Silica chloride-catalyzed one-pot isomerizationchlorination, arylation, and etherification of BaylisHillman adducts

Article abstract of DOI:10.1071/CH07123

A convenient and efficient one-pot isomerization?chlorination, arylation, and etherification of several Baylis?Hillman adducts with silica chloride, an eco-friendly heterogeneous catalyst, silica chloride?arenes, and silica chloride?saturated and unsatura

Full text of DOI:10.1071/CH07123

Full Paper
CSIRO PUBLISHING
Aust. J. Chem. 2007, 60, 850–856
www.publish.csiro.au/journals/ajc
Silica Chloride-Catalyzed One-Pot Isomerization–
Chlorination, Arylation, and Etherification
of Baylis–Hillman Adducts
Ponnusamy Shanmugam,A,B Baby Viswambharan,A
and Vadivel VaithiyanathanA
AChemical Sciences and Technology Division, National Institute for Interdisciplinary Science
and Technology (NIIST), Thiruvananthapuram-695 019, Kerala, India.
BCorresponding author. Email: shanmu196@rediffmail.com
A convenient and efficient one-pot isomerization–chlorination, arylation, and etherification of several Baylis–Hillman
adducts with silica chloride, an eco-friendly heterogeneous catalyst, silica chloride–arenes, and silica chloride–saturated
and unsaturated alcohols as reagent systems are reported. These reactions furnished highly functionalized isomerized
Baylis–Hillman derivatives in good yield. The efficiency and necessity of silica chloride catalyst was compared with
thionyl chloride. A plausible mechanism of the reaction is proposed.
Manuscript received: 25 April 2007.
Final version: 1 August 2007.
Introduction
and arylation of Baylis–Hillman adducts under neat and sealed
tube conditions.
Silica chloride (SiO2Cl) is an extensively used heterogeneous
solid catalyst for a number of chemical transformations partic-
ularly in the area of novel synthetic methodologies.[1–16] The
advantages of silica-modified silica chloride in organic synthesis
are that the catalyst is stable, efficient, operationally sim-
ple, convenient in handling, inexpensive, solid, heterogeneous,
and acidic in nature.[1–16] The Baylis–Hillman reaction is one
of the important reactions for the construction of carbon–
carbon bonds and leads to δ-methylene β-hydroxyalkanoates
and alkane nitriles. The reaction generally affords densely
functionalized molecules and the reaction is considered as atom-
economic.[17] Stereoselective construction of (E)-trisubstituted
alkenes appended with functional groups are one of the difficult
tasks in organic synthesis and a few methods are known.[18–22]
The isomerization of acetates of the Baylis–Hillman adducts
catalyzed by trimethylsilyl trifluoromethanesulfonate,[20,21] tri-
fluoroacetic acid,[23] benzyl trimethylammonium fluoride,[24]
and Montmorillonite K10 clay–microwave[25] are known. The
isomerization of non-activated Baylis–Hillman adducts to allyl
bromides using bromodimethyl sulfonium bromide,[26] and
isomerization–arylation using expensive metal catalysts with
aryl boronic acid[27] have been reported. To the best of our
knowledge, the synthesis of functionalized trisubstituted olefins
appended with chlorine, aryl, and ether functional groups cat-
alyzed by silica chloride, a heterogeneous catalyst, is unknown.
We have been working on the development of novel syn-
thetic transformations using Baylis–Hillman adducts.[28–36] In
continuation of our work on the synthetic applications of Baylis–
Hillman adducts, herein we report the study of silica chloride-
catalyzed one-pot isomerization–chlorination, etherification,
Results and Discussion
Optimization and Choice of Baylis–Hillman Adducts
for the Silica Chloride-Catalyzed One-Pot
Isomerization–Chlorination Reaction
The preliminary study on isomerization–chlorination reaction
was carried out with Baylis–Hillman adduct 1 and SiO2Cl
(Scheme 1). Initially, the adduct 1 in dichloromethane was stirred
with freshly prepared SiO2Cl at room temperature for 12 h and
the reaction furnished unchanged starting material. Repetition
under refluxing CH2Cl2 for 12 h also provided starting mate-
rial quantitatively. The reaction mixture without any solvent was
heated at 140◦C to afford only the dimerized compound 3 in
30% yield. However, the reaction mixture on irradiation in a
microwave oven (750 PL) for 5 min afforded the isomerized–
chlorinated compound 2 and dimerized compound 3 in 30 and
H
CO2Me
OH
Cl
MeO
MeO
ꢀ
CO2Me
SiO2Cl
2
Conditions
Table 1
H
ꢀ
CO2Me
2O
MeO
1
3
Scheme 1. Optimization of isomerization–chlorination of the Baylis–
Hillman adduct.
© CSIRO 2007
10.1071/CH07123
0004-9425/07/110850

SiO2Cl Isomerization of Baylis–Hillman Adducts
851
Cl
OH
H
Sealed tube,
100°C, 12h
R1
R2
Z
R1
R2
Z
HO
CO2Me
CO2Me
CO2Me
ꢀ
SiO2Cl
Table 1
Cl
O
O
S
OH
R3
N
N
R3
R
R
1 ꢁ H, OMe; R2 ꢁ Cl, Me, OMe
3 ꢁ H, OMe; Z ꢁ CO2Me, CN
4
5
6
OH
OH
Scheme 2. Isomerization–chlorination of Baylis–Hillman adducts.
CN
CO2Me
Cl
CO2Me
N
Table 1. Isomerization–chlorination of Baylis–Hillman adducts
O
OH
7
8
9
Entry SubstrateA
1
Products
Yield [%]B
75C
Fig. 1. Adducts tested for the isomerization using silica chloride.
1
9
2
CN
Cl
50% yields, respectively. To improve the yield of isomerized–
chlorinated product 2, optimized conditions were found to be
the mixture of starting material and SiO2Cl in a sealed tube and
heating at 100◦C for 12 h to afford the desired chlorinated com-
pound 2 in 75% yield along with 10% of dimerized compound 3.
The compounds were separated by column chromatography and
characterized by spectroscopic methods.
To find the reactivity and suitability of various Baylis–
Hillman adducts for the reaction, adduct derived from isatin 4
(Fig. 1)furnishedonlyatrace(∼5%)ofchlorinatedcompound 5.
Adducts derived from heteroaromatic aldehydes bearing thio-
phene, furan, and pyridine substituents (6, 7, and 8, respectively)
yielded neither chlorinated nor dimerized compounds. However,
the simple nitrile adduct 9 furnished chlorinated compound 10
and the corresponding dimerized compound in 50 and 8% yields,
respectively. Thus, only simple aryl-derived Baylis–Hillman
adducts are suitable for the isomerization–chlorination reaction
with SiO2Cl.
2
50
Cl
10
CO2Me
Cl
OH
CO2Me
3
4
5
6
58
11
12
OH
CO2Me
Cl
CO2Me
13
78
Me
Cl
Me
Cl
14
16
OH
CO2Me
Cl
CO2Me
15
39
OH
MeO
MeO
CO2Me
Cl
42D
MeO
MeO
CO2Me
OMe
OMe
17
18
Silica Chloride-Catalyzed One-Pot Isomerization–
Chlorination of Baylis–Hillman Adducts
OH
CO2Me
As the preliminary experiments showed promising results on the
isomerization–chlorinationreaction, wewerepromptedtoexam-
ine the reaction with several simple Baylis–Hillman adducts
(Scheme 2). Thus, the adduct 11 under optimized conditions
afforded the isomerized–chlorinated derivative 12 in 58% yield
along with the corresponding dimerized product in 30% yield
(Table 1, entry 3). Similarly, the other Baylis–Hillman adducts
underwent the isomerization–chlorination reaction under opti-
mized conditions to produce good yields of the desired products
(Table 1, entries 1–6). It should be noted that adduct 19, bearing
an electron-withdrawing group at the aryl ring, and adduct 20,
with a nitrile group at the activated position, afforded neither
desired isomerization–chlorination products nor the dimerized
compounds (Table 1, entries 7 and 8). However, adduct 9,
bearing halogen substitutions on the aryl ring and a nitrile
group at the activated alkene, afforded only moderate yields of
isomerized–chlorinated and dimerized compounds, respectively
(Table 1, entry 2). Longer reaction times and variation of temper-
ature (80–120◦C) did not minimize the formation of dimerized
products.
7
8
–
–
–
NO2
OH
19
CN
–
20
ASiO2Cl, sealed tube, 100◦C, 12 h.
BOnly Z-isomers were obtained.
CBased on isolation of starting material.
DSiO2Cl, 1 h, sealed tube, 100◦C.
explore the reaction in the presence of simple aromatic hydro-
carbons to trap the reactive intermediate with aromatic hydro-
carbons (Scheme 3).The Friedel–Crafts reaction afforded highly
functionalized arylated trisubstituted alkenes in excellent yields.
Thus, the adduct 11 with two equivalents of benzene afforded
an excellent yield of isomerized phenylated compound 21
(Table 2, entry 1). It was observed that only the E-isomer 21
was formed as evidenced by 1H NMR (chemical shifts of alkene
proton; see Experimental). To show the general nature of the
reaction, experiments with other aromatic hydrocarbons such
as toluene, mesitylene, o-xylene, and ethyl benzene afforded
the corresponding isomerized–arylated compounds in excellent
yields (Table 2, entries 3–5 and 8). Gas chromatography–mass
Silica Chloride-Catalyzed One-Pot Isomerization–
Arylation of Baylis–Hillman Adducts
The successful isomerization–chlorination reaction of Baylis–
Hillman adducts with silica chloride prompted us to further

852
P. Shanmugam, B. Viswambharan, and V. Vaithiyanathan
H
OH
OH
H
SiO2Cl, sealed
tube, 100°C, 12h
SiO2Cl, sealed
tube, 100°C, 12h
CO2Me
O-R
CO2Me
CO2Me
CO2Me
Ar
ꢀ R-OH
ꢀ Ar-H
Table 3
Table 2
R1
R1
R1
R1
R
1 ꢁ H, Cl, OMe
Ar ꢁ benzene, toluene, mesitylene,
ethyl benzene, o-xylene
R ꢁ propargyl, homopropargyl, 2-butyne-1,2-diol, CH3
R1 ꢁH, Cl
Scheme 4. Isomerization–etherification of Baylis–Hillman adducts.
Scheme 3. Isomerization–arylation of Baylis–Hillman adducts.
to explore the reaction in the presence of saturated and unsat-
urated alcohols to functionalize the adducts by trapping the
intermediate with alcohols. The reaction was highly success-
ful and afforded functionalized trisubstituted alkenyl ethers
in excellent yields (Scheme 4). Thus, adduct 11 with silica
chloride–propargyl alcohol afforded isomerized–etheriated E-
and Z-isomers 27a and 27b in 75% combined yield (Table 3,
entry 1). It should be noted that the p-methoxy-substituted
adduct 1, with propargyl and homopropargyl alcohol, furnished
only the Z-isomer of isomerized–ether derivatives 29 and 30
as determined by 1H NMR spectroscopy (Table 3, entries 3
and 4) and GCMS analysis. The adducts 11 and 15 furnished
Table 2. Isomerization–arylation of Baylis–Hillman adducts
Entry SubstrateA Ar–H
Product
Yield [%]B
90
CO2Me
1
11
Benzene
21
CO2Me
CO2Me
2
15
Benzene
96
Cl
Cl
1
both E- and Z-isomers in the ratio of 2:1 as determined by H
22
NMR analysis. Adduct 11 with methanol produced both E- and
Z-isomers 32a,b, which were separated by column chromato-
graphy. The reaction of adduct 11 with but-2-yne-1,4-diol fur-
nished the corresponding ether derivative 31 in 51% yield
(Table 3, entry 5) as a single isomer. To our surprise, the
reactions with allyl alcohol and benzyl alcohol did not yield
any isomerized–ether products (Table 3, entries 6 and 8). A
trace amount (<5%) of isomerized–chlorinated compounds was
found in all reaction mixtures.
3
4
5
15
11
11
Toluene
95C
90C
52
23
CO2Me
o-Xylene
Mesitylene
24
Reactivity and Efficiency of Silica Chloride Catalyst v.
Thionyl Chloride
CO2Me
The efficiency and necessity of silica chloride (conditions B,
Table 4) were compared with thionyl chloride (conditions A,
Table 4) in the isomerization–chlorination, arylation, and etheri-
fication reactions. The reaction was compared and demonstrated
with adduct 11. As shown in Table 4, in the case of the
isomerization–chlorination reaction, there was not much differ-
ence in the product formation (Table 4). However, in the cases
of arylation and etherification reactions, it was found that the
silica chloride catalyst is essential as the yields are significantly
higher with silica chloride than thionyl chloride (Table 4). Fur-
ther, unlike thionyl chloride, which is difficult to handle, the
advantages of the silica chloride catalyst are that it is stable, effi-
cient, and easy to handle. The reactivity of the SiO2Cl of this
reaction was also tested by variation in loading weight % of the
catalyst and the reaction time. We have used 100% w/w of the
catalyst and varying the catalyst by percentage loading did not
alter the yields.
Silica chloride has been used as a multipurpose catalyst
for the one-pot transformation of isomerization–chlorination,
arylation, and ether formation of activated and non-activated
Morita–Baylis–Hillman adducts without the use of solvent. It
should be noted that the arylation reaction afforded excellent
yields of the products. The advantages of silica chloride in
organic synthesis are that the catalyst is stable, efficient, opera-
tionally simple, and the fact that it is convenient in handling,
inexpensive, solid, heterogeneous, and acidic in nature have
been exploited. Of particular note is the advantage that all
three synthetic transformations as reported in the manuscript
are performed with silica chloride alone; different reagent and
25
6
7
11
11
Indole
Naphthalene
–
–
–
–
CO2Me
8
11
Ethylbenzene
70C
Et
26
ASiO2Cl, sealed tube, 100◦C, 12 h.
BOnly E-isomer was obtained.
CMixture of o, p-derivatives (3:7) inseparable by column chromatography.
spectrometry coupled technique (GCMS) analysis of the toluene
derivative 23 showed two peaks having the same mass with dif-
ferent retention times and we found these o- and p-isomers
inseparable by column chromatography in the ratio of 3:7.
Experiments with naphthalene and indole did not yield any char-
acterized products (Table 2, entries 6 and 7). The results are
collected in Table 2.
Silica Chloride-Catalyzed Isomerization–Etherification
of Baylis–Hillman Adducts
The successful isomerization of Baylis–Hillman adducts with
SiO2Cl and SiO2Cl–aromatic compounds prompted us further

SiO2Cl Isomerization of Baylis–Hillman Adducts
853
Table 3. Isomerization–etherification of Baylis–Hillman adducts
Entry
1
SubstrateA
Alcohol
Ether products
CO2Me
Yield [%]
75
11
Propargyl alcohol
O
27a,b
CO2Me
O
2
3
15
1
Propargyl alcohol
Propargyl alcohol
85
64
Cl
28a,b
CO2Me
MeO
O
29
CO2Me
4
5
1
Homopropargyl alcohol
But-2-yne-1,4-diol
68
51
MeO
MeO
O
30
HO
CO2Me
11
O
31
6
7
11
11
Allyl alcohol
Methanol
_
_
CO2Me
O
60B
32a,b
8
17
Benzyl alcohol
_
_
ASiO2Cl, sealed tube, 100◦C, 12 h.
BCombined yield of E to Z (2:1) isomers separable by column chromatography.
Table 4. Comparison of silica chloride catalyst v. thionyl chloride
No. Substrate
Conditions
B
Product
Yield [%]
A
A
B
A
B
1
2
3
11
11
11
SOCl2, neat, room temp.
Benzene, 12 h, SOCl2, sealed tube, 100◦C Benzene, SiO2Cl, sealed tube, 100◦C, 2 h
Propargyl alcohol, 12 h, SOCl2, 100◦C
SiO2Cl, sealed tube, 100◦C, 12 h
12
21
12
21
27
77
0
10
73
90
75
Propargyl alcohol, 12 h, SiO2Cl, sealed tube, 100◦C 27
conditions are required to carry out the reactions as reported in
the literature.[1–27]
HO
SiO2Cl ꢀ
Ar
SiO2O
Ar
ꢂ
ꢀ
Z
SiO2O
ꢂHCl
Z
Z
Ar
Mechanistic Considerations
Nu
Nuꢂ ꢁ Cl, ROH, Ar
Nuꢂ
ꢂ
SiO2O
A plausible mechanism for the reaction of isomerization–
chlorination, arylation, and etherification is postulated and
shown in Fig. 2. The Si–Cl bond is weak and can give rise
to Lewis acid-centred intermediates. The chloride ion in sil-
ica chloride could be displaced by the hydroxyl group of the
Baylis–Hillman adduct to form tight ion pairs that upon nucleo-
philic attack with chloride or aryl or alkoxy nucleophiles in an
ꢂ
Nuꢂ
ꢀ
ꢀ
SiO2O
Z
Z
Z
Ar
Ar
Ar
Fig. 2. Plausible mechanism for the reaction.

854
P. Shanmugam, B. Viswambharan, and V. Vaithiyanathan
S1N fashion form isomerized derivatives of the Baylis–Hillman
adducts.
(E)-2-(Chloromethyl)-3-(4-chlorophenyl)acrylonitrile 10
Colourless oil. νmax/cm−1 (CH2Cl2) 2219, 1618, 823. δH
(CDCl3/TMS, 300.1 MHz) 4.31 (s, 2H), 7.18 (s, 1H), 7.43 (d, J
8.7, 2H), 7.73 (d, J 8.7, 2H). δC (CDCl3/TMS, 75.3 MHz) 45.6,
108.1, 117.8, 129.3 (2C), 130.4 (2C), 137.4, 145.1, 146.5. Calc.
for C10H7Cl2N: 210.9956. Found: 210.9968.
Conclusions
We have demonstrated a simple method for a one-pot
isomerization–chlorination, arylation, and etherification of
Baylis–Hillmanadductsderivedfromsimplearylaldehydeswith
silica chloride, an eco-friendly heterogeneous catalyst, by using
a simple experimental procedure. As the products obtained here
are highly functionalized, they can be manipulated for further
synthetic transformations. Further work on the use of the SiO2Cl
catalyst for novel synthetic methodologies is in progress in our
laboratory.
(E)-Methyl 2-(Chloromethyl)-3-phenyl Acrylate 12
Colourless oil. νmax/cm−1 (CH2Cl2) 1714, 1626, 761. δH
(CDCl3/TMS, 300.1 MHz) 3.85 (s, 3H), 4.24 (s, 2H), 7.38–7.53
(m, 5H), 7.93 (s, 1H). δC (CDCl3/TMS, 75.3 MHz) 52.2, 58.3,
114.4, 128.5 (2C), 128.6, 129.8 (2C), 134.7, 144.7, 168.1. Calc.
for C11H11ClO2: 210.0448. Found: 210.0454.
(E)-Methyl 2-(Chloromethyl)-3-p-tolyl Acrylate 14
Experimental
Colourless oil. νmax/cm−1 (CH2Cl2) 1714, 1629, 812. δH
(CDCl3/TMS, 300.1 MHz) 2.40 (s, 3H), 3.87 (s, 3H), 4.49 (s,
2H), 7.26 (d, J 8.1, 2H), 7.46 (d, J 8.1, 2H), 7.85 (s, 1H). δC
(CDCl3/TMS, 75.3 MHz) 21.4, 39.1, 52.3, 123.0, 126.0, 127.7,
129.7 (2C), 141.2, 143.9 (2C), 166.0. Calc. for C12H13ClO2:
224.0604. Found: 224.0615.
General
All experiments were carried out in oven-dried glassware. Ana-
lyticalTLC was performed on silica gelTLC plates. Purification
by gravity column chromatography was carried out with silica
gel (100–200 mesh). Mixtures of ethyl acetate and hexane and
pure hexane were used as eluent as required. Infrared (IR) spectra
were run on a Nicolet (impact 400D FT-IR) spectrophotometer.
NMR spectra were obtained using CDCl3 as solvent on a Bruker
DPX 300 MHz NMR spectrometer. Chemical shifts are given in
the δ scale with tetramethylsilane (TMS) as internal reference.
High resolution mass spectroscopy were measured on a JMS 600
JEOL mass spectrometer.Yields refer to quantities obtained after
column chromatography. Solvents used are reagent grade and
were purified before use according totheliteratureprocedure.[37]
(E)-Methyl 2-(Chloromethyl)-3-(4-chlorophenyl)
Acrylate 16
Colourless oil. νmax/cm−1 (CH2Cl2) 1716, 1632, 836. δH
(CDCl3/TMS, 300.1 MHz) 3.88 (s, 3H), 4.43 (s, 2H), 7.42 (d, J
8.4, 2H), 7.49 (d, J 8.4, 2H), 7.81 (s, 1H). δC (CDCl3/TMS,
75.3 MHz) 38.5, 52.7, 123.5, 129.4 (2C), 131.1 (2C), 141.3,
142.5, 146.5, 166.6. Calc. for C11H10Cl2O2: 244.0058. Found:
244.0072.
(E)-Methyl 2-(Chloromethyl)-3-(3,4,5-trimethoxy
Phenyl) Acrylate 18
General Experimental Procedure
A mixture of Baylis–Hillman adduct (1 mmol), freshly prepared
silica chloride (100% w/w), and alcohol (2 equiv.) or benzene
(as reagent, 2 equiv.) were taken in an oven-dried sealed tube and
heated in an oil bath at 100◦C for 12 h. The crude mixture was
diluted with dichloromethane (2 × 10 mL) and filtered through
a pad of Celite. The organic layer was dried over anhydrous
sodium sulfate and concentrated under vacuum.The mixture was
purified by silica gel (100–200 mesh) column chromatography,
with hexane and a gradient mixture of hexane/ethyl acetate as
eluent.
Colourless oil. νmax/cm−1 (CH2Cl2) 1714, 1622, 1259,
1042, 779. δH (CDCl3/TMS, 300.1 MHz) 3.88 (s, 3H), 3.90
(s, 9H), 4.52 (s, 2H), 6.86 (s, 2H), 7.83 (s, 1H). δC (CDCl3/
TMS, 75.3 MHz) 39.6, 52.4, 56.1 (2C), 60.8, 106.9, 127.4, 129.4
(2C), 141.0, 144.1, 153.3 (2C), 166.6. Calc. for C14H17ClO5:
300.0765. Found: 300.0775.
Spectroscopic Data for Arylated Compounds
Methyl-2-benzyl-3-phenyl Acrylate 21
Colourless oil. νmax/cm−1 (CH2Cl2) 3060, 1714, 1633.79,
1592.50, 1493. δH (CDCl3/TMS, 300.1 MHz) 3.74 (s, 3H), 3.95
(s, 2H), 7.34–7.19 (m, 10H), 7.93 (s, 1H). δC (CDCl3/TMS,
75.3 MHz) 33.1, 51.5, 109.5, 126.8, 128.5, 128.5, 128.7, 128.8,
128.9, 129.1, 129.5, 129.6, 130.7, 139.3, 168.6. Calc. for
C17H16O2: 252.1168. Found: 252.1158.
Preparation of SiO2Cl Catalyst
Silica gel (10 g) was oven-dried (120◦C under vacuum) in a
round-bottomed flask (250 mL) equipped with a condenser and
a drying tube, and thionyl chloride (40 mL) was added. The mix-
ture was refluxed for 40 h. The unreacted thionyl chloride was
distilled off under vacuum. The resulting white greyish powder
was flame-dried and stored in a tightly capped bottle. This silica
chloride can be used for a month without losing its activity.
Methyl-2-benzyl-3-(4-chlorophenyl) Acrylate 22
Colourless oil. νmax/cm−1 (CH2Cl2) 3060, 1714, 1633,
1592, 1493. δH (CDCl3/TMS, 300.1 MHz) 3.73 (s, 3H), 3.97
(s, 2H), 7.83–7.15 (m, 9H), 7.86 (s, 1H). δC (CDCl3/TMS,
75.3 MHz) 33.0, 52.1, 128.5, 128.5, 128.7 (2C), 128.9 (2C),
129.1, 129.4 (2C), 130.4 (2C), 130.8, 133.6, 139.5, 168.3. Calc.
for C17H15ClO2: 286.0761. Found: 286.0755.
Spectroscopic Data for Chlorinated Compounds
(E)-Methyl 2-(Chloromethyl)-3-(4-methoxyphenyl)
Acrylate 2
Colourless oil. νmax/cm−1 (CH2Cl2) 1712, 1604, 1259, 1026,
837. δH (CDCl3/TMS, 300.1 MHz) 3.87 (s, 6H, 2OMe), 4.52
(s, 2H), 6.97 (d, J 8.7, 2H), 7.56 (d, J 8.7, 2H), 7.83 (s, 1H).
δC (CDCl3/TMS, 75.3 MHz) 39.5, 52.3, 55.3, 113.5, 114.3 (2C),
125.8, 126.6, 131.8 (2C), 143.7, 160.9. Calc. for C12H13ClO3:
240.0553. Found: 240.0564.
Methyl-2-(4-methylbenzyl)-3-(4-chlorophenyl)
Acrylate 23; Mixture of Inseparable
o- and p-Isomers 23
Colourless oil. νmax/cm−1 (CH2Cl2) 3060, 1714, 1633, 1592,
1493. δH (CDCl3/TMS, 300.1 MHz) 2.20 (s, 3H), 2.22 (s, 3H),

SiO2Cl Isomerization of Baylis–Hillman Adducts
855
3.64 (s, 3H), 3.65 (s, 3H), 3.78 (s, 2H), 3.79 (s, 2H), 6.8–7.3 (m,
18H), 7.75 (s, 1H), 7.82 (s, 1H). δC (CDCl3/TMS, 75.3 MHz)
19.2, 20.8, 30.8, 32.5, 38.6, 51.5, 126.1, 126.6, 128.6, 130.4
(3C), 133.4 (3C), 139.3, 139.8, 168.2. Calc. for C18H17ClO2:
300.0917. Found: 300.0915.
(Z)-Methyl 3-(4-Chlorophenyl)-2-(prop-2-ynyloxy)
Methylacrylate (Major Isomer) 28b
Colourless oil. νmax/cm−1 (CH2Cl2) 3297, 2951, 2116, 1714,
1633, 1077. δH (CDCl3/TMS, 300.1 MHz) 2.54–2.52 (t, J 2.4,
1H), 3.83 (s, 3H), 4.39 (s, 2H), 4.85–4.84 (d, J 2.4, 2H), 7.39–
7.35 (m, 2H), 7.87–7.51 (m, 2H), 7.92 (s, 1H). δC (CDCl3/TMS,
75.3 MHz) 52.5, 58.0, 63.8, 74.9, 79.3, 128.74, 129.7, 131.3,
132.5, 135.8, 144.6, 166.2. Calc. for C14H13ClO3: 264.0553.
Found: 264.0530.
Methyl-2-(3,4-dimethylbenzyl)-3-phenyl Acrylate 24
Colourless oil. νmax/cm−1 (CH2Cl2) 3060, 1714, 1633, 1592,
1493. δH (CDCl3/TMS, 300.1 MHz) 2.26 (s, 6H), 3.65 (s,
3H), 3.92 (s, 2H), 6.8–7.3 (m, 8H, ArH), 7.82 (s, 1H). δC
(CDCl3/TMS, 75.3 MHz) 19.2, 19.5, 20.87, 30.8, 32.5, 38.6,
51.5, 126.1, 126.6, 128.6, 130.4 (3C), 133.4 (3C), 139.3, 139.8,
168.6. Calc. for C19H20O2: 280.1463. Found: 280.1455.
Methyl 3-(4-Methoxyphenyl)-2-((prop-
2-ynyloxy)methyl) Acrylate 29
Colourless oil. νmax/cm−1 (CH2Cl2) 3289, 2113, 1714, 1605,
1178. δH (CDCl3/TMS, 300.1 MHz) 2.50–2.49 (t, J 3, 1H), 3.82
(s, 3H), 3.83 (s, 3H), 4.29–4.28 (d, J 3, 2H), 4.43 (s, 2H), 6.94–
6.91 (d, J 8.7, 2H), 7.57–7.55 (d, J 8.7, 2H), 7.90 (s, 1H). δC
(CDCl3/TMS, 75.3 MHz) 52.0, 53.6, 55.2, 57.8, 64.3, 74.6, 79.6,
98.8, 113.9, 125.4, 127.0, 132.0, 145.1, 160.8, 168.1. Calc. for
C15H16O4: 260.1049. Found: 260.1072.
Methyl-2-(2,4,6-trimethylbenzyl)-3-phenyl Acrylate 25
Colourless oil. νmax/cm−1 (CH2Cl2) 3060, 1714, 1633, 1592,
1493. δH (CDCl3/TMS, 300.1 MHz) 2.20 (s, 9H), 3.62 (s,
3H), 3.92 (s, 2H), 6.81–7.32 (m, 7H, ArH), 7.62 (s, 1H). δC
(CDCl3/TMS, 75.3 MHz) 19.2, 19.5, 20.1, 20.8, 30.8, 32.5, 38.6,
51.5, 126.1, 126.6, 128.6, 130.4 (3C), 133.4 (3C), 139.3, 139.8,
168.4. Calc. for C20H22O2: 294.1625. Found: 294.1620.
Methyl 2-((But-3-ynyloxy)methyl)-3-(4-methoxyphenyl)
Acrylate 30
Methyl-2(4-ethylbenzyl)-3-phenylacrylate 26
Colourless oil. νmax/cm−1 (CH2Cl2) 3295.5, 2119.62,
1715.43, 1605.53, 1121. δH (CDCl3/TMS, 300.1 MHz) 2.03–
2.01 (t, J 2.7, 1H), 2.57–2.51 (dt, J 2.7, 6.9, 2H), 3.72–3.70
(t, J 6.6, 2H), 3.82 (s, 3H), 3.83 (s, 3H), 4.36 (s, 2H), 6.95–
6.90 (m, 2H), 7.59–7.55 (m, 2H), 7.90 (s, 1H). δC (CDCl3/TMS,
75.3 MHz) 19.7, 51.9, 55.2, 64.9, 68.4, 69.1, 81.4, 113.9,
125.7, 127.1, 131.9, 144.9, 160.7, 168.2. Calc. for C16H18O4:
274.1205. Found: 274.1210.
Colourless oil. νmax/cm−1 (CH2Cl2): 3062, 1711, 1630,
1592, 1493. δH (CDCl3/TMS, 300.1 MHz) 1.31 (t, 3H, CH3),
2.26 (q, 2H, CH2), 3.65 (s, 3H), 3.92 (s, 2H), 6.8–7.3 (m, 9H,
ArH), 7.92 (s, 1H). δC (CDCl3/TMS, 75.3 MHz) 19.2, 19.5, 20.8,
30.8, 32.5, 38.6, 51.5, 126.1, 126.6, 128.6, 130.4 (3C), 133.4
(3C), 139.3, 139.8, 168.6. Calc. for C19H20O2: 280.1463. Found:
280.1456.
Spectral Data for Ether Derivatives
Methyl 2-((4-Hydroxybut-2-ynyloxy)methyl)-3-phenyl
Acrylate 31
(Z)-Methyl-3-phenyl-2-((prop-2-ynyloxy)methyl)
Acrylate (Minor Isomer) 27a
Colourless oil. νmax/cm−1 (CH2Cl2) 3445.5, 2319.72, 1745,
1632.38, 1436, 1119.31, 1069. δH (CDCl3/TMS, 300.1 MHz)
2.20 (br s, 1H), 3.76 (s, 3H), 4.23 (s, 4H), 4.32 (s, 2H), 7.48–
7.30 (m, 5H), 7.86 (s, 1H). δC (CDCl3/TMS, 75.3 MHz) 50.8,
52.21, 58.1, 63.9, 81.3, 85.0, 129.9, 134.3, 136.7, 145.1, 168.0.
Calc. for C15H16O4: 260.1049. Found: 260.1035.
Colourless oil. νmax/cm−1 (CH2Cl2) 3291, 2116, 1714, 1633,
1076. δH (CDCl3/TMS, 300.1 MHz) 2.53–2.51 (t, J 2.4, 1H),
3.83 (s, 3H), 4.40 (s, 2H), 4.84–4.83 (d, J 2.4, 2H), 7.40–7.30
(m, 3H), 7.58–7.54 (m, 2H), 7.99 (s, 1H). δC (CDCl3/TMS,
75.3 MHz) 52.5, 58.0, 64.0, 74.9, 79.5, 127.3, 128.5, 129.7,
130.0, 134.2, 146.0, 166.5. Calc. for C14H14O3: 230.0943.
Found: 230.0935.
(Z)-Methyl-2-(methoxymethyl)-3-phenylacrylate 32a
Colourless oil. νmax/cm−1 (CH2Cl2) 1715, 1633, 1237. δH
(CDCl3/TMS, 300.1 MHz) 3.44 (s, 3H), 3.846 (s, 3H), 4.24
(s, 2H), 7.53–7.37 (m, 5H), 7.94 (s, 1H). δC (CDCl3/TMS,
75.3 MHz) 52.1, 58.2, 66.4, 128.4, 128.6, 129.3, 129.7, 134.6,
144.7, 168.0. Calc. for C12H14O3: 206.0943. Found: 206.0942.
(E)-Methyl-3-phenyl-2-((prop-2-ynyloxy)methyl)
Acrylate (Major Isomer) 27b
Colourless oil. νmax/cm−1 (CH2Cl2) 3291, 2116, 1714, 1633,
1076. δH (CDCl3/TMS, 300.1 MHz) 2.48–2.47 (t, J 2.1, 1H),
3.83 (s, 3H), 4.28–4.27 (d, J 2.1, 2H), 4.41 (s, 2H), 7.40–7.30
(m, 3H), 7.58–7.54 (m, 2H), 7.94 (s, 1H). δC (CDCl3/TMS,
75.3 MHz) 52.1, 57.9, 64.1, 74.6, 79.5, 127.9, 128.4, 129.3,
129.9, 134.4, 145.1, 167.8. Calc. for C14H14O3: 230.0943.
Found: 230.0929.
(E)-Methyl-2-(methoxymethyl)-3-phenylacrylate 32b
Colourless oil. νmax/cm−1 (CH2Cl2) 1715, 1633, 1237. δH
(CDCl3/TMS, 300.1 MHz) 3.412 (s, 3H), 3.68 (s, 3H), 4.25
(s, 2H), 6.90 (s, 1H), 7.35–7.28 (m, 5H). δC (CDCl3/TMS,
75.3 MHz) 51.8, 58.2, 74.2, 124.8, 127.7, 128.4, 130.7, 135.2,
135.8, 168.6. Calc. for C12H14O3: 206.0943. Found: 206.0943.
(E)-Methyl 3-(4-Chlorophenyl)-2-(prop-2-ynyloxy)
Methylacrylate (Minor Isomer) 28a
Colourless oil. νmax/cm−1 (CH2Cl2) 3297, 2951, 2116, 1714,
1633, 1077. δH (CDCl3/TMS, 300.1 MHz) 2.51–2.50 (t, J 2.1,
1H), 3.84 (s, 3H), 4.28–4.27 (d, J 2.2.1, 2H), 4.37 (s, 2H), 7.39–
7.35 (m, 2H), 7.87 (s, 1H), 7.87–7.51 (m, 2H). δC (CDCl3/TMS,
75.3 MHz) 52.5, 58.0, 63.8, 74.8, 79.4, 128.3, 128.6, 131.2,
132.7, 135.5, 143.7, 167.5. Calc. for C14H13ClO3: 264.0553.
Found: 264.0534.
Acknowledgements
P.S. thanks Professor Dr T. K. Chandrashekar, Director-NIST, for infrastruc-
ture facilities. Financial support (SR/S1/OC-38/2005) from the DST (New
Delhi) is gratefully acknowledged. B.V. andV.V. thank CSIR (New Delhi) for
the award of a Senior Research Fellowship. Constructive suggestions for the
improvement of the manuscript from the referees are greatly acknowledged.

856
P. Shanmugam, B. Viswambharan, and V. Vaithiyanathan
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