-2-carboxylic acid with 3-dimethylaminoacetanilide and subsequent hydrolysis, was diazotized in sulfuric acid and the resultant diazonium salt treated with copper powder to yield 26. However, better yields are reportedly obtained by carrying out ring closure of the diazonium salt in phosphoric acid.103 A further synthetic route has also been described in which phthalides undergo intramolecular cyclization in the presence of aluminum chloride and urea.104,105 Thus, Crystal Violet lactone (2) has been directly converted into phthalide 26.106... 

It is worth noting that the Ullmann-Goldberg condensation of aryl halides with phenols and anilines worked efficiently in the presence of copper in water.50 For example, the coupling of 2-chlorobenzoic acid with 4-chlorophenol (K2C03/pyridine/copper powder) gave 2-(4-chlorophenoxy)carboxylic acid (Eq. 6.23).51 The Cu(I)-catalyzed transformation of 2-bromobenzoic acid into salicylic acid has also been studied in aqueous media (Eq. 6.24).52... 

CENTRAL RING CONTAINING ONE HETEROATOM Reaction of 2-bromobenzoic acid (1) with chloroSulfonic acid proceeds to afford the sulfonyl chloride 2 treatment with dimethylamine leads to the corresponding sulfonamide (3). Condensation of bromoacid 3 with the anion from thiophenol in the presence of copper powder results in displacement of halogen by sulfur... 

B. m-Nitrostyrene. In a 250-ml. two-necked flask equipped with a 250° thermometer and an air condenser are placed 30 g. (0.155 mole) of m-nitrocinnamic acid, 2 g. of copper powder, and 60 ml. of dry quinoline (Note 3). The flask is heated with a Bunsen burner to 185-195°, during which time a steady stream of carbon dioxide is evolved. After 2-3 hours (Note 4), the reaction mixture is cooled and poured into a mixture of 75 ml. of concentrated hydrochloric acid and 175 g. of ice. The m-nitro-styrene is isolated by steam distillation, approximately 1 1. of... 

Ammonia, Ammonium nitrate, Diphenyl carbonate Buzard, J. et al., J. Amer. Chem. Soc., 1952, 74, 2925-2926 During the synthesis of 15N-labelled urea by interaction of labelled ammonium nitrate, liquid ammonia and diphenyl carbonate in presence of copper powder, a series of explosions of the refrigerated sealed tubes was encountered. This was almost certainly caused by condensation of traces of oxygen in the tubes cooled to — 196°C dining condensation of ammonia before sealing the tubes. Cooling to —80°C would have been adequate and have avoided the hazard. 

B. 3-Methylfuran. A mixture of 25 g. of 3-methyl-2-furoic acid, 50 g. of quinoline (Note 2), and 4.5 g. of copper powder is placed in a 125-ml. round-bottomed flask attached by a ground joint to a 30-cm. simple Vigreux column which delivers to a water-cooled condenser. The condenser is connected to a small distilling flask which serves as a receiver, with the tip of the condenser extending to the edge of the bulb of the flask. The receiver is cooled in an ice-salt bath (Note 3). The round-bottomed flask is heated by means of an electric mantle or liquid bath. 

B. Tetracycmoethylene. A mixture of 254 g. (0.25 mole) of the dibromomalononitrile-potassium bromide salt and 1 1. of dry benzene is placed in a 2-1. three-necked flask fitted with a sealed mechanical stirrer and a reflux condenser. The stirrer is started (Note 6), and 100 g. (1.57 g.-atoms) of precipitated copper powder (Note 7) is added. The mixture is heated at reflux with constant stirring for 10-16 hours. The benzene layer becomes progressively deeper yellow as the reaction proceeds. At the end of the reaction period, the hot mixture is filtered by gravity, using a fluted paper. Most of the heavy solid is easily retained in the flask and is heated under reflux with 300 ml. of dry benzene, with stirring, for 30 minutes. Filtration of the hot mixture is carried out as before. Two 25-ml. portions of hot benzene are used to wash the precipitate and are decanted through the filter. 

The direct synthesis of PPP by condensation polymerization represents one of the oldest preparations of a conjugated polymer. This is exemplified by the Ull-mann coupling of dihalobenzenes using copper powder [56] and by Wurtz [57, 58] chemistry where dihalobenzenes are reacted with sodium metal to give oligomeric PPPs [59]. 

In a 1- or 1.5-litre round-bottomed flask prepare a solution of 53.5 g (0.5 mol) of o-toluidine in 170 ml of 40 per cent w/w hydrobromic acid cool to 5 °C by immersion in a bath of ice and salt. Diazotise by the gradual addition of a solution of 36.5 g (0.53 mol) of sodium nitrite in 50 ml of water stopper the flask after each addition and shake until all red fumes are absorbed. Keep the temperature between 5 and 10 °C. When the diazotisation is complete, add 2g of copper powder or copper bronze (Section 4.2.79, p. 426), attach a reflux condenser to the flask and heat very cautiously on a water bath. Immediately evolution of gas occurs, cool the flask in crushed ice unless the flask is rapidly removed from the water bath, the reaction may become so violent that the contents may be shot out of the flask. When the vigorous evolution of nitrogen moderates, heat the flask on a water bath for 30 minutes. Then dilute with 400 ml of water, and steam distil the mixture until about 750 ml of distillate are collected. Render the distillate alkaline with 10 per cent sodium hydroxide solution (about 50 ml) and separate the lower red layer of crude o-bromotoluene. Wash it with two 20 ml portions of concentrated sulphuric acid (which removes most of the colour) and then twice with water. Dry with magnesium sulphate or anhydrous calcium chloride, and distil from a flask fitted with a lagged fractionating column. Collect the o-bromotoluene at 178— 181 °C. The yield is 40 g (47%). The spectral features are noted in Expts 6.72 and 6.81. 

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