Chlorination of Ketones with Trichloroisocyanuric Acid

cyclohexanone and 2-methylcyclohexanone.
ratio of boron trifluoride unsymmetrical ketones gave
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Department o f Chemistry, California State University, Fullerton, Fullerton, California 92631
ABSTRACT: Trichloroisocyanuric acid is a n effective reagent for the chlorination o f ketones in the alpha position.
acetophenone (1.20 g , 10.0 mmol) in 2 0 m L acetic acid was refluxed for 5 hr. After cooiing, the precipitate
was filtered and washed with acetic acid, the filtrate was diluted with water, and the mixture extracted with
CHLORINATION OF KETONES
387
Table 11.
For volatile ketones, like 2-propanone and
2-butanone, the reaction was carried out using excess ketone as the solvent. Acetic acid was the solvent for With a high
for 15 min. in an 80'
precipitate was filtered and washed with acetic acid, and the filtrate poured into 100 mL crushed ice and
Downloaded By: [Singh, Abhar][University of Toronto] At: 22:38 19 February 2010
Monochlorination o f aliphatic ketones i s readily accomplished using 1 - in the presence of boron trifluoride etherate. The results are summarized in
o f aromatic systems,6 alkanes,'
Previously
include the chlorination fatty acid esters, and cyclic
8
allylic thioethers,9 cyclic ethers"
*
T o whom correspondence should be addressed.
Time, min Temp Major Product
GC Purity 9fja
0.023
c , l ! ,
88% (44-46OC, 40 torr)
4
1 : 17.4 : 2.40
90 - rm temp
1 : 2.40
: 0.0054
58% (43-46OC. 40 torr)
93b
5 0 - 80°C
4
x
2 0 m L pentane.
The pentane solution was washed After
with 2 0 m L sat NaCl and dried over MgS04.
filtration, the pentane was removed in vacuo and the residue purified by Kugelrohr distillation (oil bath temp 150-170°C at 35 torr): 1.88 g (81%); IR (neat)
4 0 0
CHLORINATION OF KETONES
389
water.
After the ice melted, the crystals were
filtered, washed with water, and dissolved in pentane. The solution was dried over MgS04, filtered, and freed of solvent to give 0.798 g (50%); 14 (reported m p 54.O°C) mp 53.8-54.8OC
% Yield,
Isolated 50a 81b 81‘
1.00 : 1 : 0.315
2.00
:
1 7-80°C
5-reflux
1 : 0
a M p 53.5-54. 2 O C ( reported mp ‘54. O°C) GC purity, 99%. C GC purity, 98%.
.14
Ketones can be chlorinated in the alpha position using chlorine,' N-chlorosuccinimide,2 sulfuryl
~hloride, selenium ~ o~ychloride, and ~ cupric chloride. We wish to report that trichloroisocyanuric acid [1,3,5-trichloro-1,3,5-triazine-Z,4,6-(1H,3H,5H)-trione
o f acetophenone at 8 0 C did not increase the rate of
0
reaction indicating that an ionic pathway is probably involved. Trichloroisocyanuric acid is a safe, convenient, and selective chlorinating agent for ketones. Experimental All products, except for trichloroacetophenone, were characterized by comparison of the IR and NMR spectra to those of authentic samples. a-Chloroacetophenone
385
Copyright 0 1985 by Marcel Dekker, Inc.
0039-79 1 1 /8S/ lSOS438S S3.50/0
386
HEIGEL AND P N T O N
acetals,”
the allylic chlorination of alkenes,” 13 the oxidation o f ethers to esters.
chlorination preferentially at the more substituted position as do other chlorinating agents under acidic conditions.
16
Addition of azobisisobutyronitrile to a reaction
( 5 ) , 385-392 (1985)
CHLORINATION OF KETONES WITH TRICHLOROISOCYANURIC ACID
Gene A. Hiegel* and Kim B. Peyton
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.
Downloaded By: [Singh, Abhar][University of Toronto] At: 22:38 19 February 2010
a , o , a -Trichloroacetophenone
A solution o f L(4.686
g,
20.0 mmol) and
5
(L)] can
also be used to chlorinate ketones in the
alpha position. Trichloroisocyanuric acid i s a stable, nonvolatile solid used commercially as a disinfectant and to a limited extent a s a laboratory reagent. reported reactions utilizing
A solution of = 1 (0.774
(1.20 g , 10.0 mmol),
(0.45
g,
g,
3.33
mmol),
acetophenone
and boron trifluoride etherate
3.15
mmol) in 2 0 m L acetic acid was stirred oil bath. After cooling, the
Table I 1 Chlorination of Aliphatic Ketones with Trichloroisocyanuric Acid Mole Ratio Reactants 1 : Ketone : BF3-