A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1943, 23, 92
DOI: 10.15227/orgsyn.023.0092
[Cyclopentadienone, tetraphenyl-]
Submitted by John R. Johnson and Oliver Grummitt.
Checked by Nathan L. Drake and Stuart Haywood.
1. Procedure
In a 500-ml. round-bottomed flask, 21 g. (0.1 mole) of benzil and 21 g. (0.1 mole) of dibenzyl ketone (Note 1) are dissolved in 150 ml. of hot ethanol. The flask is fitted with a reflux condenser, the temperature of the solution is raised nearly to the boiling point, and a solution of 3 g. of potassium hydroxide in 15 ml. of ethanol is added slowly in two portions through the condenser. When the frothing has subsided the mixture is refluxed for 15 minutes and then cooled to 0°. The dark crystalline product is filtered with suction and washed with three 10-ml. portions of 95% ethanol. The product melts at 218–220° and weighs 35–37 g. (91–96%) (Note 2).
2. Notes
1. The dibenzyl ketone should melt at 34–35°.
2. This product is sufficiently pure for most purposes. It may be crystallized from a mixture of ethanol and benzene, using 155–160 ml. solvent for 5 g. of tetraphenylcyclopentadienone; the melting point of the recrystallized material is 219–220°.
3. Discussion
Tetraphenylcyclopentadienone has been prepared by the action of phenylmagnesium bromide on benzaldiphenylmaleide,1 and by reduction, dehydration, and oxidation of the methylenedesoxybenzoin obtained by condensing formaldehyde with desoxybenzoin.2 The present procedure is essentially that of Dilthey.3.

References and Notes
  1. Lowenbein and Uhlich, Ber., 58, 2662 (1925).
  2. Ziegler and Schnell, Ann., 445, 266 (1925).
  3. Dilthey and Quint, J. prakt. Chem., (2) 128, 146 (1930); Ger. pat. 575,857 [Frdl., 20, 503 (1933); C. A., 28, 1356 (1934)].

Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)




ethanol (64-17-5)

Benzene (71-43-2)

formaldehyde (630-08-0)

Benzil (134-81-6)

potassium hydroxide (1310-58-3)

Phenylmagnesium bromide (100-58-3)

dibenzyl ketone (102-04-5)

Cyclopentadienone, tetraphenyl- (479-33-4)