[OH:1][C:2]1[CH:3]=[C:4]([C:8]([C:10]([C:12]2[CH:17]=[CH:16][CH:15]=[C:14]([OH:18])[CH:13]=2)=O)=[O:9])[CH:5]=[CH:6][CH:7]=1>CN(C)C=O.O.C(OCC)(=O)C.[Zn]>[OH:1][C:2]1[CH:3]=[C:4]([C:8](=[O:9])[CH2:10][C:12]2[CH:17]=[CH:16][CH:15]=[C:14]([OH:18])[CH:13]=2)[CH:5]=[CH:6][CH:7]=1A mixture of 3,3'-dihydroxybenzil (3.0 g.) and powdered zinc (5.0 g.) in N,N-dimethylformamide (25 ml.) and water (10 ml.) was stirred and heated under reflux for 6 hours. The cooled mixture was filtered through Celite and the filtrate was evaporated under oil pump vacuum to give a syrup. The syrup was dissolved in ethyl acetate and the solution was washed consecutively with dilute hydrochloric acid and saturated brine (thrice). The dried (MgSO4) solution was evaporated to smaller volume and benzene was added. A by-product (0.45 g., m.p. 225°-228°) crystallized on standing. The mother liquor was evaporated to a syrup which was crystallized by seeding from ethyl acetate benzene to give the title product (0.88 g., m.p. 151°-154°) which was shown to be identical with material produced from the two stage reduction (1, Sn/HCl; 2, Zn/chromic sulfate).
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