Direct dichlorovinylation of some carbonyl compounds by trichloroethylene under conditions of phase-transfer catalysis

Article abstract of DOI:10.1016/S0040-4020(00)00557-3

Reaction of ketones 1 and 3 with trichloroethylene (TRI) carried out in the presence of 50% aq. NaOH and TBAHS as a catalyst, in ethyl ether (phase-transfer catalysis, PTC) afford 1,2-dichlorovinylated ketones 2 and 4, respectively in good yields, usually as mixtures of Z and E isomers. PTC reaction of aldehydes 5 with TRI, carried out with DMSO instead of TBAHS, yields O-dichlorovinylated products 6, as mixtures of isomers in the case of 6a. These products are formed via C- or O-addition of ambident enolate anions to dichloroacetylene (generated from TRI by a base) and fast protonation of highly basic dichlorovinyl anions thus formed. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00557-3

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 6083±6087
Direct Dichlorovinylation of Some Carbonyl Compounds by
Trichloroethylene Under Conditions of Phase-Transfer Catalysis
*
Andrzej Jonczyk and Agnieszka H. Gierczak
Â
Warsaw University of Technology, Faculty of Chemistry, Koszykowa 75, PL-00-662 Warsaw, Poland
Received 9 March 2000; revised 24 May 2000; accepted 8 June 2000
AbstractÐReaction of ketones 1 and 3 with trichloroethylene (TRI) carried out in the presence of 50% aq. NaOH and TBAHS as a catalyst,
in ethyl ether (phase-transfer catalysis, PTC) afford 1,2-dichlorovinylated ketones 2 and 4, respectively in good yields, usually as mixtures of
Z and E isomers. PTC reaction of aldehydes 5 with TRI, carried out with DMSO instead of TBAHS, yields O-dichlorovinylated products 6, as
mixtures of isomers in the case of 6a. These products are formed via C- or O-addition of ambident enolate anions to dichloroacetylene
(generated from TRI by a base) and fast protonation of highly basic dichlorovinyl anions thus formed. q 2000 Elsevier Science Ltd. All
rights reserved.
Introduction
2g,h) to afford ketones 2 of purity at least 95%, except 2d
and 2f (Table 1). In the case of 2e pure samples of both
isomers were isolated by careful fractional crystallization.
Comparison of measured and calculated chemical shifts of
Treatment of trichloroethylene (TRI) with a base generates
dichloroacetylene (DCA), which is prone to add carbanions
with the formation of 1,2-dichlorovinyl substituted deriva-
tives, and occasionally other products.1 Thus, tertiary
enolates formed from esters, chain and cyclic ketones by
means of LDA in HMPA,1,2 and carbanions generated from
2-substituted phenylacetonitriles3 under conditions of
phase-transfer catalysis (PTC),4 both give with TRI
products of dichlorovinylation. The latter reaction is carried
out under particularly convenient conditions, and affords the
products in good yields.
1
vinylic protons in H NMR spectra5 allowed us to ascribe
tentatively Z and E stereochemistry to both isolated samples
of ketone 2e6 (Fig. 1).
Taking into account that the vinylic proton in the Z isomer
absorbs at higher ®eld than E-isomer of 2e, we determined Z
and E stereochemistry of other products 2 (Table 1). In all
cases E isomers prevail (2a±e) or are the only products
isolated (2f±h).
To determine the scope of this simple PTC dichlorovinyla-
tion procedure, some ketones and aldehydes were allowed
to react with TRI.
Phenylacetone derivatives, namely 3-phenylheptan-2-one
and 3,4-diphenylbutan-2-one,7 formed rather complex
products mixtures when allowed to react with TRI under
different PTC conditions (above described liquid±liquid
system with TBAHS or DMSO and solid±liquid system
with powdered sodium hydroxide and TBAHS, at 220±
358C). It seems that in the case of these two ketones
isomeric methyl enolate anions participate in reactions
with TRI. However, attempted reaction of isobutyrophe-
none, which possesses only one acidic site, with TRI
under PTC conditions revealed that it remains intact, prob-
ably because of relatively low acidity. On the other hand, 3-
cyano-3-phenylpropan-2-one (3) does react with TRI to give
one, (presumably E) isomer of the expected product of
dichlorovinylation 4. Due to formation of large amounts
of tarry material in this reaction, the ketone 4 was isolated
in moderate yield (Scheme 2). The high acidity of the
methine hydrogen in 3 (and the activity of enolate anion
thus formed), totally prevents competitive generation of
the methyl enolate.
Results and Discussion
We found that stirring of ketones 1 with TRI in the presence
of 50% aq. sodium hydroxide and tetra-n-butylammonium
hydrogen sulfate (TBAHS) as a catalyst (phase-transfer
catalysis, PTC), at temperature 5±258C, produces 1,2-
dichlorovinyl substituted derivatives 2, usually as mixtures
of Z and E isomers, in 54±83% yield (Scheme 1, Table 1).
The crude reaction mixtures were puri®ed by Kugelrohr
distillation (products 2a±f) or crystallization (products
Keywords: phase-transfer; enolates; dichloroacetylene; addition reactions.
* Corresponding author. Tel.: 148-22-621-4230; fax: 148-22-628-2741;
e-mail: anjon@ch.pw.edu.pl
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00557-3

Â
A. Jonczyk, A. H. Gierczak / Tetrahedron 56 (2000) 6083±6087
6084
Scheme 1.
Finally, aldehydes 5 when allowed to react with TRI under
PTC conditions with DMSO, afforded O-alkylated products,
the corresponding enol ethers 6, in good yields (Scheme 3).
Under these conditions, less intractable material is formed
than in reactions catalyzed by TBAHS.
alkenes. The simultaneous formation of Z and E isomers of
products 2 is probably result of competitive cis (minor path-
way) and trans (major pathway) addition of 1 to DCA. Due
to more sterically crowded carbon center in enolate anions,
in comparison with nitrile ones, some products 2 are formed
in a non-stereoselective fashion. On the other hand, forma-
tion of 6a,b with possibly E-geometry of dichlorovinyl
group, indicates trans-addition of enolate anion to DCA.
The O-center of the enolate anion is less sterically crowded
than the C-centered anion and this explains why in the case
of aldehydes 5 only one, possibly E-isomer of 6, is isolated.
Calculated and measured chemical shifts of vinylic protons
in 6a are consistent, and indicate that possibly Z-6a is the
main product (Fig. 2).
Apart from correct analytical data (e.g. lack of strong band
of carbonyl group in IR spectra at n,1700 cm21) the enol
ether structure of 6 was con®rmed by acid catalyzed hydro-
lysis, which gave starting aldehydes 5 and other products.
As a result of our investigations, PTC dichlorovinylation is
extended to relatively acidic ketones 1, cyanoketone 3 and
phenylacetaldehyde derivatives 5, to afford respectively, C-
2,4 or O-substituted derivatives 6. The process is very
simple, performed on easily available substrates (ketones
1a±e can be prepared by PTC alkylation of desoxyben-
zoine10), and affords the products in good yields. Chloroa-
cetylenes are strong lachrymators and react violently with
oxygen from air.11 However, the described reactions are safe
since they are carried out in ethyl ether which forms a stable
complex with DCA.12
To collect more information on the above described
processes we carried out reaction of ketone 1b with inde-
pendently synthesized dichloroacetylene (DCA).8b It led to
formation of ketone 2b as mixture of Z and E isomers of
similar ratio like in reaction of 1b with TRI, but produced
rather complex product mixtures which contained some
unreacted 1b. This result is not unexpected since DCA,
apart from the desired reaction with enolate anion (the
concentration of which in PTC processes is low not exceed-
ing that of the catalyst4), can react with water and/or hy-
droxy anions with formation of side products. On the other
hand, concentration of DCA generated from TRI in the
presence of C±H acid is much lower, therefore it is able
to react more selectively with enolate anions from 1. The
experiment described above indicates that DCA is indeed
involved in PTC reactions of carbonyl compounds with TRI
(Scheme 4).
Experimental
General
Boiling points and melting points (determined in open capil-
lary tube apparatus) are uncorrected. 1H NMR spectra were
measured in CDCl3 on a Varian Gemini 200 or Varian
Gemini 500 (at 200 or 500 MHz, respectively), 13C NMR
spectra on a Varian Gemini 200 (at 50 MHz). Chemical
shifts (d) are given in ppm relative to TMS and coupling
constants (J) are given in Hz. Gas chromatography (GC)
Carbanions usually add trans to acetylenes to generate a
highly basic vinylic anion.9 In the case of symmetrically
disubstituted acetylenes, protonation of this anion gives E
Table 1. 1,2-Dichlorovinylated ketones 2a±h
Entry
2
Reaction conditions
Temp. (8C) Time (h)
Yield (%)
Bp (8C/Torr)a or mp (8C)
E/Zb
Purity (%)b
1
2
3
4
5
6
7
8
a
b
c
d
e
f
20±25
20±25
20±25
5±10
5±10
5±10
6
6.5
6
6.5
7
6
63
71
62
54
79
62
76
83
155±160/0.2
2.3
95
99
98
82
98.5
89
ca 100
ca 100
155±160/0.15
160±165/0.1
150±155/0.3
170±175/0.1
155±160/0.2
2.3c
2.0d
2.0
1.8e
f
f
f
g
h
20±25
20±25
6
5.5
116±117 (MeOH)
114±115 (MeOH)
a Kugelrohr distillation (bath temperature).
b Determined in distilled or crystallized products by GC and/or 1H NMR.
c E-2b, mp 92±938C (EtOH).
d E-2c, mp 68±698C (EtOH).
e Z-2e, mp 94±958C (MeOH), E-2e, mp 100±101.58C (MeOH).
1
f One, possibly E isomer (by GC and/or H NMR).

Â
A. Jonczyk, A. H. Gierczak / Tetrahedron 56 (2000) 6083±6087
6085
isomers of 2e were isolated from distillates respectively by
crystallization or by fractional crystallization (Table 1).
Analytical samples of 2a,d,f were prepared by column chro-
matography.
(Z1E)-2a, yellow oil [Found C, 64.91; H, 5.44; Cl, 24.24.
C16H16Cl2O requires C, 65.09; H, 5.46; Cl, 24.02]; nmax
(®lm) 3108, 3060, 2972, 2932, 1624, 1492, 1444, 1096,
760, 700 cm21; dH (500 MHz, CDCl3, in parentheses data
for E isomer) 0.93 (1.02) [3H, t, Jˆ18.5 Hz (19.0 Hz), CH3],
2.42 (2.68) [2H, q, Jˆ18.5 Hz (19.0 Hz), CH2], 5.26 (5.46)
[1H, s, HCv], 7.04±7.56 (10H, m, ArH of both isomers).
Figure 1.
analyses were performed with a Hewlett±Packard 5890
Series II chromatograph, equipped with HP501 capillary
column (30 m). IR spectra were recorded on Perkin±
Elmer 577 spectrometer, liquids as ®lms and solids as potas-
sium bromide pellets. Elemental analyses were performed
with a Perkin±Elmer CHNO/S Series II, 2400 microanaly-
zer. Column chromatography was carried out on Merck
Kieselgel 60 (230±400 mesh) with hexane±ethyl acetate
as eluent. Ketones 1a±e,10 1f,13 1g,14 1h,15 and 316 were
prepared according to literature procedures. Commercially
available aldehydes 5a,b were vacuum distilled before use.
Z-2b, colorless oil; nmax (®lm) 3104, 3060, 2960, 2928,
1624, 1464, 1444, 1100, 760, 700 cm21; dH [200 MHz,
CDCl3, read from the spectrum of (Z1E)-2b] 0.77 (3H, t,
Jˆ7.1 Hz, CH3), 1.20±1.31 (4H, m, CH2), 2.40 (2H, t,
Jˆ7.4 Hz, CH2), 5.28 (1H, s, HCv), 7.28±7.35 (1H, m,
ArH), 7.38±7.45 (7H, m, ArH), 7.50±7.55 (2H, m, ArH).
E-2b, colorless crystals [Found C, 68.96; H, 5.79; Cl, 20.19.
C20H20Cl2O requires C, 69.17; H, 5.80; Cl, 20.42]; nmax
(KBr) 3104, 3060, 2956, 2928, 1620, 1496, 1444, 1100,
768, 704 cm21; dH (500 MHz, CDCl3) 0.88 (3H, t,
Jˆ7.0 Hz, CH3), 1.33±1.38 (4H, m, CH2), 2.66 (2H, t,
Jˆ7.5 Hz, CH2), 5.46 (1H, s, HCv), 7.07±7.18 (6H, m,
ArH), 7.23±7.42 (3H, m, ArH), 7.50±7.52 (1H, m, ArH).
Caution: We have never encountered the explosive nature
of dichloroacetylene but its fumes may explode on contact
with air.
Z-2c, pale yellow oil; nmax (KBr) 3100, 3062, 2954, 2928,
1622, 1494, 1444, 1104, 764, 702 cm21; dH [200 MHz,
CDCl3, read from the spectrum of (Z1E)-2c] 0.83 (3H, t,
Jˆ7.7 Hz, CH3), 1.05±1.41 (8H, m, CH2), 2.38 (2H, t,
Jˆ6.4 Hz, CH2), 5.28 (1H, s, HCv), 7.26±7.55 (10H, m,
ArH).
Preparation of dichlorovinyl substituted derivatives
2a±h and 4
A mixture of ketone 1a±h or 3 (20 mmol), 50% aq. NaOH
(6.6 g, 4.3 mL, 80 mmol), ethyl ether (5 mL; 10 mL in the
case of 3) and TBAHS (0.07 g, 0.2 mmol) was stirred, while
a solution of TRI (3.4 g, 2.3 mL, 26 mmol) in ethyl ether
(3 mL) was slowly added (ca 0.5 h) at the temperature indi-
cated in Table 1, in the case of 3 at 20±258C (small exother-
mal effect was observed). The mixture was stirred at the
temperature and for the time given in Table 1 (in the case
of 3 at 20±258C for 6 h), diluted with water (25 mL), the
phases were separated, the water phase was extracted with
ethyl ether (2£15 mL), combined organic extracts were
washed with water (2£20 mL), dried (MgSO4), the solvent
was evaporated, the residue was distilled on Kugelrohr
E-2c, colorless crystals [Found C, 70.3; H, 6.41; Cl,
18.69. C22H24Cl2O requires C, 70.4; H, 6.44; Cl,
18.89]; nmax (KBr) 3100, 3060, 2960, 2928, 1624,
1492, 1444, 1104, 764, 700 cm21
; dH (500 MHz,
CDCl3) 0.95 (3H, t, Jˆ7.7 Hz, CH3), 1.44±1.68 (8H,
m, CH2), 2.64 (2H, t, Jˆ6.7 Hz, CH2), 5.49 (1H, s,
HCv), 7.12±7.51 (10H, m, ArH).
(Z1E)-2d, yellow oil [Found C, 68.75; H, 4.60; Cl, 21.12.
C19H16Cl2O requires C, 68.89; H, 4.68; Cl, 21.41]; nmax
(®lm) 3104, 3060, 3028, 2960, 2928, 2864, 1688, 1624,
1448, 1268, 1104, 828, 760, 700 cm21; dH (200 MHz,
1
apparatus or crystallized, and analyzed by GC and/or H
NMR to determine ratio of Z/E isomers as well as their
purity (Table 1). Pure E isomers of 2b,c and pure Z and E
Scheme 2.
Scheme 3.

Â
A. Jonczyk, A. H. Gierczak / Tetrahedron 56 (2000) 6083±6087
6086
7.03±7.31 (8H, m, ArH), 7.36±7.39 (3H, m, ArH), 7.61±
7.68 (4H, m, ArH).
4, pale yellow oil [Found C, 56.66; H, 3.54; N, 5.45; Cl,
27.66. C12H9NOCl2 requires C, 56.72; H, 3.56; N, 5.51; Cl,
27.80]; nmax (®lm) 2956, 2864, 2244, 1616, 1460, 1036,
760, 700 cm21; dH (200 MHz, CDCl3) 2.48 (3H, s, CH3),
6.02 (1H, s, HCv), 7.36±7.57 (5H, m, ArH).
Figure 2.
Preparation of enol ethers 6a,b
CDCl3) 1.82±1.88 (2.22±2.31) [2H, m, CH2], 4.93±5.14
(2H, m, H2Cv for both isomers), 5.68±5.95 (1H, m,
HCv for both isomers), 6.45 (6.95) [1H, s, HCClv],
7.06±8.11 (10H, m, ArH of both isomers).
Aldehyde 5 (50 mmol), TRI (8.5 g, 6.0 mL, 65 mmol), ethyl
ether (7.3 mL) and DMSO (10 mL) were stirred, while 50%
aq. NaOH (16.0 g, 10.0 mL, 200 mmol) was added slowly
dropwise at 208C, and the mixture was stirred at 20±258C
for 5±5.5 h, worked-up as above and distilled on Kugelrohr
apparatus. Fresh analytical samples of 6a,b were isolated by
column chromatography.
Z-2e, colorless crystals [Found C, 72.60; H, 4.60; Cl, 18.48.
C23H18Cl2O requires C, 72.68; H, 4.77; Cl, 18.65]; nmax
(KBr) 3084, 3060, 2920, 2852, 1620, 1496, 1444, 1100,
1056, 700 cm21; dH (500 MHz, CDCl3) 3.80 (2H, s, CH2),
5.34 (1H, s, HCv), 7.10±7.14 (3H, m, ArH), 7.19±7.23
(3H, m, ArH), 7.26±7.30 (2H, m, ArH), 7.38±7.40 (5H,
m, ArH), 7.57±7.59 (2H, m, ArH); dC (50 MHz, CDCl3)
39.17, 99.35, 126.04, 126.73, 127.04, 127.78, 127.93,
128.22, 128.28, 128.53, 128.93, 129.05, 129.21, 129.45,
218.46.
(Z1E)-6a, colorless oil (8.0 g, 70%), purity 98%, bp 125±
1308C/0.3 Torr; [Found C, 57.62, H, 4.38, Cl, 30.81.
C11H10Cl2O requires C, 57.67, H, 4.4, Cl, 30.94]; nmax
(®lm) 3100, 2920, 1620, 1115, 760, 700 cm21; dH
(200 MHz, CDCl3, in parentheses data for Z isomer) 2.08
(2.21) [3H, d, Jˆ1.4 Hz (1.4 Hz), CH3], 5.64 (5.68) [1H, s,
HCClv], 6.48 (6.76) [1H, q, Jˆ1.4 Hz (1.4 Hz), HCv),
7.22±7.40 (3H, m, ArH of both isomers), 7.60±7.65 (2H,
m, ArH of both isomers).
E-2e, colorless crystals [Found C, 72.55; H, 4.62; Cl, 18.42.
C23H18Cl2O requires C, 72.68; H, 4.77; Cl, 18.65]; nmax
(KBr) 3096, 3060, 2920, 2852, 1620, 1496, 1444, 1100,
1054, 700 cm21; dH (200 MHz, CDCl3) 3.92 (2H, s, CH2),
5.55 (1H, s, HCv), 7.08±7.19 (6H, m, ArH), 7.25±7.31
(2H, m, ArH), 7.37±7.41 (5H, m, ArH), 7.52±7.61 (2H,
m, ArH); dC (50 MHz, CDCl3) 38.42, 99.12, 125.96,
126.09, 126.78, 127.66, 127.93, 128.16, 128.33, 129.01,
129.76, 129.92, 212.03.
6b, colorless oil (10.9 g, 75%), purity 98%, bp 165±1708C/
0.3 Torr; [Found C, 65.89; H, 4.08, Cl, 24.15. C16H12Cl2O
requires C, 65.99, H, 4.15, Cl, 24.35]; nmax (®lm) 3050,
1615, 1100, 770, 700 cm21; dH (200 MHz, CDCl3) 5.71
(1H, s, HCv), 6.84 (1H, s, HCv), 7.25±7.68 (10H, m,
ArH).
Acidic cleavage of enol ethers 6
E-2f, pale yellow oil [Found C, 58.91; H, 3.35; Cl, 32.34.
C16H11Cl3O requires C, 59.02; H, 3.40; Cl, 32.66]; nmax
(KBr) 3104, 3072, 1612, 1440, 1248, 1096, 824,
696 cm21; dH (200 MHz, CDCl3) 5.29 (1H, s, HCv),
7.10±7.55 (7H, m, ArH), 7.56±7.96 (3H, m, ArH).
Divinyl ether 6 (0.4 mmol), dioxane (5 mL), water (5 mL)
and conc. hydrochloric acid (0.1 mL) were re¯uxed for 2 h,
diluted with water (15 mL), extracted with ethyl ether
(3£10 mL), the organic extracts were washed with water
(2£15 mL), dried (MgSO4) and evaporated. The residue
was analyzed by GC to show aldehydes 5 (main component)
and other products.
E-2g, colorless crystals [Found C, 68.83; H, 4.36; Cl, 18.21.
C22H16Cl2O2 requires C, 68.94; H, 4.20; Cl, 18.49]; nmax
(KBr) 3108, 3020, 1612, 1476, 1444, 1096, 828,
700 cm21; dH (200 MHz, CDCl3) 5.52 (1H, s, HCv),
6.88±7.00 (3H, m, ArH), 7.15±7.37 (9H, m, ArH), 7.55±
7.71 (3H, m, ArH).
Reaction of ketone 1b with DCA
Complex8b of DCA with ethyl ether (0.9 g, ca 5 mmol of
DCA) was added dropwise to a mixture of 1b (1.0 g,
4 mmol), TBAHS (0.01 g, 0.04 mmol), 50% aq. NaOH
(1.3 g, 0.85 mL, 16 mmol) and ethyl ether (5 mL), during
stirring. The mixture was stirred at 20±258C for 5 h, and
worked up as described above for preparation of 2a±h and
E-2h, yellow crystals [Found C, 66.07; H, 4.19; Cl, 16.85.
C22H16Cl2OS requires C, 66.17; H, 4.04; Cl, 17.05]; nmax
(KBr) 3100, 3028, 1624, 1488, 1444, 1132, 760,
692 cm21; dH (200 MHz, CDCl3) 5.58 (1H, s, HCv),
Scheme 4.

Â
A. Jonczyk, A. H. Gierczak / Tetrahedron 56 (2000) 6083±6087
6087
5. GuÈnther, H. NMR Spectroscopy. An Introduction, Wiley:
Chichester, 1980 (Polish translation; PWN: Warszawa, 1983; pp
118±123).
4. The residue after evaporation of the solvent was analyzed
by GC to show ca 58% of E and Z-2b (ratio ca 1.5:1), ca
14% of unreacted 1b, and other products.
6. The differences in calcd versus measured chemical shifts dHCv
for Z-2e and E-2e are possibly due to unknown values of incre-
ments of PhCOC(CH2Ph)Ph substituent. To calculate dZ-HCv and
dE-HCv of 2e we assumed dZˆ20.26 ppm and dEˆ20.29 ppm,5
respectively.
Acknowledgements
Financial support from the State Committee for Scienti®c
Research, Warszawa, Poland (Grant no. 3 T09A 013 15) is
gratefully acknowledged.
Â
7. Jonczyk, A.; Sera®n, B.; MaÎkosza, M. Roczniki Chem. 1971, 45,
1027±1039; Chem. Abstr. 1971, 75, 109997e.
8. (a) Pielichowski, J.; Popielarz, R. Synthesis 1984, 433±434. (b)
Pielichowski, J.; Bogdal¤, D. J. Prakt. Chem. 1989, 331, 145±148.
9. (a) Deslongchamps, P. Stereoelectronic Effects in Organic
Chemistry; Baldwin, J. E., Ed.; Organic Chemistry Series; Perga-
Â
mon: Oxford, 1983; Vol. 1, pp 291±294. (b) Jonczyk, A.; Pakulski,
Z. Tetrahedron Lett. 1996, 37, 8909±8912 and references cited
therein.
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