New simple convergent synthetic method for benzyl aryl ether dendritic structures

Article abstract of DOI:10.1016/S0040-4020(01)00198-3

Phenolic benzyl aryl ether based dendrons with an ester periphery are easily prepared by convergent strategy through hydroxy substituted methyl benzoates and easily attainable benzoyl protected 3,5-bis(bromomethyl)phenol. The dendrons obtained can afford dendronized styrenes.

Full text of DOI:10.1016/S0040-4020(01)00198-3

TETRAHEDRON
Pergamon
Tetrahedron 57 -2001) 3397±3401
New simple convergent synthetic method for benzyl aryl ether
dendritic structures
p
Amiya Krishna Maiti, Ricardo Martõnez, Ramon Mestres, Amparo Tortajada and Felix Villar
Â
Â
  Á Á
Departament de Quõmica Organica, Universitat de Valencia, Bujassot, E-46100 Valencia, Spain
Received 15 December 2000; revised 1 February 2001; accepted 16 February 2001
AbstractÐPhenolic benzyl aryl ether based dendrons with an ester periphery are easily prepared by convergent strategy through hydroxy
substituted methyl benzoates and easily attainable benzoyl protected 3,5-bis-bromomethyl)phenol. The dendrons obtained can afford
dendronized styrenes. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Synthesis of dendritic polymers is a ®eld under continuous
expansion, because of the multiplicity of structures which
can be attained, architectures of the resulting materials, vari-
ety of synthetic strategies, and especially because of the
numerous applications of dendrimers as slow releasing
systems, photophysical and electrochemical devices, or
liquid crystals.1±8 The panorama of these applications is
widened up when dendritic structures are grafted to poly-
meric chains.9±15 In general terms dendrimers include a
core, a branching structure and a periphery. Physico-chemi-
cal properties, and hence applications, depend on the nature
of these three basic constituents. A variety of branching
structures have been developed, including those based on
trivalent elements, namely, nitrogen, boron or phosphorus,
tetravalent elements, such as silicon, germanium or
bismuth,5 besides the multiple possibilities offered by the
tetravalent carbon atom. Among the widely used structures,
benzene rings constitute ¯at polyvalent building blocks, and
aryl and benzyl ethers and esters are found as the structural
base of numerous dendrimers and dendritic polymers.
The synthetic strategy in the present approach is entirely
convergent. The basic building block is the doubly bis-bro-
momethyl)phenyl benzoate 3, which can be easily prepared
from the handy 3,5-dimethylphenol 1 by protection of the
phenolic hydroxyl group with benzoyl chloride, to give the
benzoate 2. Bromination of the latter with NBS leads to the
bis-bromomethyl)phenyl benzoate 3 which, although
obtained in pure form only in moderate to low yield
²
-36%), has proved shelf stable for months in its crystalline
form. Ether bonds may be most easily formed by substitu-
tion of the benzylic bromine by a phenol, under the mild
Â
conditions, well established by Frechet, with potassium car-
bonate as base, acetone as solvent and 18-crown-6 as phase
transfer catalyst.16 Methanolytic deprotection of the pheno-
lic oxygen with a catalytic amount of sodium methoxide
then allows isolation of the dendron. The same procedure
can be carried out again in order to obtain a dendron of a
higher generation. For the periphery we have employed two
Br
Br
In order to have dendrimers that may ®nd application for
concentration of low polar organic matter in water, we
needed structures suf®ciently stable to long term hydrolytic,
oxidative and photolytic processes. The benzyl aryl ether
OCOPh
OX
1; X = H
3
Â
2; X = COPh
type of wedge structures described by Frechet seemed a
convenient start,16 but we felt that a new approach could
be introduced in order to employ handier materials and to
simplify the synthetic procedure, by shortening the number
of conversions and avoiding the frequently troublesome
quantitative deprotonation of alcohols. We wanted to
avoid ester reductions as well, although this implied intro-
duction of a benzylic bromination instead.
CO2Me
OH
MeO2C
CO2Me
OH
4a
4b
Keywords: dendrimers; ethers; phenols; esters; polymers.
Corresponding author. Tel./fax: 196-398-3152;
e-mail: ramon.mestres@uv.es
p
²
Improvement of the procedure has not been attempted.
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020-01)00198-3

3398
A. K, Maiti et al. / Tetrahedron 57 .2001) 3397±3401
R
R
MeONa
K2CO3
acetone
O
O
4
5
+ 3
MeOH
OH
6a; R = 3,5-(MeO2C)2C6H3
6b; R = 4-(MeO2C)C6H4
R
O
R
O
K2CO3
acetone
6 + 3
7
O
O
O
O
R
R
MeONa/MeOH
OH
8a; R = 3,5-(MeCO2)2C6H3
8b; R = 4-(MeCO2)C6H4
Scheme 1.
commercially available phenolic carboxylic acid methyl
esters 4 -Scheme 1).
tion dendron 6a reacted as well with the tribromo mesityl-
ene 917 and dendrimer 11 was obtained in a 93% yield.
Again NMR and MS spectra were in agreement with the
assigned structures. However, the reaction failed for the
second-generation dendron 8a.
Thus, reaction of the phenolic methyl esters 4 with the
dibromo benzoate 3 gave the ®rst generation dendrons 5,
which were deprotected by alkaline methanolysis to afford
the phenolic dendrons 6. These were puri®ed by precipi-
tation from solution in dichloromethane by careful
addition of hexane. Puri®cation of the protected dendron
5a was ®rst attempted, but it was found that puri®cation
after removal of the benzoyl rest sample was easier and
spectroscopically pure -1H and 13C NMR and MS) dendrons
6a and 6b were obtained in 84 and 73% yields, respectively.
These dendrons were allowed to react similarly with the
bis-bromomethyl)phenyl benzoate 3 to give the second
generation dendrons 7 and 8 in spectroscopically pure
forms in 63 and 50% yields, for 8a and 8b, respectively.
We were interested as well in the preparation of dendritic
polystyrenes, as Percec has stressed the effect of self-assem-
bly on the acceleration, control and self-encapsulation of the
radical polymerization of styrenic monodendrons.9±13 When
the phenolic esters 4a and 6a were allowed to react with
4-chloromethylstyrene 12 the substituted phenoxymethyl-
styrenes 13 and 14 were obtained as crystalline compounds
in 71 and 35% yields, respectively. Polymerization of the
former -0.7±1 mol L21) with AIBN -0.03±0.05 mol L21) in
THF for 48 h under argon atmosphere reached a yield of
72±87%. The polymer was characterized by 1H NMR, size
exclusion chromatography -SEC) with polystyrene stan-
dard, and differential scanning calorimetry -DSC). Thus,
R
O
R
O
R
O
R
O
O
O
R
O
O
R
O
O
R
O
O
R
R
Å
number-average molecular weights -Mn) from 1.3 to
11
3.2£104 and glass transition temperatures -Tg) ranging
10
from 82 to 888C were obtained.
R = 3,5-(MeO2C)2C6H3
The second phenoxymethylstyrene 14 underwent polymeri-
zation under uncontrolled conditions, affording an insoluble
vitreous material. Controlled polymerization of phenoxy-
methylstyrene 14 and more detailed study of the polymeri-
zation of compound 13 will be published elsewhere.
Synthesis of dendrimers with the rather small 1,3,5-
trimethylbenzene as a core was essayed. The dimethoxy-
carbonyl phenol 4a gave dendrimer 10 in 94% yield on
reaction with tris-bromomethylbenzene 9. The ®rst genera-

A. K. Maiti et al. / Tetrahedron 57 .2001) 3397±3401
3399
3. Conclusions
with CCl4.The combined ®ltered solutions were evaporated
to give a yellow solid material -3.91 g; 100%) of a crude,
which crystallized from benzene±hexane as faint yellow
In conclusion, benzyl, phenyl ether based dendrons with a
methyl ester periphery can be easily prepared, at least up to
the second generation, according to a convergent strategy
with 3,5-bis-bromomethyl)phenol and phenolic methyl-
carboxylic esters as basic synthons.
needles of 3,5-bis-bromomethyl)phenyl benzoate
3
-1.38 g; 36%), mp 124±1268C. Found: C, 46.94; H, 3.22;
Br, 41.36. C15H12Br2O2 requires: C, 46.91; H, 3.12; Br,
41.61%. nmax 1741 -CO), 1597, 1450 -Ar) 1259 -C±O)
and 698 cm21; dH 8.19 -2H, d, Jˆ7.8 Hz, H-20), 7.66 -1H,
t, Jˆ7.2 Hz, H-40), 7.52 -2H, t, Jˆ7.7 Hz, H-30), 7.33 -1H, s,
H-4), 7.23 -2H, s, H-2), and 4.48 -4H, s, Ar±CH2Br) ppm;
dC 164.81, 151.15, 139.8, 133.85, 130.19, 129.08, 128.65,
126.94, 122.41 and 31.95 ppm;
4. Experimental
4.1. General
4.1.3. 1,3,5-Tris/bromomethyl)benzene 9. This was
obtained from mesitylene and NBS by substantially the
IR spectra were recorded as KBr discs with a Perkin±Elmer
1750 FTIR spectrophotometer. NMR spectra were recorded
with Brucker 300 or Varian Unity -300 MHz) instruments
using CDCl3 as solvent and TMS as internal reference,
unless otherwise stated. Mass spectra were determined
with a VG AutoSpec spectrometer. Melting points are
uncorrected and were measured with a Reichert apparatus.
Bulb-to-bulb distillations were carried out with a BuÈchi
GKR-50 apparatus and given boiling points stand for the
temperature of the furnace. Acetone was distilled from
anhydrous K2CO3. Acetone containing 18-crown-6
17
È
same procedure described by Vogtle, as white needles
-35%), mp 98±1008C -lit.17 mp 948C). nmax 1636 -Ar),
1455, 1212, 704 cm21 -Ar±H); dH 7.29 -3H, s Ar±H) and
4.37 -6H, s, ArCH2Br) ppm; dC 139.45, 129.98 and
32.60 ppm.
4.1.4. 3,5-3,5-/Dimethoxycarbonylphenoxymethyl)phenyl
benzoate 5a and 3,5-3,5-/dimethoxycarbonylphenoxy-
methyl)phenol 6a. A mixture of dimethyl 5- hydroxyiso-
phthalate 4a -1.26 g; 6 mmol), 3,5-bis-bromomethyl)phenyl
benzoate 3 -1.15 g; 3 mmol), K2CO3 -1.28 g; 9.3 mmol) and
18-crown-6 -176 mg; 0.7 mmol) in acetone -90 mL) was
heated under re¯ux and stirred vigorously for 24 h. The
mixture was allowed to cool and the solvent evaporated to
dryness. The residue was partitioned between water and
dichloromethane and the aqueous layer was extracted with
dichloromethane -3£20 mL) and the combined extracts
dried. Evaporation of the solvent gave an amorphous
white material -1.84 g; 95%), which was dissolved in
dichloromethane. Centrifugation followed by precipitation
of the solution with hexane gave the title compound in crude
form as an amorphous white material -1.72 g; 89%). Found
-MS, EI1) 642.1726 -M)1. C35H30O12 requires 642.1737.
nmax 1728 -CO), 1596, 1456, 1434 -Ar), 1246 -C±O) and
756 cm21 -Ar±H).
-1 mg mL21) was stored over 3 A molecular sieves. Metha-
Ê
Ê
nol was distilled from Mg and stored over 3 A molecular
sieves. NBS was crystallized from hot water. Centrifugation
was performed with an ALC centrifugette 4206 model
-15 min, 5000 rpm). Pyridine was dried over CaH2. All
other reagents were purchased from Aldrich or Fluka and
used without further puri®cation.
All reactions were carried under argon atmosphere and with
the standard precautions for exclusion of moisture. Evapo-
ration of solvents was carried out under vacuum with a
rotatory evaporator and a water bath at 408C.
4.1.1. 3,5-Dimethylphenyl benzoate 2. 3,5-Dimethylphenol
-5.28 g; 40 mmol) was added portionwise to stirred pyridine
-10 mL) at 08C and the solution stirred for 10 min. Benzoyl
chloride -5.62 g; 40 mmol) was added dropwise under
stirring and the mixture was allowed to warm up to room
temperature and stirred for 3 h. The mixture was poured into
ice water and extracted with diethyl ether. The organic layer
was washed with cold 2 M HCl, water and dried -MgSO4).
Evaporation of the solvent gave a yellow oil of almost pure
product. Bulb-to-bulb distillation -178±1818C, 0.1 mmHg)
gave 3,5-dimethylphenyl benzoate 2 as a light yellow oil
-7.13 g; 31.6 mmol; 73%) -lit.18 mp 558C). nmax 1737 -CO),
1618, 1591 -Ar), 1261 -C±O) and 707 cm21 -Ar±H); dH
8.31 -2H, d, Jˆ7.8 Hz, H-20), 7.67 -1H, t, Jˆ7.5 Hz,
H-40), 7.55 -2H, t, Jˆ7.7 Hz, H-30), 6.98 -1H, s, H-4),
6.95 -2H, s, H-2) and 2.43 -6H, s, Ar±CH3) ppm; dC
165.81, 151.42, 139.78, 133.99, 130.61, 130.23, 129.05,
128.13, 119.84 and 21.76 ppm.
The above crude compound 5a -128.4 mg; 0.2 mmol) was
suspended in 1:1 benzene±methanol -10 mL), sodium meth-
oxide -16.2 mg; 0.3 mmol) was added and the mixture
heated under re¯ux for 30 min while monitored by TLC.
The mixture was cooled to 08C, acidi®ed with aqueous
acetic acid to pH 6, diluted with water -50 mL) and
extracted with dichloromethane. The solution was washed
with water, dried and the solvent evaporated. The resulting
solid material was dissolved in dichloromethane and pre-
cipitated with hexane to give the compound 3,5-3,5-
-dimethoxycarbonylphenoxymethyl)phenol 6a as a white
amorphous material -101.1 mg; 94%), mp 155±1578C.
Found -MS, EI1) 538.1460 -M)1. C28H26O11 requires
538.1475. nmax 3402 -OH), 1728 -CO), 1596, 1456, 1434
-Ar), 1250 -C±O) and 756 cm21 -Ar±H); dH 8.28 -2H, t,
Jˆ1.2 Hz, H-40), 7.80 -4H, d, Jˆ1.5 Hz, H-20), 7.06 -1H, s,
H-4), 6.91 -2H, s, H-2), 5.09 -4H, s, ArCH2O) and 3.93
-12H, s, OCH3) ppm; dC 166.37, 158.80, 156.61, 138.61,
131.97, 123.54, 120.33, 118.59, 114.31, 70.05 and
52.67 ppm.
4.1.2. 3,5-Bis/bromomethyl)phenyl benzoate 3. 3,5-
Dimethylphenyl benzoate 2 -2.26 g; 10 mmol) was dis-
solved in CCl4 -40 mL) and NBS -3.91 g; 22 mmol) and
tert-butylperoxide -0.1 mL) were added. The mixture was
heated under re¯ux for 24 h in the presence of light -160 W,
230 V). The reaction mixture was cooled to room tempera-
ture, the supernatant precipitate was ®ltered off and washed
4.1.5.
3,5-4-/Methoxycarbonylphenoxymethyl)phenyl

3400
A. K, Maiti et al. / Tetrahedron 57 .2001) 3397±3401
benzoate 5b and 3,5-4-/methoxycarbonylphenoxy-
methyl)phenol 6bBy the same procedures as above,
methyl p-hydroxybenzoate 4b -1.21 g; 9 mmol), the bis-
bromomethyl benzoate 3 -1.52 g; 4 mmol), anhydrous
potassium carbonate -1.8 g; 13 mmol) and 18-crown-6
-100 mg; 0.4 mmol) in acetone -100 mL) heated under
re¯ux for 24 h, work-up and precipitation from dichloro-
methane±hexane gave crude 5b as an amorphous material
-1.61 g; 73.5%).
carbonylphenoxymethyl)phenoxymethyl]phenol 8b. By
the same procedures as above compound 6b -1.26 g;
3 mmol), the bis-bromomethyl benzoate 3 -0.57 g; 1.5
mmol), anhydrous potassium carbonate -0.70 g; 5 mmol),
18-crown-6 -80 mg; 0.3 mmol) and acetone -80 mL), heat-
ing under re¯ux for 41 h and work-up gave an amorphous
material -1.43 g), which was dissolved in dichloromethane
and precipitated by addition of hexane to give the title
compound 7b -1.21 g; 76%) as a white amorphous material.
As above, the latter material 5b -1.61 g; 2.9 mmol), sodium
methoxide -216 mg; 4 mmol) and methanol -40 mL), after
heating for 0.5 h under re¯ux and work-up, gave
4--methoxycarbonylphenoxymethyl)phenol 6b -1.22 g;
99%) as a white amorphous material, mp 133±1378C.
Found -MS, EI1) 422.1218 -M)1. C24H22O7 requires
422.1365. nmax 3364 -OH), 1719 -CO), 1596, 1456, 1434
-Ar), 1255 -C±O) and 847 cm21 -Ar±H); dH 7.90 -4H, d,
Jˆ6.87 Hz, H-30), 6.94 -1H, s, H-4), 6.87 -4H, d, Jˆ6.9 Hz,
H-20), 6.82 -2H, s, H-2), 4.97 -4H, s, ArCH2O) and 3.83
-6H, s, OCH3) ppm; dC 167.35, 162.71, 156.90, 138.99,
132.04, 123.28, 118.43, 114.86, 114.34, 69.95 and
52.36 ppm.
The latter material -0.80 g; 0.75 mmol), sodium methoxide
-54 mg; 1 mmol), and 1:1 methanol±benzene -40 mL)
heated under re¯ux for 2 h and work-up as above gave an
amorphous material -548 mg; 76%), which was puri®ed by
dissolution/precipitation from dichloromethane±hexane to
give 3,5-bis-[4--methoxycarbonylphenoxymethyl)phenoxy-
methyl]phenol 8b as a white amorphous material -475 mg;
66%), mp 139±1428C. Found -MS, FAB1) 963.3230
-M11)1. C56H51O15 requires 963.3228. nmax 3403 -OH),
1713 -CO), 1510, 1434 -Ar), 1250 -C±O) and 847 cm21
-Ar±H); dH 7.89 -8H, d, Jˆ6.93 Hz, H-30 0), 6.98 -2H, s,
H-40), 6.90 -4H, s, H-20), 6.86 -8H, d, Jˆ6.95 Hz, H-20 0),
6.83 -1H, s, H-4), 6.76 -2H, s, H-2), 5.00 -8H, s, ArCH2O),
4.94 -4H, s, ArCH2O) and 3.80 -12H, s, OCH3) ppm; dC
167.29, 162.65, 159.60, 156.92, 139.22, 138.81, 132.03,
123.32, 119.01, 118.35, 114.86, 114.30, 113.83, 70.05 and
52.34 ppm..
4.1.6. 3,5-Bis-[3,5-3,5-/dimethoxycarbonylphenoxymethyl)-
phenoxymethyl]phenyl benzoate 7a and 3,5-bis-[3,5-3,5-
/dimethoxycarbonylphenoxymethyl)phenoxymethyl]-
phenol 8a. A mixture of -MeO2C)2[G-1]±OH 6a -0.59 g;
1.09 mmol), 3,5-bis-bromomethyl)phenyl benzoate
3
4.1.8. 1,3,5-Tris-/3,5-dimethoxycarbonyl)phenoxymethyl-
benzene 10. A mixture of 1,3,5-tris-bromomethyl)benzene
9 -120.8 mg; 33.7 mmol), dimethyl 5-hydroxyisophthalate
4a -222.5 mg; 1.06±1.1 mmol), K2CO3 -143.5 mg; 1.07
mmol), 18-crown-6 -30 mg; 0.12 mmol) and acetone
-30 mL) was stirred vigorously and heated under re¯ux
under argon atmosphere for 24 h. The mixture was allowed
to cool and the solvent evaporated to dryness; aqueous
Na2CO3 was added to the residue, the mixture stirred for
10 min and the solid material ®ltered off, washed with water
and dried under vacuum. The product was puri®ed by pre-
cipitation with hexane from its solution in dichloromethane,
and 1,3,5-tris--3,5-dimethoxycarbonyl)phenoxymethylben-
zene 10 was obtained as a white amorphous material
-246 mg; 94%), mp 1718C. Found -MS, FAB1) 745.2125,
-M11)1. C39H37O15 requires 745.2132. nmax 1728 -CO),
1595 -Ar), 1434 -CH3), 1244 -C±O) and 756 -Ar±H); dH
8.21 -3H, s, H-40), 7.77 -6H, s, H-20), 7.48 -3H, s, H-2), 5.15
-6H, s, ArCH2O) and 3.87 -18H, s, CO2CH3) ppm; dC
166.43, 158.98, 137.64, 132.28, 126.67, 123.80, 120.47,
70.36 and 52.86 ppm.
-0.21 g; 0.55 mmol), K2CO3 -0.22 g; 1.6 mmol), 18-
crown-6 -0.05 g; 0.2 mmol) and acetone -50 mL) was
heated under re¯ux for 41 h, while monitored by TLC.
The mixture was cooled, the solvent partially evaporated,
water added and the mixture stirred for 20 min. The white
precipitate was ®ltered off and dried and puri®ed by solution
in dichloromethane and precipitation with hexane to obtain
-MeO2C)2[G-2]±OCOPh 7a as a white amorphous material
-0.515 g; 73%). Found -MS, FAB1) 1299.3690 -M1H)1.
C71H63O24 requires 1299.3709. nmax 1728 -CO), 1596, 1456,
1434 -Ar), 1246 -C±O) and 756 cm21 -Ar±H).
The above compound 7a -800 mg; 0.62 mmol) was
suspended in 1:1 benzene±methanol -50 mL), sodium
methoxide -54 mg; 1 mmol) was added, the mixture was
heated under re¯ux for 2 h while monitored by TLC, and
then cooled to 08C and acidi®ed with aqueous acetic acid to
pH 6. The precipitate -0.571 mg; 72%) was ®ltered off and
dried and puri®ed by solution in dichloromethane and pre-
cipitation with hexane to obtain 3,5-bis-[3,5-3,5--dimethoxy-
carbonylphenoxymethyl)phenoxymethyl]phenyl 8a -412
mg; 52%) as a white amorphous solid, mp 1358C. Found
-MS, FAB1) 1217.3290 -M1Na)1, C64H58O23Na requires
1217.3266. nmax 3431 -OH), 1724 -CO), 1596, 1456, 1434
-Ar), 1245 -C±O) and 757 cm21 -Ar±H); dH 8.26 -4H, t,
Jˆ1.5 Hz, H-40 0), 7.78 -8H, d, Jˆ1.5 Hz, H-20 0), 7.07 -2H,
s, H-30), 7.00 -5H, s, H-201H-4), 6.87 -2H, s, H-2), 5.09
-8H, s, ArCH2O), 5.08 -4H, s, ArCH2O) and 3.91 -24H, s,
OCH3) ppm; dC 166.34, 159.47, 158.79, 139.32, 138.49,
132.01, 123.53, 120.44, 118.75, 117.83, 113.58 -£2),
70.26, 69.97 and 52.70 ppm.
4.1.9. 1,3,5-Tris-[3,5-3,5-/dimethoxycarbonyl)phenoxy-
methyl]benzene 11. A mixture of 1,3,5-tris-bromomethyl)-
benzene -27.97 mg; 0.787 mmol), -MeO2C)2[G1]±OH
-127 mg; 0.236 mmol), K2CO3 -33 mg; 2.4 mmol),
18-crown-6 -15 mg; 0.6 mmol) and acetone -15 mL) was
stirred vigorously and heated under re¯ux for 48 h. The
mixture was allowed to cool to rt and the solvent evapo-
rated. The residue was dissolved in dichloromethane and
water; the aqueous layer was washed twice with dichloro-
methane -2£20 mL). The combined organic layers were
dried -Na2SO4) and the solvent evaporated to give a
white solid material -145 mg), which was dissolved in
dichloromethane and precipitated with hexane to give
4.1.7. 3,5-Bis-[4-/methoxycarbonylphenoxymethyl)phen-
oxymethyl]phenyl benzoate 7b and 3,5-bis-[4-/methoxy-

A. K. Maiti et al. / Tetrahedron 57 .2001) 3397±3401
3401
1,3,5-tris-[3,5-3,5--dimethoxycarbonyl)phenoxymethyl]ben-
zene. Found -MS, FAB1) 1752 -M1Na)1. 1729 -M11)1,
C93H84O33Na requires 1752.66. C93H85O33 requires 1730.68.
nmax 1724 -CO), 1596 -Ar), 1455, 1434, 1242 -C±O) and
757 -Ar±H); dH 8.41 -6H, d, Jˆ1.3 Hz, H-400), 7.94 -12H, d,
Jˆ1.4 Hz, H-20 0), 7.65 -3H, s, H-2), 7.19 -3H, s, H-40), 7.04
-6H, s, H-20), 5.28 -6H, s, ArCH2O), 5.25 -12H, s, Ar±
CH2O) and 4.05 -36H, s, CO2CH3) ppm; dC 166.40,
159.66, 159.00, 138.61, 138.06, 132.24, 123.72, 120.47,
113.93, 70.42 and 52.82 ppm.
AB, Jˆ6 Hz, H-2 and H-3), 7.10 -1H, s, H-40), 7.03 -2H, s,
H-20), 6.71 -1H, dd, Jˆ13.2.6 and 8.1 Hz, Ar±CHvCH2),
5.75 -1H, d, Jˆ13.2 Hz, Ar±CHvCH2), 5.32 -1H, d,
Jˆ8.1 Hz, Ar±CHvCH2), 5.12 -4H, s, ArCH2O), 5.07
-2H, s, ArCH2O) and 3.93 -12H, s, OCH3) ppm; dC
166.44, 159.74, 159.00, 138.55, 137.80, 136.78, 136.51,
132.23, 128.12, 126.83, 123.72, 120.48, 119.07, 114.56,
113.95, 70.42, 70.29 and 52.85.
Acknowledgements
4.1.10. 4-/3,5-Dimethoxycarbonylphenoxymethyl)styrene
13. Dimethyl 5-hydroxyisophthalate 5 -0.63 g; 3.3 mmol),
4-vinylbenzyl chloride 12 -0.56 g; 3 mmol), K2CO3 -0.65 g;
4.7 mmol), 18-crown-6 -50 mg; 0.2 mmol) and acetone
-50 mL) were heated under re¯ux for 48 h. The solvent
was evaporated and the residue was dissolved in water
and dichloromethane. The water layer was washed with
dichloromethane. The combined organic fractions were
dried -Na2SO4) and the solvent evaporated to give an almost
pure white solid -0.96 g; 80%), which was crystallized from
dichloromethane±hexane as white needles, mp 75±76%,
of 4--3,5-dimethoxycarbonylphenoxymethyl)styrene 13
-0.85 g; 71%). Found -MS, EI) 326.1151. Calculated for
C19H18O5 326.1154. nmax 1730 -CO), 1596 -CvC), 1441
-Me), 1250 -C±O), 1039, 1001 and 912 -RCHvCH2), and
880 cm21; dH 8.22 -1H, t, Jˆ1.5 Hz, H-40), 7.76 -2H, d,
Jˆ1.4 Hz, H-20), 7.37 -2H, d, Jˆ6.3 Hz, H-3), 7.33 -2H,
d, Jˆ6.2 Hz, H-2), 6.66 -1H, dd, Jˆ17.6 and 10.9 Hz,
Ar±CHvCH2), 5.70 -1H, dd, Jˆ17.6 and 0.8 Hz, Ar±
CHvCH2), 5.20 -1H, dd, Jˆ10.9 and 0.8 Hz, Ar±
CHvCH2), 5.06 -2H, s, ArCH2O) and 3.86 -6H, s, OCH3)
ppm; dC 166.51, 159.12, 137.99, 136.72, 135.91, 132.19,
128.20, 126.90, 123.63, 120.57, 114.74, 70.60 and
52.86 ppm.
The present work has been ®nanced by DGICYT. Two of us
-A. K. M. and Ricardo M.) thank a grant of the Spanish
Agency for International Co-operation -AECI) and
Á
Universitat de Valencia for a Research Fellowship, respec-
tively.
References
È
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4.1.11. 4-[3,5-3,5-/Dimethoxycarbonylphenoxymethyl)]-
phenoxymethylstyrene 14. The compound 6a -1.51 g;
2.80 mmol), anhydrous potassium carbonate -0.69 g;
5 mmol), 18-crown-6 -121 mg; 0.46 mmol) and acetone
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under re¯ux for 48 h. The solvent was evaporated and the
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white amorphous solid -0.25 g; 35%), mp 113±1158C.
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654.2101. nmax 1718 -CO); dH 8.28 -2H, t, Jˆ1.2 Hz,
H-400), 7.81 -4H, d, Jˆ1.2 Hz, H-200), 7.41 and 7.37 -4H,
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Â
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