Copper-Catalyzed Multicomponent Reaction of DABCO·(SO2)2, Alcohols, and Aryl Diazoniums for the Synthesis of Sulfonic Esters

Article abstract of DOI:10.1021/acs.joc.8b00447

A Cu-catalyzed multicomponent cascade reaction of DABCO·(SO₂)₂ (DABSO), alcohol, and aryl diazonium tetrafluoroborate was developed which afforded sulfonic esters in moderate to good chemical yields. In this reaction, the SO₂ surrogate DABSO was used for the first time in the synthesis of sulfonic aliphatic esters. This multicomponent reaction was carried out under mild conditions and tolerated a wide range of substrates, which provides a new and efficient strategy for the synthesis of sulfonic esters.

Full text of DOI:10.1021/acs.joc.8b00447

Article
pubs.acs.org/joc
Cite This: J. Org. Chem. XXXX, XXX, XXX−XXX
Copper-Catalyzed Multicomponent Reaction of DABCO·(SO2)2,
Alcohols, and Aryl Diazoniums for the Synthesis of Sulfonic Esters
Yang Wang, Lingling Deng, Yu Deng, and Jianlin Han*
School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of
Advanced Organic Materials, Nanjing University, Nanjing 210093, China
S
* Supporting Information
ABSTRACT: A Cu-catalyzed multicomponent cascade reac-
tion of DABCO·(SO2)2 (DABSO), alcohol, and aryl
diazonium tetrafluoroborate was developed which afforded
sulfonic esters in moderate to good chemical yields. In this
reaction, the SO2 surrogate DABSO was used for the first time
in the synthesis of sulfonic aliphatic esters. This multi-
component reaction was carried out under mild conditions and tolerated a wide range of substrates, which provides a new and
efficient strategy for the synthesis of sulfonic esters.
hazardous sulfonyl chlorides.4b Thiophenol was also reported
to construct sulfonic esters under photopromoted oxidative
INTRODUCTION
■
Sulfur dioxide is a kind of hazardous air pollutant and is known
reaction conditions with 9-mesityl-10-meth-ylacridinium ion
as one of the main causes of acid rain.1 However, sulfur dioxide
(Acr+−Mes) as photocatalyst.16 Recently, the Wu group
is an important type of organic synthetic intermediate and
shows several advantages such as abundance in nature,
designed a method based on DABSO to synthesize O-
aminosulfonates via the direct coupling with strongly
nucleophilic hydroxylamines (Scheme 1a).17 To the best of
inexpensive materials, and easy conversion to sulfonyl structural
unit via insertion reactions.2 Thus, the use of sulfur dioxide as
sulfonyl precursor has become an active research area in the
Scheme 1. Synthesis of Sulfonic Esters
past decades.3 Due to the toxic and gaseous nature of SO2, SO2
surrogate may be a better choice in the laboratory to achieve
those SO2 insertion reactions.4 Recently, DABCO·(SO2)2
(DABSO) has been developed as a SO2 surrogate and resulted
in a significant development for assembling sulfonyl deriva-
tives.5 The previous work by the Willis, Wu, and other groups6
focused on the synthesis of sulfonohydrazides, sulfones, and
sulfonamides by the use of aryl halide,7 arylboronic acids,8
arylsilanes,9 organometallic reagents,10 aryldiazonium salts,11
and phenylhydrazine12 as the coupling partners.
our knowledge, alcohols as nucleophiles for the reaction with
Sulfonic ester is a common fragment in many pharmaceut-
icals and other bioactive compounds.13 For example,
DABSO to synthesize sulfonic esters has never been explored,
which severely restricts the practical applications of DABSO. It
compound A could prevent or treat undesired thrombosis.
should be mentioned that the Ball group developed a Pa-
Compound B represents a kind of novel inhibitor of bacterial
catalyzed reaction between aryl iodides, DABSO, and
thymidylate synthase (Figure 1).14
Selectfluor for the synthesis of aryl sulfonyl fluorides. In this
Traditional methods for the synthesis of sulfonic esters were
work, they mentioned the reaction of obtained sulfonyl
usually focused on esterification reaction of sulfonyl chlorides
fluorides and phenols to give sulfonic aryl esters.18 Inspired
in the presence of bases,15 which required the preparation of
by the previous reports6−11 and our continuous research
interests in the synthesis of sulfonic esters,19 we herein would
like to report a new Cu-catalyzed strategy based on DABSO for
the construction of sulfonic esters via a multicomponent
reaction with aryl diazonium salts and alcohols. The reaction
was conducted under room temperature without the need of
protection of an inert atmosphere. Furthermore, aliphatic
Received: February 16, 2018
Figure 1. Bioactive compounds containing sulfonic esters.
© XXXX American Chemical Society
A
DOI: 10.1021/acs.joc.8b00447
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The Journal of Organic Chemistry
Article
alcohols were well-tolerated in this catalytic system, which
makes this new methodology more attractive and useful.
temperature to 40 °C resulted in a decreased yield (25% yield,
entry 13). Finally, variations on the loading amount of DABSO
(entries 14−17) or the amount of CF3COOH (entry 18) did
not show any obvious improvement on the chemical yield.
With the optimized conditions in hand, we then carried out
the substrate scope study of this reaction by using various aryl
diazonium salts 1 and methanol 2a, and the results are shown
in Scheme 2. The reaction showed good substrate generality,
and a wide range of aryl diazonium salts were well-tolerated in
this catalytic system. Generally, aryl diazonium salts with
electron-donating groups such as methyl, methoxyl, tert-butyl,
ethyl, and phenyl on the para-position of the aromatic ring
worked better in this system, affording the corresponding
sulfonic esters in 50−64% yields (3aa−3fa). Reactions of aryl
diazonium salts with electron-withdrawing groups also
proceeded smoothly to give the desired product, however,
with a less efficient outcome (32−41% yields, 3ga−3ia). In
particular, aryl diazonium salt 1h with strong electron-
withdrawing group (nitro) still reacted smoothly with
DABSO and methanol to give the corresponding methyl 4-
nitrobenzenesulfonate 3ha with 36% yield. The position of
substituted group on the benzene ring also showed an effect on
the reaction. The substrate with ortho-substituted group
afforded a lower yield comparedto that from meta- or para-
substituted substrates, which is mainly due to the steric
hindrance (47% for 3na vs 51% for 3ka and 65% for 3ca).
Notably, the disubstituted substrate 1o worked well in this
reaction and provided the product 3,5-dimethylbenzenediazo-
nium 3oa in 49% yield. Finally, we found that the substrate with
naphthyl group was also suitable for this reaction, and the
corresponding product 3pa was obtained in 57% yield.
Then, we turned our attentions to another part of substrate
generality study by using various aliphatic alcohols 2 and aryl
diazonium salts 1. As shown in Scheme 3, all of the primary,
secondary, and tertiary aliphatic alcohols were well-tolerated in
this system and reacted with DABSO and aryl diazonium salts
smoothly to give the corresponding sulfonic esters. It should be
mentioned that the reaction of bulky t-butyl alcohol 2e gave
only 29% yield mainly because of the steric hindrance. We also
found that when the length of alkyl chain increased, the yield
decreased accordingly. For example, the reaction of ethyl
alcohol 2b gave the corresponding sulfonic ester 3ab in 49%
yield, while 41% yield was obtained from the reaction of n-
propyl alcohol 2c. We tried to use 2-methoxyethan-1-ol 2f as
substrate for this reaction, and the result indicated that it was a
suitable substrate for this reaction, resulting in 2-methoxyethyl
4-methylbenzenesulfonate 3fa in 22% yield. Finally, phenol and
benzyl alcohol were examined in this system under the standard
reaction conditions. However, no desired product was obtained.
To get insight of the reaction mechanism, two control
experiments were carried out (Scheme 4). First, 3 equiv of a
radical scavenger, TEMPO [(2,2,6,6-tetramethylpiperidin-1-
yl)oxyl], was added to the reaction under the standard
conditions (Scheme 4a). The reaction was completely sup-
pressed, and no target sulfonic ester 3aa was detected. To
confirm the formation of sulfonyl radical, another radical
scavenger, 1,1-diphenylalkene, was added to the catalytic
system (Scheme 4b). Almost no expected coupling product
3aa was found. Fortunately, the adduct 4 of p-toluene sulfonyl
radical with ethene-1,1-diyldibenzene and methanol was
obtained in 47% yield after careful isolation and purification.
The chemical structure of this compound 4 was confirmed by
X-ray single analysis (see Supporting Information Table S1).
RESULTS AND DISCUSSION
■
Initially, we chose 4-methylbenzenediazonium tetrafluoroborate
1a, DABSO, and methanol 2a as model substrates for the
optimization of reaction conditions (Table 1). When CuCl was
Table 1. Optimization of the Reaction Conditions for the
a
Cu-Catalyzed Multicomponent Reaction of DABSO
b
entry catalyst
additive
none
DABSO (equiv) solvent yield (%)
1
CuCl
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.8
1.2
1.5
2.0
1.2
13
38
39
18
nr
2
CuBr
none
3
CuBr2
CuCl2
none
none
4
none
5
none
c
6
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
CuBr2
none
35
10
34
50
55
60
55
25
21
64
46
42
51
7
NaHCO3
HCOONa
HOAc
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
8
9
10
11
12
13
14
15
16
17
18
HCOOH
CF3COOH
HCl
d
CF3COOH
CF3COOH
CF3COOH
CF3COOH
CF3COOH
CF3COOH
e
a
Reaction conditions: 4-methylbenzenediazonium (1a, 0.2 mmol),
DABSO, additive (1.0 equiv), catalyst (10 mol %), alcohol (2 mL),
b
and solvent (2 mL) under air at room temperature for 12 h. Isolated
c
d
e
yield based on 1a. Under an argon atmosphere. 40 °C. 0.5 equiv of
CF3COOH was used.
used as catalyst for this multicomponent reaction, the
corresponding ester 3aa was obtained with 13% isolated yield
under air at room temperature (entry 1). Then, several other
copper salts such as CuBr, CuBr2, and CuCl2 were screened for
this reaction (entry 2−4), and the results of entries 2−4
indicated clearly that CuBr2 was the most efficient catalyst for
this reaction (39% yield, entry 3). No reaction happened when
the reaction was performed without use of any copper catalyst
(entry 5). To further improve the outcome of this reaction, we
conducted the reaction under an argon atmosphere. However,
no improvement on the yield was found (35% yield, entry 6)
compared to that under an air atmosphere. Then, investigation
on the addition of inorganic acids or bases as additives was
carried out (entries 7−12). In the presence of bases, the
reaction was obviously restrained, and only 10% yield was
found with the addition of NaHCO3 (entry 7). In a sharp
contrast, with the use of acids as additives, the reaction
proceeded very well (entries 9−12), and the corresponding
product was obtained with dramatically improved yields. The
highest yield was obtained from the reaction in the presence of
CF3COOH (60% yield, entry 11). This might because that the
presence of acid would promote the release of sulfur dioxide
from the complex of DABCO·(SO2)2.20 Increasing the reaction
B
DOI: 10.1021/acs.joc.8b00447
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The Journal of Organic Chemistry
Article
a
Scheme 2. Substrate Scope of Aryl Diazonium Salts
a
Reaction conditions: 1 (0.2 mmol), DABSO (0.24 mmol), CuBr2 (10 mol %), CF3COOH (1.0 equiv), methanol 2a (2 mL), and CH2Cl2 (2 mL)
under air at room temperature for 12 h. Isolated yield.
a
Scheme 3. Substrate Scope of Alcohols
a
Reaction conditions: 1a (0.2 mmol), DABSO (0.24 mmol), CuBr2 (10 mol %), CF3COOH (1.0 equiv), alcohol 2 (2 mL), and vCH2Cl2 (2 mL)
under air at room temperature for 12 h. Isolated yield.
According to the previous reports11 and the above
experimental results, a possible catalytic cycle for this Cu-
catalyzed multicomponent reaction of DABSO is shown in
Scheme 5. Initially, benzyldiazonium tetrafluoroborate 1b reacts
with DABSO to generate benzylsulfonyl radical C and tertiary
amine radical cation A. Meanwhile, the Cu(II)-OMe inter-
mediate D forms from the reaction between Cu(II) catalyst B
and methanol 2a. Subsequently, intermediate D reacts with
benzenesulfonyl radical C, affording Cu(III) intermediate E,
which undergoes reductive elimination to give the final product
3ba and Cu(I) intermediate F. The intermediate F is oxidized
to Cu(II) B for the next catalytic cycle via SET process with
tertiary amine radical cation A. It should be mentioned that the
generation of aryl radical from the reaction of diazonium salt
with alcohol could not be excluded.21
CONCLUSIONS
■
In conclusion, we developed a new strategy to prepare sulfonic
esters via a copper-catalyzed SO2 insertion reaction. This
multicomponent cascade reaction is the first example of the use
of DABSO as SO2 surrogate to synthesize sulfonic esters. This
methodology features mild conditions, readily available
C
DOI: 10.1021/acs.joc.8b00447
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The Journal of Organic Chemistry
Article
Scheme 4. Control Experiments
MHz, Chloroform-d) δ 163.8, 130.3, 126.5, 114.5, 56.1, 55.7. HRMS
(TOF MS ESI): calcd for C8H10NaO4S+ [M + Na]+ 225.0192, found
225.0189. IR (cm-1): 2919, 1597, 1500, 1357, 1262, 1167, 1100, 990,
811, 766, 665, 563.
Scheme 5. Proposed Mechanism
Methyl 4-(tert-Butyl)benzenesulfonate (3da). Light yellow solid,
(23 mg, 50% yield), mp 65−66 °C. 1H NMR (400 MHz, Chloroform-
d) δ 7.86−7.81 (m, 2H), 7.59−7.55 (m, 2H), 3.76 (s, 3H), 1.36 (s,
9H). 13C NMR (101 MHz, Chloroform-d) δ 157.9, 132.1, 127.9,
126.3, 56.2, 35.3, 31.0. HRMS (TOF MS ESI): calcd for
C11H16NaO3S+ [M + Na]+ 251.0712, found 251.0715. IR (cm−1):
2963, 1594, 1359, 1178, 1115, 988, 843, 785.
Methyl 4-Ethylbenzenesulfonate (3ea). Colorless oil, (24 mg, 59%
1
yield). H NMR (400 MHz, Chloroform-d) δ 7.85−7.80 (m, 2H),
7.38 (d, J = 8.5 Hz, 2H), 3.75 (s, 3H), 2.75 (q, J = 7.6 Hz, 2H), 1.28 (t,
J = 7.6 Hz, 3H). 13C NMR (101 MHz, Chloroform-d) δ 151.0, 132.4,
128.7, 128.2, 56.2, 28.9, 15.1. HRMS (TOF MS ESI): calcd for
C9H12NaO3S+ [M + Na]+ 223.0399, found 223.0393. IR (cm−1): 2969,
1597, 1357, 1172, 1098, 986, 837.
Methyl [1,1′-Biphenyl]-4-sulfonate (3fa). White solid, (29 mg, 58%
yield), mp 67−68 °C.1H NMR (400 MHz, Chloroform-d) δ 8.00−
7.95 (m, 2H), 7.78−7.73 (m, 2H), 7.61 (dd, J = 8.3, 1.4 Hz, 2H),
7.52−7.46 (m, 2H), 7.46−7.41 (m, 1H), 3.80 (s, 3H). 13C NMR (101
MHz, Chloroform-d) δ 146.9, 139.0, 133.7, 129.2, 128.8, 128.6, 127.9,
127.4, 56.4. HRMS (TOF MS ESI): calcd for C13H12NaO3S+ [M +
Na]+ 271.0399, found 271.0391. IR (cm−1): 2958, 1593, 1355, 1172,
1098, 984, 839.
arylation reagents, and broad substrate generality, which
renders this multicomponent system more attractive and useful.
Furthermore, this study enriches the research contents of
reactions with DABSO.
Methyl 4-Chlorobenzenesulfonate (3ga). Colorless oil, (17 mg,
1
41% yield). H NMR (400 MHz, Chloroform-d) δ 7.90−7.82 (m,
EXPERIMENTAL SECTION
■
2H), 7.59−7.51 (m, 2H), 3.78 (s, 3H). 13C NMR (101 MHz,
Chloroform-d) δ 130.9, 129.6, 129.5, 128.8, 56.5. HRMS (TOF MS
ESI): calcd for C7H7ClNaO3S+ [M + Na]+ 228.9697, found 228.9685.
IR (cm−1): 2958, 1724, 1590, 1478, 1362, 1185, 1087, 984, 781, 619,
561.
General Procedure for the Cu-Catalyzed Multicomponent
Cascade Reaction. To a dried tube, 0.2 mmol of diazonium 1, 0.2
mmol of DABSO, and 0.02 mmol of CuBr2 were added. Then, 0.2
mmol of acid, alcohol 2 (2 mL), and DCM (2 mL) were added. The
reaction mixture was stirred for 12 h under air at room temperature.
The solvent was removed under reduced pressure, and the residue was
purified by silica gel column chromatography (PE:EA = 10:1) to afford
products 3.
Methyl 4-Nitrobenzenesulfonate (3ha). Light yellow solid, (16 mg,
1
36% yield), mp 75−76 °C. H NMR (400 MHz, Chloroform-d) δ
8.45−8.40 (m, 2H), 8.15−8.11 (m, 2H), 3.86 (s, 3H). 13C NMR (101
MHz, Chloroform-d) δ 141.1, 129.4, 126.9, 124.5, 57.0. HRMS (TOF
MS ESI): calcd for C7H7NNaO5S+ [M + Na]+ 239.9937, found
239.9935. IR (cm−1): 3107, 2924, 1532, 1351, 1310, 1094, 975, 855,
788, 729, 682, 608.
Methyl 4-Methylbenzenesulfonate (3aa). Colorless oil, (24 mg,
64% yield). 1H NMR (400 MHz, Chloroform-d) δ 7.79 (d, J = 8.0 Hz,
2H), 7.36 (d, J = 7.9 Hz, 2H), 3.74 (s, 3H), 2.46 (s, 3H). 13C NMR
(101 MHz, Chloroform-d) δ 145.0, 132.2, 129.9, 128.1, 56.2, 21.6.
HRMS (TOF MS ESI): calcd for C8H10NaO3S+ [M + Na]+ 209.0243,
found 209.0242. IR (cm−1): 2928, 1598, 1355, 1173, 1096, 986, 815.
Methylbenzenesulfonate (3ba). Light yellow oil, (17 mg, 50%
Methyl 4-(Methoxysulfonyl)benzoate (3ia). Light yellow solid, (15
mg, 32% yield), mp 82−83 °C. 1H NMR (400 MHz, Chloroform-d) δ
8.25−8.21 (m, 2H), 8.02−7.98 (m, 2H), 3.98 (s, 3H), 3.80 (s, 3H).
13C NMR (101 MHz, Chloroform-d) δ 165.4, 139.1, 135.0, 130.9,
130.4, 128.8, 128.1, 56.6, 52.8. HRMS (TOF MS ESI): calcd for
C9H10NaO5S+ [M + Na]+ 253.0141, found 253.0144. IR (cm−1): 2958,
1944, 1720, 1579, 1439, 1362, 1279, 1189, 1092, 982, 725, 606.
Methyl 3-Methylbenzenesulfonate (3ja). Colorless oil, (18 mg,
1
yield). H NMR (400 MHz, Chloroform-d) δ 7.97−7.89 (m, 2H),
7.72−7.63 (m, 1H), 7.58 (ddt, J = 8.3, 6.7, 1.2 Hz, 2H), 3.77 (s, 3H).
13C NMR (101 MHz, Chloroform-d) δ 135.2, 133.9, 129.3, 128.1,
56.4. HRMS (TOF MS ESI): calcd for C7H8NaO3S+ [M + Na]+
195.0086, found 195.0093. IR (cm−1): 2956, 1448, 1357, 1185, 1094,
982, 751.
1
48% yield). H NMR (400 MHz, Chloroform-d) δ 7.76−7.68 (m,
2H), 7.51−7.40 (m, 2H), 3.76 (s, 3H), 2.45 (s, 3H). 13C NMR (101
MHz, Chloroform-d) δ 139.6, 135.0, 134.7, 129.1, 128.3, 125.2, 56.3,
21.3. HRMS (TOF MS ESI): calcd for C8H10NaO3S+ [M + Na]+
Methyl 4-Methoxybenzenesulfonate (3ca). Yellow oil, (26 mg,
1
65% yield). H NMR (400 MHz, Chloroform-d) δ 7.82−7.73 (m,
2H), 7.00−6.91 (m, 2H), 3.82 (s, 3H), 3.66 (s, 3H). 13C NMR (101
D
DOI: 10.1021/acs.joc.8b00447
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The Journal of Organic Chemistry
Article
209.0243, found 209.0243. IR (cm−1): 2956, 1457, 1357, 1172, 984,
870.
tert-Butyl 4-Methylbenzenesulfonate (3ae). Colorless oil, (12 mg,
1
26% yield). H NMR (400 MHz, Chloroform-d) δ 7.59−7.54 (m,
2H), 7.34−7.28 (m, 2H), 2.41 (s, 3H), 1.55 (s, 9H). 13C NMR (101
MHz, Chloroform-d) δ 143.7, 142.0, 129.6, 124.8, 82.6, 29.9, 21.5.
HRMS (TOF MS ESI): calcd for C11H16NaO3S+ [M + Na]+ 251.0712,
found 251.0715. IR (cm−1): 2924, 2111, 1720, 1597, 1452, 1288, 1174,
1114, 1032, 1004, 814.
Methyl 3-Methoxybenzenesulfonate (3ka). Colorless oil, (21 mg,
1
51% yield). H NMR (400 MHz, Chloroform-d) δ 7.86 (dd, J = 8.2,
1.7 Hz, 1H), 7.54 (td, J = 8.2, 1.7 Hz, 1H), 7.00 (t, J = 7.6 Hz, 2H),
3.91 (s, 3H), 3.75 (s, 3H). 13C NMR (101 MHz, Chloroform-d) δ
157.6, 135.8, 131.6, 123.2, 120.3, 112.5, 56.7, 56.4. HRMS (TOF MS
ESI): calcd for C8H10NaO4S+ [M + Na]+ 225.0192, found 225.0194.
IR (cm−1): 2924, 1579, 1482, 1344, 1284, 1169, 984, 809.
2-Methoxyethyl 4-Methylbenzenesulfonate (3af). Colorless oil,
(10 mg, 22% yield). 1H NMR (400 MHz, Chloroform-d) δ 7.66−7.58
(m, 2H), 7.34 (d, J = 7.9 Hz, 2H), 4.21−4.10 (m, 1H), 3.75−3.64 (m,
1H), 3.62−3.50 (m, 2H), 3.36 (s, 3H), 2.43 (s, 3H). 13C NMR (101
MHz, Chloroform-d) δ 142.8, 141.5, 129.7, 125.4, 71.2, 62.8, 59.0,
21.5. HRMS (TOF MS ESI): calcd for C10H14NaO4S+ [M + Na]+
253.0505, found 253.0501. IR (cm−1): 2928, 2111, 1927, 1724, 1597,
1452, 1353, 1172, 1096, 1014, 915, 773.
Methyl 3-Phenoxybenzenesulfonate (3la). Brown oil, (21 mg,
1
40% yield). H NMR (400 MHz, Chloroform-d) δ 7.61 (dt, J = 7.9,
1.0 Hz, 1H), 7.50 (t, J = 8.0 Hz, 2H), 7.43−7.37 (m, 2H), 7.28−7.24
(m, 1H), 7.23−7.18 (m, 1H), 7.08−7.02 (m, 2H), 3.78 (s, 3H). 13C
NMR (101 MHz, Chloroform-d) δ 158.4, 155.6, 136.7, 130.7, 130.2,
124.7, 123.4, 122.1, 119.7, 117.2, 56.5. HRMS (TOF MS ESI): calcd
for C13H12NaO4S+ [M + Na]+ 287.0349, found 287.0348. IR (cm−1):
2954, 1584, 1474, 1362, 1232, 1176, 984, 919.
Methyl 2-Methylbenzenesulfonate (3ma). Light yellow oil, (21
mg, 56% yield). 1H NMR (400 MHz, Chloroform-d) δ 7.92 (d, J = 8.0
Hz, 1H), 7.46 (td, J = 7.6, 1.4 Hz, 1H), 7.30 (d, J = 7.8 Hz, 2H), 3.66
(s, 3H), 2.58 (s, 3H). 13C NMR (101 MHz, Chloroform-d) δ 138.5,
133.8, 133.6, 132.6, 130.2, 126.2, 56.0, 20.2. HRMS (TOF MS ESI):
calcd for C8H10NaO3S+ [M + Na]+ 209.0243, found 209.0239. IR
(cm−1): 2956, 1457, 1351, 1180, 1066, 982, 809.
Isopropyl 4-Methoxybenzenesulfonate (3cd). Colorless oil, (18
mg, 40% yield). 1H NMR (400 MHz, Chloroform-d) δ 8.01−7.74 (m,
2H), 7.08−6.92 (m, 2H), 4.86−4.56 (m, 1H), 3.89 (s, 3H), 1.27 (d, J
= 6.3 Hz, 6H). 13C NMR (101 MHz, Chloroform-d) δ 163.5, 129.8,
129.1, 114.3, 55.7, 29.7, 22.8. HRMS (TOF MS ESI): calcd for
C10H14NaO4S+ [M + Na]+ 253.0505, found 253.0499. IR (cm−1):
2928, 1597, 1465, 1347, 1262, 1167, 1086, 1023, 915, 807, 685.
(1-Methoxy-2-tosylethane-1,1-diyl)dibenzene (4). Light yellow
1
solid, (34 mg, 47% yield), mp 155−156 °C. H NMR (400 MHz,
Chloroform-d) δ 7.54−7.48 (m, 2H), 7.22−7.09 (m, 12H), 4.33 (s,
2H), 3.01 (s, 3H), 2.37 (s, 3H). 13C NMR (101 MHz, Chloroform-d)
δ 143.9, 143.0, 137.6, 129.3, 128.4, 128.2, 127.2, 126.5, 80.5, 61.0, 51.3,
21.6. HRMS (TOF MS ESI): calcd for C22H22NaO3S+ [M + Na]+
389.1182, found 389.1177. IR (cm−1): 2932, 1735, 1597, 1489, 1448,
1319, 1148, 1070, 785.
Methyl 2-Methoxybenzenesulfonate (3na). Colorless oil, (19 mg,
1
47% yield). H NMR (400 MHz, Chloroform-d) δ 7.93 (dd, J = 8.0,
1.7 Hz, 1H), 7.65−7.58 (m, 1H), 7.07 (td, J = 7.7, 1.1 Hz, 2H), 3.98
(s, 3H), 3.83 (s, 3H). 13C NMR (101 MHz, Chloroform-d) δ 157.6,
135.8, 131.6, 123.3, 120.3, 112.5, 56.7, 56.4. HRMS (TOF MS ESI):
calcd for C8H10NaO4S+ [M + Na]+ 225.0192, found 225.0192. IR
(cm−1): 2954, 1592, 1482, 1353, 1282, 1180, 1072, 990, 807, 758, 594.
Methyl 3,5-Dimethylbenzenesulfonate (3oa). White solid, (20 mg,
49% yield), mp 80−81 °C. 1H NMR (400 MHz, Chloroform-d) δ 7.52
(dt, J = 1.6, 0.8 Hz, 2H), 7.30−7.27 (m, 1H), 3.75 (s, 3H), 2.40 (s,
6H). 13C NMR (101 MHz, Chloroform-d) δ 139.4, 135.5, 134.8,
125.5, 56.2, 21.2. HRMS (TOF MS ESI): calcd for C9H12NaO3S+ [M
+ Na]+ 223.0399, found 223.0393. IR (cm−1): 2920, 1726, 1607, 1351,
1169, 988, 865, 757, 684, 606,542.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.joc.8b00447.
1
Copies of H and 13C NMR spectra (PDF)
X-ray single crystal analysis of 4 (CIF)
Methyl Naphthalene-1-sulfonate (3pa). Red solid, (25 mg, 57%
yield), mp 71−72 °C. 1H NMR (400 MHz, Chloroform-d) δ 8.61 (d, J
= 8.6 Hz, 1H), 8.29 (dd, J = 7.3, 1.3 Hz, 1H), 8.14 (d, J = 8.3 Hz, 1H),
7.96 (d, J = 8.1 Hz, 1H), 7.74−7.68 (m, 1H), 7.66−7.61 (m, 1H),
7.60−7.55 (m, 1H), 3.72 (s, 3H). 13C NMR (101 MHz, Chloroform-
d) δ 135.4, 134.2, 130.8, 130.4, 128.9, 128.7, 128.5, 127.3, 125.0, 124.0,
56.4. HRMS (TOF MS ESI): calcd for C11H10NaO3S+ [M + Na]+
245.0243, found 245.0244. IR (cm−1): 2920, 1593, 1508, 1455, 1344,
1172, 982, 807.
AUTHOR INFORMATION
Corresponding Author
*E-mail: hanjl@nju.edu.cn.
ORCID
Jianlin Han: 0000-0002-3817-0764
Notes
The authors declare no competing financial interest.
■
Ethyl 4-Methylbenzenesulfonate (3ab). Colorless oil, (20 mg, 49%
1
yield). H NMR (400 MHz, Chloroform-d) δ 7.82−7.78 (m, 2H),
ACKNOWLEDGMENTS
7.35 (d, J = 7.9 Hz, 2H), 4.11 (q, J = 7.1 Hz, 2H), 2.45 (s, 3H), 1.30 (t,
J = 7.1 Hz, 3H). 13C NMR (101 MHz, Chloroform-d) δ 144.7, 133.3,
129.8, 127.9, 66.8, 21.6, 14.7. HRMS (TOF MS ESI): calcd for
C9H12NaO3S+ [M + Na]+ 223.0399, found 223.0395. IR (cm−1): 2928,
1597, 1444, 1351, 1174, 1094, 1001, 911, 814.
■
We gratefully acknowledge the financial support from the
National Natural Science Foundation of China (Grants
21472082, 21772085, and 21761132021). The support from
the Collaborative Innovation Center of Solid-State Lighting and
Energy-Saving Electronics, and Changzhou Jin-Feng-Huang
program (to J.H.) is also acknowledged.
Propyl 4-Methylbenzenesulfonate (3ac). Colorless oil, (18 mg,
41% yield). 1H NMR (400 MHz, Chloroform-d) δ 7.80 (d, J = 8.3 Hz,
2H), 7.35 (d, J = 8.1 Hz, 2H), 3.99 (t, J = 6.5 Hz, 2H), 2.45 (s, 3H),
1.72−1.62 (m, 2H), 0.90 (t, J = 7.4 Hz, 3H). 13C NMR (101 MHz,
Chloroform-d) δ 144.6, 133.3, 129.8, 127.9, 72.2, 22.3, 21.6, 10.0.
HRMS (TOF MS ESI): calcd for C10H14NaO3S+ [M + Na]+ 237.0556,
found 237.0549. IR (cm−1): 2973, 1597, 1457, 1355, 1174, 1098, 1047,
941, 813, 744.
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