Stereoselective synthesis of (E)-?-aryloxyl and alkyloxyl acrylates through DABCO-catalysed Michael additions of phenols and alcohols to ethyl 2,3-butadienoate

Article abstract of DOI:10.3184/174751916X14631336104179

The development of DABCO-catalysed Michael addition of phenols and alcohols to ethyl 2,3-butadienoate provides an efficient synthetic pathway to (E)-?-aryloxyl and alkyloxyl acrylates in i-PrOH or under solvent-free conditions. The major advantages of the present method are wide substrate scope, mild reaction conditions, high stereoselectivity, and good reaction yields.

Full text of DOI:10.3184/174751916X14631336104179

364 RESEARCH PAPER
VOL. 40 JUNE, 364–367
JOURNAL OF CHEMICAL RESEARCH 2016
Stereoselective synthesis of (E)-ß-aryloxyl and alkyloxyl acrylates through
DABCO-catalysed Michael additions of phenols and alcohols to ethyl
2,3-butadienoate
Feng Weia, Wu Haiboa, Qian Houjuna, Li Zhengyia,b, Sun Xiaoqianga,b and Wang Zhiminga,b*
aJiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou, Jiangsu
213164, P.R. China
bAdvanced Catalysis and Green Manufacturing Collaborative Innovation Center, Changzhou University, Changzhou, Jiangsu 213164, P.R. China
The development of DABCO-catalysed Michael addition of phenols and alcohols to ethyl 2,3-butadienoate provides an efficient
synthetic pathway to (E)-β-aryloxyl and alkyloxyl acrylates in i-PrOH or under solvent-free conditions. The major advantages of the
present method are wide substrate scope, mild reaction conditions, high stereoselectivity, and good reaction yields.
Keywords: aryloxyl acrylate, alkyloxyl acrylate, ethyl 2,3-butadienoate, Michael addition
β-Aryloxyl/alkyloxyl acrylates and their derivatives are valuable
intermediates in synthetic strategies to pharmaceutically
interesting oxygen-containing heterocycles, such as furans,1
benzofurans,2–4 phthalans,5 and chromones.6 They also are
useful substrates involved in the Stetter reaction7,8 and in
asymmetric hydrogenations.9 Conventionally, protocols for
the synthesis of β-aryloxyl/alkyloxyl acrylates include the
Michael addition of phenols to propiolates,10–12 the Brønsted
acid-catalysed O-alkylation of ethyl acetoacetate,13 the copper-
catalysed O-arylation of enoates,14 and the transition metal-
catalysed coupling reaction of vinyl halides.15 Very recently, the
Wan group reported a new copper-catalysed multicomponent
reaction of phenols, acyl chlorides, and Wittig reagents for
the preparation of β-aryloxyl acrylates with high diversity.16
Despite the impressive progress, some examples suffer from the
limitation of undesirable stereoselectivities, high temperatures,
and relatively low reaction yields. Moreover, the synthetic
pathways leading to the efficient synthesis of β-alkyloxyl
acrylates are rather limited.3 In this regard, a milder, more
stereoselective, and convenient methodology for the synthesis
of β-aryloxyl/alkyloxyl acrylates is worthy of exploration.
In recent years, Lewis base catalysed reactions of allenoates
have attracted much attention to become one of the most
powerful tools for the carbon–carbon bond and carbon-
heteroatom bond formations.17–19 In sharp contrast to the well-
developed phosphine catalysed additions of allenoates with
various nucleophiles,20,21 the corresponding amine catalysed
examples are relatively rare.22,23 Although DABCO-catalysed
Michael additions of phenols to allenoates have been reported
sporadically,22,23 the synthesis of β-aryloxyl acrylates through
DABCO-catalysed Michael addition of phenols to allenoates
has not been studied systematically. Furthermore, to the best
of our knowledge, the DABCO-catalysed Michael addition
of alcohols to allenoates has not been reported previously.
Herein, we report a mild, efficient, and highly stereoselective
synthesis of (E)-β-aryloxyl and alkyloxyl acrylates from ethyl
2,3-butadienoate with various phenols and alcohols catalysed
by DABCO in i-PrOH or under solvent-free conditions.
To begin our study, we chose ethyl 2,3-butadienoate (1)
and phenol (2a) as reaction partners to optimise the reaction
conditions by varying the solvents, catalysts, and reaction
temperature (Scheme 1, Table 1). To our delight, the DABCO-
catalysed Michael addition of phenol to ethyl 2,3-butadienoate
took place smoothly at room temperature with good reaction
yields and high E/Z-selectivities in various solvents, such as
CH2Cl2, EtOH, i-PrOH, t-BuOH, CH3CN, and toluene (entries
1–6). In particular, the use of the protic polar solvent i-PrOH
improves the reaction efficiency and leads to the product
(E)-ethyl 3-phenoxybut-2-enoate (3a) stereospecifically
(entry 3). It is noteworthy that the reaction provided lower
reaction yields and stereoselectivities at elevated temperatures,
albeit with shorter reaction times (entries 7 and 8). When
DBU, Et3N, K2CO3, and Cs2CO3 were applied as the catalysts,
60–87% yields of ethyl 3-phenoxybut-2-enoate (3a and 4) were
obtained with satisfactory E/Z-selectivities (entries 9–12). The
stereochemistry of 3a and 4 was determined by the comparison
of their NMR spectra with the known literature.9 Thus, the
optimal conditions for the Michael addition of phenol to ethyl
2,3-butadienoate was 5 mol% of DABCO as the catalyst in
i-PrOH at room temperature (entry 3).
With the optimised reaction conditions in hand, the reaction
scope was explored with a variety of phenols (see Scheme 2). As
shown in Table 2, all kinds of phenols with electron-donating
groups (Me, OMe, OBn) or electron-withdrawing groups (F, Cl,
Table 1 Optimisation of reaction conditionsa
Entry Catalyst
Solvent
CH2Cl2
EtOH
Time (h)
Yield/hb
82
78
92
81
80
75
90c
88d
87
3a : 4e
16 : 1
24 : 1
> 99 : 1
> 99 : 1
24 : 1
20 : 1
48 : 1
24 : 1
> 99 : 1
24 : 1
1
DABCO
DABCO
DABCO
DABCO
DABCO
DABCO
DABCO
DABCO
DBU
20
12
9
2
3
4
5
i-PrOH
t-BuOH
CH3CN
Toluene
i-PrOH
i-PrOH
i-PrOH
i-PrOH
i-PrOH
i-PrOH
9
12
16
5
2
9
6
7
8
9
10
11
12
Et3N
K2CO3
Cs2CO3
16
12
12
60
80
55
Me
Catalyst
solvent
48 : 1
48 : 1
OPh
+
Et
CO2
PhOH
+
Et
CO2
Et
CO2
PhO
Me
a0.6 mmol of 1, 0.5 mmol of 2a, 5 mol% catalyst and 2 mL of solvent at r.t.
bIsolated yields obtained by flash chromatography on silica gel. cat 60 °C. dat 80 °C.
eDetermined through 1H NMR spectroscopic analysis.9
1
2a
3a
4
Scheme 1 Optimisation of reaction conditionsa.
* Correspondent. E-mail: zhiming@cczu.edu.cn

JOURNAL OF CHEMICAL RESEARCH 2016 365
Me
Me
cat. 5 mol% DABCO
cat. 5 mol% DABCO
+
+
Et
ROH
CO2
Et
ArOH
CO2
Et
CO2
Et
CO2
rt
solvent-free, 80 °C
i-PrOH,
RO
ArO
1
4
1
2
5
3
Scheme 2 DABCO-catalysed Michael additions for various phenols to
ethyl 2,3-butadienoate.
Scheme 3 DABCO-catalysed Michael additions of various alcohols to
ethyl 2,3-butadienoate.
Table 2 DABCO-catalysed Michael additions of various phenols to ethyl
Table 3 DABCO-catalysed Michael additions of various alcohols to ethyl
2,3-butadienoatea,b
2,3-butadienoatea,b
R
Me
Me
Me
Me
CO2Et
CO2Et
CO2Et
CO2Et
3i, 91%
O
O
O
O
Me
O
3a, R = H, 92% (90%c) 3b, R = Me, 91%
3c, R = OMe, 79% 3d, R = OBn, 79%
3e, R = F, 92% 3f, R = Cl, 94%
R
Me
5e, 60%
Me
R
O
Me
5a, R = H, 68% (Tracec,d) 5b, R = Me, 66%
5c, R = OMe, 62% 5d, R = NO2, 56%
CO2Et
CO2
Et
3g, R = Br, 88% 3h, R = I, 82%
3j, R = Me, 91% 3k, R = I, 97%
Me
I
R
CO2Et
Me
Me
O
Me
5i, 65%
Me
CO2Et
I
Me
O
3l, R = 90%
3n, R = 90%
Me
5f, R = H, 61%
CO2Et
CO2Et
5g, R = Me, 65% 5h, R = N(Me)2, 58%
Me
O
O
CO2Et
Me
O
3m, R = 99%
R
I
Cl
CO2Et
O
5k, R = Me, 64%
5l, R = Cl, 69%
5m, R = CF3, 63%
a0.6 mmol of 1, 0.5 mmol of 2, 5 mol% of DABCO, and 2 mL of i-PrOH at r.t. for 9 h.
bIsolated yields obtained by flash chromatography on silica gel.
cReaction performed on a 5 mmol scale.
I
Cl
5j, 62%
I
Me
Me
CO2Et
Br, I) at the para-position of the aromatic rings were suitable
for this reaction, achieving the corresponding final products
with good to excellent yields stereospecifically (3a–3h). Both
the meta-substituted and the ortho-substituted phenols, such as
m-cresol, o-cresol, and o-iodophenol, reacted well with ethyl
2,3-butadienoate (1) under the optimised reaction conditions
(3i–3k). When 3,5-dimethylphenol was used as the substrate,
the desired product was isolated in 90% yield (3l). The α- and
β-naphthalenols also provided their corresponding products in
90% and 99% yields, respectively (3m and 3n). Gratifyingly,
the current DABCO-catalysed Michael addition could be
easily performed on a 5 mmol scale and the product (E)-ethyl
3-phenoxybut-2-enoate could be isolated in 90% yield (3a).
Encouraged by the results described above, we decided to
apply this new catalytic system to the synthesis of β-alkyloxyl
acrylates. We were disappointed that no desired product could
be detected under our standard reaction conditions when using
benzyl alcohol as a nucleophile (see Scheme 3). The desired
product was formed, however, in 68% yield when the reaction
was conducted under solvent-free conditions at 80 °C by using
DABCO as the catalyst (Table 3, 5a) and no (Z)-isomer of
compound 5a was observed according to the crude 1H NMR of
the reaction mixture. The stereochemistry of 5a was determined
through NOESY spectroscopic analysis. In the presence of
different electron-donating groups [Me, OMe, N(Me)2] and
electron-withdrawing groups (NO2, Cl, I, CF3) on the benzene
ring of the benzyl alcohols, the DABCO-catalysed Michael
addition of ethyl 2,3-butadienoate (1) worked well, giving the
corresponding (E)-β-alkyloxyl acrylates as the sole products
in 56–69% yields (5b–5m). When 1-naphthalenemethanol,
diarylmethanols and propargyl alcohol were used as the
substrates, the reaction took place smoothly, affording the
expected products 5n–5q in 50–69% yields. Significantly,
alcohols having an aliphatic chain also gave good yields under
the standard catalysed conditions (5r and 5s).
CO2Et
O
O
5o, R = Me, 50%
5p, R = OMe, 54%
R
5n, 69%
I
Me
Me
Me
CO2Et
O
BnH
CO2Et
Et
2C
CO2Et
O
O
5q, 60%
5r, 56%
5s, 40%
a0.6 mmol of 1, 0.5 mmol of 4, and 5 mol% of DABCO at 80 °C for 12 h.
bIsolated yields obtained by flash chromatography on silica gel.
c0.6 mmol of 1, 0.5 mmol of 4a, 5 mol% of DABCO, and 2 mL of i-PrOH at r.t. for 9 h.
dLess than 3% of 5a was obtained and more than 90% of 4a was recovered.
Experimental
Synthesis of (E)-β-aryloxyl acrylates; general procedure
To a solution of phenol (0.5 mmol) and ethyl 2,3-butadienoate
(0.6 mmol) in i-PrOH (2 mL) was added DABCO (2.8 mg). The
reaction mixture was stirred at room temperature until the substrate
phenol was consumed (TLC monitored). The resulting mixture was
purified by flash column chromatography on silica gel (petroleum
ether/ethyl acetate) to give the desired product (3a–3m and 4).
(E)-Ethyl 3-phenoxybut-2-enoate (3a);9 92% yield; colourless oil;
1H NMR (300 MHz, CDCl3): δ 7.39 (t, J = 9.0 Hz, 2H), 7.24–7.19 (m,
1H), 7.02 (d, J = 9.0 Hz, 2H), 4.86 (s, 1H), 4.09 (q, J = 7.5 Hz, 2H), 2.49
(s, 3H), 1.20 (t, J = 7.5 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 172.7,
167.7, 153.4, 130.0, 125.6 121.6, 96.2, 59.5, 18.5, 14.4; HRMS (ESI)
m/z: calcd for C12H15O3+ [M + H]+ 207.1016; found: 207.1019.
(E)-Ethyl 3-(p-tolyloxy)but-2-enoate (3b);9 91% yield; colourless
oil; H NMR (300 MHz, CDCl3): δ 7.17 (d, J = 8.4 Hz, 2H), 6.90 (d,
J = 8.4 Hz, 2H), 4.85 (s, 1H), 4.08 (q, J = 7.2 Hz, 2H), 2.48 (s, 3H), 2.35
(s, 3H), 1.20 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.1,
167.9, 151.1, 135.4, 130.6, 121.4, 95.8, 59.6, 20.9, 18.6, 14.4; HRMS
(ESI) m/z: calcd for C13H17O3+ [M + H]+ 221.1172; found: 221.1173.
(E)-Ethyl 3-(4-methoxyphenoxy)but-2-enoate (3c); 79% yield;
1
1
colourless oil; H NMR (300 MHz, CDCl3): δ 6.94–6.86 (m, 4H),

366 JOURNAL OF CHEMICAL RESEARCH 2016
4.82 (s, 1H), 4.07 (q, J = 7.2 Hz, 2H), 3.79 (s, 3H), 2.46 (s, 3H), 1.20
(t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 173.5, 167.9, 157.3,
146.8, 122.5, 115.0, 95.7, 59.6, 55.7, 18.6, 14.4; HRMS (ESI) m/z: calcd
for C13H17O4+ [M + H]+ 237.1121; found: 237.1119.
3H); 13C NMR (75 MHz, CDCl3): δ 172.8, 167.8, 149.3, 135.1, 128.2,
126.8, 126.7, 126.0, 125.9, 121.7, 118.1, 96.4, 59.7, 18.4, 14.4; HRMS
(ESI) m/z: calcd for C16H17O3+ [M + H]+ 257.1172; found: 257.1175.
(E)-Ethyl 3-(naphthalen-2-yloxy)but-2-enoate (3n); 90% yield;
brown solid; m.p. 89–91 °C; 1H NMR (300 MHz, CDCl3): δ 7.89–7.79
(m, 3H), 7.54–7.46 (m, 3H), 7.18 (dd, J = 9.0, 2.4 Hz, 1H), 4.91 (s, 1H),
4.08 (q, J = 7.2 Hz, 2H), 2.56 (s, 3H), 1.19 (t, J = 7.2 Hz, 3H); 13C NMR
(75 MHz, CDCl3): δ 172.8, 167.6, 150.9, 134.1, 131.3, 130.2, 127.9,
127.5, 126.8, 125.8, 121.2, 118.5, 96.6, 59.6, 18.5, 14.3; HRMS (ESI)
m/z: calcd for C16H17O3+ [M + H]+ 257.1172, found: 257.1174.
(Z)-Ethyl 3-phenoxybut-2-enoate (4);9 colourless oil; 1H NMR (300
MHz, CDCl3): δ 7.35–7.29 (m, 2H), 7.14–7.09 (m, 1H), 7.03–7.00 (m,
2H), 5.33 (s, 1H), 4.12 (q, J = 7.2 Hz, 2H), 1.88 (s, 3H), 1.22 (t, J =
7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 164.8, 164.1, 155.0, 129.7,
124.2, 119.5, 103.1, 59.7, 20.3, 14.4; HRMS (ESI) m/z: calcd for
C12H15O3+ [M + H]+ 207.1016; found: 207.1020.
(E)-Ethyl 3-[4-(benzyloxy)phenoxy]but-2-enoate (3d); 79% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.46–7.32 (m, 5H),
6.99–6.91 (m, 4H), 5.05 (s, 2H), 4.85 (s, 1H), 4.09 (q, J = 7.2 Hz, 2H),
2.47 (s, 3H), 1.21 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
173.4, 167.9, 156.5, 147.0, 136.9, 128.8, 128.2, 127.6, 122.6, 116.1, 95.7,
70.6, 59.6, 18.6, 14.5; HRMS (ESI) m/z: calcd for C19H21O4+ [M + H]+
313.1434; found: 313.1432.
(E)-Ethyl 3-(4-fluorophenoxy)but-2-enoate (3e);9 92% yield;
1
colourless oil; H NMR (300 MHz, CDCl3): δ 7.09–6.95 (m, 4H),
4.81 (s, 1H), 4.08 (q, J = 7.2 Hz, 2H), 2.47 (s, 3H), 1.20 (t, J = 7.2 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 172.9, 167.6, 160.2 (d, J = 242.9
Hz), 149.2 (d, J = 2.8 Hz), 123.1 (d, J = 8.5 Hz), 116.8 (d, J = 23.3 Hz),
96.2, 59.7, 18.5, 14.4; HRMS (ESI) m/z: calcd for C12H14FO3+ [M + H]+
225.0921, found: 225.0924.
Synthesis of (E)-β-alkyloxyl acrylates; general procedure
To a mixture of alcohol (0.5 mmol) and ethyl 2,3-butadienoate
(0.6 mmol) was added DABCO (2.8 mg). The reaction mixture was
stirred at 80 °C until the substrate alcohol or ethyl 2,3-butadienoate
was consumed (TLC monitored). The resulting mixture was purified
by flash column chromatography on silica gel (petroleum ether/ethyl
acetate) to give the desired product (5a–5s).
(E)-Ethyl 3-(4-chlorophenoxy)but-2-enoate (3f); 94% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.38–7.33 (m, 2H),
7.00–6.94 (m, 2H), 4.84 (s, 1H), 4.09 (q, J = 7.2 Hz, 2H), 2.47 (s, 3H),
1.21 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 172.5, 167.5,
152.0, 131.2, 130.2, 123.1, 96.7, 59.8, 18.5, 14.4; HRMS (ESI) m/z:
calcd for C12H14ClO3+ [M + H]+ 241.0626; found: 241.0627.
(E)-Ethyl 3-(4-bromophenoxy)but-2-enoate (3g); 88% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.50 (m, 2H), 6.91
(m, 2H), 4.84 (s, 1H), 4.09 (q, J = 7.2 Hz, 2H), 2.47 (s, 3H), 1.21 (t,
J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 172.4, 167.5, 152.5,
133.2, 123.6, 118.8, 96.8, 59.8, 18.5, 14.4; HRMS (ESI) m/z: calcd for
C12H14BrO3+ [M + H]+ 285.0121; found: 285.0120.
(E)-Ethyl 3-(benzyloxy)but-2-enoate (5a);24 68% yield; colourless
1
oil; H NMR (300 MHz, CDCl3): δ 7.42–7.34 (m, 5H), 5.16 (s, 1H),
4.83 (s, 2H), 4.15 (q, J = 7.2 Hz, 2H), 2.37 (s, 3H), 1.28 (t, J = 7.2 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ 172.2, 168.0, 135.7, 128.8, 128.4,
+
127.8, 92.1, 70.2, 59.5, 19.2, 14.6; HRMS (ESI) m/z: calcd for C13H17O3
[M + H]+ 221.1172; found: 221.1174.
(E)-Ethyl 3-[(4-methylbenzyl)oxy]but-2-enoate (5b); 66% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.23–7.18 (m, 4H), 5.14
(s, 1H), 4.78 (s, 2H), 4.14 (q, J = 7.2 Hz, 2H), 2.36 (s, 3H), 2.35 (s, 3H),
1.28 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 172.3, 168.1,
138.3, 132.6, 129.5, 128.0, 92.0, 70.2, 59.5, 21.3, 19.3, 14.6; HRMS
(ESI) m/z: calcd for C14H19O3+ [M + H]+ 235.1329; found: 235.1331.
(E)-Ethyl 3-[(4-methoxybenzyl)oxy]but-2-enoate (5c). 62% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.30–7.27 (m, 2H),
6.93–6.90 (m, 2H), 5.15 (s, 1H), 4.75 (s, 2H), 4.15 (q, J = 7.2 Hz, 2H),
3.82 (s, 3H), 2.34 (s, 3H), 1.28 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 172.3, 168.1, 159.8, 129.6, 127.7, 114.2, 91.9, 70.1, 59.5, 55.4,
(E)-Ethyl 3-(4-iodophenoxy)but-2-enoate (3h); 82% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.71–7.68 (m, 2H),
6.80–6.77 (m, 2H), 4.85 (s, 1H), 4.09 (q, J = 7.2 Hz, 2H), 2.47 (s, 3H),
1.21 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 172.3, 167.5,
153.3, 139.2, 124.0, 96.8, 89.7, 59.8, 18.5, 14.4; HRMS (ESI) m/z: calcd
for C12H14IO3+ [M + H]+ 332.9982; found: 332.9984.
(E)-Ethyl 3-(m-tolyloxy)but-2-enoate (3i); 91% yield; colourless
1
oil; H NMR (300 MHz, CDCl3): δ 7.25 (t, J = 8.1 Hz, 1H), 7.02 (d,
J = 7.5 Hz, 1H), 6.83–6.80 (m, 2H), 4.86 (s, 1H), 4.08 (q, J = 7.2 Hz,
2H), 2.48 (s, 3H), 2.35 (s, 3H), 1.21 (t, J = 7.2 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 172.9, 167.8, 153.4, 140.3, 129.7, 126.5, 122.2, 118.6,
96.1, 59.6, 21.4, 18.6, 14.4; HRMS (ESI) m/z: calcd for C13H17O3+ [M +
H]+ 221.1172; found: 221.1174.
19.3, 14.6; HRMS (ESI) m/z: calcd for C14H19O4 [M + H]+ 251.1278;
+
found: 251.1276.
(E)-Ethyl 3-(o-tolyloxy)but-2-enoate (3j);9 91% yield; colourless oil;
1H NMR (300 MHz, CDCl3): δ 7.25–7.18 (m, 2H), 7.14 (dd, J = 7.5, 1.5
Hz, 1H), 6.94 (d, J = 7.2 Hz, 1H), 4.72 (s, 1H), 4.07 (q, J = 7.2 Hz, 2H),
2.51 (s, 3H), 2.16 (s, 3H), 1.20 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 172.0, 167.9, 151.6, 131.7, 130.5, 127.5, 126.0, 121.9, 95.0,
59.6, 18.4, 15.9, 14.4; HRMS (ESI) m/z: calcd for C13H17O3+ [M + H]+
221.1172; found: 221.1173.
(E)-Ethyl 3-[(4-nitrobenzyl)oxy]but-2-enoate (5d); 56% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 8.24 (d, J = 9.0 Hz, 2H),
7.53 (d, J = 9.0 Hz, 2H), 5.11 (s, 1H), 4.94 (s, 2H), 4.14 (q, J = 7.2 Hz,
2H), 2.38 (s, 3H), 1.26 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3):
δ 171.3, 167.6, 147.8, 143.0, 127.8, 124.0, 92.9, 68.6, 59.7, 19.0, 14.5;
HRMS (ESI) m/z: calcd for C13H16NO5 [M + H]+ 266.1023; found:
+
266.1025.
(E)-Ethyl 3-(2-iodophenoxy)but-2-enoate (3k);9 97% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.84 (dd, J = 7.8, 1.5 Hz,
1H), 7.40 (t, J = 7.8 Hz, 1H), 7.05 (dd, J = 8.1, 1.5 Hz, 1H), 6.97 (t,
J = 7.2 Hz, 1H), 4.72 (s, 1H), 4.09 (q, J = 7.2 Hz, 2H), 2.54 (s, 3H), 1.21
(t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 171.3, 167.4, 153.3,
140.1, 130.0, 127.6, 122.9, 96.4, 90.5, 59.8, 18.4, 14.4; HRMS (ESI)
m/z: calcd for C12H14IO3+ [M + H]+ 332.9982; found: 332.9979.
(E)-Ethyl 3-(2,5-dimethylphenoxy)but-2-enoate (3l); 90% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.10 (d, J = 7.5 Hz, 1H),
6.94 (d, J = 7.5 Hz, 1H), 6.75 (s, 1H), 4.72 (s, 1H), 4.08 (q, J = 6.9 Hz,
2H), 2.50 (s, 3H), 2.31 (s, 3H), 2.10 (s, 3H), 1.21 (t, J = 6.9 Hz, 3H);
13C NMR (75 MHz, CDCl3): δ 172.1, 168.0, 151.4, 137.5, 131.4, 127.1,
126.8, 122.3, 94.9, 59.6, 21.0, 18.4, 15.5, 14.5; HRMS (ESI) m/z: calcd
for C14H19O3+ [M + H]+ 235.1329; found: 235.1331.
(E)-Ethyl 3-[(2-methylbenzyl)oxy]but-2-enoate (5e); 60% yield;
colourless oil; 1H NMR (300 MHz, CDCl3): δ 7.34–7.20 (m, 4H), 5.19
(s, 1H), 4.81 (s, 2H), 4.17 (q, J = 7.2 Hz, 2H), 2.36 (s, 3H), 2.32 (s, 3H),
1.30 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 172.3, 168.0,
137.0, 133.6, 130.6, 129.0, 128.8, 126.2, 92.0, 68.8, 59.6, 19.2, 18.9,
14.6 HRMS (ESI) m/z: calcd for C14H19O3+ [M + H]+ 235.1329; found:
235.1331.
(E)-Ethyl 3-[(2-iodobenzyl)oxy]but-2-enoate (5f); 61% yield; white
solid; m.p. 92–93 °C; 1H NMR (300 MHz, CDCl3): δ 7.86 (dd, J = 7.5,
0.6 Hz, 1H), 7.43–7.35 (m, 2H), 7.07–7.01 (m, 1H), 5.17 (s, 1H), 4.81
(s, 2H), 4.16 (q, J = 7.2 Hz, 2H), 2.39 (s, 3H), 1.29 (t, J = 7.2 Hz, 3H);
13C NMR (75 MHz, CDCl3): δ 171.7, 167.9, 139.5, 137.9, 130.0, 129.0,
128.5, 97.8, 92.5, 73.9, 59.7, 19.1, 14.6; HRMS (ESI) m/z: calcd for
C13H16IO3+ [M + H]+ 347.0139; found: 347.0140.
(E)-Ethyl 3-[(2-iodo-5-methylbenzyl)oxy]but-2-enoate (5g); 65%
yield; white solid; m.p. 101–102 °C; H NMR (300 MHz, CDCl3):
δ 7.72 (d, J = 8.1 Hz, 1H), 7.22 (s, 1H), 6.87 (dd, J = 8.1, 1.8 Hz, 1H),
5.16 (s, 1H), 4.77 (s, 2H), 4.16 (q, J = 7.2 Hz, 2H), 2.40 (s, 3H), 2.33
(E)-Ethyl 3-(naphthalen-1-yloxy)but-2-enoate (3m); 99% yield;
brown solid; m.p. 101–102 °C; 1H NMR (300 MHz, CDCl3): δ
7.90–7.73 (m, 3H), 7.55–7.48 (m, 3H), 7.15 (dd, J = 7.5, 0.9 Hz, 1H),
4.80 (s, 1H), 4.04 (q, J = 7.2 Hz, 2H), 7.65 (s, 3H), 1.16 (t, J = 7.2 Hz,
1

JOURNAL OF CHEMICAL RESEARCH 2016 367
(s, 3H), 1.29 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 171.9,
167.9, 139.3, 138.7, 137.5, 131.0, 130.0, 93.9, 92.4, 73.9, 59.6, 21.2, 19.1,
14.6; HRMS (ESI) m/z: calcd for C14H18IO3+ [M + H]+ 361.0295; found:
361.0296.
13C NMR (75 MHz, CDCl3): δ 170.5, 168.0, 159.6, 142.0, 139.9, 130.5,
129.9, 129.1, 128.8, 128.2, 114.1, 98.9, 94.6, 83.9, 59.6, 55.4, 19.3, 14.5;
HRMS (ESI) m/z: calcd for C20H22IO4 [M + H]+ 453.0557; found:
+
453.0555.
(E)-Ethyl 3-(prop-2-yn-1-yloxy)but-2-enoate (5q);1 60% yield;
(E)-Ethyl 3-{[5-(dimethylamino)-2-iodobenzyl]oxy}but-2-enoate
1
1
(5h); 58% yield; white solid; m.p. 119–120 °C; H NMR (300 MHz,
colourless oil; H NMR (300 MHz, CDCl3): δ 5.09 (s, 1H), 4.48 (d,
CDCl3): δ 7.60 (d, J = 8.7 Hz, 1H), 6.77 (d, J = 3.0 Hz, 1H), 6.43 (dd,
J = 8.7, 3.0 Hz, 1H), 5.17 (s, 1H), 4.76 (s, 2H), 4.15 (q, J = 7.2 Hz, 2H),
2.95 (s, 6H), 2.39 (s, 3H), 1.29 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 172.0, 168.0, 150.8, 139.5, 137.9, 114.4, 113.5, 92.4, 80.8,
74.4, 59.6, 40.5, 19.1, 14.6; HRMS (ESI) m/z: calcd for C15H21INO3+ [M
+ H]+ 390.0561; found: 390.0562.
J = 2.4 Hz, 2H), 4.13 (q, J = 7.2 Hz, 2H), 2.56 (t, J = 2.4 Hz, 1H), 2.31
(s, 3H), 1.26 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 172.5,
168.2, 91.2, 63.9, 59.4, 29.8, 19.3, 14.6, 14.4; HRMS (ESI) m/z: calcd
for C9H13O3+ [M + H]+ 169.0859; found: 169.0861.
(E)-Ethyl 3-phenethoxybut-2-enoate (5r); 56% yield; colourless oil;
1H NMR (300 MHz, CDCl3): δ 7.33–7.21 (m, 5H), 5.00 (s. 1H), 4.11
(q, J = 7.2 Hz, 2H), 3.96 (t, J = 7.2 Hz, 2H), 3.01 (t, J = 7.2 Hz, 2H),
2.29 (s, 3H), 1.25 (t. J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ
172.2, 168.0, 137.8, 129.0, 128.6, 126.7, 91.5, 68.8, 59.4, 35.2, 19.1,
14.5; HRMS (ESI) m/z: calcd for C14H19O3+ [M + H]+ 235.1329; found:
235.1330.
(E)-Ethyl 3-[(2-iodo-3-methylbenzyl)oxy]but-2-enoate (5i); 65%
1
yield; white solid; m.p. 100–101 °C; H NMR (300 MHz, CDCl3): δ
7.29–7.19 (m, 3H), 5.17 (s, 1H), 4.85 (s, 2H), 4.16 (q, J = 7.2 Hz, 2H),
2.49 (s, 3H), 2.40 (s, 3H), 1.29 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz,
CDCl3): δ 171.9, 168.0, 142.6, 138.5, 129.6, 128.2, 126.2, 105.0, 92.5,
75.0, 59.6, 29.4, 19.1, 14.6; HRMS (ESI) m/z: calcd for C14H18IO3+ [M +
H]+ 361.0295; found: 361.0296.
(E)-Ethyl 3-[(3,5-dichloro-2-iodobenzyl)oxy]but-2-enoate (5j);
62% yield; white solid; m.p. 129–130 °C; 1H NMR (300 MHz, CDCl3):
δ 7.47 (d, J = 2.4 Hz, 1H), 7.31 (d, J = 2.4 Hz, 1H), 5.13 (s, 1H), 4.80
(s, 2H), 4.17 (q, J = 7.2 Hz, 2H), 2.42 (s, 3H), 1.29 (t, J = 7.2 Hz, 3H);
13C NMR (75 MHz, CDCl3): δ 171.1, 167.6, 142.2, 140.3, 135.5, 128.5,
126.4, 98.7, 93.1, 74.2, 59.8, 19.0, 14.6; HRMS (ESI) m/z: calcd for
C13H14Cl2IO3+ [M + H]+ 414.9359; found: 414.9356.
(E)-Ethyl 3-ethoxybut-2-enoate (5s);25 40% yield; colourless oil;
1H NMR (300 MHz, CDCl3): δ 4.99 (s, 1H), 4.12 (q, J = 7.2 Hz, 2H),
3.81 (q, J = 7.2 Hz, 2H), 2.29 (s, 3H), 1.33 (t, J = 7.2 Hz, 3H), 1.26 (t,
J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 170.8, 167.6, 92.7, 76.3,
59.7, 55.8, 18.9, 14.5; HRMS (ESI) m/z: calcd for C8H15O3 [M + H]+
+
159.1016; found: 159.1014.
This work was financially supported by the Natural Science
Foundation of China (Grant no. 21372033), the Priority
Academic Program Development of Jiangsu Higher Education
Institutions, Jiangsu Key Laboratory of Advanced Catalytic
Materials and Technology (BM2012110), the Qing Lan Project,
and the Natural Science Foundation of the Jiangsu Higher
Education Institutions of China (Grant no. 12KJA150002 and
no. 14KJA150002). The authors also thank Professor Hongchao
Guo for providing allenes (synthesized in the National Key
Technologies R&D Program of China, 2015BAK45B01, CAU).
(E)-Ethyl 3-[(2-iodo-4-methylbenzyl)oxy]but-2-enoate (5k); 64%
1
yield; white solid; m.p. 86–87 °C; H NMR (300 MHz, CDCl3): δ
7.68–7.67 (m, 1H), 7.24 (s, 1H), 7.16–7.14 (m, 1H), 5.13 (s, 1H), 4.75
(s, 2H), 4.13 (q, J = 7.2 Hz, 2H), 2.35 (s, 3H), 2.29 (s, 3H), 1.26 (t,
J = 7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): δ 171.9, 168.0, 140.3,
140.1, 134.9, 129.3, 129.0, 98.1, 92.4, 73.8, 59.6, 20.7, 19.1, 14.6; HRMS
(ESI) m/z: calcd for C14H18IO3+ [M + H]+ 361.0295; found: 361.0296.
(E)-Ethyl 3-[(4-chloro-2-iodobenzyl)oxy]but-2-enoate (5l); 69%
yield; white solid; m.p. 92–93 °C; 1H NMR (300 MHz, CDCl3): δ 7.86
(d, J = 1.8 Hz, 1H), 7.39–7.31 (m, 2H), 5.14 (s, 1H), 4.77 (s, 2H), 4.16
(q, J = 7.2 Hz, 2H), 2.39 (s, 3H), 1.29 (t, J = 7.2 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 171.5, 167.8, 138.8, 136.6, 134.7, 129.5, 128.8, 97.5,
92.8, 73.2, 59.7, 19.1, 14.6; HRMS (ESI) m/z: calcd for C13H15ClIO3+ [M
+ H]+ 380.9749; found: 380.9746.
Received 2 April 2016; accepted 4 April 2016
Paper 1603892 doi: 10.3184/174751916X14631336104179
Published online: 25 May 2016
(E)-Ethyl 3-{[2-iodo-4-(trifluoromethyl)benzyl]oxy}but-2-enoate
(5m); 63% yield; white solid; m.p. 84–85 °C; H NMR (300 MHz,
References
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1
69% yield; white solid; m.p. 89–90 °C; H NMR (300 MHz, CDCl3):
δ 7.91–7.81 (m, 3H), 7.57–7.50 (m, 3H), 5.39 (s, 1H), 5.38 (s, 2H), 4.22
(q, J = 7.2 Hz, 2H), 2.36 (s, 3H), 1.34 (t, J = 7.2 Hz, 3H); 13C NMR (75
MHz, CDCl3): δ 172.3, 167.9, 136.2, 133.7, 133.4, 133.0, 131.0, 128.7,
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50% yield; white solid; m.p. 113–115 °C; 1H NMR (300 MHz, CDCl3):
δ 7.84 (dd, J = 8.1, 0.9 Hz, 1H), 7.35–7.27 (m, 4H), 7.16–7.13 (m, 2H),
7.00–6.95 (m, 1H), 6.24 (s, 1H), 4.99 (s, 1H), 4.10–4.03 (m, 2H),
2.39(s, 3H), 2.32 (s, 3H), 1.24 (t, J = 7.2 Hz, 3H); 13C NMR (75 MHz,
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128.4, 127.5, 99.0, 94.6, 84.0, 59.5, 21.3, 19.3, 14.5; HRMS (ESI) m/z:
calcd for C20H22IO3+ [M + H]+ 437.0608; found: 437.0609.
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1
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7.03–6.97 (m, 1H), 6.90–6.85 (m, 2H), 6.21 (s, 1H), 4.96 (s, 1H),
4.12–4.02 (m, 2H), 3.80 (s, 3H), 2.38 (s, 3H), 1.22 (t, J = 7.2 Hz, 3H);
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