Benzalacetophenone, reduction

A solution of 20.8 g. (0.1 mole) of benzalacetophenone (Note 1) (Org. Syn. 2, 1) in 150 cc. of c.p. ethyl acetate (Note 2) is placed in the reaction bottle of the catalytic reduction apparatus (p. 10) and 0.2 g. of platinum oxide catalyst (p. 92) is added. The apparatus is evacuated, then filled with hydrogen, and the mixture shaken with hydrogen until 0.1 mole has been absorbed. The time required is usually about fifteen to twenty-five minutes (Note 3). The platinum is filtered off and the solvent removed from the filtrate by distillation. The benzylacetophenone is recrystallized from about 25 cc. of alcohol and melts at 72-730. The yield is 17-20 g. (81-95 per cent of the theoretical amount). 

Owing to the comparatively slight solubility of benzalacetophenone in alcohol, ethyl acetate is used as a solvent during the reduction. 

Benzylacetophenone has been prepared by the reduction of benzalacetophenone with zinc and acetic acid1 and catalytic-ally with palladium and hydrogen 2 by the reduction of /3-duplo-benzylidene acetophenone monosulfide 3 by the oxidation of the corresponding car bind with chromic acid 4 by the hydrolysis of ethyl benzyl benzoylacetate 5 from acetophenone and benzyl chloride by the action of sodamide 6 and from benzoic and hydrocinnamic adds using as catalysts manganese oxide 7 and ferric oxide.8... 

Electrolysis of benzalacetophenone in the presence of C02 gave a-phenylben-zoylpropionic acid 306 Reduction of stilbene in the presence of C02 yielded 92% meso-2,3-diphenylsuccinic acid 307 The reduction of anthracene at -2,3 V in the presence of S02 and 02 yields 9,10-dihydroanthracene-9,10-disulfonic acid 307a) An interesting intramolecular addition was found in the reduction of the thiocyanato steroid 77 to the mercaptoimine 78 308 ... 

Electrochemical studies in DMSO solvent show that the mechanisms of the one-electron reductions of bis(benzalacetophenone) chromium (31), as in equation (19), and free benzalacetophenone are virtually identical ... 

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