An efficient and green approach for the synthesis of vinyl aryl ethers in the presence of guanidine hydrochloride

Article abstract of DOI:10.3906/kim-1002-24

A stereoselective procedure for vinyl aryl ether bond formation by direct coupling of dialkyl acetylenedicarboxylates and substituted phenols or naphthols under mild reaction conditions has been developed. Using guanidine hydrochloride as a new catalyst a

Full text of DOI:10.3906/kim-1002-24

Turk J Chem
34 (2010) , 869 – 874.
¨
˙
c
ꢀ TUBITAK
doi:10.3906/kim-1002-24
An efficient and green approach for the synthesis of vinyl
aryl ethers in the presence of guanidine hydrochloride
Robabeh BAHARFAR∗, Seyed Mohammad VAHDAT
Department of Chemistry, Mazandaran University, Babolsar, 47415, IRAN
e-mail: baharfar@umz.ac.ir
Received 04.02.2010
A stereoselective procedure for vinyl aryl ether bond formation by direct coupling of dialkyl acetylenedi-
carboxylates and substituted phenols or naphthols under mild reaction conditions has been developed. Using
guanidine hydrochloride as a new catalyst and water-acetone as green solvent, dialkyl acetylenedicarboxy-
lates were reacted with substituted phenols or naphthols in room temperature to produce vinyl aryl ethers
in good to excellent yields.
Key Words: Guanidine hydrochloride, dialkyl acetylenedicarboxylates, vinyl aryl ether, O-vinylation, water
solvent
Introduction
Vinyl ethers of alcohols and phenols are well established monomers, building blocks and auxiliaries in organic
synthesis, steadily expanding their scope of applications.1−4 These compounds are important raw materials as
practical chemicals for the production of glutaraldehyde5,6 as well as vinyl polymer materials7−9 containing
oxygen, which are expected to degrade easily in nature. Methods for their synthesis include alcohol addition
to acetylene under high pressure (20∼50 atm) and high temperature (180∼200 ◦ C), Michael-type addition–
elimination processes,10 transition metal catalyzed vinyl transfer,11 and elimination of the alcohol moiety or
HBr from acetals or α-bromo ethers, respectively.12,13 Moreover, there are many studies on the reaction between
acetylenic esters and phenols in organic solvents or under solvent-free conditions to produce fumarate or maleate
isomer as the major product.14−19
In the last decade, green chemistry has been recognized as a new approach in environmental protection. 20
Thus demands for substitutes for toxic and/or volatile molecular solvents are increasing.
∗Corresponding author
869

An efficient and green approach for the synthesis of..., R. BAHARFAR, S. M. VAHDAT
In this paper we wish to report a stereoselective synthesis of dialkyl (Z)- aryloxy butenedioates from the
reaction of a wide range of functionalized phenols or naphthols and dialkyl acetylenedicarboxylates in water-
acetone solution as a green solvent using guanidine hydrochloride as a novel and effective catalyst. Guanidines
can be categorized as organic superbases21,22 owing to the resonance stabilization of their conjugated acids23
and are therefore expected to catalyze various types of base-mediated organic reactions.
Experimental
General
Melting points were measured on an Electrothermal 9100 apparatus. Elemental analyses for C, H, and N
were performed using a Heraeus CHN–O-Rapid analyzer. IR spectra were measured on a Shimadzu IR-
460 spectrometer. 1 H- and 13 C-NMR spectra were measured with a Bruker DRX-500 AVANCE instrument
with CDCl3 as solvent at 500.1 and 125.7 MHz, respectively. Mass spectra were recorded on a Finnigan-
Matt 8430 mass spectrometer operating at an ionization potential of 70 eV. Guanidine hydrochloride, dialkyl
acetylenedicarboxylates, and phenol or naphthol derivatives were obtained from Fluka (Buchs, Switzerland) and
were used without further purification.
General procedure
A water-acetone (6:4 v/v) solution (10 mL) of phenol or naphthol derivatives (2 mmol) and the dialkyl
acetylenedicarboxylates (2 mmol) was mixed with solid guanidine hydrochloride (10 mol%). The mixture
was stirred for 2 h under room temperature. The products were isolated by filtration (for solid products) or the
organic layer was separated, dried over Na2 SO4 , and concentrated under reduced pressure. The crude product
was purified by silica gel column chromatography (Merck 230-400 mesh) using n-hexane–ethyl acetate as eluent
(for liquid products) to yield the highly pure vinyl aryl ether derivatives. Compounds 3a and 3b25 , 3c, 3f and
3g14 , 3e26 , 3h25 , 3i14 , 3j27 , 3k and 3l25 , 3s and 3t14 are known compounds.
Dimethyl (Z)-2-(2-hydroxyphenoxy)-2-butenedioate (3d)
Yellow Oil, yield 68%. IR (KBr) (νmax /cm−1): 3460 (OH), 1675-1712 (C=O), 1195 (CO) cm−1 MS, m/z
(%) = 252 (M+ , 78), 193 (76), 161 (100), 110 (24). Anal. Calcd for C12 H12 O6 (252.2): C, 57.09; H, 4.76%;
Found: C, 57.00; H, 4.79%. 1 H-NMR (500.13 MHz, CDCl3): δ = 3.71 (s, OCH3 , 3H), 3.85 (s, OCH3 , 3H),
6.77 (s, CH, 1H), 6.83-6.97 (m, CH, 4H). 13 C-NMR (125.77 MHz, CDCl3): δ = 52.3, 53.4, 109.0, 109.6, 115.4,
121.0, 122.3, 133.7, 143.8, 146.3, 166.3, 168.2.
Dimethyl (Z)-2-(4-acetyl-3-hydroxyphenoxy)-2-butenedioate (3m)
Yellow powder, yield 80%, mp 85-86 ◦ C. IR (KBr) (νmax /cm−1): 3300-3464 (OH), 1650-1732 (C=O), 1135
(CO) cm−1 . MS, m/z (%) = 294 (M+ , 68), 279 (39), 235 (100), 193 (55), 151 (32), 43 (47). Anal. Calcd
for C14 H14 O7 (294.3): C, 57.09; H, 4.76%; Found: C, 57.01; H, 4.72%. 1 H-NMR (500.13 MHz, CDCl3): δ =
4
2.57 (s, CH3 , 3H), 3.71 (s, OCH3 , 3H), 3.78 (s, OCH3 , 3H), 6.41 (d, JHH = 2.4 Hz, CH, 1H), 6.54 (dd,
870

An efficient and green approach for the synthesis of..., R. BAHARFAR, S. M. VAHDAT
4
3JHH = 8.8, JHH = 2.4 Hz, CH, 1H), 6.73 (s, CH, 1H), 7.70 (d,3JHH = 8.8 Hz, CH, 1H), 12.61 (s, OH, 1H).
13 C-NMR (125.77 MHz, CDCl3): δ = 26.5, 52.2, 53.3, 103.8, 107.8, 117.1, 132.8, 115.8, 148.5, 161.9, 162.6,
163.3, 164.7, 203.1.
Diethyl (Z)-2-(4-acetyl-3-hydroxyphenoxy)-2-butenedioate (3n)
Yellow oil, yield 60%. IR (KBr) (νmax /cm−1): 3310-3520 (OH), 1640-1738 (C=O), 1128 (CO) cm−1 . MS,
m/z (%) = 322 (M+ , 80), 277 (32), 249 (100), 221 (56), 153 (70), 43 (88). Anal. Calcd for C16 H18 O7 (322.3):
C, 59.57; H, 5.58%; Found: C, 59.52; H, 5.50%. 1 H-NMR (500.13 MHz, CDCl3): δ = 1.18(t,3 JHH = 7.1
3
3
Hz, CH3 , 3H), 1.23 (t, JHH = 7.1 Hz, CH3 , 3H), 2.55 (s, 3H, CH3), 4.15 (q, JHH = 7.1 Hz, OCH2 , 2H),
3
4
3
4
4.20 (q, JHH = 7.1 Hz, OCH2 , 2H), 6.41 (d, JHH = 2.4 Hz, CH, 1H), 6.53 (dd, JHH = 8.8, JHH = 2.4
Hz, CH, 1H), 6.71 (s, CH, 1H), 7.69 (d,3JHH = 8.8 Hz, CH, 1H), 12.60 (s, OH, 1H). 13 C-NMR (125.77 MHz,
CDCl3): δ = 13.9, 14.0, 26.4, 61.2, 62.6, 103.8, 107.8, 117.3, 132.7, 115.7, 148.5, 161.4, 162.7, 162, 164.7, 203.2.
Dimethyl (Z)-2-(3-acetyl-4-hydroxyphenoxy)-2-butenedioate (3o)
White powder, yield 85%, mp 93-94 ◦ C. IR (KBr) (νmax /cm−1): 3348-3438 (OH), 1662-1737 (C=O), 1179
(CO) cm−1 . MS, m/z (%) = 294 (M+ , 66), 279 (40), 235 (100), 193 (56), 151 (32), 43 (49). Anal. Calcd
for C14 H14 O7 (294.3): C, 57.09; H, 4.76%; Found: C, 57.00; H, 4.70%. 1 H-NMR (500.13 MHz, CDCl3): δ =
3
2.61 (s, CH3 , 3H), 3.75 (s, OCH3 , 3H), 3.77 (s, OCH3 , 3H), 6.59 (s, CH, 1H), 6.93 (d, JHH = 9.0 Hz, CH,
3
4
1H), 7.14 (dd, JHH = 9.0, JHH = 2.9 Hz, CH, 1H), 7.36 (d,3JHH = 2.9 Hz, CH, 1H), 11.99 (s, OH, 1H).
13 C-NMR (125.77 MHz, CDCl3): δ = 26.8, 52.1, 53.2, 114.9, 117.6, 119.5, 125.4, 119.3, 148.2, 149.8, 158.6,
162.4, 163.9, 203.9.
Diethyl (Z)-2-(3-acetyl-4-hydroxyphenoxy)-2-butenedioate (3p)
White powder, yield 75%, mp 96-97 ◦ C. IR (KBr) (νmax /cm−1): 3380-3555 (OH), 1653-1734 (C=O), 1203
(CO) cm−1 . MS, m/z (%) = 322 (M+ , 82), 277 (33), 249 (100), 221 (56), 153 (72), 43 (88). Anal. Calcd
for C16 H18 O7 (322.3): C, 59.57; H, 5.58%; Found: C, 59.50; H, 5.51%. 1 H-NMR (500.13 MHz, CDCl3): δ =
3
3
3
1.21 (t, JHH = 7.1 Hz, CH3 , 3H), 1.26 (t, JHH = 7.1 Hz, CH3 , 3H), 2.60 (s, CH3 , 3H), 4.20 (q, JHH
=
3
3
4
7.1 Hz, OCH2 , 4H), 6.57 (s, CH, 1 H), 6.93 (d, JHH = 9.0 Hz, CH, 1H), 7.15 (dd, JHH = 9.0, JHH
=
2.9 Hz, CH, 1H), 7.36 (d,3JHH = 2.9 Hz, CH, 1H), 11.99 (s, OH, 1H). 13 C-NMR (125.77 MHz, CDCl3): δ =
14.0, 14.1, 26.8, 61.1, 62.4, 115.0, 117.6, 119.4, 125.6, 119.3, 148.3, 150.0, 158.5, 161.9, 163.5, 203.9.
Dimethyl (Z)-2-(4-benzoyl-3-hydroxyphenoxy)-2-butenedioate (3q)
White powder, yield 85%, mp 104-105 ◦ C. IR (KBr) (νmax /cm−1): 3310-3438 (OH), 1633-1729 (C=O), 1158
(CO) cm−1 . MS, m/z (%) = 356 (M+ , 65), 297 (61), 105 (100), 77 (32). Anal. Calcd for C19 H16 O7 (356.3):
C, 63.99; H, 4.49%; Found: C, 63.90; H, 4.41%. 1 H-NMR (500.13 MHz, CDCl3): δ = 3.73 (s, CH3 , 3H), 3.83
(s, OCH3 , 3H), 6.53 (m, CH, 2H), 6.76 (s, CH, 1H), 7.47-7.52 (m, CH, 2H), 7.56-7.60 (m, CH, 2H), 7.63-7.66
871

An efficient and green approach for the synthesis of..., R. BAHARFAR, S. M. VAHDAT
(m, CH, 2H), 12.52 (s,OH, 1H). 13 C-NMR (125.77 MHz, CDCl3): δ = 52.2, 53.3, 104.0, 107.6, 117.3, 128.4,
128.9, 135.7, 138.0, 115.2, 131.8, 148.4, 161.9, 162.6, 163.3, 165.7, 200.4.
Diethyl (Z)-2-(4-benzoyl-3-hydroxyphenoxy)-2-butenedioate (3r)
Yellow oil, yield 65%. IR (KBr) (νmax /cm−1): 3300-3423 (OH), 1658-1734 (C=O), 1123 (CO) cm−1 . MS,
m/z (%) = 384 (M+ , 60), 311 (75), 105 (100), 77 (48). Anal. Calcd for C21 H20 O7 (384.4): C, 65.56; H,
3
5.20%; Found: C, 65.50; H, 5.22%. 1 H-NMR (500.13 MHz, CDCl3): δ = 1.19 (t, JHH = 7.1 Hz, CH3 , 3H),
3
3
3
1.24 (t, JHH = 7.1 Hz, CH3 , 3H), 4.15 (q, JHH = 7.1 Hz, OCH2 , 2H), 4.22 (q, JHH = 7.1 Hz, OCH2 ,
2H), 6.51 (m, CH, 2H), 6.73 (s, CH, 1H), 7.42-7.61 (m, CH, 6H), 12.50 (s, OH, 1 H). 13 C-NMR (125.77 MHz,
CDCl3): δ = 13.8, 14.0, 61.2, 62.5, 104.0, 107.6, 117.5, 128.5, 129.0, 135.6, 137.9, 116.7, 131.8, 148.4, 161.4,
162.8, 162.9, 165
Results and discussion
The chemoselective reaction of OH-acids 1 with dialkyl acetylenedicarboxylates 2 in the presence of guanidine
hydrochloride as the vinylation agent led to the synthesis of vinyl aryl ethers 3a-t. In this paper, we introduce
guanidine hydrochloride as an excellent catalyst for the stereoselective synthesis of various (Z)-O-vinyl aryl
ethers. This catalyst is completely soluble in water and the products 3a-t are more easily worked up. The
reactions were carried out by mixing the OH-acids 1 with acetylenic esters 2 and then guanidine hydrochloride
(10 mol%) was added to the mixture. The reactions proceeded spontaneously in water/acetone (60:40) at room
temperature for 2 h to afford the ether products 3a-t in 55%-85% isolated yield (Table).
The structures of compounds 3a-t were determined on the basis of their elemental analyses, mass spectra,
1 H- and 13 C-NMR, and IR spectroscopic data. Observation of a single peak at about δ = 6.70 in the 1 H-NMR
spectra is consistent with O-vinylation of the aromatic ring and formation of dialkyl (Z)-aryloxy butenedioates
3a-t as major products. The assignment of the Z configuration of 3a-t is based on the chemical shift of
the vinylic proton.24 The 13 C-NMR spectra of 3a-t show distinct resonances in agreement with the proposed
structures. Partial assignments of these resonances are given in the Experimental section. A possible mechanism
for the formation of products 3a-t is proposed in the Scheme.
..
..
R OC
- C
C - CO2R
2
_
_
H2N
H2N
..
+
+
2
H2O
Cl
NH
Cl
+
NH2
H3O
H2N
H2N
..
..
..
H2N
H
H2N
H
N
H2N
Ar-O
R2OC
Ar-OH
CO2R
H
_
N
CO2R
H
+
CO2R
..
+
NH
1
+
O-Ar
H2N
H2N
_
H2N
R2OC
..
R2OC
3
Scheme. The formation mechanism for vinyl aryl ethers.
872

An efficient and green approach for the synthesis of..., R. BAHARFAR, S. M. VAHDAT
Table. O-Vinylation of aryl alcohols with dialkyl acetylenedicarboxylates in the presence of guanidine hydrochloride.
H
R2OC
Guanidine Hydrochloride (10 mol%)
R OC
- C
C - CO2R
C
C
Ar-OH
+
2
H2O/Acetone (60:40), r.t, 2 h
Ar-O
=
2
R
Me, Et
CO2R
3
1
Entry
3a
3b
3c
Ar
R
(Z) - Isolated yields%
phenyl
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
72
58
55
68
85
60
78
85
68
75
78
72
80
60
85
75
85
65
60
65
4-chlorophenyl
2,4-dichlorophenyl
2-hydroxyphenyl
4-hydroxyphenyl
2-nitrophenyl
3d
3e
3f
3g
3h
3i
3-nitrophenyl
4-nitrophenyl
2-acetylphenyl
2-formylphenyl
2-methoxyphenyl
3j
3k
3l
2-methoxy-4-formylphenyl Me
3m
3n
3o
3p
3q
3r
4-acetyl-3-hydroxyphenyl
4-acetyl-3-hydroxyphenyl
3-acetyl-4-hydroxyphenyl
3-acetyl-4-hydroxyphenyl
Me
Et
Me
Et
4-benzoyl-3-hydroxyphenyl Me
4-benzoyl-3-hydroxyphenyl Et
3s
1-naphthyl
2-naphthyl
Me
Me
3t
Conclusion
We have developed a stereoselective, simple and efficient method for the synthesis of a new family of stable and
safe in handling O-vinyl aryl ethers. This method has several advantages such as mild conditions, easy work
up, and good to excellent yields for products, which make it attractive for researchers.
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An efficient and green approach for the synthesis of..., R. BAHARFAR, S. M. VAHDAT
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