Superbasic system CsOH/DMSO as a catalyst of nucleophilic addition of acetophenone to phenylacethylene

Full text of DOI:10.1134/S1070363210070327

ISSN 1070-3632, Russian Journal of General Chemistry, 2010, Vol. 80, No. 7, pp. 1385–1386. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © B.A. Trofimov, E.Yu. Schmidt, N.V. Zorina, A.I. Mikhaleva, 2010, published in Zhurnal Obshchei Khimii, 2010, Vol. 80, No. 7,
pp. 1219–1220.
LETTERS
TO THE EDITOR
Superbasic System CsOН/DMSO as a Catalyst
of Nucleophilic Addition of Acetophenone to Phenylacethylene
B. A. Trofimov, E. Yu. Schmidt, N. V. Zorina, and A. I. Mikhaleva
Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: boris_trofimov@irioch.irk.ru
Received March 18, 2010
DOI: 10.1134/S1070363210070327
So far, the base-catalyzed addition of ketones to
acetylenes was unknown. The reason, apparently, is
the assumption that acetylenes, as a rather strong СН-
acids under the action of strong bases would be
deprotonated into acetylenide anions, which are inert
with respect to other nucleophiles. Moreover,
acetylenide anions readily (at room and lower
temperatures) add to the carbonyl group of ketones
Following this logic, we have studied the reaction
of acetophenone I with phenylacetylene II in the
о
superbasic system CsOH/DMSO at 100 С. Indeed, it
turned out that ketone I adds to acetylene II to afford
styrylmethyl phenyl ketone III in up to 70% yield. The
reaction is characterized by high chemoselectivity: the
product of the Favorsky reaction, acetylenic alcohol
IV, cannot be even detected in the reaction mixture by
1
(
the Favorsky reaction [1, 2]).Yet, however, the fact
the Н NMR spectroscopy (Scheme 1).
that upon heating above 60°С tertiary acetylenic
alcohols decompose into the starting components,
ketones and acetylenes (the reverse Favorsky reaction
An important preparative advantage of the new
reaction is its stereospecificity: Adduct III is obtained
exclusively as the Е-isomer. However, this
stereospecificity is not a result of the kinetic control,
since if the reaction is stopped after 1 h the ratio of the
E- and Z-isomers is 1:1. Therefore, it is evident that
first the Z-isomer is formed (in accordance with the
rule of the trans-nucleophilic addition to mono-
substituted acetylenes [5]) which upon further heating
[
3]) is disregarded. It can be assumed, therefore, that at
elevated temperature carbanions of ketones will add to
non-ionized molecules of acetylenes existing in
equilibrium with acetylenide anions. Such an addition
is the more probable since ketones are stronger СН-
acids than acetylenes (pKa in DMSO for acetophenone
is ~22–24, for phenylacetylene ~26–29 [4]).
Scheme 1.
m
p
o
i
α
o'
i'
m'
p'
β
CsОН/DMSO
O
о
1
00 С, 2 h
III
Me
+
O
Me
OH
II
I
IV
1
385

1
386
TROFIMOV et al.
completely isomerizes into the Е-isomer, that is, the
stereochemistry is thermodynamically controlled.
hexane). Yield 0.64 g (69%). White crystals, mp 92–
94°C. IR spectrum, ν, cm : 3082, 3061, 3023, 1683,
–
1
1
1
597, 1496, 1449, 1399, 1356, 1334, 1296, 1277,
208, 1071, 983, 908, 749, 732, 688, 566, 501. Н
Noteworthy is also the regiospecificity of the
reaction: The carbanion of acetophenone adds only to
the terminal acetylenic carbon atom. We also failed to
detect in the reaction mixture chalcone V, which could
be formed due to prototropic migration of the double
bond towards the carbonyl group. This is indicative of
a stronger conjugation in the Е-styryl fragment as
compared to that in chalcone V (Scheme 2).
1
NMR spectrum, δ, ppm: 7.99 m (2H, H ), 7.56 m (1H,
H ), 7.46 m (2H, H ), 7.36 m (2H, H ), 7.28 m (2H,
H ), 7.20 m (1H, H ), 6.53 d (1H, H , J 16.1 Hz),
6
o
p
m
o'
3
m'
p'
α
3
3
.45 d.t (1H, H , J 16.1 Hz, J 6.1 Hz), 3.90 d (2H,
b
3
13
CH , J 6.1 Hz). C NMR spectrum, δ, ppm: 197.9
2
(
C=O), 137.0 (C ), 136.5 (C ), 133.5 (C ), 133.1 (C ),
i' i α p
)
1
28.6 (C ), 128.4 (C ), 128.3 (C ), 127.3 (C , 126.2
m m' o p'
(
6
C ), 122.5 (C ), 42.7 (CH ). Found, %: C, 86.67; H
o' b 2
Scheme 2.
.57. Calculated, %: C, 86.45; H, 6.35. (222.28).
Apparently, there are no principal restrictions to
expand this reaction to other ketones, acetylenes, and
superbasic media. We continue investigations in this
direction.
III
O
V
REFERENCES
(
E)-1,4-Diphenyl-3-buten-1-one
(III).
The
mixture of acetophenone I (0.50 g, 4 mmol),
1
.
Favorskii, А.Е. and Skosarevskii, M.P., Zh. Ross. Khim.
Ob–va, 1900, vol. 32, p. 652.
.
phenylacetylene II (0.43 g, 4 mmol), and CsOH H O
2
(
0.70 g, 4 mmol) in 15 ml of DMSO was heated for 2 h
2
3
.
.
Trofimov, B.A., Curr. Org. Chem., 2002, vol. 6, p. 1121.
Crisp, G.T. and Jiang, Y.-L., Synth. Commun., 1998,
no. 28, p. 2571.
o
at 100 C with stirring on a magnetic stirrer. The
reaction mixture was diluted with water (40 ml),
neutralized with NH Cl, and extracted with ether (4 ×
4
4. Reutov, О.А., Beletskaya, I.P., and Butin, K.P., СН-
Kisloty (CH Acids), Мoscow: Nauka, 1980.
5
5
ml). The ether extract was washed with water (3 ×
ml), dried over potassium carbonate, ether was
5
.
Dickstein, J.I. and Miller, S.I., in The Chemistry of the
Carbon-Carbon Triple Bond, Patai, S., Ed., part 2, New
York: Wiley, 1978, p. 813.
removed. From the residue (0.81 g), pure ketone III
was isolated by column chromatography (Al O ,
2
3
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 7 2010