Synthesis of 1-phenylbut-3-ene-1,2-dione and its attempted radical polymerization

Article abstract of DOI:10.2478/s11696-010-0023-9

1,2-Diketone moiety-bearing monomer 1-phenylbut-3-ene-1,2-dione, an analogue of phenyl vinyl ketone, was synthesized from 4-chlorobutyryl chloride in a 29 % overall yield in five steps. Following acylation of benzene with 4-chlorobutyryl chloride, the resulting α-methylene group was oxidized to 1,2-diketone in three steps: successive bromination, substitution with lithium hydroxide, and oxidation of α-hydroxyketone with potassium dichromate. The final step was dehydrochlorination of 4-chloro-1-phenyl-butane-1,2-dione. The attempted copolymerization of this monomer with styrene, using AIBN as the initiator, was unsuccessful.

Full text of DOI:10.2478/s11696-010-0023-9

Chemical Papers 64 (4) 499–503 (2010)
DOI: 10.2478/s11696-010-0023-9
ORIGINAL PAPER
Synthesis of 1-phenylbut-3-ene-1,2-dione and its attempted radical
polymerization
a
a
b
b
a,bBranislav Husár*, Ivan Lukáč, Štefan Chmela, Jean-Louis Canet, Yves Troin
aPolymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 842 36 Bratislava, Slovak Republic
bLaboratoire de Chimie des Hétérocycles et des Glucides, B. P. 10448, Clermont Université, ENSCCF, EA 987, 63000
Clermont-Ferrand, France
Received 22 September 2009; Revised 9 December 2009; Accepted 12 December 2009
1,2-Diketone moiety-bearing monomer 1-phenylbut-3-ene-1,2-dione, an analogue of phenyl vinyl
ketone, was synthesized from 4-chlorobutyryl chloride in a 29 % overall yield in five steps. Following
acylation of benzene with 4-chlorobutyryl chloride, the resulting α-methylene group was oxidized
to 1,2-diketone in three steps: successive bromination, substitution with lithium hydroxide, and
oxidation of α-hydroxyketone with potassium dichromate. The final step was dehydrochlorination of
4-chloro-1-phenyl-butane-1,2-dione. The attempted copolymerization of this monomer with styrene,
using AIBN as the initiator, was unsuccessful.
c
ꢀ 2010 Institute of Chemistry, Slovak Academy of Sciences
Keywords: 1,2-diketones, phenyl vinyl ketone, benzil, photodegradable polymer
CH2 CH2
H2C
C
C
CH2 CH
C
CH2 CH
C
Introduction
C
O
O
O
O
λ = 366 nm
Preparation of photodegradable polymers using
light with wavelength greater than 400 nm, which is
supposed to be harmless to human tissue, is of great
interest. Benzil and other 1,2-dicarbonyl structures
fulfill this criterion of light adsorption. For example,
poly(phenyl vinyl ketone) and its derivatives have a
low lying n → π* absorption band at 366 nm that has
been studied extensively (Lukáč et al., 1971; Hrdlovič
& Lukáč, 1982; Hrdlovič et al., 1972, 1986; Rabek,
1987). Irradiation leads to a decrease in the molecular
weight through a Norrish type II reaction (Fig. 1).
Similarly as for the monoketone (Fig. 1), pho-
todegradation of a polymer bearing the 1,2-dicarbonyl
structure (Fig. 2) can be conceptualized. This polymer
is also expected to have an absorption band at above
400 nm.
+
Fig. 1. Norrish type II photoreaction of poly(phenyl vinyl ke-
tone) leading to main chain scission.
CH2 CH
CH2 CH
H2C
C
C
C
CH2 CH2
C
C
O
O
C
C
O
O
C
C
O
O
O
O
hν
hν
+
Fig. 2. Possible Norrish type II reaction of poly(1-phenylbut-
3-ene-1,2-dione) leading to main chain scission.
Photochemistry of low molecular 1-alkyl-2-phenyl-
1,2-diketones, in solution and under an inert atmo-
sphere, was studied thoroughly by Wagner et al.
(1976). In the presence of molecular oxygen from air,
irradiation of a polymer film may give completely dif-
ferent results as it acts similarly to the photoreaction
*Corresponding author, e-mail: branislav.husar@savba.sk

500
B. Husár et al./Chemical Papers 64 (4) 499–503 (2010)
O
O
O
O
O
V
O
Cl
Cl
Cl
Cl
iii
v
i
ii
iv
Cl
Cl
Br
OH
III
O
O
I
IV
II
Fig. 3. Synthesis of 1-phenylbut-3-ene-1,2-dione (V ). Reaction conditions: i) benzene, AlCl3; ii) Br2, CH3COOH; iii) LiOH, aq.
MeOH; iv) K2Cr2O7, Bu4NHSO4, CH2Cl2, H2SO4; v) Et3N, cyclohexane.
of benzil in a polymer matrix. 1,2-Dicarbonyl struc-
tures of benzil insert oxygen between two carbonyls to
form benzoylperoxide (Husár & Lukáč, 2008). A sim-
ilar insertion reaction is presumed for the structures
in Fig. 2.
252 mmol) in benzene (40 mL) was added dropwise
during 1 h keeping the temperature under 5◦C. The
resulting mixture was stirred for 30 min. The reaction
was quenched by pouring the reaction mixture into a
mixture of ice (500 mL) and concentrated hydrochlo-
ric acid (30 mL). The aqueous layer was extracted
with benzene (3 × 100 mL). The combined organic
layers were washed with water, and dried with anhy-
drous sodium sulfate. After evaporation of benzene,
the product was purified by distillation at 117◦C and
67 Pa, yielding 42.3 g (92 %) of I as a colorless oil.
The monomer for the preparation of the polymer
shown in Fig. 2 is 1-phenylbut-3-ene-1,2-dione (V )
(Fig. 3). Compound V is an analogue of phenyl vinyl
ketone that polymerizes easily (Mosnáček et al., 2004).
At the same time, V also contains a 1,2-dicarbonyl
structure absorbing light in the desired region of wave-
lengths. During the preparation of V (Husár, 2004), a
new universal method of vinyl 1,2-diketone prepara-
tion from crotonaldehyde was proposed by Habel et
al. (2004). Very recently, Kashiwabara and Tanaka
(2009) reported the synthesis of V from oxopheny-
lacetyl chloride and vinyl tri-n-butylstannane. In this
paper, an alternative synthesis of monomer V and the
attempt to prepare copolymers using V and styrene
as the monomers are presented.
2-Bromo-4-chloro-1-phenylbutan-1-one (II)
To a stirred solution of ketone I (10.0 g, 54.7 mmol)
in glacial acetic acid (20 mL), bromine (2.8 mL, 55
mmol) was added dropwise during 1 h keeping the
temperature at 20–30◦C by occasional cooling in an
ice bath. Then, the mixture was stirred at 20–30◦C for
3 h. After evaporation of the solvent, the product was
distilled at 140◦C and 400 Pa, yielding 12.6 g (88 %) of
II as a colorless oil. This α-bromoketone is stable for
several years if stored in a dark flask in the refrigerator
(+4◦C).
Experimental
1
NMR spectra (400 MHz for H and 100 MHz for
13C, respectively) were recorded with a Bruker AC
400 spectrometer, using CDCl3 as a solvent. The sol-
vent signal was used as a reference. FTIR spectra
of the neat compound between two KBr plates were
recorded on an Impact 400 (Nicolet Instrument Corpo-
ration, WI, USA) FT spectrophotometer. Mass spec-
tra were recorded with a Hewlett Packard 5989B in-
strument. UV-VIS absorption spectra were measured
on a SPECORD M40 (Carl Zeiss, Jena, Germany)
spectrophotometer.
4-Chlorobutyryl chloride, azobisisobutyronitrile
(AIBN) (Fluka, Germany), LiOH· H2O, Bu4NHSO4,
triethylamine (Aldrich, Germany), AlCl3 (Merck, Ger-
many), bromine (Acros, Belgium), K2Cr2O7, H2SO4
(Lachema, Czech Republic), and all solvents (p.a.
quality) were used as received. Stabilized styrene
(Aldrich, Germany) was washed with diluted sodium
hydroxide solution and water, dried with anhydrous
MgSO4, and distilled.
4-Chloro-2-hydroxy-1-phenylbutan-1-one (III)
A solution of bromoketone II (5.0 g, 19 mmol) in
methanol (100 mL) and a solution of LiOH · H2O
(0.80 g, 19 mmol) in water (10 mL) were combined and
stirred for 1 h at room temperature. The reaction was
quenched by acidification with aqueous hydrochloric
acid. The mixture was evaporated to dryness and ex-
tracted with CH2Cl2 (2 × 15 mL). After evaporation
of CH2Cl2, the residue was purified by column chro-
matography (silica gel, ethyl acetate/cyclohexane, ϕr
= 1 : 8) to afford 2.7 g (71 %) of III as a colorless oil.
4-Chloro-1-phenylbutane-1,2-dione (IV)
A solution of K2Cr2O7 (0.44 g, 1.5 mmol) in con-
centrated sulfuric acid (4.5 mL) and water (9 mL) was
cooled to room temperature. Then, a solution of hy-
droxyketone III (0.90 g, 4.5 mmol) in dichloromethane
(11 mL) was added. After addition of Bu4NHSO4
(0.135 g, 0.40 mmol), the reaction mixture was stirred
for 5 min. The organic layer was separated, washed
with water (3 × 5 mL), and concentrated. The residue
was purified by column chromatography (silica gel,
4-Chloro-1-phenylbutan-1-one (I)
To a stirred suspension of anhydrous AlCl3 (33.6 g,
252 mmol) in benzene (170 mL) cooled in an ice
bath, a solution of 4-chlorobutyryl chloride (35.5 g,

B. Husár et al./Chemical Papers 64 (4) 499–503 (2010)
501
ethyl acetate/cyclohexane, ϕr = 1 : 10) to afford (af-
ter evaporation of the solvent at room temperature)
0.45 g (51 %) of IV (yellow oil) and 0.29 g (32 %) of
unreacted hydroxyketone III.
1,2-Diketones can also be prepared in three steps
starting with the α-bromination of ketone I, trans-
formation of so-formed II to α-hydroxyketone III, fol-
lowed by oxidation of the hydroxyl group. Accordingly,
α-bromination of ketone I using Br2 in glacial acetic
acid gave bromoketone II in a 88 % yield after dis-
tillation. Bromoketone II was described previously by
Wagner and Lindstrom (1987).
Originally, preparation of III from II in two steps:
nucleophilic substitution of Br by OAc, followed by
hydrolysis of the acetate, was attempted. The first
step, involving potassium acetate in refluxing acetoni-
trile, was quantitative. However, the following step
(using both alkaline and acidic hydrolysis conditions)
led to numerous undesired products. Hydroxyketone
III was finally prepared by alkaline hydrolysis of II
with lithium hydroxide in aqueous methanol in a 71 %
yield after chromatographic separation.
For oxidation of hydroxyketone III to diketone
IV, pyridinium chlorochromate (PCC) in refluxing
dichloromethane was used. The yield was only 20 %.
Treatment with poly(4-vinylpyridinium chlorochro-
mate) in cyclohexane at room temperature or under
reflux afforded no IV. Diketone IV was prepared in a
51 % yield by a very fast oxidation (5 min) of III in
dichloromethane by K2Cr2O7 in 9 M sulfuric acid in
the presence of a phase transfer catalyst. The product
was purified chromatographically. It was possible to
recover 32 % of unreacted III. Extended reaction time
led to lower yields.
Monomer V was then prepared quantitatively by
dehydrochlorination of IV using triethylamine in cy-
clohexane. Compounds IV and V were treated in dark-
ness or with red light illumination, where IV and V
do not absorb.
1-Phenylbut-3-ene-1,2-dione (V)
A solution of diketone IV (0.45 g, 2.3 mmol) and
triethylamine (0.32 mL, 2.3 mmol) in cyclohexane (10
mL) was stirred for 30 min in dark at room tem-
perature. The reaction was monitored by FTIR spec-
troscopy. The reaction was quenched by adding a so-
lution of concentrated hydrochloric acid (0.19 mL)
in water (2 mL). The organic layer was separated,
washed with water, dried with CaCl2, and concen-
trated to afford 0.366 g (100 %) of V as a yellow
oil. Because an unidentified mixture of products was
formed during the storage of a cyclohexane solution
of V in a lightproof flask at −20◦C overnight, prod-
uct V was used in the next step immediately after its
preparation.
Polymerization reactions
An ampoule containing styrene (5 mL, 43.6 mmol)
and AIBN (5 mg) was sealed under argon and poly-
merized at 60◦C for 24 h. The polymer was precip-
itated from the chloroform solution into methanol.
Conversion was 85 mass %.
An ampoule containing V (0.366 g, 2.3 mmol),
styrene (5 mL, 43.6 mmol), and AIBN (5 mg) was
sealed under argon and polymerized at 60◦C for 24
h. The polymerization mixture was precipitated into
methanol. Conversion of monomers was lower than
1 mass %.
Spectral characteristics of the corresponding prod-
ucts are summarized in Table 1.
Results and discussion
The present new synthetic route to 1-phenylbut-
3-ene-1,2-dione (V ) starts from simple and cheap
molecules. The route uses simple organic reactions.
Products I and II can be distilled, compounds III and
IV can be isolated easily by column chromatography.
The last reaction proceeds quantitatively. When this
new preparation method of V (Fig. 3) is compared
with that previously published (Fig. 4) for the prepa-
ration of aryl vinyl 1,2-diketones (Habel et al., 2004),
the present contribution may be seen as advantageous.
The creation of a sensitive double bond in the last
step according to the present contribution allows the
use of a straightforward oxidation method for the hy-
droxyl group. Hydroxyketone III is also an interesting
intermediate. The previous method reported the use
of photochemical hydroperoxidation by singlet oxy-
gen (Habel et al., 2004), a method that is both time-
consuming and which on a larger scale can generate
potentially hazardous amounts of hydroperoxides.
Finally, an attempt to copolymerize monomer V
with styrene using AIBN as the initiator of rad-
—
Because the C C double bond of enones is unsta-
—
ble in the presence of many reagents it is often ad-
visable to generate this functional group in the last
step of the synthesis (Fig. 3). Accordingly, the fol-
lowing synthetic route was used. Ketone I was pre-
pared by the Friedel–Crafts acylation of benzene with
4-chlorobutyryl chloride at 5◦C in a 92 % yield after
distillation, as described by Close (1957). When the
reaction temperature was increased to 30◦C, the ma-
jor product was 1,4-diphenylbutan-1-one.
Selective oxidation of the α-methylene group of I
by selenium dioxide was not satisfactory as the de-
sired diketone IV could not be separated from by-
products. A method for selective oxidation of the α-
methylene group proposed by Oka and Hara (1977)
was also unsuccessful. Although the corresponding α-
chlorosulfenyl chloride was prepared by refluxing with
SOCl2 in the first step, subsequent treatment with
morpholine at 5◦C followed by hydrolysis did not lead
to IV.

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B. Husár et al./Chemical Papers 64 (4) 499–503 (2010)
Table 1. Spectral data of prepared compounds
Compound
Spectral data
IR, ν˜/cm−1: 1687 (C O), 1597 (C C aromatic)
—
—
—
—
I
1H NMR (CDCl3), δ: 7.98 (m, 2H, Hortho), 7.57 (tt, 1H, J = 7.5 Hz, J = 1.5 Hz, Hpara), 7.47 (m, 2H, Hmeta), 3.68
(t, 2H, J = 6.0 Hz, CH2Cl), 3.18 (t, 2H, J = 7.0 Hz, COCH2), 2.23 (quintet, 2H, J = 6.5 Hz, CH2CH2Cl)
13
—
C NMR (CDCl3), δ: 199.0 (C O), 136.7 (Cipso), 133.2 (Cpara), 128.6 (Car), 128.0 (Car), 44.7 (CH2Cl),
—
35.3(COCH2), 26.8 (CH2CH2Cl)
MS, m/z (Ir/%): 185 (43) [M + 3], 183 (100) (M+), 165 (3), 147 (55), 120 (8), 105 (53), 91 (2), 77 (1)
IR, ν˜/cm−1: 1687 (C O), 1597 (C C aromatic)
—
—
—
—
II
1H NMR (CDCl3), δ: 8.04 (m, 2H, Hortho), 7.62 (tt, 1H, J = 7.5 Hz, J = 1.0 Hz, Hpara), 7.51 (t, 2H, J = 7.5 Hz,
Hmeta), 5.48 (dd, 1H, J = 8.0 Hz, J = 6.0 Hz, CHBr) 3.86–3.73 (m, 2H, CH2Cl), 2.61–2.54 (m, 2H, CH2CH2Cl)
13
—
C NMR (CDCl3), δ: 192.5 (C O), 134.0 (Cpara), 131.2 (Cipso), 128.9 (Car), 128.8 (Car), 43.6 (CH2), 42.4 (CH2),
—
35.7 (CH2CH2Cl)
MS, m/z (Ir/%): 265 (31) [M + 5], 263 (100) [M + 3], 261 (72) (M+), 227 (33), 225 (30), 183 (16), 181 (14), 147
(3), 105 (97), 91 (4), 77 (2)
UV-VIS (CHCl3), λmax/nm (log ε): 258 (3.98), 326 (2.24)
IR, ν˜/cm−1: 3463 (O—H), 1684 (C O), 1597 (C C aromatic), 1095 (C—O)
—
—
—
—
III
1H NMR (CDCl3), δ: 7.95 (d, 2H, J = 7.5 Hz, Hortho), 7.64 (t, 1H, J = 7.5 Hz, Hpara), 7.52 (t, 2H, J = 7.5 Hz,
Hmeta), 5.31 (ddd, 1H, J = 9.5 Hz, J = 6.5 Hz, J = 2.5 Hz, CHOH), 3.89 (td, 1H, J = 10.5 Hz, J = 4.5 Hz, CH2Cl),
3.77–3.70 (m, 2H, OH and CH2Cl), 2.33–2.24 (m, 1H, CH2CH2Cl), 1.91–1.81 (m, 1 H, CH2CH2Cl)
13
—
C NMR (CDCl3), δ: 201.2 (C O), 134.3 (Cpara), 133.0 (Cipso), 129.0 (Car), 128.7 (Car), 70.0 (CHOH), 41.5
—
(CH2Cl), 38.9 (CH2CH2Cl)
MS, m/z (Ir/%): 201 (44) [M + 3], 199 (100) (M+), 181 (21), 163 (23), 145 (13), 105 (14), 91 (2)
UV-VIS (CHCl3), λmax/nm (log ε): 255 (3.98), 282 (3.10)
—
—
IV
V
IR, ν˜/cm−1: 1716 (C O), 1673 (C O), 1597 (C C aromatic)
— —
— —
1H NMR (CDCl3), δ: 8.03 (m, 2H, Hortho), 7.66 (m, 1H, Hpara), 7.50 (m, 2H, Hmeta), 3.88 (t, 2H, J = 6.5 Hz,
CH2Cl), 3.38 (t, 2H, J = 6.5 Hz, COCH2)
13
—
—
—
—
C NMR (CDCl3), δ: 199.0 (C O), 190.7 (C O), 134.8 (Cpara), 131.6 (Cipso), 130.4 (Car), 128.9 (Car), 41.3
(CH2Cl), 37.6 (CO—CH2)
MS, m/z (Ir/%): 199 (36) [M + 3], 197 (89) (M+), 161 (75), 143 (15), 105 (100), 91 (15)
IR, ν˜/cm−1: 1670 (C O), 1599 (C C aromatic)
1H NMR (CDCl3), δ: 7.96 (d, 2H, J = 8.0 Hz, Hortho), 7.65 (t, 1H, J = 7.5 Hz, Hpara), 7.50 (t, 2H, J = 7.5 Hz,
—
—
—
—
—
meta), 6.73 (dd, 1H, J = 18.0 Hz, J = 10.5 Hz, CH CH2), 6.40 (d, 1H, J = 18.0 Hz, CH CH2), 6.24 (d, 1H, J
—
—
H
—
—
= 10.5 Hz, CH CH2)
—
13
—
—
—
—
—
—
—
—
C NMR (CDCl3), δ: 193.3 (C O), 192.8 (C O), 134.7 (CH CH2), 134.7 (Cpara), 132.7 (CH CH2), 132.5
(Cipso), 130.0 (Car), 128.9 (Car
)
MS, m/z (Ir/%): 161 (100) (M+), 143 (36), 105 (9)
UV-VIS (CHCl3), λmax/nm (log ε): 263 (4.04), 387 (1.47)
OH
O
OH
O
OH
iii
ii
iv
i
R
R
R
H
R
OH
O
OOH
Fig. 4. Universal method of vinyl 1,2-diketones preparation from crotonaldehyde described by Habel et al. (2004). Reaction con-
ditions: i) RMgBr, Et2O, 0◦C; ii) 5,10,15,20-tetraphenyl-21H,23H-porphine, O2, hν, CCl4, 0◦C; iii) Ph3P, 0◦C; iv) 4-
acetamido-TEMPO, p-TsOH, CH2Cl2; R = methyl, butyl, hexyl, isopropyl, phenyl, 2-phenylethyl.
ical polymerization was made. While a reference
polystyrene sample (from styrene and AIBN) reached
a high degree of polymerization, co-polymerization of
V with styrene resulted only in a very small amount
of a low molecular weight polymer. As IR bands cor-
responding to a dicarbonyl moiety (1707 cm−1 and
1673 cm−1) were observed in the FTIR spectrum of
the obtained polymer, V indeed underwent reaction.
success. Therefore, this polymer is useless for the in-
tended purpose. Most probably, monomer V reacts
quickly with the growing polystyrene radical forming
radicals with low propagating activity. Hence, only in-
hibition of styrene polymerization occurs similarly as
with some quinone derivatives (Bevington, 1989).
Acknowledgements. One of the authors (B.H.) thanks Prof.
Yves Troin for his acceptance in his laboratory. The au-
thors thank grant agencies VEGA and APVV for the support
through projects 2/0082/08 and APVV-0562-07. NMR mea-
surements provided by the Slovak State Program Project No.
2003SP200280203 are also gratefully acknowledged.
The molar masses were too low (Mn = 4800 g mol−1
,
Mw = 7300 g mol−1) to carry out further photochem-
ical evaluation of the copolymer as a film. Repeated
efforts to improve the polymerization were without

B. Husár et al./Chemical Papers 64 (4) 499–503 (2010)
503
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