Synthesis of polymers bearing sulfoxide groups by oxidation of monothio-orthoesters and their rearrangement into carboxylic ester-containing monomers and polymers

Article abstract of DOI:10.1016/S0040-4020(00)01132-7

Reaction of monomers, polymers and copolymers containing monothio-orthoester groups with meta-chloroperoxybenzoic acid in CH₂Cl₂ at 20°C affords the corresponding S-oxides. The chemoselective conversion of alkythio group into a sulfoxide moiety was achieved with monomers, polymers and copolymers bearing monothio-orthoester functionality to yield the first examples of sulfoxide monothio-orthoesters. These compounds are rather unstable and undergo a novel rearrangement to carboxylic esters and (co)polyesters at room temperature. The process is proposed as a convenient synthetic route for preparing (co)polymers bearing carboxylic ester functions in the side-chains.

Full text of DOI:10.1016/S0040-4020(00)01132-7

TETRAHEDRON
Pergamon
Tetrahedron 57 (2001) 1289±1295
Synthesis of polymers bearing sulfoxide groups by oxidation of
monothio-orthoesters and their rearrangement into carboxylic
ester-containing monomers and polymers
p
Huu-Nh aà n Tr aà n and Thi-Nh aÁ n Pham
Laboratoire de Chimie Mol e culaire et Thio-organique, Groupe Polym eÁ res et Interfaces (UMR CNRS 6507), Universit e de Caen,
Institut des Sciences de la Mati eÁ re et du Rayonnement (ISMRA), 6 Boulevard du Mar e chal Juin, F-14050 Caen, France
Received 1 August 2000; revised 24 November 2000; accepted 27 November 2000
AbstractÐReaction of monomers, polymers and copolymers containing monothio-orthoester groups with meta-chloroperoxybenzoic acid
in CH Cl at 208C affords the corresponding S-oxides. The chemoselective conversion of alkythio group into a sulfoxide moiety was
2 2
achieved with monomers, polymers and copolymers bearing monothio-orthoester functionality to yield the ®rst examples of sulfoxide
monothio-orthoesters. These compounds are rather unstable and undergo a novel rearrangement to carboxylic esters and (co)polyesters at
room temperature. The process is proposed as a convenient synthetic route for preparing (co)polymers bearing carboxylic ester functions in
the side-chains. q 2001 Elsevier Science Ltd. All rights reserved.
1
. Introduction
Our aim was the formation of new polymer and copolymer
surfactants by chemical modi®cation of the pendent mono-
thio-orthoester group and if possible the evaluation of their
stabilities and wetting properties.
1
Sulfur plays a major role in heteroatom chemistry. The
oxidation of sulfur groups has been studied successfully
by Zwanenburg et al., Bonini±Mazzanti, Block and
2
±4
5±9
10
1
1±15
16
Metzner et al. Madesclaire has shown that the
oxidation of thioether A (R SR ) can yield either the corre-
Recently we reported a very convenient method for the
preparation, in good yield, of monothio-orthoesters
1
2
22
1
sponding sulfoxide B (R SOR ) or the corresponding
2
including monomers and (co)polymers starting from
aromatic dithioester monomers and (co)polymers. This
process was realized by reaction of excess sodium alkoxides
with aromatic (non-enethiolizable) dithioesters followed by
in situ alkylation of the resulting monothiolate-orthoester
sodium salts (Scheme 1). An association of these
1
sulfone C (R SO R ) or both, depending on the method
2
2
used. A gentle oxidation to the sulfoxide alone requires
highly selective methods that cannot usually be applied
generally, whereas complete oxidation to the sulfone is
much easier to achieve.
1
7±22
methods
that use the meta-chloroperoxybenzoic acid
The oxidation of thioether A to sulfoxides B by using
hydrogen peroxide (H O ) either alone or associated with
various solvents or catalysts is the most widely used oxidiz-
(m-CPBA) seemed an interesting way for the one-pot oxida-
tion of a variety of monothio-orthoesters 1 to attempt the
preparation of their sulfoxides 2 (Scheme 1).
2
2
1
6
ing agent for oxidizing organic sul®des. However,
oxidation can proceed further to give the corresponding
sulfone C as was reported previously for thioethers A.
However, the stabilities of the obtained monothio-ortho-
esters sulfoxides 2 have not been studied yet. Here we
demonstrate that they rapidly rearrange into carboxylic
esters 9.
1
6
1
7±20
16
Moreover Lewin
and Madesclaire have described
that meta-chloroperoxybenzoic acid (m-ClC H CO H) is
6
4
3
one of the best selective oxidizing agents for transformation
of sul®de A to sulfoxide B. In a few cases, the
Meisenheimer rearrangement of a sulfoxide to sulfenate
2
. Results and discussion
2
1
has been reported.
Monothio-orthoesters including monomers and (co)poly-
mers used for the oxidation were prepared from aromatic
2
2
dithioester monomers and (co)polymers. This process
was performed by reaction of excess sodium alkoxides
with aromatic (non-enethiolizable) dithioesters followed
by in situ alkylation of the resulting monothiolate-orthoester
Keywords: monothio-orthoesters containing monomers and polymers;
oxidation; sulfoxides; carboxylic esters; (co)polyesters; free radical poly-
merization and copolymerization.
p
Corresponding author. Tel.: 133-2-31-45-28-45; e-mail: pham@ismra.fr
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)01132-7

1
290
H.-N. Tr aà n, T.-N. Pham / Tetrahedron 57 (2001) 1289±1295
Scheme 1. Synthesis of monothio-orthoester monomers and (co)polymers 1a±g.
1
sodium salts, according to the synthetic route reported
previously (Scheme 1).
monothio-orthoester 1a (7%) [ H NMR: 1.60 ppm (SCH )
3
2
2
13
and C NMR: 7.00 ppm (SCH )]. The H NMR signal for
1
3
the methoxy group of carboxylic ester 9a is observed at
3.91 ppm and a minor signal at 2.90 and 2.60 ppm can be
assigned to the methoxy and methyl sulfoxide group of the
sulfoxide 2a.
A preliminary investigation was carried out with 4-methyl-
1
-(dimethoxy methylthio methyl) benzene 1a as a model
compound. The oxidation reaction of monothio-orthoesters
a was performed at ®rst with a slight excess of m-CPBA in
1
1
The structure of sulfoxide 2a is con®rmed by C NMR
3
dichloromethane at 208C during 1 h. After work-up and base
elimination of excess m-CPBA and meta-chlorobenzoic
acid, puri®cation was avoided with immediate NMR
analysis of the crude material. To our surprise, the products
exhibit NMR signals that are characteristic of a mixture of
the sulfoxide 2a (5%) (Scheme 2), the carboxylic ester 9a
shifts at 47.00 and 44.00 ppm related, respectively, to the
1
3
methoxy and methylsulfoxide groups. C NMR signal for
the carbonyl group CvO of carboxylic ester 9a is observed
at 167.30 ppm.
(
88%) (Table 1, Scheme 3), and some eventually remaining
The thermal stability of the sulfoxide 2a was examined at
various conditions. A set of experiments was performed.
The reaction was followed easily by monitoring IR and
NMR spectra. The results are listed in Table 1. From
these data, the following observations can be drawn.
Although a low percentage of sulfoxide was observed
always (even at 2788C), the ratio of sulfoxide 2a and mono-
thio-orthoester remaining 1a decreased with increasing
temperatures while the proportion of carboxylic ester 9a
increased. The major product was always the carboxylic
ester 9a, together with some sulfoxide 2a and unreacted
monothio-orthoester 1a (at lower temperatures). At 208C,
after 3 h of reaction the conversion was complete; in the
crude reaction mixture carboxylic ester 9a was always the
major product.
Scheme 2. Preparation of sulfoxides 2 by oxidation of monothio-ortho-
esters 1.

H.-N. Tr aà n, T.-N. Pham / Tetrahedron 57 (2001) 1289±1295
1291
Table 1. Oxidation of monothio-orthoester 1a
Temperatures (8C)
Time (h)
Ester 9a (%)
Monothio-orthoester 1a (%)
Sulfoxide 2a (%)
278
278
230
230
215
120
120
1
3
1
3
1
1
3
49
60
70
82
90
88
95
42
32
25
11
7
9
8
5
7
3
5
5
7
0
Scheme 3. Rearrangement of sulfoxide 2a into carboxylic ester 9a.
2
IR data [nCvO (KBr pellets) at 1610±1770 cm ] and NMR
1
Sulfoxide 2a is unstable, the formation of carboxylic ester
9a can be explained by the Meisenheimer rearrangement
and Metzner et al.
2
1
13
spectra (CDCl ) [ C(CvO) at 165.00±173.00 ppm and
3
1
2,23,24
We suggested that ester 9a
proton signal for OCH at 3.93±4.02 ppm].
3
formation can be interpreted through the following intra-
molecular rearrangement: electrocyclization to an inter-
mediate 10a with migration of the `alkylthio group' to
afford 11a and the latter compound decomposing according
to Scheme 3 to furnish carboxylic ester 9a and 2-oxa-3-
thiabutane.
To our knowledge, the oxidation of monothio-orthoesters
into sulfoxides and their rearrangement into carboxylic
ester are still unknown. A number of (co)polymers contain-
ing carboxylic ester groups in the side chains could be
isolated in good yields (Table 2) and characterized.
Although there exist numerous methods for the preparation
of water-soluble polyesters, they are almost exclusively
limited to condensation of different dicarboxylic acids or
Similar rearrangements were observed from oxidation of
monomer 1b, homopolymer 1c and (co)polymers 1d±f
3
5
(
Table 2) containing monothio-orthoesters. Each sulfoxide
anhydrides and polyoxyethylene or esteri®cation of poly-
3
6
2
9
b±f was converted into corresponding carboxylic ester
b±f (Schemes 1 and 4). They were characterized by their
oxyethyleneglycol with carboxylic acids. This method,
even though longer than the classical methods, offers a
Table 2. Synthesis of sulfoxides 2a±f and carboxylic esters 9a±f from monothio-orthoesters 1a±f
1
2 3
R R R
4
Used dithioesters 12
R
Monothio-orthoesters 1
Sulfoxides 2
Carboxylic ester 9
Yield (%)
12a
12b
12c
12d
12e
12f
CH
CHvCH
3
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
1a
1b
1c
1d
1e
1f
2a
2b
2c
2d
2e
2f
9a
9b
9c
9d
9e
9f
88
78
75
70
78
80
2
(CHCH
(CHCH
(CHCH
(CHCH
2
2
2
2
)
n
n
n
n
)
)
)
2 m
[CH(Me)(CO Me)]
(CH
[CH
2
CHPh)
±CH(C
m
2
5
5 m
H N)]
Scheme 4. Oxidation of (co)polymers 1d±f containing monothio-orthoesters into corresponding carboxylic esters 9d±f.

1
292
H.-N. Tr aà n, T.-N. Pham / Tetrahedron 57 (2001) 1289±1295
Scheme 5. Independent synthesis of homopolymer carboxylic ester 9c.
more ef®cient synthetic route to amorphous (co)polymers
bearing long-chain carboxylic ester groups.
Eluent is cyclohexane or cyclohexane±ethyl acetate or
cyclohexane±dichloromethane mixture in the ratio
indicated below.
3
7
The structure of 9c obtained from path a (Scheme 5) was
con®rmed by independent synthesis of homopolymer
carboxylic ester 9c through path b, at ®rst reaction of mono-
mer dithioester 12b with excess sodium methoxide and
methyl iodide followed by in situ oxidation of 1b, then
free radical polymerization or (co)polymerization using
AIBN, of the resulting mixture sulfoxide 2b±carboxylic
1
H NMR 60 and 250 MHz spectra were run on Varian EM
360 and Bruker AC 25 spectrometers with TMS as an
internal reference. The products were dissolved in the
mentioned solvent. Data are given in the following order:
chemical shift in ppm, multiplicity (s, singlet; d, doublet; t,
triplet; q, quartet; hept, heptuplet; m, multiplet), coupling
2
2
13
ester 9b, according to our previously described method
Scheme 5).
constant in hertz, assignment. C NMR spectra were deter-
mined at 20.15 MHz with a Bruker WP 80 spectrometer
(
1
operating with broad band H decoupling. The solvent
used is indicated below.
3
. Conclusions
IR absorption spectra were recorded as liquid thin ®lms
between NaCl plates or as solids in KBr pellets, or dissolved
in CDCl on a Perkin±Elmer 257 IR spectrophotometer and
3
We have described for the ®rst time the oxidation of
polymers bearing monothio-orthoester groups. Reaction of
model, monomer and (co)polymer containing monothio-
orthoester groups with the standard oxidizing agent
m-CPBA provides the corresponding sulfoxides. However,
their stabilities are very moderate. These compounds
undergo a novel rearrangement into carboxylic esters and
a Pye-Unicam SP3 100 or a Perkin±Elmer 16 PC Fourier
transform spectrometer. The mentioned IR-absorptions
were observed as strong bands in cm .
2
1
UV±Vis spectra were executed on a Perkin±Elmer l 15 or
(
(
co)polyesters. So, the synthesis of a variety of amorphous
co)polymers containing carboxylic ester groups in the side
Beckman DU-7. The products were dissolved in CHCl
CH Cl or THF.
,
3
2
2
chains have been carried out in a good yield by this way.
Such a chemical modi®cation of a reactive functional group
opens a new way for chemically grafting the polyoxy-
ethylene glycol onto the side chain of polymers containing
esters. This preliminary work has stimulated us to carry out
further studies on polyester and poly(monothio-orthoester)
Elemental analyses were performed by `Service Central
d'Analyse' of CNRS at Vernaison. The results are described
in percentages.
Molecular weights were determined by Gel Permeation
Chromatography (GPC) on Styragel columns calibrated
with standard polystyrene samples using THF at 308C as
3
7
surfactants.
2
1
the mobile phase at a ¯ow rate of 1.0 ml min .
4
. Experimental
Intrinsic viscosity measurements were carried out by using
an Ubbelohde capillary viscometer having an internal
diameter of 0.5 mm and a length of 15 cm. The ¯ow times
were measured by using viscotimer Schott Gerate AVS 400.
As the ¯ow times were relatively long (t .100 s), the
0
correction for kinetic energy could be ignored. The samples
were dissolved by adding fresh solvent and the solutions
4
.1. General
All reactions were run under a positive nitrogen pressure.
Tetrahydrofuran (THF) was distilled over sodium benzo-
phenone ketyl. Monomers and model compound were
puri®ed by ¯ash chromatographies (silica gel or alumina).

H.-N. Tr aà n, T.-N. Pham / Tetrahedron 57 (2001) 1289±1295
1293
were then introduced into the viscosimeter reservoir at
08C.
nitrogen inlet and a magnetic stirrer; methanol (3 equiv.,
0.16 g, 5 mmol) was added over a period of 1 h 30 min at
room temperature. A solution of dithioesters monomer or
(co)polymer (1 equiv.) diluted in THF (20 ml) was added
into the mixture of sodium methylate. After 2 h stirring at
room temperature, methyl iodide (3 equiv., 0.7 g, 5 mmol)
diluted in THF (20 ml) was added (the pink color dis-
appears). The mixture was stirred at room temperature over-
night, and NaI was eliminated by ®ltration of the orange- or
beige-colored solution.
3
Thermal properties of the (co)polymonothio-orthoesters
and (co)polyesters were studied by differential scanning
calorimetry (DSC) on a Perkin±Elmer DSC-7 calibrated
with an indium standard. The values of glass transition
temperatures (T ) are obtained from the second heating
g
2
run, at 108C min under a nitrogen atmosphere, and at
1
least 10 mg of the sample used for DSC measurement.
4
.2. Aromatic dithioesters
For monomers 1a,b, the work-up involved addition of a
cyclohexane/water solution (2£50 ml), extraction of the
aqueous phase with cyclohexane (2£30 ml), drying over
MgSO , ®ltration and then concentration under vacuum.
4
The monothio-orthoesters were isolated and puri®ed by
¯ash chromatography on alumina with cyclohexane/
Aromatic dithioesters 12a,b were synthesized by reaction of
carbon disul®de with a Grignard solution, prepared under
nitrogen from magnesium and alkyl halides, followed by
alkylation with methyl iodide, according to the procedures
2
2,25±30
described earlier.
CH Cl mixture (1a: 99/1; 1b: 95/5) as eluent.
2 2
4.3. Preparation of homopolymers 12c, 1c and
copolymers 12d±f, 1d±f
For (co)polymers 12d±f, after evaporation of THF, the resi-
due was dissolved in dichloromethane and precipitated from
the solution by dropwise addition to cyclohexane. The
(co)polymers were ®ltered and dried in vacuo.
0
All polymerizations were performed in THF with N,N -
azobisisobutyronitrile (AIBN) as an initiator under nitrogen
atmosphere. The radical polymerization of dithioester
monomers was conducted at 668C under conditions
described previously (according to Refs. 22, 31±34). The
polymers were isolated by precipitation in cyclohexane
and fully characterized by spectroscopy, GPC and DCS
analysis.
4.4.2. Poly[(dimethoxymethylmethylthio)-4-vinylbenzene]-
(
powder. H NMR (CDCl ): 1.1±2.5 (6H, m, CH±CH ),
co)-2-vinylpyridine 1f. Yieldˆ55%, beige color
1
3
2
3
.2 (6H, s, OCH ), 6.1±8.6 (8H, 2m, 2 systems, Harom);
3
1
3
C NMR (CDCl ): 10.0, 14.0, 18.0 (SCH ), 25.0, 30.0
3
3
(
CH, CH ), 42.0, 44.0, 50.0 (OCH ), 122.0±137.0 (Carom);
2 3
IR (KBr pellets): (C±O); GPC: M ˆ4764; M ˆ6593.
n
w
4
.3.1. Synthesis of poly[methyl (4-vinylbenzene) dithio-
T
g
ˆ1678C.
carboxylate-(co)-2-vinylpyridine] 12f. Methyl (4-vinyl-
benzene) dithiocarboxylate 12b (1 g, 5 mmol), 2-vinyl-
pyridine (2.6 g, 25 mmol) and AIBN (0.17 g, 1 mmol) in
4.5. Oxidation of monothio-orthoesters 1a±f
5
0 ml of anhydrous freshly distilled THF were placed in a
4.5.1. Model and monomer. General procedure. In a
round-bottomed, three-necked ¯ask equipped with a nitro-
gen inlet and a magnetic stirrer were placed monothio-
orthoester (1 equiv.) in 25 ml of dry dichloromethane. A
solution of dry m-CPBA (70%; 1.2 equiv.) diluted in
CH Cl (30 ml) was added dropwise to the stirred mono-
thio-orthoester solution previously cooled to 08C (215,
230, 2788C or at room temperature). The stirred mixture
was allowed to react during about 3 h at room temperature
and the dichloromethane solution was washed successively
septum-sealed, 100 ml round-bottomed, three-necked ¯ask
equipped with a condenser, a nitrogen inlet and a magnetic
stirrer. The ¯ask was then immersed in an oil bath at 708C
and the polymerization allowed to proceed during 28 h
before cooling. The red mixture was concentrated, then
diluted with chloroform and precipitated from solution by
dropwise addition to petroleum ether. The red powder was
2
2
®ltered, washed repeatedly with diethylether and dried. The
recovery procedure was repeated twice before the polymer
was dried under vacuum to furnish 0.9 g of red powder.
with saturated aqueous NaHCO (3£20 ml) and saturated
3
1
Yieldˆ25%. H NMR (CDCl ): 1.1±2.6 (6H, m, CH±
brine (30 ml). The organic layer was dried with MgSO ,
4
3
CH ), 2.8 (3H, s, SCH ), 6.0±8.7 (8H, 2 m, 2 systems
2
®ltered and then concentrated under reduced pressure with-
out heating to leave the sulfoxide 2. NMR analysis was
carried out right away, i.e. approximately one hour after
the oxidation step. No dithioester signal, or some eventually
remaining dithioester, could be observed.
3
Harom); GPC: M ˆ5173; M ˆ6472, T ˆ1068C.
n
w
g
4.4. Preparation of monothio-orthoesters 1a±f
The starting monothio-orthoesters 1a±f including mono-
mers and (co)polymers were synthesized by reaction of
excess sodium alkoxides with aromatic (non-enethiolizable)
dithioesters followed by in situ alkylation of the resulting
monothiolate, according to the methods described
4.5.2. Oxidation of monothio-orthoester 1a. Synthesis of
methyl (4-methylbenzoate) 9a. 9a was obtained by
reaction of monothio-orthoester 1a (0.5 g, 2.5 mmol)
with m-CPBA (70%, 0.75 g, 3 mmol) in dichloro-
methane. The puri®cation by ¯ash chromatography in
aluminum oxide and cyclohexane/CH Cl mixture (98/2)
2
2
previously.
2
2
4
3
.4.1. General methods. A mixture of sodium hydride,
equiv. (60%, 0.12 g, 5 mmol), in dry freshly distilled
furnishes the pure ester 9a. Yieldˆ88%, white powder.
1
H NMR (CDCl ): 2.44 (3H, s, CH ±Ph), 3.91 (3H, s,
3
3
THF was placed in a septum-sealed, 100 ml round-
bottomed, three-necked ¯ask equipped with a condenser, a
CH ), 7.18±7.82 (4H, 2d, AB system, J ˆ6 Hz, Harom);
C NMR (CDCl ): 20.0, 21.6 (CH ±Ph), 49.9, 51.0,
3 3
3
AB
1
3

1
294
H.-N. Tr aà n, T.-N. Pham / Tetrahedron 57 (2001) 1289±1295
5
2.0 (OCH ), 127.3, 127.9, 128.7, 133.5, 138.2, 143.7
3
4.5.7. Oxidation of poly[(dimethoxymethylthio) methyl-
4-vinylbenzene-(co)-styrene] 1e. Synthesis of poly[methyl
(4-vinylbenzoate)-(co)-styrene] 9e. Reaction of monothio-
orthester copolymer 1e (50 mg, 0.1 mmol) with m-CPBA
(70%, 0.05 g, 0.3 mmol) diluted in dry dichloromethane
(
Carom), 167.3 (CvO); IR (KBr pellets): 1145 (C±O),
1600 (CvCarom), 1723 (CvO).
4.5.3. Oxidation of monothio-orthoester 1b. Synthesis of
1
methyl (4-vinylbenzoate) 9b. Reaction was carried out on
monothio-orthoester 1b (0.25 g, 1.1 mmol) and m-CPBA
(0.32 g, 1.3 mmol). Ester 9b was puri®ed by ¯ash chromato-
graphy in aluminum oxide and cyclohexane/CH Cl mixture
affords (co)polyester 9e. Yieldˆ78%, white powder. H
NMR (CDCl ): 0.74, 2.57 (6H, m, CH±CH ), 3.92 (3H, s,
2
3
1
OCH ), 6.26±8.18 (9H, m, 2 arom. systems; C NMR
3
3
(CDCl ) 22.5, 22.9, 23.4, 25.0, 25.9, 32.4 (CH, CH ),
2
2
2
3
1
(
(
95/5). Yieldˆ78%, white powder. H NMR (CDCl ): 3.93
127.0, 127.8, 128.0, 128.4, 130.4, 132.4, 133.9, 134.6
(Carom), 170.5 (CvO); IR (KBr pellets): 1086, 1195 (C±
3
3H, s, OCH ), 5.46±5.96±6.81 (3H, m, ABX system,
3
J ˆ1.2 Hz, J ˆ9.8 Hz, J ˆ17 Hz, CHvCH ), 7.42±
O), 1418, 1602 (Ph), 1698, 1772 (CvO); GPC: M ˆ1996,
AB
BX
AX
2
n
1
3
8.05 (4H, 2d, AB system, J ˆ8.4 Hz, H ). C NMR
CDCl ): 25.3, 42.6 (OCH ), 118.4 (vCH ), 132.8, 135.9,
3 3 2
M ˆ3858, T ˆ688C.
AB
arom
w
g
(
1
36.0 (HCv), 125.9±143.2 (Carom), 169.2 (CvO); IR (KBr
4.5.8. Oxidation of poly[(dimethoxymethylthio) methyl-
4-vinylbenzene-(co)-2-vinylpyridine] 1f. Synthesis of
poly[methyl (4-vinylbenzoate)-(co)-styrene] 9f. Reaction
was carried out on monothio-orthoester copolymer 1f
(0.20 g, 0.6 mmol) and m-CPBA (70%, 0.2 g, 1.3 mmol)
diluted in dry dichloromethane. Puri®cation of the resulting
(co)polyester 9f was accomplished by re-precipitation from
pellets): 1098, 1260 (C±O), 1400, 1610 (CvC), 1720
CvO), 1818 (vinyl).
(
4
.5.4. (Co)polymers. General procedure. To a stirred
solution of monothio-orthoester (co)polymers (1 equiv.) in
anhydrous freshly distilled THF (25 ml), under an inert
atmosphere of nitrogen, a solution of dry m-CPBA (70%;
dichloromethane using petroleum ether as the non-solvent.
1
1
.2 equiv.) diluted in CH Cl (25 ml) was added dropwise,
2
Yieldˆ80%, white powder. H NMR (CDCl
3
): 0.70±2.70
), 6.10±7.90 (8H, m, 2
: 12.0, 15.0, 23.0 (CH,
), 115.0, 120.0, 128.0, 133.0, 138.0 (Carom), 167.0,
175.0 (CvO); IR (KBr pellets): 1086, 1195 (C±O), 1418,
1602 (Ph), 1698, 1772 (CvO); T
ˆ1218C.
2
and the mixture was stirred at room temperature for 10 h.
After evaporation of THF under reduced pressure, the
residue was dissolved in chloroform. The work-up involved
washing the organic layer with saturated aqueous NaHCO3,
then saturated brine (30 ml), drying of the organic phase
(6H, m, CH±CH
2
1
), 3.90 (3H, s, OCH
3
3
arom. systems); C NMR (CDCl
CH
3
2
g
over MgSO , ®ltration and concentration under vacuum.
4
The product was diluted with chloroform and precipitated
by adding slowly to 100 ml of petroleum ether. The puri®ed
polymer was then dried in vacuo for 3 h to furnish
carboxylic esters (co)polymers 9.
Acknowledgements
The authors gratefully acknowledge Professor P. Beslin and
Dr S. Masson for helpful discussions during the preparation
of this manuscript.
4
4
.5.5. Oxidation of poly[(dimethoxymethylthio) methyl-
-vinylbenzene] 1c. Synthesis of poly [methyl (4-vinyl-
benzoate)] 9c. Reaction of homopolymer 1c (0.1 g,
.4 mmol) with m-CPBA (70%, 0.2 g, 1.2 mmol) diluted
0
References
1
in THF (50 ml) affords 9c. Yieldˆ75%, white powder. H
NMR (CDCl ): 0.77±2.32 (3H, m, CH±CH ); 3.95 (3H, s,
3
1. Metzner, P.; Thuillier, A. Sulfur Reagents in Organic
Synthesis; Academic: London, 1994.
2
1
3
OCH ), 6.52±7.78 (4H, AB system, 2m, Harom); C NMR
3
(
1
1
CDCl ): 25.6, 29.5, 34.7 (CH±CH ), 52.3 (OCH ), 127.2,
2
28.0, 129.9, 130.4, 134.0, 134.6, 135.3 (Carom), 161.9,
63.0, 163.6, 165.4 (CvO); IR (KBr pellets): 1049±1203
2. Zwanenburg, B. Recl. Trav. Chim. Pays-Bas 1982, 101, 1.
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3
3
(
C±O), 1418±1610 (Ph), 1710 (CvO); GPC: M ˆ2881,
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4
.5.6. Oxidation of (co)poly[methylmethacrylate-(di-
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methoxymethylthio) methyl-4-vinyl benzene] 1d. Synthe-
sis of (co)polymethylmethacrylate [methyl (4-vinyl
benzoate)] 9d. The reaction was performed with mono-
thio-orthester copolymer 1d ((0.11 g, 0.3 mmol) and
m-CPBA (70%, 0.15 g, 0.9 mmol) diluted in THF. Puri®ca-
tion of the resulting (co)polyester 9d was accomplished by
re-precipitation from chloroform using petroleum ether as
1
the non-solvent. Yieldˆ70%, white powder. H NMR
9. Bonini, B. F.; Busi, F.; de Laet, R. C.; Mazzanti, C.; Thuring,
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(
non-arom), 4.02 (3H, s, OCH3 arom), 6.66±8.26 (4H, AB system,
CDCl ): 0.54±2.24 (5H, m, CH±CH ), 3.63 (3H, s, OCH
3 2 3
1
m, Harom); C NMR (CDCl ): 19.4, 21.4, 25.9, 28.6, 29.4
3
2
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3
(
CH, CH ), 44.7, 50.3, 51.2, 53.9, 55.1 [MeC(COOMe)],
2
1
25.7, 126.8, 127.6, 129.1, 138.2 (Carom), 173.2 (CvO);
IR (KBr pellets): 1090, 1150 (C±O), 1315, 1592 (CvCarom),
710, 1729 (CvO); GPC: M ˆ2003, M ˆ3174, T ˆ1228C.
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