Palladium-Catalyzed Regio- and Stereoselective Hydrosulfonation of Propiolate Esters

Article abstract of DOI:10.1055/s-0036-1588501

An efficient palladium-catalyzed addition reaction of alkyl- and arylsulfonic acids to propiolate esters to yield alkenyl sulfonates is demonstrated. The formation of alkenyl sulfonates is highly regio- and stereoselective with favorable yields of up to 95%, and two of the alkenyl sulfonates are utilized for a Sonogashira cross-coupling reaction to produce (Z)-1,3-enynoates.

Full text of DOI:10.1055/s-0036-1588501

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2017, 49, A–J
paper
A
en
S. Raju et al.
Paper
Synthesis
Palladium-Catalyzed Regio- and Stereoselective Hydrosulfonation
of Propiolate Esters
Selvam Rajua
Pratheepkumar Annamalaia
Pd-catalyzed
hydrosulfonation
Fu-Wei Chana
Po-Yen Tsenga
Po-Yen Chena
Ting-Shen Kuob
Shih-Ching Chuang*a
O
cat. Pd(OAc)2
Z-stereoselective products
28 examples
up to 95% yield
Substrates for Sonogashira cross-
coupling and precursors to (Z)-1,3-
enynoates
R1 SO3H
R2
CO2R3
R1
S
O
CO2R3
H
K2S2O8
O
R2
CH2Cl2, 60 °C
0
0
0
0
0-
0
0
2
6-
9
2
6
9-
8
1
2
a Department of Applied Chemistry, National Chiao
Tung University, Hsinchu 30010, Taiwan, R.O.C.
b Department of Chemistry, National Taiwan Normal
University, Taipei 11677, Taiwan, R.O.C.
jscchuang@faculty.nctu.edu.tw
Received: 15.04.2017
Accepted after revision: 09.06.2017
Published online: 31.07.2017
on cationic gold to achieve hydrosulfonation of alkynes.
Cui et al. demonstrated an efficient gold-catalyzed
Markovnikov addition of aryl/methanesulfonic acids to
aryl/alkylacetylenes with phthalimide as an additive in 1,2-
dichloroethane at 100 °C, providing stereo- and regioselec-
tive access to substituted vinyl sulfonates in favorable yields
(Scheme 1, a).14 In addition, Rioux and co-workers demon-
strated a ligand-controlled rhodium-catalyzed addition of
aryl/alkylsulfonic acids to arylacetylenes in 1,2-dichlo-
roethane at 70 °C (Scheme 1, b).15 However, the developed
methods are limited to aryl- or alkylacetylenes and are not
applicable to propiolates, likely due to known reactivity of
propiolates with liberated phosphines from metal complex-
es.16 Other metal-free methods by superacid-catalyzed ad-
dition of triflic or fluorosulfonic acid to electron-poor
alkynes provided vinyl triflates or fluorosulfonates.17
DOI: 10.1055/s-0036-1588501; Art ID: ss-2017-h0257-op
Abstract An efficient palladium-catalyzed addition reaction of alkyl-
and arylsulfonic acids to propiolate esters to yield alkenyl sulfonates is
demonstrated. The formation of alkenyl sulfonates is highly regio- and
stereoselective with favorable yields of up to 95%, and two of the alke-
nyl sulfonates are utilized for a Sonogashira cross-coupling reaction to
produce (Z)-1,3-enynoates.
Key words palladium, sulfonic acid, propiolate, regioselective, stereo-
selective, alkenyl sulfonate, Sonogashira cross-coupling
Transition-metal-catalyzed reactions are powerful syn-
thetic tools for molecular functionalization and functional
group transformations.1 Alkynes often have been the incor-
porated units for developing acyclic/cyclic structures for
use in pharmaceutical and material science applications.2
In this context, metal-catalyzed nucleophilic addition to
alkynes has been a reliable tool for synthesizing alkenyl
compounds.3 In particular, the Pd catalysis associated with
alkynes has efficiently expanded access to various molecu-
lar scaffolds.4 In addition, the evolved gold-catalyzed nucleo-
philic addition with alkynes is another approach for scaf-
fold synthesis because of the acidic nature of gold.5 Transi-
tion metals, such as gold,6 palladium,7 silver,8 ruthenium,9
and mercury,10 catalyze the addition of weak acid nucleo-
philes, such as sulfonic acids, carboxylic acids or alcohols, to
alkynes through an O-attack to produce compounds with
an enol ether moiety. Alkenyl sulfonates are substantial
building blocks for polymer syntheses11 and metal-cata-
lyzed coupling reagents.12 Although alkenyl sulfonates can
be prepared through robust stoichiometric tosylation of β-
keto esters with TsCl and appropriate bases,13 metal-cata-
lyzed synthesis of alkenyl sulfonates with regio- and stereo-
selective control is challenging. Previous approaches relied
(a) Cui et al., 2009
R1O2S
O
2 mol% (Ph3P)AuNO3
R2
R3
R1 SO3H
+
phthalimide
Cl(CH2)2Cl
R2
R3
R1, R2, R3 = aryl, alkyl
100 °C
(b) Rioux and co-workers, 2013
R1O2S
O
1 mol% [RhCl(cod)]2
R2
R3
R1 SO3H
+
3 mol% Ph3P
Cl(CH2)2Cl
R2
R3
R
1 = aryl, alkyl; R2 or R3 = H, alkyl, aryl
70 °C
(c) This work
O
O
O
cat. Pd(OAc)2
R1 SO3H
R2
+
R1
S
O
OR3
OR3
K2S2O8
CH2Cl2, 60 °C
O
1
2
R2
3a–y
R1 = aryl, alkyl; R2 = H, aryl, alkyl, alkenyl; R3 = alkyl
Scheme 1 Reactivity of (a), (b) aryl/alkylacetylenes, and (c) propiolates
toward metal-catalyzed aryl/alkylsulfonic acid addition
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

B
S. Raju et al.
Paper
Synthesis
Our recent study in anti-Michael addition of phosphines
with propiolate esters inspired us to prepare conjugated
alkynoates.18 Previous methods for synthesizing alkyl (Z)-5-
phenylpent-2-en-4-ynoates entails using relatively labile
alkyl (Z)-2-iodoacrylates as substrates in a Sonogashira cou-
pling reaction. Our interest in developing another surrogate
intermediate without using labile iodo substrates prompted
us to evaluate the effectiveness of using alkenyl sulfonates
prepared from a metal-catalyzed anti-Markovnikov addi-
tion of arylsulfonic acids to propiolate esters. In lieu of
gold-catalysis, herein we present a new, general, cost-effec-
tive, and phosphine-free method for synthesizing alkyl (Z)-
β-arylsulfonate-substituted α,β-unsaturated carboxylate
esters by Pd-catalysis in high stereo- and regioselectivity
and favorable yields (Scheme 1, c). Two of the obtained
alkenyl sulfonates can be efficient substrates for a Sonogashira
cross-coupling reaction to provide conjugated (Z)-1,3-en-
ynoates in favorable yields.
We first investigated the optimal reaction conditions
with p-toluenesulfonic acid (1a, PTSA) and methyl propio-
late (2a) as substrates under various catalysts, oxidants, sol-
vents, and temperatures (Table 1). Initially, the reaction
performed with 1 equivalent of 1a (0.15 mmol), 3 equiva-
lents of 2a, 5 mol% of Pd(OAc)2, and 3 equivalents of K2S2O8
as oxidants in dichloromethane/trifluoroacetic acid (5
mL:0.1 mL) at 50 °C for 24 hours exclusively afforded (Z)-3a
in a 48% yield (Table 1, entry 1). When the reaction time
was extended to 40 hours, the yield decreased to 44 % (en-
try 2). Doubling the molar amounts of PTSA decreased the
yield markedly to 13% (entry 3). Furthermore, elevating the
reaction temperature to 60 or 70 °C produced a mixture of
Z- and E-isomers (1:1) in an overall 31% yield (entry 4), but
provided only the E-isomer 3a′ in a poor yield at 80 °C (en-
try 5, 12%). Notably, only trace amounts of products were
observed in 1,4-dioxane/TFA at 100 °C (entry 6). In addi-
tion, increasing the loading of TFA deteriorated the perfor-
mance of yields (entry 7). We next found that the reaction
also proceeded without TFA as an additive (entry 8).
56% of product (entry 23). Our attempts at using other cata-
lysts, such as AgOAc, AgOTf, AgNO3, PdCl2, CuOAc, and AuCl3
(entries 24–29) revealed that only the reaction with AuCl3
gave noticeable yield and regioselectivity – 34% with a Z/E
ratio of 38:62.
Under the optimized conditions, the reaction scope of
sulfonic acid addition to alkynes was examined next
(Scheme 2). First, we noted that reactions with electron-
donating arylsulfonic acids 1a–e and methyl propiolate (2a)
produced favorable yields, and those with ethyl propiolate
(2b) provided only slightly lower yields of (Z)-3 (Scheme 2,
entries 1–10, 65–93%). Steric hindrance from the ortho-
methyl moiety of arylsulfonic acids, as well as the ethyl
moiety of the propiolate 2b, lowered the yield by approxi-
mately 10%. The isolated products 3a–j were all highly re-
gio- and stereoselective with a Z-configuration, corroborat-
ed with crystallographic analysis.19 The addition of
electron-withdrawing 4-chlorophenylsulfonic acid was
evaluated next by using this catalysis and found that (Z)-
3k,l were formed in 74–75% yields (entries 11, 12). Howev-
er, more electron-deficient 2,4-dinitrobenzenesulfonic acid
resulted in poor yields (entry 13, 17%). An addition of 2-
and 1-naphthalenesulfonic acids to alkynes was then car-
ried out (entries 14–16), and gave the alkenyl sulfonates
(Z)-3n–p in 56–82% yields; it was noteworthy that 1-naph-
thalenesulfonic acid performed relatively poorly because of
the steric effect (entry 16). However, we could not produce
the corresponding alkenyl sulfonates while using the 2-
naphthyl propiolate (2c) as a substrate; only 3H-naph-
tho[2,1-b]pyran-3-one (A) (Figure 1) was isolated in 31–
33% yield through cyclization (entries 17, 18).20
O
O
A
Figure 1 Structure of product A
A similar loss of stereoselectivity was observed at an el-
evated temperature (Table 1, entry 9). Unexpectedly, the re-
action yields were largely improved while the amounts of
2a (entries 10, 11) were increased – a 92% yield was
achieved with 6 equivalents of 2a (entry 11). This observed
reaction required Pd(OAc)2 as a catalyst because a control
experiment in the absence of catalyst produced no (Z)-3a
(entry 12). The present reaction became less efficient with
other oxidants such as KHSO5 and Cu(OAc)2 (entries 13–15).
However, reaction with p-benzoquinone as an oxidant pro-
duced an 84% yield (entry 16). We also used 2.5 mol% of
Pd(OAc)2 as a catalyst and obtained an 83% yield of (Z)-3a
(entry 17). Finally, using other metal catalysts, such as
PdCl2(PPh3)2, Co(acac)2, Co(OAc)2, Mn(OAc)3, and Ag2O (en-
tries 18–22), revealed that only PdCl2(PPh3)2 can catalyze to
produce an 18% yield of (Z)-3a (entry 18). It is noteworthy
that without the oxidant K2S2O8, the reaction produced only
Next, the chemical reactivity of alkylsulfonic acids –
methanesulfonic and ethanesulfonic acids – was tested,
which showed that the hydrosulfonation produced moder-
ate to favorable yields (Scheme 2, entries 19–21, 66–86%).
The reaction with trifluoromethanesulfonic acid as a nucle-
ophile did not produce corresponding product 3s′. This is
likely due to the presence of strong electron-withdrawing
trifluoromethyl moiety. Furthermore, longer carbon-chain
internal alkynes were also reactive, but relatively less reac-
tive than shorter ones. Products 3v and 3w were obtained
in 51% and 31% yield, respectively, for p-tolylsulfonation
and methanesulfonation to methyl 2-hexynoate (entries 22,
23). However, the chemical reactivity with the short inter-
nal alkyne, ethyl 2-butynoate, was superior; 95% of p-tolyl-
sulfonation product 3x was isolated (entry 24). In the case
of ethyl 3-phenylpropynoate and dimethyl acetylenedicar-
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

C
S. Raju et al.
Paper
Synthesis
boxylate, no corresponding addition products were ob-
served (entries 25, 26). Finally, we found that other nucleo-
philes, ethanol, 2,4-dimethylbenzoic acid, and 4-methyl-
benzenesulfonamide, did not work under the standard
conditions (entries 27–29). In short, the examples with
electron-withdrawing functionality on sulfonic acids gave
lower yields, such as 2,4-dinitrophenyl substitution (entry
13), and that with electron-donating moiety gave better
yields, such as ethyl substitution (entry 21).
We further noted that these isolated alkenyl sulfonates
3 can undergo a Sonogashira cross-coupling reaction21 with
arylacetylenes catalyzed by Pd(PPh3)4. A previously report-
Table 1 Optimization of the Reaction Conditionsa
O
O
O
OH
O
S
S
oxidant, catalyst
O
O
O
+
OMe
solvent, temp.
24 h
Me
Me
H
1a
2a
OMe
Entry
2a (equiv) Oxidant
Catalyst
Solvent (mL)
Temp (°C) Yield (%)b Ratio Z/E
of 3a
1
2c
3
3
3
3
3
3
3
3
3
4
6
6
6
3
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
K2S2O8 (3 equiv)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
none
CH2Cl2/TFA (5:0.1)
CH2Cl2/TFA (5:0.1)
CH2Cl2/TFA (5:0.1)
CH2Cl2/TFA (5:0.1)
CH2Cl2/TFA (5:0.1)
50
50
50
48
44
13
100:0
100:0
100:0
1:1
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
KHSO5 (3 equiv)
KHSO5 (3 equiv)
3d
4
60 or 70 31
5
80
100
60
60
70
60
60
60
60
70
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
12
trace
9
0:100
6
1,4-dioxane/TFA (5:0.1)
CH2Cl2/TFA (5:1)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
CH2Cl2 (5)
–
7
100:0
100:0
54:46
100:0
100:0
–
8
52
39
78
92
0
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (5 mol%)
Pd(OAc)2 (2.5 mol%)
PdCl2(PPh3)2 (10 mol%)
Co(acac)2 (10 mol%)
Co(OAc)2 (10 mol%)
Mn(OAc)3 (10 mol%)
Ag2O (10 mol%)
48
31
0
100:0
100:0
–
Cu(OAc)2 (3 equiv)
p-benzoquinone (3 equiv)
K2S2O8 (1.5 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
none
84
83
18
ND
ND
ND
ND
56
6
100:0
100:0
100:0
–
–
–
–
Pd(OAc)2 (5 mol%)
AgOAc (5 mol%)
AgOTf (5 mol%)
100:0
100:0
100:0
100:0
100:0
100:0
38:62
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
K2S2O8 (3 equiv)
13
11
25
9
AgNO3 (10 mol%)
PdCl2 (5 mol%)
CuOAc (5 mol%)
AuCl3 (5 mol%)
34
a Reaction conditions: PTSA (0.15 mmol, 1 equiv), 2a, oxidant, catalyst, under N2 for 24 h, unless otherwise noted.
b Yields were determined by 1H NMR analysis using mesitylene as an internal standard. ND: Not detected.
c Reaction time: 40 h.
d Reaction was carried out with 0.30 mmol of PTSA.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

D
S. Raju et al.
Paper
Synthesis
ed condition was used, which worked effectively with tri-
substituted alkenes having an OTs group.13 Because of the
relatively higher reactivity of our prepared disubstituted
alkenyl sulfonates, a new condition was optimized, as
shown in Table S1 (Supporting Information). Alkyl (Z)-5-
phenylpent-2-en-4-ynoates (5)22 were obtained in favor-
able yields with 4-chlorophenyl-substituted sulfonate 3k
and arylacetylenes 4 under Pd(0) catalysis in a combination
of solvents, THF/i-Pr2NEt (4:1.5), at 90 °C for 24 hours (Table
S2). This cross-coupling reaction can also be expanded to
substrate 3x, producing β-methyl-substituted enynoate 5b
in 79% yield (Table S2, entry 2).
R3
O
S
O
O
R1
O
O
5 mol% Pd(OAc)2
R1 SO3H
R2
O
R3
O
K2S2O8, CH2Cl2, 60 °C, 24 h
R2
1
2
3a–x
O
S
O
S
O
S
O
Me
O
Et
O
Et
O
O
Me
Me
Me
O
O
O
H
O
Me
O
H
O
Me
S
O
H
O
O
O
O
O
H
4) 3d, 80% (Z)
3) 3c, 89% (Z)
2) 3b, 89% (Z)
1) 3a, 92% (Z)
Me
O
Me
O
S
O
Me
O
Et
O
O
Et
O
O
S
O
H
O
O
H
O
Et
S
O
H
O
Et
S
O
H
O
O
O
O
O
Me
Me
7) 3g, 84% (Z)
8) 3h, 80% (Z)
6) 3f, 82% (Z)
5) 3e, 93% (Z)
Me
O
Me
O
O
O
O
Et
O
Me
O
O
Et
Me
S
O
H
O
Cl
S
O
H
O
Me
S
O
H
O
Cl
S
O
H
O
O
O
O
O
Me
Me
11) 3k, 75% (Z)
12) 3l, 74% (Z)
10) 3j, 65% (Z/E = 99:1)
9) 3i, 78% (Z)
O
O
O
Et
O
Et
O
O
Me
O
S
O
Me
S
O
H
O
S
O
H
O
O2N
S
O
H
O
O
H
O
O
O
O
NO2
O
15) 3o, 82% (Z)
16) 3p, 56% (Z)
14) 3n, 79% (Z)
13) 3m, 17% (Z)
O
O
O
O
O
O
Me
Et
O
S
O
R
S
O
H
O
Me
S
O
O
S
O
O
Me
O
H
O
O
O
O
O
H
H
20) 3t, 68% (Z)
17)a 3q, 0%
19) 3s, 66% (Z), R = Me
3s', 0%, R = CF3
18)a 3r, 0%
O
O
O
Me
O
Et
O
S
O
Me
O
O
Me
Et
S
O
H
O
Me
S
O
O
Me
O
O
Me
S
O
O
O
O
O
O
nPr
Me
nPr
23) 3w, 31% (Z)
24) 3x, 95% (Z)
22) 3v, 51% (Z/E = 96:4)
21) 3u, 86% (Z)
Me
Me
Me
Et
O
O
O
O
O
O
Me
O
O
Me
O
O
O
H
O
O
EtO
H
O
O
N
S
O
S
O
C
S
O
Me
O
H
Me
O
CO2Me
Me
H
Ph
Me
25) 0%
26) 0%
27)b 0%
28)c 0%
29)d 0%
Scheme 2 Hydrosulfonation of substituted alkynoates. Reagents and conditions: The reactions of entries 1–26 were performed using 0.15 mmol of
sulfonic acid 1, 0.90 mmol of alkyne 2, 0.45 mmol of K2S2O8, and 0.0075 mmol of Pd(OAc)2 in CH2Cl2 (5 mL) at 60 °C for 24 h under N2. a Product A was
isolated in 31% in entry 17, and 33% in entry 18. b EtOH was used instead of 1. c 2,4-Dimethylbenzoic acid was used instead of 1. d 4-Methylbenzenesul-
fonamide was used instead of 1.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

E
S. Raju et al.
Paper
Synthesis
The studied Pd-catalyzed hydrosulfonation reaction can
also be extended to enynedioate 2i to produce β-arylsulfon-
ated dienedioates 3y,z and 3aa–ad in 47% to 89% yields (Ta-
ble 2). Instead of using 5 mol% of metal catalysts, hydrosul-
fonation of 2i demanded for 10 mol% of Pd(OAc)2 to achieve
comparable yields under the same reaction time and tem-
perature, likely due to relatively poor reactivity of 2i. This
hydrosulfonation tolerated aryl- and alkylsulfonic acids,
and took place regioselectively at β(γ′)-carbon, which is
likely due to pre-coordination of alkynyl moiety to Pd(II)
that enabled β(γ′)-carbon more electrophilic toward nucleo-
philic attack. It is noteworthy that phosphines18 and
amines23 underwent addition at the α(δ′)-carbon of 2i, but
Gilman reagents18f and the present studied hydrosulfona-
tion reaction proceeded with β(γ′)-addition.
COOR3
O
R1
O
O
S
R2
OH
Pd(II)
IA
O
R2
2
1
R3
– H+
O
COOR3
Pd(II)
Pd(II)
O
S
R1
R2
O
IB
K2S2O8
Pd(0)
route a
+ H+
route b
COOR3
AcO Pd(II)
O
O
O
S
Pd(II)
R1
R1
S
O
COOR3
H
R2
O
H
O
IC
R2
(Z)-3
Scheme 3 displays the proposed reaction mechanism.
First, alkynoates 2 coordinate with the Pd(II) to form inter-
mediate IA. The OH group of sulfonic acids undergoes a nu-
cleophilic attack at the β-position of intermediate IA in an
antiperiplanar fashion to produce intermediate IB after the
loss of a proton. Protonation of intermediate IB provides the
(Z)-3 (route a). In route b, protonation on the sulfonated
carbon of intermediate IB allows a C–C bond rotation on in-
termediate IC and furnishes (E)-3 on protonation of IE.
Route b is relatively less plausible because a cation is next to
an ester moiety in higher energy intermediate IC. This ra-
tionale accounts for the Z-stereoselective hydrosulfonation
of propiolate esters. The Pd(II) species may be possibly re-
duced to Pd(0) during the reaction course through other
slow-rate pathway,24 thus rendering loss of active Pd(II)
species. The oxidant K2S2O8 was used to reoxidize Pd(0) to
produce Pd(II) and thus complete the catalytic cycle.
R2
O
COOR3
COOR3
Pd(II)
R2
O
H
COOR3
R2
O
O
O
H+
– Pd(II)
R1
S
H
R1
S
R1
S
O
Pd(II)
– H+
O
O
O
(E)-3
ID
IE
Scheme 3 Proposed catalytic cycle
In conclusion, we have successfully demonstrated an ef-
fective methodology for the highly regio- and stereoselec-
tive syntheses of alkenyl sulfonates through Pd(II)-cata-
lyzed aryl/alkylsulfonic acid addition to electron-deficient
alkynoates. The alkenyl sulfonates can undergo a Sonoga-
shira-type cross-coupling reaction with arylacetylenes by
Pd(0)-catalysis to yield conjugated 1,3-enynoates (Support-
ing Information).
All reactions were carried out under N2, unless otherwise mentioned.
All the obtained products were characterized by 1H NMR, 13C NMR,
mass spectrometry, and IR spectroscopy. Melting points were mea-
sured on an Electrothermal MEL-TEMP melting point apparatus. IR
spectra were recorded on a Bruker spectrophotometer. 1H NMR and
13C NMR spectra were obtained on a Bruker-300 MHz spectrometer
and chemical shifts were reported in parts per million (ppm, δ) with
CHCl3 as a reference. Standard abbreviations are used to describe pro-
ton coupling patterns; coupling constants J are quoted in Hz. 13C NMR
data were acquired at 75 or 100 MHz. Pd(OAc)2, trifluoroacetic acid
(TFA), alkyl or arylsulfonic acids, methyl or ethyl propiolates, and oth-
er reagents or chemicals were used as purchased without further pu-
rification.
Table 2 Hydrosulfonation of Enynedioatesa
R1 SO3H
10 mol% Pd(OAc)2
K2S2O8
O
S
O
1
R1
O
OMe
O
O
O
α(δ')
β(γ')
CH2Cl2, 60 °C, 24 h
3
MeO2C
MeO2C
Me
2i
Entry
R1
Product
Yield (%)
Z/E
1
2
3
4
5
6
Ph 1b
3y
79
89
81
76
47
71
Z
Z
Z
Z
Z
Z
4-MeC6H4 1a
4-EtC6H4 1c
3z
Alkenyl Sulfonates 3a–x; General Procedure
3aa
3ab
To a pressure-affordable thick-wall glass tube containing aryl/alkyl-
sulfonic acid 1 (0.15 mmol), alkyne 2 (0.90 mmol), Pd(OAc)2 (1.7 mg,
0.0075 mmol), and K2S2O8 (122 mg, 0.45 mmol) were added anhyd
CH2Cl2 (5 mL). The tube was sealed with an O-ring and a teflon cap.
The mixture was then stirred at 60 °C for 24 h. Upon completion of
the reaction, CH2Cl2 was removed under reduced pressure. Elution
with CH2Cl2/hexanes (2:1) gave the desired product (Z)-3.
2,5-Me2C6H3 1d
2,4,6-Me3C6H2 1e
Et 1k
3ac
3ad19
a Reactions were performed using 0.25 mmol of sulfonic acid 1, 1.0 mmol
of enynedioate 2, 0.25 mmol of K2S2O8, and 0.025 mmol of Pd(OAc)2 in
CH2Cl2 (4 mL) under N2.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

F
S. Raju et al.
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Synthesis
Methyl (Z)-3-(Tosyloxy)acrylate (3a)
13C NMR (75 MHz, CDCl3): δ = 162.7, 144.2, 135.3, 134.6, 129.5, 127.9,
106.6, 60.5, 14.1.
Yield: 35 mg (92%); white solid; mp 73–74 °C; Rf = 0.28 (CH2Cl2/hex-
HRMS (EI+): m/z [M+] calcd for C11H12O5S: 256.0405; found: 256.0401.
anes, 5:1).
FT-IR (KBr): 2956, 2924, 2851, 1727, 1662, 1596, 1380, 1285, 1260,
1194, 1169, 1054, 936, 829, 809, 707, 692, 692, 597, 551 cm–1
.
Methyl (Z)-3-(4-Ethylphenylsulfonyloxy)acrylate (3e)
1H NMR (300 MHz, CDCl3): δ = 7.84 (d, J = 8.4 Hz, 2 H), 7.38 (d, J = 8.4
Hz, 2 H), 6.95 (d, J = 7.0 Hz, 1 H), 5.32 (d, J = 7.0 Hz, 1 H), 3.68 (s, 3 H),
2.46 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 163.2, 146.0, 144.6, 132.3, 130.1, 128.0,
105.8, 51.6, 21.7.
Yield: 38 mg (93%); colorless liquid; Rf = 0.38 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 2969, 2921, 2852, 1732, 1661, 1439, 1381, 1283, 1262,
1195, 1169, 1050, 997, 935, 873, 829, 693, 655, 599, 564, 533 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.87 (d, J = 8.4 Hz, 2 H), 7.40 (d, J = 8.4
Hz, 2 H), 6.96 (d, J = 7.0 Hz, 1 H), 5.32 (d, J = 7.0 Hz, 1 H), 3.68 (s, 3 H),
2.75 (q, J = 7.6 Hz, 2 H), 1.28 (t, J = 7.6 Hz, 3 H).
HRMS (EI+): m/z [M+] calcd for C11H12O5S: 256.0405; found: 256.0394.
13C NMR (75 MHz, CDCl3): δ = 163.2, 152.0, 144.7, 132.4, 128.9, 128.1,
Methyl (E)-3-(Tosyloxy)acrylate (3a′); Table 1, entry 5
105.7, 51.6, 28.9, 14.9.
HRMS (EI+): m/z [M+] calcd for C12H14O5S: 270.0562; found: 270.0559.
Yield: 7 mg (18%); colorless liquid; Rf = 0.4 (hexanes/EtOAc, 5:1).
FT-IR (KBr): 3001, 2953, 2922, 2853, 1724, 1648, 1545, 1517, 1388,
1315, 1284, 1190, 1078, 936, 812, 787, 698, 548 cm–1
.
Ethyl (Z)-3-(4-Ethylphenylsulfonyloxy)acrylate (3f)
1H NMR (300 MHz, CDCl3): δ = 7.82 (d, J = 8.3 Hz, 2 H), 7.69 (d, J = 12.2
Hz, 1 H), 7.39 (d, J = 8.3 Hz, 2 H), 5.69 (d, J = 12.2 Hz, 1 H), 3.72 (s, 3 H),
2.48 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 166.0, 150.9, 146.7, 132.3, 130.7, 128.5,
108.7, 52.2, 22.2.
Yield: 35 mg (82%); colorless liquid; Rf = 0.53 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 2974, 2935, 2877, 1729, 1660, 1412, 1384, 1196, 1177,
1050, 942, 840, 696, 656, 596, 562 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.87 (d, J = 8.4 Hz, 2 H), 7.39 (d, J = 8.4
Hz, 2 H), 6.95 (d, J = 7.0 Hz, 1 H), 5.31 (d, J = 7.0 Hz, 1 H), 4.13 (q, J = 7.1
Hz, 2 H), 2.75 (q, J = 7.6 Hz, 2 H), 1.21–1.30 (m, 6 H).
HRMS (EI+): m/z [M+] calcd for C11H12O5S: 256.0405; found: 256.0408.
13C NMR (75 MHz, CDCl3): δ = 162.8, 152.0, 144.4, 132.5, 128.9, 128.1,
Ethyl (Z)-3-(Tosyloxy)acrylate (3b)
106.3, 60.5, 29.0, 14.9, 14.1.
HRMS (EI+): m/z [M+] calcd for C13H16O5S: 284.0718; found: 284.0717.
Yield: 36 mg (89%); white solid; mp 71–72 °C; Rf = 0.38 (CH2Cl2/hex-
anes, 2:1).
FT-IR (KBr): 2994, 2929, 2909, 1725, 1659, 1410, 1387, 1374, 1201,
1167, 1201, 1055, 1028, 942, 903, 838, 810, 709, 694, 665, 593, 553,
Methyl (Z)-3-(2,5-Dimethylphenylsulfonyloxy)acrylate (3g)
Yield: 34 mg (84%); white solid; mp 77–78 °C; Rf = 0.33 (hexanes/EtOAc,
2:1).
521 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.84 (d, J = 8.3 Hz, 2 H), 7.37 (d, J = 8.3
Hz, 2 H), 6.94 (d, J = 7.0 Hz, 1 H), 5.31 (d, J = 7.0 Hz, 1 H), 4.13 (q, J = 7.2
Hz, 2 H), 2.46 (s, 3 H), 1.24 (t, J = 7.2 Hz, 3 H).
13C NMR (75 MHz, CDCl3): δ = 162.8, 145.9, 144.4, 132.3, 130.1, 128.0,
106.3, 60.5, 21.7, 14.1.
FT-IR (KBr): 3071, 2955, 2929, 2862, 1723, 1655, 1366, 1269, 1205,
1175, 1054, 947, 890, 824, 711, 601 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.79 (s, 1 H), 7.37 (d, J = 7.7 Hz, 1 H),
7.27 (d, J = 7.7 Hz, 1 H), 6.96 (d, J = 7.0 Hz, 1 H), 5.30 (d, J = 7.0 Hz, 1 H),
3.71 (s, 3 H), 2.70 (s, 3 H), 2.39 (s, 3 H).
HRMS (EI+): m/z [M+] calcd for C12H14O5S: 270.0562; found: 270.0562.
13C NMR (75 MHz, CDCl3): δ = 163.2, 144.6, 136.3, 136.0, 135.3, 133.5,
132.7, 129.8, 104.9, 51.5, 20.7, 19.6.
Methyl (Z)-3-(Phenylsulfonyloxy)acrylate (3c)
HRMS (EI+): m/z [M+] calcd for C12H14O5S: 270.0562; found: 270.0560.
Yield: 32 mg (89%); colorless liquid; Rf = 0.31 (CH2Cl2/hexanes, 2:1).
FT-IR (KBr): 3078, 3008, 2955, 1730, 1660, 1450, 1381, 1286, 1259,
Ethyl (Z)-3-(2,5-Dimethylphenylsulfonyloxy)acrylate (3h)
1193, 1171, 1049, 994, 935, 829, 757, 735, 688, 603, 580 cm–1
.
Yield: 34 mg (80%); white solid; mp 62–63 °C; Rf = 0.28 (CH2Cl2/hex-
1H NMR (300 MHz, CDCl3): δ = 7.97 (d, J = 7.2 Hz, 2 H), 7.69–7.72 (m, 1
H), 7.57–7.60 (m, 2 H), 6.97 (d, J = 7.0 Hz, 1 H), 5.35 (d, J = 7.0 Hz, 1 H),
3.68 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 163.6, 145.0, 135.7, 135.1, 129.9, 128.4,
106.5, 52.1.
anes, 2:1).
FT-IR (KBr): 3074, 2984, 2926, 1717, 1657, 1367, 1264, 1204, 1178,
1052, 955, 834, 713, 594 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.79 (s, 1 H), 7.36 (d, J = 7.8 Hz, 1 H),
7.27 (d, J = 7.8 Hz, 1 H), 6.95 (d, J = 7.0 Hz, 1 H), 5.28 (d, J = 7.0 Hz, 1 H),
4.19 (q, J = 7.1 Hz, 2 H), 2.39 (s, 3 H), 2.70 (s, 3 H), 1.26 (t, J = 7.1 Hz, 3
H).
HRMS (EI+): m/z [M+] calcd for C10H10O5S: 242.0249; found: 242.0250.
Ethyl (Z)-3-(Phenylsulfonyloxy)acrylate (3d)
13C NMR (75 MHz, CDCl3): δ = 162.8, 144.3, 136.3, 136.0, 135.3, 133.5,
132.7, 129.8, 105.3, 60.5, 20.7, 19.7, 14.1.
Yield: 31 mg (80%); colorless liquid; Rf = 0.33 (hexanes/EtOAc, 2:1).
HRMS (EI+): m/z [M+] calcd for C13H17O5S: 285.0797; found: 285.0789.
FT-IR (KBr): 3096, 3077, 2985, 2940, 2907, 1726, 1660, 1450, 1385,
1194, 1176, 1048, 943, 842, 736, 688, 600, 580 cm–1
.
Methyl (Z)-3-(Mesitylsulfonyloxy)acrylate (3i)
1H NMR (300 MHz, CDCl3): δ = 7.97 (d, J = 7.9 Hz, 2 H), 7.68–7.72 (m, 1
H), 7.57–7.62 (m, 2 H), 6.96 (d, J = 6.9 Hz, 1 H), 5.34 (d, J = 6.9 Hz, 1 H),
4.13 (q, J = 7.2 Hz, 2 H), 1.23 (t, J = 7.2 Hz, 3 H).
Yield: 33 mg (78%); white solid; mp 72–73 °C; Rf = 0.5 (hexanes/EtOAc,
2:1).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

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Synthesis
FT-IR (KBr): 3081, 3030, 2994, 2952, 2854, 1730, 1659, 1605, 1440,
1370, 1281, 1262, 1192, 1165, 1052, 998, 932, 854, 823, 692, 658,
13C NMR (75 MHz, CDCl3): δ = 162.7, 150.7, 148.2, 143.3, 134.3, 133.2,
127.4, 120.7, 107.1, 51.9.
HRMS (EI+): m/z [M+] calcd for C10H8N2O9S: 331.9951; found:
300.9756 (M – 31, C9H5N2O8S).
601, 575, 538 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.00 (s, 2H), 6.96 (d, J = 7.1 Hz, 1H),
5.28 (d, J = 7.1 Hz), 3.71 (s, 3H), 2.69 (s, 6H), 2.32 (s, 3H).
13C NMR (75 MHz, CDCl3): δ = 163.3, 144.5, 140.3, 131.8, 130.1, 104.5,
Methyl (Z)-3-(Naphthalen-2-ylsulfonyloxy)acrylate (3n)
51.5, 22.4, 21.0 ppm.
Yield: 35 mg (79%); colorless liquid; Rf = 0.43 (hexanes/EtOAc, 2:1).
HRMS (EI+): m/z [M+] calcd for C13H16O5S: 284.0718; found: 253.0534
(M – 31; C12H13O4S).
FT-IR (KBr): 3081, 3009, 2953, 2924, 2853, 1730, 1660, 1438, 1381,
1184, 1184, 1169, 1050, 933, 862, 816, 751, 695, 656, 617, 590, 550
cm–1
.
1H NMR (300 MHz, CDCl3): δ = 8.54 (s, 1 H), 7.89–8.03 (m, 4 H), 7.62–
Ethyl (Z)-3-(Mesitylsulfonyloxy)acrylate (3j)
Yield: 29 mg (65%) (Z/E = 99:1); white solid; Rf = 0.53 (hexanes/EtOAc,
7.73 (m, 2 H), 7.02 (d, J = 7.0 Hz, 1 H), 5.33 (d, J = 7.0 Hz, 1 H), 3.65 (s, 3
2:1).
H).
FT-IR (KBr): 3103, 2990, 2943, 2909, 1728, 1657, 1603, 1566, 1386,
1369, 1266, 1199, 1161, 1097, 1028, 943, 899, 834, 811, 738, 717,
13C NMR (75 MHz, CDCl3): δ = 163.1, 144.6, 135.5, 131.9, 131.7, 130.0,
129.9, 129.8, 129.4, 128.0(2C), 122.1, 105.9, 51.5.
HRMS (EI+): m/z [M+] calcd for C14H12O5S: 292.0405; found: 292.0400.
700, 661, 594, 575, 540 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.00 (s, 2 H), 6.94 (d, J = 7.1 Hz, 1 H),
5.26 (d, J = 7.1 Hz, 1 H), 4.17 (q, J = 7.2 Hz, 2 H), 2.69 (s, 6 H), 2.32 (s, 3
H), 1.26 (t, J = 7.2 Hz, 3 H).
13C NMR (75 MHz, CDCl3): δ = 163.0, 144.4, 144.2, 140.3, 131.9, 130.2,
104.9, 60.5, 22.5, 21.1, 14.1.
Ethyl (Z)-3-(Naphthalen-2-ylsulfonyloxy)acrylate (3o)
Yield: 37.6 mg (82%); colorless liquid; Rf = 0.4 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 3080, 2984, 2937, 2906, 1726, 1658, 1384, 1271, 1174,
1048, 1020, 950, 861, 816, 751, 699, 655, 617, 550 cm–1
.
HRMS (EI+): m/z [M+] calcd for C14H18O5S: 298.0875; found: 298.0858.
1H NMR (300 MHz, CDCl3): δ = 8.53 (s, 1 H), 7.89–8.03 (m, 4 H), 7.62–
7.73 (m, 2 H), 7.01 (d, J = 7.0 Hz, 1 H), 5.33 (d, J = 7.0 Hz, 1 H), 4.11 (q,
J = 7.2 Hz, 2 H), 1.20 (t, J = 7.2 Hz, 3 H).
Methyl (Z)-3-(4-Chlorophenylsulfonyloxy)acrylate (3k)
Yield: 31 mg (75%); white solid; mp 62–63 °C; Rf = 0.48 (CH2Cl2/hex-
anes, 2:1).
13C NMR (75 MHz, CDCl3): δ = 162.6, 144.4, 135.5, 131.9, 131.7, 130.0,
129.9, 129.8, 129.4, 128.0(2C), 122.1, 106.4, 60.5, 14.0.
FT-IR (KBr): 3099, 3012, 2960, 2925, 2853, 1726, 1658, 1387, 1193,
HRMS (EI+): m/z [M+] calcd for C15H14O5S: 306.0562; found: 306.0568.
1170, 1091, 1049, 933, 822, 808, 706, 687, 620, 594, 526 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.91 (d, J = 8.8 Hz, 2 H), 7.57 (d, J = 8.8
Hz, 2 H), 6.95 (d, J = 6.9 Hz), 5.38 (d, J = 6.9 Hz, 1 H), 3.68 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 162.9, 144.2, 141.5, 133.7, 129.8, 129.4,
Ethyl (Z)-3-(Naphthalen-1-ylsulfonyloxy)acrylate (3p)
Yield: 25.7 mg (56%); colorless liquid; Rf = 0.38 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 3083, 2983, 2933, 1726, 1659, 1509, 1378, 1273, 1174,
106.6, 51.6.
1048, 979, 941, 842, 805, 770, 698, 586, 503 cm–1
.
HRMS (EI+): m/z [M+] calcd for C10H9ClO5S: 275.9859; found:
275.9860.
1H NMR (300 MHz, CDCl3): δ = 8.69 (d, J = 8.6 Hz, 1 H), 8.31 (dd, J = 1.1,
7.4 Hz, 1 H), 8.17 (d, J = 8.3 Hz, 1 H), 7.78–8.03 (m, 1 H), 7.55–7.78 (m,
3 H), 6.95 (d, J = 7.0 Hz, 1 H), 5.24 (d, J = 7.0 Hz, 1 H), 4.08 (q, J = 7.2 Hz,
2 H), 1.16 (t, J = 7.2 Hz, 3 H).
Ethyl (Z)-3-(4-Chlorophenylsulfonyloxy)acrylate (3l)
Yield: 32 mg (74%); white solid; mp 72–73 °C; Rf = 0.48 (CH2Cl2/hex-
anes, 2:1).
13C NMR (75 MHz, CDCl3): δ = 162.7, 143.9, 136.3, 130.8, 130.3, 129.0,
128.8, 128.2, 128.0, 127.5, 124.8, 123.9, 106.1, 60.5, 14.0.
FT-IR (KBr): 3100, 2991, 1722, 1657, 1391, 1274, 1204, 1172, 1094,
HRMS (EI+): m/z [M+] calcd for C15H14O5S: 306.0562; found: 306.0561.
1051, 1028, 945, 903, 823, 809, 766, 706, 694, 631, 588, 521 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.91 (d, J = 8.8 Hz, 2 H), 7.56 (d, J = 8.8
Hz, 2 H), 6.94 (d, J = 6.9 Hz, 1 H), 5.37 (d, J = 6.9 Hz, 1 H), 4.14 (q, J = 7.2
Hz, 2 H), 1.24 (t, J = 7.2 Hz, 3 H).
13C NMR (75 MHz, CDCl3): δ = 162.4, 144.0, 141.4, 133.7, 129.8, 129.3,
107.0, 60.5, 14.0.
Methyl (Z)-3-(Methylsulfonyloxy)acrylate (3s)
Yield: 17.8 mg (66%); colorless liquid; Rf = 0.2 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 3006, 2957, 2851, 1729, 1436, 1317, 1294, 1256, 1070,
990, 822, 754 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 6.98 (d, J = 6.9 Hz, 1 H), 5.45 (d, J = 6.9
Hz, 1 H), 3.73 (s, 3 H), 3.19 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 163.2, 144.2, 106.3, 51.7, 38.6.
HRMS (EI+): m/z [M+] calcd for C11H11ClO5S: 290.0016; found:
290.0012.
HRMS (EI+): m/z [M+] calcd for C5H8O5S: 180.0092; found: 180.0099.
Methyl (Z)-3-(2,4-Dinitrophenylsulfonyloxy)acrylate (3m)
Yield: 8.5 mg (17%); white solid; mp 87–88 °C: Rf = 0.33 (hex-
anes/EtOAc, 2:1).
Ethyl (Z)-3-(Methylsulfonyloxy)acrylate (3t)
Yield: 20 mg (68%); colorless liquid; Rf = 0.3 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 3109, 2957, 2921, 2850, 1737, 1660, 1544, 1443, 1350,
1166, 1037, 991, 938, 829, 751, 696, 618, 588 cm–1
.
FT-IR (KBr): 3086, 3030, 2987, 2939, 2909, 1726, 1660, 1407, 1374,
1257, 1167, 1054, 1023, 971, 944, 900, 844, 795, 685, 579, 525 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 8.72 (d, J = 2.0 Hz, 1 H), 8.55–8.65 (m, 2
H), 7.04 (d, J = 6.8 Hz, 1 H), 5.54 (d, J = 6.8 Hz, 1 H), 3.72 (s, 3 H).
1H NMR (300 MHz, CDCl3): δ = 6.98 (d, J = 6.9 Hz, 1 H), 5.47 (d, J = 6.9
Hz, 1 H), 4.21 (q, J = 7.1 Hz, 2 H), 3.21 (s, 3 H), 1.29 (t, J = 7.1 Hz, 3 H).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

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S. Raju et al.
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Synthesis
13C NMR (75 MHz, CDCl3): δ = 163.2, 144.4, 107.3, 61.1, 39.0, 14.6.
HRMS (EI+): m/z [M+] calcd for C6H10O5S: 194.0249; found: 148.9902
Upon completion of the reaction, CH2Cl2 was removed under reduced
pressure. Elution with hexanes/EtOAc (4:1) gave the respective de-
sired products 3y,z and 3aa–ad.
(M – 45, C4H5O4S).
Dimethyl (2Z,4E)-3-(Phenylsulfonyloxy)hexa-2,4-dienedioate (3y)
Methyl (Z)-3-(Ethylsulfonyloxy)acrylate (3u)
Yield: 64 mg (79%); white solid; mp 96–77 °C; Rf = 0.3 (hexanes/EtOAc,
4:1).
Yield: 25 mg (86%); colorless liquid; Rf = 0.23 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 3085, 2989, 2954, 2852, 1729, 1659, 1440, 1398, 1370,
1283, 1244, 1201, 1164, 1067, 1042, 997, 936, 870, 829, 782, 747,
FT-IR (KBr): 3071, 3004, 2953, 2919, 2850, 1722, 1620, 1434, 1384,
1280, 1222, 1176, 1091, 939, 853, 738, 687, 608, 670, 522 cm–1
.
674, 539 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.98–8.01 (m, 2 H), 7.68–7.73 (m, 1 H),
7.56–7.61 (m, 2 H), 7.04 (d, J = 15.5 Hz, 1 H), 6.09 (d, J = 15.5 Hz, 1 H),
5.99 (s, 1 H), 3.72 (s, 3 H), 3.66 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 165.5, 163.0, 150.9, 137.2, 135.9, 134.6,
129.3, 128.4, 126.3, 118.0, 52.1, 51.9.
1H NMR (300 MHz, CDCl3): δ = 7.01 (d, J = 6.9 Hz, 1 H), 5.40 (d, J = 6.9
Hz, 1 H), 3.73 (s, 3 H), 3.31 (q, J = 7.4 Hz, 2 H), 1.49 (t, J = 7.4 Hz, 3 H).
13C NMR (75 MHz, CDCl3): δ = 163.3, 144.6, 105.2, 51.6, 46.7, 8.0.
HRMS (EI+): m/z [M+] calcd for C6H10O5S: 194.0249; found: 194.0243.
HRMS (EI+): m/z [M+] calcd for C14H14O7S: 326.0460; found: 326.0462.
Methyl (Z)-3-(Tosyloxy)hex-2-enoate (3v)
Yield: 22.7 mg (51%); colorless liquid; Rf = 0.35 (hexanes/EtOAc, 2:1).
Dimethyl (2Z,4E)-3-[(4-Methylphenyl)sulfonyloxy]hexa-2,4-di-
enedioate (3z)
FT-IR (KBr): 3094, 3073, 2966, 2877, 1736, 1672, 1598, 1460, 1374,
1380, 1289, 1205, 1174, 1136, 1091, 1018, 934, 815, 767, 710, 692,
Yield: 76 mg (89%); white solid; mp 94–95 °C; Rf = 0.25 (hexanes/EtOAc,
4:1).
972, 633, 551, 524 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.90 (d, J = 8.3 Hz, 2 H), 7.36 (d, J = 8.3
Hz, 2 H), 5.53 (s, 1 H), 3.59 (s, 3 H), 2.60 (s, 3 H), 2.36 (t, J = 7.5 Hz, 2
H), 1.51–1.61 (m, 2 H), 0.90 (t, J = 7.4 Hz, 3 H).
13C NMR (75 MHz, CDCl3): δ = 163.9, 160.4, 145.8, 133.9, 130.1, 128.8,
110.5, 51.8, 37.5, 22.1, 20.0, 13.6.
FT-IR (KBr): 3068, 2992, 2948, 1730, 1618, 1434, 1384, 1309, 1281,
1227, 1173, 991, 934, 900, 760, 686, 666, 598, 542, 522 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.84 (d, J = 8.4 Hz, 2 H), 7.34 (d, J = 8.4
Hz, 2 H), 7.02 (d, J = 15.6 Hz, 1 H), 6.06 (d, J = 15.6 Hz, 1 H), 5.97 (s, 1
H), 3.70 (s, 3 H), 3.64 (s, 3 H), 2.43 (s, 3 H).
HRMS (EI+): m/z [M+] calcd for C14H18O5S: 298.0875; found: 298.0882.
13C NMR (75 MHz, CDCl3): δ = 165.5, 163.0, 150.9, 145.9, 137.2, 132.7,
129.8, 128.4, 126.1, 118.0, 52.0, 51.8, 21.6.
HRMS (EI+): m/z [M+] calcd for C15H16O7S: 340.0617; found: 340.0612.
Methyl (Z)-3-(Methylsulfonyloxy)hex-2-enoate (3w)
Yield: 10.3 mg (31%); colorless liquid; Rf = 0.33 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 2964, 2938, 2878, 2850, 1730, 1671, 1520, 1464, 1436,
Dimethyl (2Z,4E)-3-[(4-Ethylphenyl)sulfonyloxy]hexa-2,4-diene-
dioate (3aa)
1358, 1229, 1210, 1168, 1018, 975, 938, 914, 888, 793, 631, 523 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 5.62 (s, 1 H), 3.72 (s, 3 H), 3.33 (s, 3 H),
2.45 (t, J = 7.4 Hz, 2 H), 1.60–1.71 (m, 2 H), 0.97 (t, J = 7.3 Hz, 3 H).
Yield: 72 mg (81%); white solid; mp 92–93 °C; Rf = 0.25 (hexanes/EtOAc,
4:1).
13C NMR (75 MHz, CDCl3): δ = 163.6, 160.9, 109.2, 51.5, 39.6, 37.9,
19.4, 13.2.
FT-IR (KBr): 3434, 3072, 2955, 2850, 1724, 1620, 1436, 1386, 1282,
1223, 1176, 1093, 1009, 975, 940, 840, 761, 681, 604, 561, 532 cm–1
.
HRMS (EI+): m/z [M+] calcd for C8H14O5S: 222.0562; found: 222.0558.
1H NMR (300 MHz, CDCl3): δ = 7.88 (d, J = 8.4 Hz, 2 H), 7.38 (d, J = 8.4
Hz, 2 H), 7.02 (d, J = 15.6 Hz, 1 H), 6.03 (d, J = 15.6 Hz, 1 H), 5.98 (s, 1
H), 3.70 (s, 3 H), 3.66 (s, 3 H), 2.73 (q, J = 7.8 Hz, 2 H), 1.24 (t, J = 7.8 Hz,
3 H).
13C NMR (75 MHz, CDCl3): δ = 165.6, 163.2, 152.1, 151.0, 137.2, 133.1,
128.8, 128.6, 126.2, 118.1, 52.1, 51.9, 29.0, 15.1.
Ethyl (Z)-3-(Tosyloxy)but-2-enoate (3x)
Yield: 40.5 mg (95%); colorless liquid; Rf = 0.4 (hexanes/EtOAc, 2:1).
FT-IR (KBr): 3073, 2984, 2929, 1729, 1676, 1598, 1445, 1372, 1303,
1277, 1211, 1175, 1366, 1093, 1048, 1018, 924, 859, 816, 762, 711,
692, 655, 606, 553 cm–1
.
HRMS (EI+): m/z [M+] calcd for C16H18O7S: 354.0773; found: 354.0775.
1H NMR (300 MHz, CDCl3): δ = 7.82 (d, J = 8.1 Hz, 2 H), 7.28 (d, J = 8.1
Hz, 2 H), 5.42 (s, 1 H), 3.98 (q, J = 7.1 Hz, 2 H), 2.38 (s, 3 H), 2.03 (s, 3
H), 1.13 (t, J = 7.1 Hz, 3 H).
Dimethyl (2Z,4E)-3-[(2,5-Dimethylphenyl)sulfonyloxy]hexa-2,4-
dienedioate (3ab)
13C NMR (75 MHz, CDCl3): δ = 163.3, 156.6, 145.8, 133.8, 130.1, 128.7,
Yield: 67 mg (76%); yellow liquid; Rf = 0.25 (hexanes/EtOAc, 4:1).
111.2, 60.7, 22.1, 22.0, 14.5.
HRMS (EI+): m/z [M+] calcd for C13H16O5S: 284.0718; found: 284.0711.
FT-IR (KBr): 3069, 2998, 2954, 2847, 1725, 1620, 1493, 1369, 1282,
1222, 1178, 1031, 975, 938, 856, 764, 707, 638, 585, 553, 491 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.66 (s, 1 H), 7.32 (d, J = 7.7 Hz, 1 H),
7.25 (d, J = 7.7 Hz, 1 H), 7.03 (d, J = 15.6 Hz, 1 H), 6.06 (d, J = 15.6 Hz, 1
H), 5.95 (s, 1 H), 3.69 (s, 3 H), 3.51 (s, 3 H), 2.68 (s, 3 H), 2.32 (s, 3 H).
Dialkyl (2Z,4E)-3-(Aryl/Alkylsulfonyloxy)hexa-2,4-dienedioates
3y,z and 3aa–ad
To a pressure-affordable thick-wall glass tube containing aryl/alkyl-
sulfonic acid 1 (0.25 mmol), enyndioate 2i (168 mg, 1.00 mmol),
Pd(OAc)2 (6 mg, 0.025 mmol), and K2S2O8 (68 mg, 0.25 mmol) were
added anhyd CH2Cl2 (4 mL) under N2. The tube was sealed with an O-
ring and a teflon cap. The mixture was then stirred at 60 °C for 24 h.
13C NMR (75 MHz, CDCl3): δ = 165.3, 162.8, 150.8, 137.5, 136.2, 135.3,
134.9, 134.8, 132.5, 129.6, 125.7, 117.7, 51.8, 51.5, 20.4, 20.0.
HRMS (EI+): m/z [M+] calcd for C16H18O7S: 354.0773; found: 354.0777.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J

I
S. Raju et al.
Paper
Synthesis
Dimethyl (2Z,4E)-3-(Mesitylsulfonyloxy)hexa-2,4-dienedioate
(3ac)
115, 12045. (f) Patil, N. T.; Kavthe, R. D.; Shinde, V. S. Tetrahe-
dron 2012, 68, 8079. (g) Shi, Z.; Zhang, C.; Tang, C.; Jiao, N. Chem.
Soc. Rev. 2012, 41, 3381. (h) Comprehensive Organic Synthesis;
1
V–o.9
l
Yield: 43 mg (47%); white solid; mp 110–111 °C; Rf = 0.35 (hex-
Trost, B. M.; Fleming, I., Eds.; Pergamon Press: Oxford, 1991.
(i) Kadikova, R. N.; Ramazanov, I. R.; Vyatkin, A. V.; Dzhemilev,
U. M. Synthesis 2017, 49, 1889. (j) Zhang, M.; Zhao, Y.; Chen, W.
Synthesis 2017, 49, 1342.
anes/EtOAc, 4:1).
FT-IR (KBr): 3074, 2985, 2952, 2926, 2852, 1725, 1620, 1437, 1374,
1281, 1222, 1175, 1033, 974, 939, 855, 762, 726, 683, 604, 537 cm–1
.
1H NMR (300 MHz, CDCl3): δ = 7.07 (d, J = 15.6 Hz, 1 H), 7.00 (s, 2 H),
6.12 (d, J = 15.6 Hz, 1 H), 5.96 (s, 1 H), 3.72 (s, 3 H), 3.53 (s, 3 H), 2.63
(s, 6 H), 2.31 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 165.6, 163.1, 151.3, 144.0, 139.8, 137.9,
132.3, 131.8, 126.0, 117.8, 52.0, 51.7, 22.8, 21.0.
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HRMS (EI+): m/z [M+] calcd for C17H20O7S: 368.0930; found: 368.0927.
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Molander, G. A., Eds.; Elsevier: Amsterdam, 2014. (b) Indukuri,
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T.; Wang, Q.; Li, L.-H.; Liu, X.-Y.; Xu, P.-F.; Liang, Y.-M. Org. Lett.
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Diphenyl (2Z,4E)-3-(Ethylsulfonyloxy)hexa-2,4-dienedioate (3ad)
Yield: 49 mg (71%); white solid; mp 98–100 °C; Rf = 0.28 (hex-
anes/EtOAc, 4:1).
FT-IR (KBr): 3073, 2993, 2949, 2844, 1717, 1614, 1436, 1356, 1313,
1288, 1221, 1171, 996, 938, 904, 872, 789, 760, 685, 592, 533, 458
cm–1
.
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1H NMR (300 MHz, CDCl3): δ = 7.15 (d, J = 15.6 Hz, 1 H), 6.65 (d, J =
15.6 Hz, 1 H), 5.99 (s, 1 H), 3.77 (s, 3 H), 3.74 (s, 3 H), 3.61 (q, J = 7.5
Hz, 2 H), 1.56 (t, J = 7.5 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 165.8, 163.2, 152.0, 137.9, 127.4,
116.6, 52.1, 51.9, 47.9, 8.1.
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136, 6255. (b) Tsukada, N.; Takahashi, A.; Inoue, Y. Tetrahedron
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thesis 2017, 49, 1767.
HRMS (EI+): m/z [M+] calcd for C10H14O7S: 278.0460; found: 278.0458.
Funding Information
Ministry of Science and Technology of Taiwan (MOST104-2113-M-
009-014-MY3 and MOST105-2628-M-009-002-MY3)
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(8) (a) Fang, G.; Bi, X. Chem. Soc. Rev. 2015, 44, 8124. (b) Lv, S.;
Wang, J.; Zhang, C.; Xu, S.; Shi, M.; Zhang, J. Angew. Chem. Int. Ed.
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Wong, K.-Y. Chem. Commun. 2013, 49, 710. (b) Doucet, H.;
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Acknowledgment
We thank the Ministry of Science and Technology of Taiwan for finan-
cial support of this research.
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0036-1588501. Scanned photocopies of
NMR (CDCl3) spectral data for all new compounds and X-ray crystallo-
(10) (a) Newman, M. S.; Addor, R. W. J. Am. Chem. Soc. 1955, 77,
3789. (b) Ravindar, K.; Sridhar Reddy, M.; Deslongchamps, P.
Org. Lett. 2011, 13, 3178.
graphic (CIF) data of compounds 3a, 3g, 3k, and 3ad are included.
S
u
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ortioInfgrmoaitn
S
u
p
p
ortiInfogrmoaitn
(11) Nguyen, T. H.; Paluck, S. J.; McGahran, A. J.; Maynard, H. D. Bio-
macromolecules 2015, 16, 2684.
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The
Cambridge
Crystallographic
Data
Centre
via
www.ccdc.cam.ac.uk/getstructures.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–J