Benzoins benzils

F. Dobler, on aromatio aldehydes F. Bidet, on primary amines, etc. G. Baume, and A. M. Wasilieff studied the system with methyl ether and ethyl alcohol with ammonia and C. A. Kraus and E. H. Zeitfuchs, equilibrium in liquid mixtures of ammonia and xylene. H. H. Schlubach and H. Miedel observed that ammonia or ammonium salts may act as a reducing agent on some organic compounds—phenyl-butylene, styryl methyl ketone, pyridine, and nitrobenzene, but not acetophenone, benzil, benzoin, and deoxybenzoin. A soln. of sodium in liquid ammonia is added gradually to a soln. of ammonium chloride in the same solvent in which the substance to be reduced is at least partly dissolved at —80° to —50°. If the compound under investigation is not sufficiently soluble in liquid ammonia, benzene or ether... 

Benzoins Benzils Benzoins are oxidized to benzils in high yield (75-98%) by treatment with triphenylphosphine dibromide in acetonitrile. 

Benzils. Benzoins are readily oxidized by FeCl3-6H20 without solvent at 80°. Cyclobutenediones and p-henzoquinones. Iron carbonyl species are formed by reaction of the FeCl,-NaBH4 system with carbon monoxide. When alkynes are present, they are converted to cyclobutenediones or benzoquinones in situ. 

Oxidation of benzoins to benzils. Benzoins can be converted to benzils by oxidation with cupric sulfate in HMPT with air (or O2) ebullition yields are 60-95%. This method was used for preparation of 4,4 -divinylbenzil from 4,4 -divinylbenzoin (73% yield). 

Oxidation of benzoins to benzils Benzoins (1) are oxidized to benzils(2) in high yield by catalytic amounts of this lanthanide nitrate and 1 eq. of HCl in aqueous glyme. Benzil can also be obtained from desoxybenzoin and diphenyl-acetylene under these conditions. This oxidation has recently been reported with... 

Medium dehyde Ethers Benzil benzoin Oxetanol... 

Aldehyde Product Benzil Benzoin Benzil Benzoin... 

The synthesis of 2,4,5-trisubstituted-lH-imidazoles via the one-pot three-component condensation of benzil/benzoin, aldehydes and ammonium acetate under solvent-free conditions has been achieved using the BAIL, (4-sulfobutyl)tris(4-sul-fophenyl) phosphonium hydrogen sulfate as a catalyst [142] (Scheme 4.13). 

A simple and efficient protocol for microwave-assisted solvent-free oxidation of hydrobenzoins to benzoins or benzils, benzoins to benzils, and alcohols to the corresponding aldehydes or ketones, using N-bromosuccinimide over neutral alumina has been also reported (Khurana and Arora, 2008). 

The secondary alcohol group, -CH(OH) in benzoin is readily oxidised to a ketone group, and thus benzil, a diketone, is obtained. 

Oxidation of benzoin with concentrated nitric acid or by catalytic amounts of cupric salts in acetic acid solution, which are regenerated continuously by ammonium nitrate, yields the diketone benzil ... 

The latter procedure gives a purer product it is difficult to remove the last traces of benzoin from the benzil obtained by the nitric acid method. 

Benzilic acid may be obtained in a high state of purity by the action of an alkaline bromate solution upon benzoin at 85-90° ... 

Recrystallise 5 0 g. from about 40 ml. of hot rectified (or methylated) spirit upon cooling, 4-5 g. of pure benzoin (a white, crystaUine solid, m.p, 137°) separate. Reserve the remainder of the preparation for benzil and benziUc acid (Sections IV.126 and IV.127 respectively). 

Method 1. Place 20 g. of crude benzoin (preceding Section) and 100 ml. of concentrated nitric acid in a 250 ml. round-bottomed flask. Heat on a boiling water bath (in the fume cupboard) with occasional shaking until the evolution of oxides of nitrogen has ceased (about 1 -5 hours). Pour the reaction mixture into 300-400 ml. of cold water contained in a beaker, stir well until the oil crystallises completely as a yellow solid. Filter the crude benzil at the pump, and wash it thoroughly with water to remove the nitric acid. RecrystaUise from alcohol or methylated spirit (about 2-5 ml. per gram). The yield of pure benzil, m.p. 94-96°, is 19 g. 

Method 2. Place 0-2 g. of cupric acetate, 10 g. of ammonium nitrate, 21 2 g. of benzoin and 70 ml. of an 80 per cent, by volume acetic acid -water solution in a 250 ml. flask fitted with a reflux condenser. Heat the mixture with occasional shaking (1). When solution occurs, a vigorous evolution of nitrogen is observed. Reflux for 90 minutes, cool the solution, seed the solution with a crystal of benzil (2), and allow to stand for 1 hour. Filter at the pump and keep the mother liquor (3) wash well with water and dry (preferably in an oven at 60°). The resulting benzil has m.p. 94-95° and the m.p. is unaffected by recrystallisation from alcohol or from carbon tetrachloride (2 ml. per gram). Dilution of the mother liquor with the aqueous washings gives a further 1 Og. of benzil (4). 

Benzilic acid rearrangement Benzoin reaction (condensation) Blanc chloromethylation reaction Bouveault-Blanc reduction Bucherer hydantoin synthesis Bucherer reaction Cannizzaro reaction Claisen aldoi condensation Claisen condensation Claisen-Schmidt reaction. Clemmensen reduction Darzens glycidic ester condensation Diazoamino-aminoazo rearrangement Dieckmann reaction Diels-Alder reaction Doebner reaction Erlenmeyer azlactone synthesis Fischer indole synthesis Fischer-Speior esterification Friedel-Crafts reaction... 

Recently, Koitai et al. (17) have shown that 5,5-diphenyl-2,4-thiazolidinedithione (15) with aluminum chloride in refluxing toluene gives 4,5-diphenyl-A-4-thia2oline-2-thione (16) (Scheme 7). 3-Methyl-4,5-diphenyl (17) and 4,5-diphenyl-A-4-thia2oline-2-thiones (16) are obtained in very low yields (1 to 5%) as by-products of the reaction between deoxybenzoin. benzoin. l,2-diphenyl-1.2-ethanediol. 1.2-diphenylethanol, or benzil, and Sg in hexamethylphosphoamide (18), The transformation of A-4-thiazoline-2-ones to the corresponding thiones by P2S5 (19) is of little synthetic value since the latter are more easily prepared. 

The melting temperatures of mixtures of benzil and benzoin have been recorded by Vanstone, who showed that the maximum possible depression is about 10°. 

Reaction.—. dA Fehling s solution to benzoin dissolved in alcohol. Benzil is formed and cuprous oxide precipitated. Benzil is also formed on oxidation with nitric acid. 

Besonders ausgepragt ist die selektive Reduzierbarkeit von Dioxo-steroiden mit Na-triumboranat7 (weiteres s. S. 329, 331 f.), wahrend symmetrische Diketone nur als Mono-(2-dimethylamino-athoxyimine) selektiv zu Hydroxy-ketonen reduziert werden8. Benzil kann mit Triathyl-siliciumhydrid durch Zinkchlorid katalysiert selektiv zu Benzoin reduziert werden9 ... 

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