Regioselective thiolation of electron rich arenes and heterocycles in recyclable catalytic media

Article abstract of DOI:10.1039/c7ra02350b

A convenient and novel approach has been developed for the synthesis of unsymmetrical diaryl sulfides by the reaction of sulfonyl hydrazides with phenols using a [Bmim][Br] ionic liquid through the formation of C-S bonds. The reaction has further been extended to indole, β-naphthol and aromatic amine moieties. This protocol offers a new, versatile and greener approach for thiolation of natural phenols (monoterpenes)/aromatic phenols/β-naphthols/aromatic amines and indoles without using any catalyst. A broad range of functional groups were well tolerated in this reaction system.

Full text of DOI:10.1039/c7ra02350b

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PAPER
Regioselective thiolation of electron rich arenes
and heterocycles in recyclable catalytic media†‡
Cite this: RSC Adv., 2017, 7, 22860
*
Dushyant Singh Raghuvanshi
and Narsingh Verma
A convenient and novel approach has been developed for the synthesis of unsymmetrical diaryl sulfides by
the reaction of sulfonyl hydrazides with phenols using a [Bmim][Br] ionic liquid through the formation of
C–S bonds. The reaction has further been extended to indole, b-naphthol and aromatic amine moieties.
Received 25th February 2017
Accepted 17th April 2017
This protocol offers
a new, versatile and greener approach for thiolation of natural phenols
DOI: 10.1039/c7ra02350b
(monoterpenes)/aromatic phenols/b-naphthols/aromatic amines and indoles without using any catalyst.
rsc.li/rsc-advances
A broad range of functional groups were well tolerated in this reaction system.
In the existing green chemistry scenario and increased
concern over environmental issues, many green approaches for
Introduction
C–S bond formation have also been reported by the groups of
Xiao,9 Yan,10 Jiang,11 Tian,12 and others.13 However, the gener-
ality of the existing reports is somewhat vitiated by the severe
reaction conditions, and the catalysts and solvents used are not
acceptable in the context of green synthesis. Moreover, the
previous reports for the synthesis of diaryl suldes have
repeatedly used either iodine or iodine based catalysts (Scheme
1).9,10,12 Which is also a major drawbacks of existing reports.
Thus, the development of a new, efficient and green approach
for the preparation of diaryl suldes through C–S bond forma-
tion is highly desirable. The use of a benign and recyclable
catalyst/solvent with high activity and selectivity is an inter-
esting and rapidly growing area of synthetic chemistry. Owing to
their green credentials, ionic liquids (ILs) have attracted
considerable interest as environmentally benign reaction
media,14–17 catalysts17–19 and reagents.20
The C–S bond formation is of utmost importance and has
emerged as a key step in the syntheses of pharmaceuticals,
natural products, and organic materials.1 But the current chal-
lenges in organic synthesis are to develop convenient, selective,
and energy-efficient synthetic methods. In order to address
these concerns, the exploration of more practical and environ-
mentally benign synthetic methodologies is of contemporary
interest.2 The C–S bond formation reactions are not much
explored because thiols are very prone to dimer formation (S–S
coupling) leading to the formation of undesired disuldes and
organic sulfur compounds act as metal deactivators due to their
nature to bind with metals.3 In order to synthesize remarkably
important diaryl suldes, numerous catalytic reactions have
been developed.4 In recent decades, scientists have paid much
more attention to the development of new concepts for C–S
bond formation viz. direct oxidative coupling by selective
functionalization of the C–H bond. Such processes are endowed
with high yields and impressive regio- and stereo-selectivity and
are thus becoming a part of an ever-growing armory of useful
synthetic tools available to organic chemists today. However,
most of the present C–S bond formation methods via C–H bond
activation rely on the use of transition metals such as copper,5
iron,6a nickel,6b,c rhodium,7 palladium,8 etc. In these methods,
different S-sources are used, for example, sulfonyl hydrazides,
sodium sulnates, diaryl disuldes, and arylthiols. However,
these methods suffer from the use of toxic metal salts, harsh
reaction conditions, and narrow substrate scopes.
Department of Medicinal Chemistry, CSIR-Central Institute of Medicinal and Aromatic
Plants, P.O. CIMAP, Kukrail Road, Lucknow 226015, India. E-mail: dushyant.bhu@
gmail.com; dushyantsingh@cimap.res.in; Fax: +91 5222718695; Tel: +91 5222718588
† CIMAP Communication No. CIMAP/PUB/2016/83.
‡ Electronic supplementary information (ESI) available. See DOI:
10.1039/c7ra02350b
Scheme 1 Iodine catalysed sulfenylation of aromatic systems.
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Results and discussion
To look into the greener and efficient prospects of C–S bond
formation, a model reaction using easily available substrates,
tosylhydrazide and naturally isolated phenol i.e. thymol were
investigated in detail by varying different parameters such as
catalyst, temperature, additive, and solvent to develop the
appropriate conditions (Table 1). At the outset, different greener
and environmentally benign catalysts and reagents viz. TBAF,
TBAI, I2/SiO2, I2/Al2O3, I2/IR-400, [Bmim][Br] were screened to
determine their catalytic efficacy (Table 1, entries 1–6). We were
astonished to see that only [Bmim][Br] could bring the desired
conversion (entry 6), and other catalysts did not provide the
desired product rather gave undesired disuldes or no reaction
(Table 1, entries 1–5). Encouraged by these results, our studies
were directed to look at the prospective of other ionic liquids too
viz. [Bmim][I], [Bmim][Cl], [Emim][Cl] and [Emim][HSO4], but
none of these could match the efficacy of [Bmim][Br] which
provided diaryl sulde product 3a in 85% yield at 140 ꢀC (entry 6).
In order to screen the effect of temperature and time, the model
reaction was undertaken under conventional conditions in pres-
sure tube using [Bmim][Br] as a reagent at varying temperatures
and time periods. When the reaction temperature was elevated to
150 ꢀC (entry 8), no remarkable change was observed in the
product yield. At 130 ꢀC, low product yield was obtained (Table 1,
entry 7). The optimum conversion was achieved under catalyst-
free conditions at 140 ꢀC in 5 h (Table 1). Tosylhydrazide (1.2
equiv.) and thymol (1.0 equiv.) were established as sufficient to
obtain the maximum yield at 140 ꢀC in [Bmim][Br] in 5 h (entry 6).
Scheme 2 C–S bond formation using [Bmim][Br] ionic liquid.
Considering the signicance of developing a green and
highly efficient direct C–S bond formation, and as a part of our
ongoing research to design novel protocols including C–S bond
formation,21 we focused our attention towards the studies on
the [Bmim][Br] mediated C–S bond formation of phenols
(monoterpenes)/aromatic phenols/b-naphthol/aromatic amines
and indole (Scheme 2).
In this protocol, sulfonyl hydrazides were prime choice as a S-
source for C–S bond formation due to their stability and versatile
nature viz. as aryl sources,22 sulfonyl sources23 and reductants.24
To the best of our knowledge, this is a highly efficient and
conceptually new methodology applied rst time for C–S bond
formation of phenols, b-naphthol, aromatic amines and indole
using environmentally benign ionic liquid (Scheme 2).
Table 1 Optimization of reaction conditionsa
S. no.
Solvent
Catalyst (mol%)
Temp (ꢀC)
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
H2O
H2O
H2O
H2O
TBAF
TBAI
I2/SiO2
I2/Al2O3
I2/IR400
—
—
—
—
—
140
140
140
140
140
140
130
150
140
140
140
140
140
140
7
7
7
7
7
5
5
5
5
7
5
5
5
5
nrc
30
nr
nr
Trace
85
H2O
[Bmim][Br]
[Bmim][Br]
[Bmim][Br]
[Bmim][Br]
[Bmim][Br]
[Bmim][I]
[Bmim][Cl]
[Emim][Cl]
[Emim][HSO4]
73
81
9
80d
84
10
11
12
13
14
—
—
—
—
55
52
48
10
a
Reaction conditions: 1a (1 mmol), 2a (1.2 mmol), [Bmim][Br](2 mmol), 5 h. b Isolated yield based on ¼ 1a. c nr ¼ no reaction. d Reaction carried
out using 2a (1.5 mmol).
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Table 2 Thiolation of substituted phenols and arylsulfonyl hydrazidesa,b
a
Reaction conditions: 1 (1 mmol), 2 (1.2 mmol), [Bmim][Br] (2 mmol), 140 ꢀC and 5 h. b Isolated yield based on phenols. c 1 (7 mmol), 2 (8.4 mmol),
[Bmim][Br] (6 mmol), 140 ꢀC and 5 h. d Reaction carried out at 120 ꢀC. e nr ¼ no reaction.
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Scheme 3 C–S bond formation of indole, b-naphthol and ketone. Reaction conditions: 4, 6, 8 (1 mmol), 2 (1.2 mmol), [Bmim][Br] (2 mmol), and
5 h.
Intrigued by these observations and with the stipulated further feasibility of our methods, the aforemention conditions
reaction conditions in hand (Table 1, entry 6), the scope and were screened for ketone functionality also. For this purpose, we
versatility of this method was extended to the reaction of performed a sulfenylation of substituted tetralone and chroma-
a variety of sulfonyl hydrazides viz. phenyl-, p-tolyl-, p-tert- none with p-nitrobenzenesulfonyl hydrazide. When the above
butylphenyl-, p-nitrophenyl and 3-(triuoromethyl) benzene- reaction was accomplished and products were analysed, we were
sulfonyl hydrazide with different phenols like thymol, carvacrol, confronted with some other spectral patterns not corroborating
2,5-dimethylphenol, o-cresol, m-cresol and thymol ether to the formation of the expected product 10. The spectral analysis
afford a diverse range of unsymmetrical diaryl suldes 3a–3ab indicates the formation of product 9 (Scheme 3).
in reasonably high yields (Table 2). The ndings reveal that all
The recyclability of the ionic liquid was investigated with the
sorts of arylsulfonyl hydrazides undergo reaction smoothly. It same set of optimised reaction condition as a model reaction
was worthwhile to mention that the nature of the substituent on (Table 1, entry 6). Upon completion of the reaction, the product
the aromatic rings of the sulfonyl hydrazides did not signi- was isolated via standard work up procedure, while the aqueous
ꢀ
cantly affect the yields of this reaction.
layer containing [Bmim][Br] was dried to remove water at 60 C
Sulfonyl hydrazides with electron-donating groups gave under vacuum and then washed with diethyl ether. The recovered
slightly higher yields than those with electron-withdrawing ionic liquid was reused for four to ve times without signicant
groups. When ether of thymol was subjected to the reaction, at loss of the activity. Results were represented in Fig. 1.
the same set of optimized conditions, side product formation
On the basis of existing literature and based on my previous
was more, so the reaction was again optimized for thymol ether work,21c,25 we propose a plausible mechanism for para-sulfenyla-
and the best result was obtained at 120 ꢀC in 5 h (3j–3l). The tion of thymol, which is outlined in Scheme 4. Initially, sulfonyl
reaction was also tried with ester derivative of thymol and tosyl- hydrazide (2) is transformed to form D in the presence of [Bmim]
hydrazide (Table 2, entry 3m) but it did not succeed.
[Br]. In the next step electrophilic reaction of D with thymol (1)
b-Naphthol was also tried under the same set of optimized yields desired product 3 through the path a, or path b (Scheme 4).
reaction conditions; which was going smoothly at 100 ꢀC
(Scheme 3). Encouraged by above results, the aromatic amines
were also tried in place of phenols for C–S bond formation and
the reactions were going smoothly at the same set of optimized
reaction conditions (Table 2, entry 3ac–3ag). The substituent on
benzene ring of aromatic amine and sulfonyl hydrazide did not
signicantly affect the product yields. Further, in order to
ascertain the versatility of our reagent [Bmim][Br] towards others
functionality, we extended the scope of substrates and carried out
the reactions of various arylsulfonyl hydrazides with indole under
the aforesaid conditions (Scheme 3). It was found that indole
ꢀ
gave reasonably good yields at 100 C (Scheme 3). To check the
Fig. 1 Reusability of the ionic liquid.
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Scheme 4 Proposed mechanism.
pressure tube, was stirred at 140 ꢀC for the stipulated period
of time. Aer completion of the reaction (monitored through
TLC), the mixture was cooled to room temperature and the
reaction mixture was treated with EtOAc (5 mL) and water (10
mL). This was extracted with ethyl acetate (3 ꢁ 10 mL) and the
combined organic phase was dried over Na2SO4, and the
organic phase was concentrated under rotary vacuum evapo-
rator and the crude product was puried by column chroma-
tography using a mixture of ethyl acetate/n-hexane as eluent to
afford the desired unsymmetrical diaryl suldes 3.
Conclusions
We have developed a novel and efficient green protocol for
regioselective thiolation of phenols/b-naphthol, aromatic
amines and indole without using any catalyst. The protocol
embodies the rst time use of [Bmim][Br] ionic liquid, is effi-
cient and versatile, and renders a new way of C–S coupling. In
this procedure, various substituents, such as alkyl, nitro, tri-
uoromethyl, and methoxy groups, are well tolerated. Due to
high conversion, excellent regioselectivity, short reaction time
and use of a recyclable ionic liquid, the process promises to be
a practical and greener alternative. This method affords an
efficient alternative approach for the synthesis of biologically
important aryl sulphides.
Spectral data of the compounds
2-Isopropyl-5-methyl-4-(p-tolylthio)phenol (3a). Brown viscous
liquid. 1H NMR (500 MHz, CDCl3, d ppm): 7.33 (s, 1H, ArH), 7.03
(d, J ¼ 8.0 Hz, 2H, ArH), 6.96 (d, J ¼ 1.5 Hz, 2H, ArH), 6.68 (s, 1H,
ArH), 4.93 (s, 1H, OH), 3.17–3.11 (m, 1H, CH), 2.28 (s, 3H, CH3),
2.27 (s, 3H, CH3), 1.23 (d, J ¼ 6.5 Hz, 6H, 2 ꢁ CH3). 13C NMR
(125 MHz, CDCl3, d ppm): 153.49, 140.78, 134.92, 134.29,
133.04, 129.64, 127.06, 123.14, 117.65, 26.89, 22.52, 20.89,
20.31. EI-MS (C17H20OS): 272 [M], 273 [M + H]+.
2-Isopropyl-5-methyl-4-(phenylthio)phenol (3b). Brown viscous
liquid. 1H NMR (500 MHz, CDCl3, d ppm): 7.39 (s, 1H, ArH),
7.28–7.21 (m, 2H, ArH), 7.13–7.05 (m, 1H, ArH), 7.05–7.04 (m,
2H, ArH), 6.73 (s, 1H, ArH), 4.99 (s, 1H, OH), 3.21–3.15 (m, 1H,
CH), 2.30 (s, 3H, CH3), 1.27 (d, J ¼ 6.5 Hz, 6H, 2 ꢁ CH3). 13C
NMR (125 MHz, CDCl3, d ppm): 153.77, 141.23, 138.85, 134.81,
133.21, 128.86, 126.43, 124.93, 122.30, 117.73, 26.88, 22.54,
22.50, 20.33. ESI-MS (C16H18OS): 259 [M + H]+.
General experimental
All the reactions were carried out in 15 mL Ace-pressure tube
with constant stirring using Teon-coated magnetic stirring
bar. Column chromatography was performed using Merck silica
gel (100–200 mesh). Thin layer chromatography (TLC) was
performed using Merck GF254 plates (thickness 0.25 mm).
Visualization of spots on TLC plate was accomplished with UV
light and by staining in I2 chamber. All the chemicals were
procured from Sigma Aldrich and Alfa aessar.
General procedure for the preparation of diaryl suldes (C–S
bond)
2-Isopropyl-5-methyl-4-((4-nitrophenyl)thio)phenol (3c). Yellow
solid. Mp: 110–111 ꢀC. 1H NMR (500 MHz, CDCl3, d ppm): 8.05–
8.02 (m, 2H, ArH), 7.37 (s, 1H, ArH), 7.03–7.00 (m, 2H, ArH), 6.78
(s, 1H, ArH), 5.09 (s, 1H, OH), 3.21–3.15 (m, 1H, CH), 2.26 (s, 3H,
A mixture of phenols 1 (1 mmol), arylsulfonyl hydrazides 2 (1.2
mmol) and [Bmim][Br] (2 mmol), placed in a 15 mL Ace-
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CH3), 1.25 (d, J ¼ 7.0 Hz, 6H, 2 ꢁ CH3). 13C NMR (125 MHz, d ppm): 8.04 (d, J ¼ 8.5 Hz, 2H, ArH), 7.36 (s, 1H, ArH), 7.02 (d, J
CDCl3, d ppm): 155.27, 149.92, 144.83, 141.80, 135.35, 134.19, ¼ 8.5 Hz, 2H, ArH), 6.84 (s, 1H, ArH), 3.88 (s, 3H, OCH3), 3.30–
124.95, 124.0, 118.91, 118.18, 26.89, 22.49, 20.19. ESI-MS 3.25 (m, 1H, CH), 2.33 (s, 3H, CH3), 1.20 (d, J ¼ 7.0 Hz, 6H, 2 ꢁ
(C16H17NO3S): 303 [M], 302 [M ꢂ H]ꢂ.
CH3). 13C NMR (125 MHz, CDCl3, d ppm): 158.61, 149.92,
144.81, 141.78, 136.65, 134.65, 124.97, 124.0, 118.65, 113.10,
2-Isopropyl-5-methyl-4-((3-(triuoromethyl)phenyl)thio)phenol
(3d). Colorless liquid. 1H NMR (500 MHz, CDCl3, d ppm): 7.37 (s, 55.48, 26.59, 22.57, 20.74. EI-MS (C17H19NO3S): 317 [M], 318 [M
1H, ArH), 7.30–7.26 (m, 3H, ArH), 7.11 (d, J ¼ 7.5 Hz, 1H, ArH), + H]+.
6.74 (s, 1H, ArH), 5.13 (br s, 1H, OH), 3.18–3.14 (m, 1H, CH),
(5-Isopropyl-4-methoxy-2-methylphenyl)(p-tolyl)sulfane
(3k).
2.27 (s, 3H, CH3), 1.24 (d, J ¼ 7.0 Hz, 6H, 2 ꢁ CH3). 13C NMR Colorless viscous liquid. 1H NMR (500 MHz, DMSO-d6, d ppm):
(125 MHz, CDCl3, d ppm): 154.30, 141.43, 140.89, 135.08, 7.34 (s, 1H, ArH), 7.04 (d, J ¼ 8.0 Hz, 2H, ArH), 6.97 (m, 2H, ArH),
133.69, 131.64 (q), 129.13, 128.96, 124.97, 122.55, 121.48, 6.78 (s, 1H, ArH), 3.85 (s, 3H, OCH3), 3.29–3.23 (m, 1H, CH), 2.36
121.45, 120.76, 117.96, 26.86, 22.48, 20.25. EI-MS (C17H17F3OS): (s, 3H, CH3), 2.29 (s, 3H, CH3), 1.19 (d, J ¼ 6.5 Hz, 6H, 2 ꢁ CH3).
326 [M], 327 [M + H]+.
13C NMR (125 MHz, CDCl3, d ppm): 157.42, 140.52, 135.70,
4-(4-tert-Butylphenylthio)-2-isopropyl-5-methylphenol
(3e). 135.06, 134.86, 133.67, 129.63, 127.13, 122.60, 112.79, 55.44,
Colorless liquid. 1H NMR (300 MHz, CDCl3, d ppm): 7.28 (s, 1H, 26.58, 22.63, 20.84. EI-MS (C18H22OS): 286 [M], 287 [M + H]+.
ArH), 7.17 (d, J ¼ 8.1 Hz, 2H, ArH), 6.90 (d, J ¼ 8.4 Hz, 2H, ArH),
(5-Isopropyl-4-methoxy-2-methylphenyl)(phenyl)sulfane
(3l).
1
6.60 (s, 1H, ArH), 4.96 (br s, 1H, CH), 3.14–3.01 (m, 1H, CH), Yellow viscous liquid. H NMR (500 MHz, CDCl3, d ppm): 7.35
2.22 (s, 3H, CH3), 1.19 (s, 9H, 3 ꢁ CH3), 1.15 (d, J ¼ 7.2 Hz, 6H, 2 (s, 1H, ArH), 7.21–7.18 (m, 2H, ArH), 7.10–7.01 (m, 3H, ArH),
ꢁ CH3). 13C NMR (125 MHz, CDCl3, d ppm): 153.61, 148.15, 6.79 (s, 1H, ArH), 3.85 (s, 3H, OCH3), 3.28–3.23 (m, 1H, CH), 2.35
141.06, 135.11, 134.61, 133.06, 126.42, 125.90, 122.79, 117.62, (s, 3H, CH3), 1.19 (d, J ¼ 7.0 Hz, 6H, 2 ꢁ CH3). 13C NMR (125
34.34, 31.30, 26.88, 22.52, 20.39. EI-MS (C20H26OS): 314 [M], 315 MHz, CDCl3, d ppm): 157.64, 141.01, 138.97, 135.81, 134.16,
[M + H]+.
5-Isopropyl-2-methyl-4-(p-tolylthio)phenol (3f). Brown viscous 20.86. EI-MS (C17H20OS): 272 [M], 273 [M + H]+.
liquid. 1H NMR (500 MHz, CDCl3, d ppm): 7.26 (s, 1H, ArH), 7.03
Ethyl 2-(2-isopropyl-5-methyl-4-(p-tolylthio)phenoxy)acetate
128.82, 126.45, 124.86, 121.69, 112.79, 55.43, 26.55, 22.62,
(d, J ¼ 8.0 Hz, 2H, ArH), 6.98–6.95 (m, 2H, ArH), 6.79 (s, 1H, (3m). No reaction.
ArH), 5.12 (br s, 1H, OH), 3.53–3.48 (m, 1H, CH), 2.28 (s, 3H,
2,5-Dimethyl-4-(p-tolylthio)phenol (3n). White solid. Mp: 96–
CH3), 2.18 (s, 3H, CH3), 1.14 (d, J ¼ 6.5 Hz, 6H, 2 ꢁ CH3). 13C 97 ꢀC. 1H NMR (500 MHz, CDCl3, d ppm): 7.25 (s, 1H, ArH), 7.04
NMR (125 MHz, CDCl3, d ppm): 154.92, 151.59, 138.61, 135.80, (d, J ¼ 8.0 Hz, 2H, ArH), 6.98 (d, J ¼ 8.5 Hz, 2H, ArH), 6.70 (s, 1H,
134.94, 129.60, 127.28, 122.30, 121.96, 112.88, 30.62, 23.76, ArH), 4.84 (br s, 1H, OH), 2.28 (s, 6H, 2 ꢁ CH3), 2.20 (s, 3H,
20.89, 15.12. EI-MS (C17H20OS): 272 [M], 273 [M + H]+.
CH3). 13C NMR (125 MHz, CDCl3, d ppm): 154.41, 141.03,
5-Isopropyl-2-methyl-4-(phenylthio)phenol (3g). Brown viscous 138.18, 135.11, 134.76, 129.69, 127.44, 123.16, 122.27, 117.24,
liquid. 1H NMR (500 MHz, CDCl3, d ppm): 7.30 (s, 1H, ArH), 20.93, 20.40, 15.13. EI-MS (C15H16OS): 244 [M], 245 [M + H]+.
7.20–7.17 (m, 2H, ArH), 7.09–7.01 (m, 3H, ArH), 6.79 (s, 1H,
2,5-Dimethyl-4-(phenylthio)phenol (3o). Colorless liquid. 1H
ArH), 4.90 (br s, 1H, OH), 3.51–3.45 (m, 1H, CH), 2.19 (s, 3H, NMR (500 MHz, CDCl3, d ppm): 7.30 (s, 1H, ArH), 7.21–7.18 (m,
CH3), 1.13 (d, J ¼ 7.0 Hz, 6H, 2 ꢁ CH3). 13C NMR (125 MHz, 2H, ArH), 7.09–7.01 (m, 3H, ArH), 6.73 (s, 1H, ArH), 4.91 (s, 1H,
CDCl3, d ppm): 155.20, 152.11, 139.77, 139.21, 128.78, 126.59, OH), 2.28 (s, 3H, CH3), 2.20 (s, 3H, CH3). 13C NMR (125 MHz,
124.90, 122.40, 121.08, 113.01, 30.70, 23.79, 15.11. ESI-MS CDCl3, d ppm): 154.80, 141.58, 138.85, 138.79, 129.23, 128.85,
(C16H18OS): 259 [M + H]+.
127.83, 126.62, 124.99, 122.42, 122.12, 117.30, 20.40, 15.11. ESI-
5-Isopropyl-2-methyl-4-((4-nitrophenyl)thio)phenol (3h). Yellow MS (C14H14OS): 229 [M ꢂ H]ꢂ.
viscous liquid. 1H NMR (500 MHz, CDCl3, d ppm): 8.03 (dd, J ¼
2,5-Dimethyl-4-((4-nitrophenyl)thio)phenol (3p). Yellow solid.
1
ꢀ
2.0, 7.0 Hz, 2H, ArH), 7.31 (s, 1H, ArH), 7.03 (dd, J ¼ 2.0, 7.0 Hz, Mp: 156–157 C. H NMR (500 MHz, CDCl3, d ppm): 8.04–8.01
2H, ArH), 6.86 (s, 1H, ArH), 5.05 (s, 1H, OH), 3.37–3.31 (m, 1H, (m, 2H, ArH), 7.33 (s, 1H, CH3), 7.02–7.0 (m, 2H, ArH), 6.80 (s,
CH), 2.23 (s, 3H, CH3), 1.14 (d, J ¼ 7.0 Hz, 6H, 2 ꢁ CH3). 13C 1H, ArH), 5.13 (s, 1H, OH), 2.27 (s, 3H, CH3), 2.23 (s, 3H, CH3).
NMR (125 MHz, CDCl3, d ppm): 156.31, 152.88, 150.71, 144.80, 13C NMR (125 MHz, CDCl3, d ppm): 155.89, 149.73, 144.85,
139.78, 125.07, 123.94, 123.27, 117.91, 113.55, 30.95, 23.83, 142.34, 139.56, 125.05, 124.01, 123.25, 118.99, 117.73, 20.27,
15.15. EI-MS (C16H17NO3S): 303 [M], 304 [M + H]+.
5-Isopropyl-2-methyl-4-((3-(triuoromethyl)phenyl)thio)phenol
15.13. ESI-MS (C14H13NO3S): 274 [M ꢂ H]ꢂ.
4-((4-(tert-Butyl)phenyl)thio)-2,5-dimethylphenol (3q). Colorless
(3i). Brown viscous liquid. H NMR (500 MHz, CDCl3, d ppm): liquid. 1H NMR (500 MHz, CDCl3, d ppm): 7.29 (s, 1H, ArH), 7.24
7.31–7.24 (m, 4H, ArH), 7.12 (d, J ¼ 7.0 Hz, 1H, ArH), 6.83 (s, 1H, (dd, J ¼ 2.0, 6.5 Hz, 2H, ArH), 6.99 (d, J ¼ 0.5 Hz, 1H, ArH), 6.97
ArH), 5.00 (br s, 1H, OH), 3.43–3.38 (m, 1H, CH), 2.21 (s, 3H, (s, 1H, ArH), 6.72 (s, 1H, ArH), 5.06 (br s, 1H, OH), 2.31 (s, 3H,
CH3), 1.13 (d, J ¼ 7.0 Hz, 6H, 2 ꢁ CH3). 13C NMR (125 MHz, CH3), 2.19 (s, 3H, CH3), 1.28 (s, 9H, 3 ꢁ CH3). 13C NMR (125
CDCl3, d ppm): 155.78, 152.55, 141.74, 139.53, 131.56 (q), MHz, CDCl3, d ppm): 154.60, 148.26, 141.34, 138.57, 135.03,
129.07, 129.0, 124.98, 122.85, 122.54, 121.44, 121.40, 119.32, 126.71, 125.93, 122.69, 122.35, 117.21, 34.35, 31.31, 20.48,
113.34, 30.81, 23.78, 15.12. EI-MS (C17H17F3OS): 326 [M], 327 [M 15.15. ESI-MS (C18H22OS): 285 [M ꢂ H]ꢂ.
1
+ H]+.
(5-Isopropyl-4-methoxy-2-methylphenyl)(4-nitrophenyl)sulfane
2,5-Dimethyl-4-(3-(triuoromethyl)phenylthio)phenol
White solid. Mp: 98–99 C. H NMR (500 MHz, CDCl3, d ppm):
(3r).
1
ꢀ
1
ꢀ
(3j). Yellow solid. Mp: 104–105 C. H NMR (500 MHz, CDCl3, 7.32–7.26 (m, 4H, ArH), 7.10 (d, J ¼ 7.5 Hz, 1H, ArH), 6.76 (s, 1H,
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ArH), 4.89 (s, 1H, OH), 2.27 (s, 3H, CH3), 2.22 (s, 3H, CH3). 13
C
2-Isopropyl-4-(phenylthio)phenol (3z). Brown viscous liquid. 1H
NMR (500 MHz, CDCl3, d ppm): 7.34 (d, J ¼ 2.0 Hz, 1H, ArH),
7.24–7.11 (m, 6H, ArH), 6.74 (d, J ¼ 8.0 Hz, 1H, ArH), 4.93 (s, 1H,
OH), 3.21–3.16 (m, 1H, CH), 1.24 (d, J ¼ 6.5 Hz, 6H, 2 ꢁ CH3).
13C NMR (125 MHz, CDCl3, d ppm): 153.20, 138.85, 135.79,
132.68, 132.62, 128.90, 127.87, 125.59, 124.22, 116.39, 27.15,
22.42. ESI-MS (C15H16OS): 243 [M ꢂ H]ꢂ.
NMR (125 MHz, CDCl3, d ppm): 155.31, 141.95, 140.77, 139.26,
131.37 (q), 129.15, 129.04, 122.79, 122.63, 121.54, 121.51,
120.52, 117.53, 20.33, 15.10. EI-MS (C15H13F3OS): 298 [M], 299
[M + H]+.
2-Methyl-4-(p-tolylthio)phenol (3s). Colorless viscous liquid.
1H NMR (500 MHz, CDCl3, d ppm): 7.23 (s, 1H, ArH), 7.22–7.11
(m, 3H, ArH), 7.07 (d, J ¼ 8.5 Hz, 2H, ArH), 6.74 (d, J ¼ 8.0 Hz,
1H, ArH), 4.82 (s, 1H, OH), 2.30 (s, 3H, CH3), 2.21 (s, 3H, CH3).
13C NMR (125 MHz, CDCl3, d ppm): 153.83, 136.02, 135.84,
134.51, 132.17, 129.75, 129.23, 125.38, 125.01, 115.82, 20.99,
15.66. ESI-MS (C14H14OS): 229 [M ꢂ H]ꢂ.
2-Isopropyl-4-(3-(triuoromethyl)phenylthio)phenol
(3aa).
Colorless viscous liquid. 1H NMR (500 MHz, CDCl3, d ppm):
7.36–7.30 (m, 3H, ArH), 7.26–7.21 (m, 3H, ArH), 6.79 (d, J ¼
8.0 Hz, 1H, ArH), 5.02 (s, 1H, OH), 3.23–3.16 (m, 1H, CH), 1.25
(d, J ¼ 7.0 Hz, 6H, 2 ꢁ CH3). 13C NMR (125 MHz, CDCl3, d ppm):
153.82, 141.09, 136.31, 133.37, 133.31, 131.39, 130.07, 129.15,
124.93, 123.52, 123.49, 122.36, 121.96, 116.68, 27.12, 22.38. ESI-
MS (C16H15F3OS): 311 [M ꢂ H]ꢂ.
2-Methyl-4-(phenylthio)phenol (3t). Yellow viscous liquid. 1H
NMR (500 MHz, CDCl3, d ppm): 7.28–7.20 (m, 4H, ArH), 7.17–
7.11 (m, 3H, ArH), 6.77 (d, J ¼ 8.5 Hz, 1H, ArH), 4.90 (s, 1H, OH),
2.23 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3, d ppm): 154.25,
138.75, 136.78, 133.13, 128.90, 128.12, 125.68, 125.19, 124.10,
115.94, 16.65. ESI-MS (C13H12OS): 215 [M ꢂ H]ꢂ.
2-Isopropyl-4-(p-tolylthio)phenol (3ab). Brown viscous liquid.
1H NMR (500 MHz, CDCl3, d ppm): 7.30 (d, J ¼ 2.0 Hz, 1H, ArH),
7.13–7.10 (m, 3H, ArH), 7.06 (d, J ¼ 8.0 Hz, 2H, ArH), 6.71 (d, J ¼
8.0 Hz, 1H, ArH), 4.92 (s, 1H, OH), 3.20–3.14 (m, 1H, CH), 2.29
(s, 3H, CH3), 1.23 (d, J ¼ 6.5 Hz, 6H, 2 ꢁ CH3). 13C NMR (125
MHz, CDCl3, d ppm): 152.83, 135.88, 135.63, 134.60, 131.72,
131.70, 129.71, 128.95, 125.44, 116.29, 27.16, 22.41, 20.96. EI-
MS (C16H18OS): 258 [M], 259 [M + H]+.
4-((4-(tert-Butyl)phenyl)thio)-2-methylphenol (3u). Colorless
viscous liquid. 1H NMR (500 MHz, CDCl3, d ppm): 7.28–7.25 (m,
3H, ArH), 7.21 (dd, J ¼ 2.0, 8.5 Hz, 1H, ArH), 7.14 (d, J ¼ 8.5 Hz,
2H, ArH), 6.75 (d, J ¼ 8.5 Hz, 1H, ArH), 4.98 (br s, 1H, OH), 2.23
(s, 3H, CH3), 1.29 (s, 9H, 3 ꢁ CH3). 13C NMR (125 MHz, CDCl3,
d ppm): 154.03, 149.10, 136.37, 134.85, 132.69, 128.36, 126.02,
125.10, 124.77, 115.88, 34.43, 31.30, 15.69. EI-MS (C17H20OS):
272 [M], 273 [M + H]+.
4-(p-Tolylthio)aniline (3ac). Brown solid. Mp: 70–71 ꢀC. 1H
NMR (500 MHz, CDCl3, d ppm): 7.29–7.26 (m, 2H, ArH), 7.10–
7.03 (m, 4H, ArH), 6.67–6.64 (m, 2H, ArH), 3.76 (br s, 2H, NH2),
2.29 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3, d ppm): 146.65,
135.56, 135.47, 135.33, 129.64, 128.31, 121.79, 115.84, 20.94 EI-
MS (C13H13NS): 215 [M], 216 [M + H]+.
2-Methyl-4-(3-(triuoromethyl)phenylthio)phenol (3v). Yellow
viscous liquid. 1H NMR (500 MHz, CDCl3, d ppm): 7.37–7.29 (m,
4H, ArH), 7.25–7.23 (m, 2H, ArH), 6.81 (d, J ¼ 8.5 Hz, 1H, ArH),
5.00 (s, 1H, OH), 2.25 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3,
d ppm): 154.88, 140.97, 137.49, 133.92, 131.39, 131.13, 130.31,
129.17, 125.61, 123.80, 123.77, 122.21, 122.08, 122.05, 116.25,
15.65. EI-MS (C14H11F3OS): 284 [M], 285 [M + H]+.
4-(Phenylthio)aniline (3ad). White solid. Mp: 92–93 ꢀC. 1H
NMR (500 MHz, CDCl3, d ppm): 7.32–7.30 (m, 2H, ArH), 7.22–
7.19 (m, 2H, ArH), 7.13–7.08 (m, 3H, ArH), 6.69 (dd, J ¼ 2.0,
8.5 Hz, 2H, ArH), 3.83 (br s, 2H, NH2). 13C NMR (125 MHz,
CDCl3, d ppm): 146.99, 139.66, 136.09, 128.77, 127.26, 125.21,
120.48, 115.84. EI-MS (C12H11NS): 201 [M + H]+.
1
3-Methyl-4-(p-tolylthio)phenol (3w). Brown viscous liquid. H
NMR (500 MHz, CDCl3, d ppm): 7.33 (d, J ¼ 8.0 Hz, 1H, ArH),
7.05 (d, J ¼ 8.0 Hz, 2H, ArH), 7.00 (m, 2H, ArH), 6.77 (d, J ¼
2.5 Hz, 1H, ArH), 6.67 (dd, J ¼ 3.0, 8.5 Hz, 1H, ArH), 5.04 (br s,
1H, OH), 2.32 (s, 3H, CH3), 2.29 (s, 3H, CH3). 13C NMR (125
MHz, CDCl3, d ppm): 156.04, 143.46, 136.70, 135.40, 134.30,
129.75, 127.88, 123.99, 117.67, 113.83, 20.93, 20.88. EI-MS
(C14H14OS): 230 [M], 231 [M + H]+.
3-Methyl-4-(phenylthio)phenol (3x). Colorless viscous liquid.
1H NMR (500 MHz, CDCl3, d ppm): 7.39 (d, J ¼ 8.0 Hz, 1H, ArH),
7.22–7.19 (m, 2H, ArH), 7.11–7.08 (m, 1H, ArH), 7.04–7.03 (m,
2H, ArH), 6.80 (d, J ¼ 2.5 Hz, 1H, ArH), 6.69 (dd, J ¼ 3.0 Hz,
8.0 Hz, 1H, ArH), 4.92 (br s, 1H, OH), 2.32 (s, 3H, CH3). 13C NMR
(125 MHz, CDCl3, d ppm): 156.42, 144.17, 138.40, 137.56,
128.91, 126.95, 125.21, 122.92, 117.77, 113.93, 20.91. ESI-MS
(C13H12OS): 239 [M + Na]+.
4-(4-Nitrophenylthio)aniline (3ae). Yellow solid. Mp: 137–
1
ꢀ
138 C. H NMR (500 MHz, CDCl3, d ppm): 8.03 (d, J ¼ 9.0 Hz,
2H, ArH), 7.34 (d, J ¼ 8.5 Hz, 2H, ArH), 7.09 (d, J ¼ 9.0 Hz, 2H,
ArH), 6.74 (d, J ¼ 8.5 Hz, 2H, ArH), 3.96 (br s, 2H, NH2). 13C NMR
(125 MHz, CDCl3, d ppm): 151.04, 148.36, 144.83, 137.24,
125.24, 123.89, 116.45, 116.15. EI-MS (C12H10N2O2S): 246 [M],
247 [M + H]+.
2-Methyl-4-(phenylthio)aniline (3af). Brown solid. Mp: 59–
60 ꢀC. 1H NMR (500 MHz, CDCl3, d ppm): 7.25–7.19 (m, 4H,
ArH), 7.13–7.08 (m, 3H, ArH), 6.68 (dd, J ¼ 8.0 Hz, 1H, ArH), 3.78
(br s, 2H, NH2), 2.15 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3,
d ppm): 145.35, 139.94, 137.02, 133.88, 128.81, 128.78, 127.18,
125.14, 123.29, 120.17, 115.87, 17.23. ESI-MS (C13H13NS): 216 [M
+ H]+.
3-Methyl-4-(3-(triuoromethyl)phenylthio)phenol (3y). Brown
2-Methyl-4-(4-nitrophenylthio)aniline (3ag). Yellow solid. Mp:
121–122 ꢀC. 1H NMR (500 MHz, CDCl3, d ppm): 8.03 (dd, J ¼ 2.0,
7.0 Hz, 2H, ArH), 7.26–7.21 (m, 2H, ArH), 7.09 (dd, J ¼ 2.0,
7.0 Hz, 2H, ArH), 6.74 (d, J ¼ 8.0 Hz, 1H, ArH) 3.89 (br s, 2H,
NH2), 2.18 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3, d ppm):
151.24, 146.61, 144.78, 137.88, 134.88, 125.23, 123.87, 123.70,
116.28, 115.87, 17.23. ESI-MS (C13H12N2O2S): 261 [M + H]+.
1
viscous liquid. H NMR (500 MHz, CDCl3, d ppm): 7.43 (d, J ¼
8.0 Hz, 1H, ArH), 7.33–7.26 (m, 3H, ArH), 7.12 (d, J ¼ 7.5 Hz, 1H,
ArH), 6.83 (d, J ¼ 2.5 Hz, 1H, ArH), 6.73 (dd, J ¼ 2.5, 8.0 Hz, 1H,
ArH), 5.11 (s, 1H, OH), 2.32 (s, 3H, CH3). 13C NMR (125 MHz,
CDCl3, d ppm): 156.96, 144.66, 140.46, 138.20, 131.70 (q),
129.27, 124.93, 122.84, 121.70, 121.73, 121.20, 118.05, 114.28,
20.85. EI-MS (C14H11F3OS): 284 [M], 285 [M + H]+.
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3-(Phenylthio)-1H-indole (5a). White solid. Mp: 150–151 ꢀC. 1H
RSC Advances
6-Methoxy-1-(4-nitrophenylthio)-1,2,3,4-tetrahydronaphthalen-
NMR (500 MHz, CDCl3, d ppm): 8.41 (br s, 1H, NH), 7.62 (d, J ¼ 1-ol (9a). Yellow solid. Mp: 191–192 ꢀC. 1H NMR (500 MHz,
8.0 Hz, 1H, ArH), 7.50 (d, J ¼ 2.5 Hz, 1H, ArH), 7.45 (d, J ¼ CDCl3, d ppm): 8.38–8.35 (m, 2H, ArH), 8.24–8.21 (m, 2H, ArH),
8.5 Hz, 1H, ArH), 7.29–7.26 (m, 1H, ArH), 7.18–7.03 (m, 6H, 7.90 (d, J ¼ 9.0 Hz, 1H, ArH), 7.47 (br s, 1H, OH), 6.78 (dd, J ¼
ArH). 13C NMR (125 MHz, CDCl3, d ppm): 139.22, 136.51, 2.5, 9.0 Hz, 1H, ArH), 6.60 (d, J ¼ 2.5 Hz, 1H, ArH), 3.80 (s, 3H,
130.64, 129.13, 128.69, 125.87, 124.77, 123.07, 120.92, 119.70, OCH3), 2.71 (t, J ¼ 6.0 Hz, 2H, CH2), 2.46 (t, J ¼ 6.5 Hz, 2H, CH2),
111.55, 102.95. EI-MS (C14H11NS): 226 [M + H]+.
1.92–1.87 (m, 2H, CH2). 13C NMR (125 MHz, CDCl3, d ppm):
3-(3-(Triuoromethyl)phenylthio)-1H-indole
(5b).
Brown 161.06, 154.29, 150.39, 144.10, 141.85, 129.51, 126.68, 124.13,
viscous liquid. 1H NMR (500 MHz, CDCl3, d ppm): 8.48 (br s, 1H, 123.88, 113.29, 112.67, 55.31, 29.71, 25.44, 21.41. EI-MS
NH), 7.63 (dd, J ¼ 1.0, 7.5 Hz, 1H, ArH), 7.54 (d, J ¼ 3.0 Hz, 1H, (C17H17N4OS): 331 [M], 332 [M + H]+.
ArH), 7.49 (s, 1H, ArH), 7.48 (s, 1H, ArH), 7.44 (s, 1H, ArH), 7.34–
4-(4-Nitrophenylthio)-2-phenylchroman-4-ol (9b). White solid.
7.31 (m, 2H, ArH), 7.28–7.21 (m, 2H, ArH). 13C NMR (125 MHz, Mp: 171–172 ꢀC. 1H NMR (500 MHz, CDCl3, d ppm): 8.36 (dd, J ¼
CDCl3, d ppm): 141.0, 136.56, 131.01, 129.06 (q), 123.34, 122.36, 2.0, 7.0 Hz, 2H, ArH), 8.20 (dd, J ¼ 2.0, 7.0 Hz, 2H, ArH), 7.89 (dd, J
122.33, 121.53, 121.50, 121.20, 119.41, 111.76, 101.59. EI-MS ¼ 1.5, 8.0 Hz, 1H, ArH), 7.63 (br s, 1H, OH), 7.43–7.30 (m, 6H,
(C15H10F3NS): 294 [M + H]+.
ArH), 7.02–6.94 (m, 2H, ArH), 5.10–5.07 (m, 1H, CH), 3.04–3.00 (m,
3-(4-Nitrophenylthio)-1H-indole (5c). Brown solid. Mp: 176– 1H, CH), 2.65.04–2.59 (m, 1H, CH). 13C NMR (125 MHz, CDCl3,
177 ꢀC. 1H NMR (500 MHz, CDCl3, d ppm): 8.63 (br s, 1H, NH), d ppm): 157.41, 150.50, 150.06, 143.68, 138.94, 132.46, 129.50,
8.01–7.98 (m, 2H, ArH), 7.55–7.49 (m, 3H, ArH), 7.33–7.26 (m, 128.90, 128.86, 126.04, 124.67, 124.23, 122.02, 118.79, 118.08,
1H, ArH), 7.21–7.11 (m, 3H, ArH). 13C NMR (125 MHz, CDCl3, 76.79, 32.50. ESI-MS (C21H17NO4S): 379 [M], 380 [M + H]+.
d ppm): 149.82, 144.93, 136.61, 131.21, 128.45, 125.11, 123.88,
123.58, 121.44, 119.23, 111.97, 100.23. EI-MS (C14H10N2O2S):
Acknowledgements
270 [M], 271 [M + H]+.
3-(p-Tolylthio)-1H-indole (5d). White solid. Mp: 123–124 ꢀC.
1H NMR (500 MHz, CDCl3, d ppm): 8.36 (br s, 1H, NH), 7.62 (d, J
¼ 8.0 Hz, 1H, ArH), 7.48 (d, J ¼ 2.5 Hz, 1H, ArH), 7.44 (d, J ¼
8.0 Hz, 1H, ArH), 7.27–7.24 (m, 1H, ArH), 7.17–7.14 (m, 1H,
ArH), 7.04 (dd, J ¼ 2.0, 7.0 Hz, 2H, ArH), 6.98 (d, J ¼ 8.0 Hz, 2H,
ArH), 2.25 (s, 3H, CH3). 13C NMR (125 MHz, CDCl3, d ppm):
136.48, 135.48, 134.65, 130.38, 129.48, 129.14, 126.29, 122.99,
120.84, 119.73, 111.51, 103.62, 20.86. EI-MS (C15H13NS): 239
[M], 240 [M + H]+.
The authors are thankful to the Department of Science and
Technology for DST-INSPIRE Faculty awards (IFA 14-CH-145)
and Director CSIR-CIMAP for providing necessary facilities.
Notes and references
1 (a) C. Shen, P. Zhang, Q. Sun, S. Bai, T. S. A. Hor and X. Liu,
Chem. Soc. Rev., 2015, 44, 291–314; (b) T. Mori, T. Nishimura,
T. Yamamoto, I. Doi, E. Miyazaki, I. Osaka and K. Takimiya,
J. Am. Chem. Soc., 2013, 135, 13900–13913; (c) M. Gingras,
Y. M. Chabre, M. Roy and R. Roy, Chem. Soc. Rev., 2013, 42,
4823–4841; (d) H. Liu and X. Jiang, Chem.–Asian J., 2013, 8,
2546–2563; (e) K. Takimiya, S. Shinamura, I. Osaka and
E. Miyazaki, Adv. Mater., 2011, 23, 4347–4370; (f)
T. Nakazawa, J. Xu, T. Nishikawa, T. Oda, A. Fujita,
K. Ukai, R. E. P. Mangindaan, H. Rotinsulu, H. Kobayashi
and M. Namikoshi, J. Nat. Prod., 2007, 70, 439–442; (g)
T. Oda, T. Fujiwara, H. Liu, K. Ukai, R. E. P. Mangindaan,
M. Mochizuki and M. Namikoshi, Mar. Drugs, 2006, 4, 15–
21; (h) A. Y. Sizov, A. N. Kovergin and A. F. Ermolov, Russ.
Chem. Rev., 2003, 72, 357–374; (i) I. P. Beletskaya and
V. P. Ananikov, Chem. Rev., 2011, 111, 1596–1636; (j)
T. Kondo and T.-A. Mitsudo, Chem. Rev., 2000, 100, 3205–
3220.
2 (a) J. Hassan, M. Sevignon, C. Gozzi, E. Schulz and
M. Lemaire, Chem. Rev., 2002, 102, 1359–1470; (b) S. V. Ley
and A. W. Thoma, Angew. Chem., Int. Ed., 2003, 42, 5400–
5449; (c) S.-R. Guo, Y.-Q. Yuan and J.-N. Xiang, Org. Lett.,
2013, 15, 4654–4657.
3 T. Kondo and T. Mitsudo, Chem. Rev., 2000, 100, 3205–3220.
4 (a) Y. Zhang, K. N. Ngeow and J. Y. Ying, Org. Lett., 2007, 9,
3495–3499; (b) A. Saxena, A. Kumar and S. Mozumdar,
Appl. Catal., A, 2007, 317, 210–217; (c) D. Alves, R. G. Lara,
M. E. Contreira, C. S. Radatz, L. F. B. Duarte and G. Perin,
Tetrahedron Lett., 2012, 53, 3364–3368; (d) V. P. Reddy,
1-(Phenylthio)naphthalen-2-ol (7a). White solid. Mp: 52–53 ꢀC.
1H NMR (500 MHz, CDCl3, d ppm): 8.24 (d, J ¼ 8.0 Hz, 1H, ArH),
7.93 (d, J ¼ 9.0 Hz, 1H, ArH), 7.83 (d, J ¼ 8.0 Hz, 1H, ArH), 7.52–
7.49 (m, 1H, ArH), 7.40–7.31 (m, 2H, ArH), 7.20–7.16 (m, 2H,
ArH), 7.13–7.10 (m, 1H, ArH), 7.05–7.03 (m, 2H, ArH). 13C NMR
(125 MHz, CDCl3, d ppm): 157.03, 135.47, 135.39, 132.86,
129.52, 129.21, 128.60, 127.98, 126.40, 125.92, 124.72, 123.89,
116.90, 108.07. EI-MS (C16H12OS): 252 [M], 253 [M + H]+.
1-(4-tert-Butylphenylthio)naphthalen-2-ol (7b). White solid.
1
ꢀ
Mp: 71–72 C. H NMR (500 MHz, CDCl3, d ppm): 8.28 (d, J ¼
8.0 Hz, 1H, ArH), 7.91 (d, J ¼ 9.0 Hz, 1H, ArH), 7.83 (d, J ¼
8.5 Hz, 1H, ArH), 7.52–7.49 (m, 1H, ArH), 7.39–7.34 (m, 2H,
ArH), 7.23–7.19 (m, 3H, ArH, OH), 7.00–6.97 (m, 2H, ArH), 1.24
(s, 9H, 3 ꢁ CH3). 13C NMR (125 MHz, CDCl3, d ppm): 156.92,
149.14, 135.57, 132.68, 131.81, 129.48, 128.55, 127.89, 127.78,
126.30, 126.28, 126.15, 124.84, 123.82, 116.85, 108.57, 34.39,
31.29, 31.23. EI-MS (C20H20OS): 308 [M], 309 [M + H]+.
1-(p-Tolylthio)naphthalen-2-ol (7c). White solid. Mp: 80–81 ꢀC.
1H NMR (500 MHz, CDCl3, d ppm): 8.24 (d, J ¼ 8.5 Hz, 1H, ArH),
7.90 (d, J ¼ 9.0 Hz, 1H, ArH), 7.82 (d, J ¼ 8.0 Hz, 1H, ArH), 7.51–
7.47 (m, 1H, ArH), 7.38–7.32 (m, 2H, ArH), 7.20 (br s, 1H, OH),
7.0–6.94 (m, 4H, ArH), 2.24 (s, 3H, CH3). 13C NMR (125 MHz,
CDCl3, d ppm): 156.88, 135.90, 135.45, 132.65, 131.75, 129.96,
129.49, 128.55, 127.89, 126.70, 124.75, 123.80, 116.84, 108.71,
20.89. EI-MS (C17H14OS): 266 [M], 267 [M + H]+.
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Paper
K. Swapna, A. V. Kumar and K. R. Rao, J. Org. Chem., 2009, 74, 14 (a) S. Chowdhury, R. S. Mohan and J. L. Scott, Tetrahedron,
3189–3191; (e) X. Chen, S.-S. Hao, C. E. Goodhue and J.-Q. Yu,
J. Am. Chem. Soc., 2006, 128, 6790–6791; (f) L.-H. Zou,
2007, 63, 2363–2389; (b) Q. Zhang, S. Zhang and Y. Deng,
Green Chem., 2011, 13, 2619–2637.
D. Priebbenow, L. Wang, J. Mottweiler and C. Bolm, Adv. 15 (a) W. Bao and Z. Wang, Green Chem., 2006, 8, 1028–1033; (b)
Synth. Catal., 2013, 355, 2558–2563; (g) F.-L. Yang, X.-T. Ma
and S.-K. Tian, Chem.–Eur. J., 2012, 18, 1582–1585; (h) Y. Li,
M. A. P. Martins, C. P. Frizzo, D. N. Moreira, N. Zanatta and
H. G. Bonacorso, Chem. Rev., 2008, 108, 2015–2050.
J. Pu and X. Jiang, Org. Lett., 2014, 16, 2692–2695; (i) 16 D. Zhao, M. Wu, Y. Kou and E. Min, Catal. Today, 2002, 74,
T.-T. Wang, F.-X. Wang, F.-L. Yang and S.-K. Tian, Chem. 157–189.
Commun., 2014, 50, 3802–3805; (j) S.-R. Guo, Y.-Q. Yuan 17 (a) J. Dupont, R. F. de Souza and P. A. Z. Suarez, Chem. Rev.,
and J.-N. Xiang, Org. Lett., 2013, 15, 4654–4657; (k) X. Yu,
X. Li and B. Wan, Org. Biomol. Chem., 2012, 10, 7429–7438.
2002, 102, 3667–3691; (b) D. S. Raghuvanshi and K. N. Singh,
Tetrahedron Lett., 2011, 52, 5702–5705.
5 (a) W. Wei, C. Liu, D. Yang, J. Wen, J. You, Y. Suo and 18 (a) K. Qiao and C. Yakoyama, Chem. Lett., 2004, 33, 472–473;
H. Wang, Chem. Commun., 2013, 49, 10239–10241; (b)
S. Zhang, P. Qian, M. Zhang, M. Hu and J. Cheng, J. Org.
(b) J. P. Hallett and T. Welton, Chem. Rev., 2011, 111, 3508–
3576.
ˆ
Chem., 2010, 75, 6732–6735; (c) X. Li, Y. Xu, W. Wu, 19 (a) V. I. Parvulescu and C. Hardacre, Chem. Rev., 2007, 107,
C. Jiang, C. Qi and H. Jiang, Chem.–Eur. J., 2014, 20, 7911–
7915.
2615–2665; (b) W. Sun, C.-G. Xia and H.-W. Wang,
Tetrahedron Lett., 2003, 44, 2409–2411.
6 (a) H. Tian, C. Zhu, H. Yang and H. Fu, Chem. Commun., 20 (a) A. Kamal and G. Chouhan, Tetrahedron Lett., 2005, 46,
2014, 50, 8875–8877; (b) C. Lin, D. Li, B. Wang, J. Yao and
Y. Zhang, Org. Lett., 2015, 17, 1328–1331; (c) C. Lin, W. Yu,
1489–1491; (b) M. J. Earle, S. P. Katdare and K. R. Seddon,
Org. Lett., 2004, 6, 707–710.
J. Yao, B. Wang, Z. Liu and Y. Zhang, Org. Lett., 2015, 17, 21 (a) N. Singh, R. Singh, D. S. Raghuvanshi and K. N. Singh,
1340–1343.
Org. Lett., 2013, 15, 5874–5877; (b) N. Singh, B. K. Allam,
D. S. Raghuvanshi and K. N. Singh, Adv. Synth. Catal.,
2013, 355, 1840–1848; (c) R. Singh, D. S. Raghuvanshi and
K. N. Singh, Org. Lett., 2013, 15, 4202–4205; (d) D. P. Singh,
D. S. Raghuvanshi, K. N. Singh and V. P. Singh, J. Mol.
Catal. A: Chem., 2013, 379, 21–29; (e) D. S. Raghuvanshi,
A. K. Gupta and K. N. Singh, Org. Lett., 2012, 14, 4326–4329.
7 (a) Y. Yang, W. Hou, L. Qin, J. Du, H. Feng, B. Zhou and Y. Li,
Chem.–Eur. J., 2014, 20, 416–420; (b) Z. Chen, B. Wang,
J. Zhang, W. Yu, Z. Liu and Y. Zhang, Org. Chem. Front.,
2015, 2, 1107–1295.
8 (a) B. Liu, J. Li, F. Song and J. You, Chem.–Eur. J., 2012, 18,
10830–10833; (b) S.-R. Guo, W.-M. He, J.-N. Xiang and
Y.-Q. Yuan, Chem. Commun., 2014, 50, 8578–8581; (c) 22 (a) F.-L. Yang, X.-T. Ma and S.-K. Tian, Chem.–Eur. J., 2012,
P. Saravanan and P. Anbarasan, Org. Lett., 2014, 16, 848–
851; (d) M. Iwasaki, M. Iyanaga, Y. Tsuchiya, Y. Nishimura,
W. Li, Z. Li and Y. Nishihara, Chem.–Eur. J., 2014, 20,
2459–2462.
18, 1582–1585; (b) B. Liu, J. Li, F. Song and J. You, Chem.–
Eur. J., 2012, 18, 10830–10833; (c) X. Yu, X. Li and B. Wan,
Org. Biomol. Chem., 2012, 10, 7479–7482; (d) O. Y. Yuen,
C. M. So, W. T. Wong and F. Y. Kwong, Synlett, 2012, 23,
2714–2718.
9 (a) F. Xiao, S. Chen, J. Tian, H. Huang, Y. Liu and G.-J. Deng,
Green Chem., 2016, 18, 1538–1546; (b) X. Kang, R. Yan, G. Yu, 23 (a) X. Li, X. Xu and C. Zhou, Chem. Commun., 2012, 48,
X. Pang, X. Liu, X. Li, L. Xiang and G. Huang, J. Org. Chem.,
2014, 79, 10605–10610.
12240–12242; (b) T. Taniguchi, A. Idota and H. Ishibashi,
Org. Biomol. Chem., 2011, 9, 3151–3153; (c) I. V. Ukrainets,
A. A. Tkach, V. V. Kravtsova and S. V. Shishkina, Chem.
Heterocycl. Compd., 2008, 44, 677–681; (d) S. Kamijo, M. Al-
Masum and Y. Yamamoto, Tetrahedron Lett., 1998, 39, 691–
695; (e) R. Ballini, E. Marcantoni and M. Petrin,
Tetrahedron, 1989, 45, 6791–6798.
10 (a) D. Wang, S. Guo, R. Zhang, S. Lin and Z. Yan, RSC Adv.,
2016, 6, 54377–54381; (b) A. Hajra, A. K. Bagdi, S. Mitra
and M. Ghosh, Org. Biomol. Chem., 2015, 13, 3314–3320.
11 Y. Xu, X. Tang, W. Hu, W. Wu and H. Jiang, Green Chem.,
2014, 16, 3720–3723.
12 (a) F.-L. Yang, F.-X. Wang, T.-T. Wang, Y.-J. Wang and 24 (a) D. J. Pasto and R. T. Taylor, Org. React., 1991, 40, 91–155;
S.-K. Tian, Chem. Commun., 2014, 50, 2111–2113; (b)
G. Kumaraswamy, R. Raju and V. Narayanarao, RSC Adv.,
2015, 5, 22718–22723.
(b) D. J. Pasto, in Comprehensive Organic Synthesis, ed. B. M.
Trost and I. Fleming, Pergamon Press, Oxford, 1991, vol. 8,
pp. 471–488.
13 (a) F. Xiao, H. Xie, S. Liu and G. Deng, Adv. Synth. Catal., 25 W. Ge, X. Zhu and Y. Wei, Adv. Synth. Catal., 2013, 355, 3014–
2014, 356, 364–368; (b) R.-Y. Tang, Y.-X. Xie, Y.-L. Xie,
J.-N. Xiang and J.-H. Li, Chem. Commun., 2011, 47, 12867–
12869.
3021.
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