The Importance of Temperature Control in the Preparation of Phencyclone (1,3-Diphenyl-2-H-cyclopenta[l]phenanthrene-2-one) In an effort to develop a reliable1 preparation of phencyelone (3)suitable for use in the undergraduate organic laboratory, we have systematically investigated the base-catalyzed reaction typically2 used to prepare 3 and found, not unexpectedly, that reaction temperature is an important parameter. Specifically, we have observed that use of an of 3 in 40-50% yield, while ethanoVethanolie KOH combinatmn and temperatures of 50 or 60 'C led tn the use of either the same haseisolvent combination a t higher temperatures (e.g., 68-70 or 78 'C) or other almhoYalcoholic KOH combinations a t the boiling point (e.g., 1- or 2-prapanol) led to the excluszue formation of dihydrophencyclone (4). These results and those obtained by Allen ( 1 )indicated that a reaction temperature of approximately 60 'C was prohably optimum for the preparation of 3. We therefore investigated the use of methanoVmethanolie KOH as a combination3 and found that addition of the methanolic alkali solution tn a mixture of 1 and 2 in boiling methanol provided reasonably pure 34in approximate1 80% yield. Since that original discovery, students in our undergraduate laboratory have routinely used this procedure to obtain yields of 3 ranging between 60 and 80%.
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Literature Cited 1. AUen,C. F.H.C& J. C k m . 1984,42,2151. 2. n a m m ~ E . A . : G m w , WS.J. . ChemEdue 1m6.52, 461. 3. Dilthey. W;ter Horst, I.; %homer, W.J p m l Chem 1954143.189. 4. KreitebergsY:Ndand, O.;Kampar,V.Zh. ow.Khim. 1975,21,1941. 'WB orioinallv thought we had such a synthesis (abut our later inabilo consistenflyto produce 3 uncontaminated with 4 prompled the study that is de&ribed herein. 2Typicalcondiions' involve the addition of alcoholic KOH to a suspension of 1.3diphenyl-2-propanone(1)and 9.10-phenanlhrenequinone (2) in hot (usuallyrefluxing)alcohol. "0th Dilthey et al. (3) and Kreitsberga el al. (4)make referenceto the condensation of 1 and 2 in methanol, but no experimental details are provided. 'The black, crystalline product so obtained exhibiied a melting range of 250-258 'C (1it.S 273 '6) and mntained lmle or no 4 as judged by TLC and IR analysis. 01 the preparation of 3 will te supplied to any interested persons. S~elails
Ernest A. Harrlson, Jr. Pennsylvania State University, York Campus York, PA 17403
Volume 69 Number 7 July 1992
571
