Preparation of 1,l-Diphenyl-l-hydroxy-3-butanone We have for some years, successfully employed in our undergraduate organic laboratory course the following procedure of Paulson et al.' as an example of the use of a protecting group in organic synthesis.
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IV
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In their method the hydroxyketal(I1) is hydrolized to 1.1-diphenyl-l-huten-3-one(1V) without isolation of the intercan he mediate hydroxyketone(II1). If, however, sufficiently dilute acid is used 1,l-diphenyl-l-hydroay-3-butanone(II1) ohtained in excellent yield. Thismodification in the hydrolysis of the hydmxyketal(I1) adds to thevalueofthe experiment in demonstrating how different pmduds can he obtained by minor variation of reaction conditions and also provides a method of preparing the hydroxyketone(II1) which is more convenient than published p r o e e d ~ r e s . ~ , ~ Experimental: A mixture of I1 (LOOg), hest recrystallized from ethanol, and 0.02 M HCI (20 ml; prepared from 1.0 ml1 M HC1,5 ml Hz0 and 50 ml acetone) is refluxed for 15mi", cooled, poured into asalution of saturated sodium hiearbonate (10ml) and water (10 ml), and extracted with ether (2 X 50 ml). Thecombined ether extractsare washed with water, dried over calcium chloride and evaporated to give 111 (0.80g). Recrystallization from hexane affords pure 1,l-diphenyl-l-hydroxyd-hutanone (0.73g; 86%), m.p. 85-6°C (lit.28P50);IR (KBr) 3475and 1698cm-'; NMR (CDCh;60MHz) 2,15s (3H), 3,43 s (2H), 5,14 s (lH), 7.41 s (10H); m/e 240 (M+, 0.6%), 183 (53), 182 (30),105 (100) and 77 (38); oxime m.p. 164O; Anal. Calc'd far C16H160z: C. 80,O;H. 6.7. Found: C, 802; H, 6,8%. Paulson, D. R., Hartwig, A. L., and Moran, G. F., J. CHEM EDUC., 50,216 (1973). Wittig, G., and P. Suehanek, Tetrahedron Suppl., No. 8, Part 1,347 (1966). Grieco, P. A,, and Pagonowski, C. S.,J. Org. Chem., 39,132 (1974). Rhodes University Grahamstawn 6140 South Africa
D. E. A. Rivett
Volume 57, Number 10, October 1980 1 751
