Desoxybenzoin

To 68 g. (0.5 mole) of phenylacetic acid (Org. Syn. 2, 63) (Note 1) in a i-l. flask fitted with a reflux condenser and a system for absorbing hydrogen chloride (Org. Syn. 8, 27) (Note 2), is added 35 g. (0.25 mole) of phosphorus trichloride. The mixture is heated on a steam bath for one hour. While the contents of the flask are still warm, 400 cc. of dry benzene is added. The benzene solution of phenylacetyl chloride is decanted from the residue of phosphorous acid on 75 g. (0.56 mole) of anhydrous aluminum chloride in a dry, i-l. flask which can be fitted to the same condenser. The reaction is vigorous at first and cooling is necessary. The mixture is refluxed for one hour on a steam bath, then cooled and poured into a mixture of 500 g. of cracked ice and 200 g. of concentrated hydrochloric acid. The benzene layer is separated, and the aqueous layer is extracted once with a mixture of 100 cc. of benzene and 100 cc. of ether (Note 2). The ether-benzene solution is washed once with 100 cc. of water (Note 3), and then dried over 40-50 g. of calcium chloride. The solution is filtered (Note 4) with suction into a i-l. Claiscn flask and the solvent is removed by distillation under reduced pressure (Note 5) the residue consists of a brown oil which solidifies on cooling. 

A very high grade of phenylacetic acid is obtained from companies supplying essential oils and perfumers supplies. 

A mixture of benzene and ether is used instead of ether alone because a more efficient separation of the two layers is obtained. 

Washing with sodium hydroxide at this point is unnecessary and undesirable since, owing to formation of emulsions, it causes an 8-10 per cent loss of product and the product is of no better quality. 

It is better to remove the calcium chloride by filtration rather than by decantation even though the solution looks clear. Small particles of calcium chloride and aluminum chloride not removed from the solution may cause bumping or even decomposition during the distillation. 

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Desyl bromide (a-bromo-desoxybenzoin, m-bromo-co-phenyl acetophenone) [484-50-0] M 275.2, m 57.1-57.5 . Crystd from 95% EtOH. 

Desyl chloride (a-cbloro-desoxybenzoin, m-chloro-co-phenyl acetophenone) [447-31-4] M 230.7, m 62-64 , 66-67 ,67.5 , 68 . For the purification of small quantities recrystallise from pet ether (b 40-60°), but use MeOH or EtOH for larger quantities. For the latter solvent, dissolve 12.5g of chloride in 45mL of boiling EtOH (95%), filter and the filtrate yields colourless crystals (7.5g) on cooling. A further crop (0.9g) can be obtained by cooling in an ice-salt bath. It turns brown on exposure to sunlight but it is... 

Muiik and Kim (65) have shown that the acid-catalyzed condensation of desoxybenzoin with morpholine led only to the thermodynamically more stable CIS isomer of the corresponding enamine (128). 

Dulou et al. (66) have assigned the trans configuration to the pyrrolidine examine of desoxybenzoin (133) on the basis of the comparison of its UV SDectrum with that of tran -stilbene and triphenylethylene. This assignment is open to question in the light of the work of Munk and Kim (63). 

Benzil (Coll. Vol. i, 80) By oxidation of desoxybenzoin with selenium dioxide in acetic anhydride at 140-150°, in 90 per cent yield. Hatt, Pilgrim, and Hurran, J. Chem. Soc. 1936, 93. 

An illustrative example of the Michael reaction is that of the thiirene dioxide 19b with either hydroxylamine or hydrazine to give desoxybenzoin oxime (87) and desoxybenzoin azine (88), respectively, in good yields6 (see equation 29). The results were interpreted in terms of an initial nucleophilic addition to the a, j8-unsaturated sulfone system, followed by loss of sulfur dioxide and tautomerization. Interestingly, the treatment of the corresponding thiirene oxide (18a) with hydroxylamine also afforded 86 (as well as the dioxime of benzoin), albeit in a lower yield, but apparently via the same mechanistic pathway6. 

O- versus C-a kyIation product ratios in the methylation of desoxybenzoin by dimethyl sulphate can be varied between 0.75 and 63 by the choice of catalyst. The reaction can be steered towards enol-ether formation by large, sterically shielded ammonium ions, while C-alkylation is favoured by small ammonium ions (e.g. RMejN" ) and by crown ethers (Dehmlow and Schrader, 1990). 

Cyclopropenones can be oxidized according to several methods. When diphenyl cyclopropenone is treated with alkaline H202 desoxybenzoin is formed as the main product and is claimed to arise from primary addition of hydroperoxide ion to the Cl/C2 bond206. Treatment with KMn04 gave benzil67. ... 

Amongst other N-nucleophilic species, hydroxylamine exhibits some abnormal behavior besides oxime formation (p. 25). Thus it reacts with diphenyl cyclopropenone42 probably by 1,4-addition and subsequent oxidation and/or decarboxylation giving rise to 3,4-diphenyl isoxazolone (328) and desoxybenzoin oxime. With pentyl cyclopropenone48 hydroxylamine undergoes addition followed by normal oxima-tfon after ring fission yielding 2,3-dioximino octane (329). 

The procedure described is essentially that of Ballard and Dehn.1 Stilbene has also been prepared by reduction of desoxy-benzoin,20 benzaldehyde,23 and benzil 2o-2c by dehydrogenation of ethyl benzene,30 toluene,30- 33- 3, and bibenzyl 33-3alkaline reduction of phenylnitromethane,40 phenylnitroacetonitrile,40 and desoxybenzoin 43 by distillation of benzyl sulfone,50 benzyl sulfide,60-63 calcium cinnamate,5 cinnamic acid,5d phenyl cinna-mate,6e-6/ and diphenyl fumarate ie by dehydrohalogenation of a,a -dichlorobibenzyl60 and benzyl chloride 63 by dehalogenation of a,a,c/,a -tetrachlorobibenzyl70 and benzal chloride 73 by the coupling of cinnamic acid and phenyldiazonium chloride 8 by de-... 

Tetraphenylcyclopentadienone has been prepared by the action of phenylmagnesium bromide on benzaldiphenylmaleide,1 and by reduction, dehydration, and oxidation of the methylene-desoxybenzoin obtained by condensing formaldehyde with desoxy-benzoin.2 The present procedure is essentially that of Dilthey.3... 

DecarboxyHerung erhaltene Desoxybenzoin enthalt die gesamte Radio-aktivitat (obere Formelreihe). 

Zimmer, H. and Neue, D.M., Synthesis with a-heterosubstituted phospho-nate carbanions. VI. Desoxybenzoins and indoles, Chimia, 31, 330, 1977. 

The action of a Grignard reagent, e.g. phenyl magnesium bromide, on methyl fluoroacetate gives among other products PhaCH CH(OH)Ph and desoxybenzoin.1... 

The known property of diorganyl tellurides of reducing metallic salts, applied to tita-nium(IV) chloride, generates a titanium(III) species which is a useful reagent for some selective reductions. By this method benzaldehyde is reduced to dihydrobenzoin, and benzyl to benzoin, and successively to desoxybenzoin. ... 

Nickel prepared by reduction of nickel chloride with sodium borohydride was used for desulfurization of diethyl mercaptole of benzil. Partial desulfurization using 2 mol of nickel per mol of the mercaptole gave 71% yield of ethylthiodesoxybenzoin while treatment with a 10-fold molar excess of nickel over the mercaptole gave 61% yield of desoxybenzoin (benzyl phenyl ketone) 937. ... 

Lutz, R. E., J. A. Freek, and R. S. Miirphey Secondary and tertiary amino ketones and alcohols derived from desoxybenzoin and 1,2-di-phenylethanol. Ring-chain tautomerism of the a-(p-hydroxyethyl-amino)-ketones. J. Amer. chem. Soc. 70, 2015 (1948). 

N-Methyl-l,2-diphenylethylamine has been prepared in 8% yield by the Leuckart reaction from desoxybenzoin and methyl-ammonium formate 8 and by the present method.9... 

It is necessary to use a Claisen flask with a wide side-arm, since the desoxybenzoin may solidify and clog the apparatus. The distillation under reduced pressure is quiet if directions are followed carefully. 

The quality of the desoxybenzoin depends upon that of the phenylacetic acid used. In this preparation a high grade of phenylacetic acid was used. The compound prepared according to Org. Syn. 2, 63, is not so good as some of the commercial products. 

Methyl alcohol is the best solvent for purification. Desoxybenzoin tends to separate from ethyl alcohol as an oil. 

Desoxybenzoin has been prepared by treatment of bromo-stilbene with water in a sealed tube at 180-190° 1 by the reduction of benzoin 2 by the reduction of benzil 3 by the action of zinc and alcoholic hydrogen chloride on chlorobenzil 4 by the action of benzene on phenylacetic acid in the presence of phosphorus pentoxide 5 and by the action of benzene on phenylacetyl chloride in the presence of aluminum chloride.6... 

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