KHSO4: A highly efficient and reusable heterogeneous catalyst for hydroarylation of styrenes

Article abstract of DOI:10.1007/s00706-010-0369-2

Hydroarylation of styrenes with arenes/heteroarenes using KHSO₄ (10 mol%) as an efficient heterogeneous catalyst is described. High conversion and selectivity (>99%) were observed for hydroarylation of styrenes with 2-naphthol at reflux temperature of 1,2-dichloroethane. Yields were quantitative with all styrenes. Moderate to good conversions and selectivities were achieved with other aromatics and heteroaromatics under the same conditions. Regeneration and reusability of KHSO₄ were demonstrated. Addition of a trace amount of water could help to reactivate the KHSO₄ through dispersion and to facilitate the hydroarylation reaction. Springer-Verlag 2010.

Full text of DOI:10.1007/s00706-010-0369-2

Monatsh Chem (2010) 141:1093–1099
DOI 10.1007/s00706-010-0369-2
ORIGINAL PAPER
KHSO4: a highly efficient and reusable heterogeneous catalyst
for hydroarylation of styrenes
•
Rajendra D. Patil Girdhar Joshi
•
Subbarayappa Adimurthy
Received: 15 December 2009 / Accepted: 3 August 2010 / Published online: 27 August 2010
Ó Springer-Verlag 2010
Abstract Hydroarylation of styrenes with arenes/hetero-
arenes using KHSO4 (10 mol%) as an efficient heterogen-
eous catalyst is described. High conversion and selectivity
([99%) were observed for hydroarylation of styrenes with
2-naphthol at reflux temperature of 1,2-dichloroethane.
Yields were quantitative with all styrenes. Moderate to
good conversions and selectivities were achieved with
other aromatics and heteroaromatics under the same con-
ditions. Regeneration and reusability of KHSO4 were
demonstrated. Addition of a trace amount of water could
help to reactivate the KHSO4 through dispersion and to
facilitate the hydroarylation reaction.
metal- and acid-catalyzed C–H transformations of arenes
and heteroarenes have been reported [1–6]. A number of
catalytic systems, including ruthenium [7–10], palladium
[11–17], platinum [18–20], nickel [21], and indium [22],
have been employed for functionalization of heterocycles
through carbon–carbon bond formation. Prominent sys-
tems, Bi(OTf)3 [23], BiCl3 [24], and FeCl3 [25] catalyzed
hydroarylation of styrenes were also reported for synthesis
of a variety of 1,1-diarylalkanes in good yields. Boronic
esters/acids with palladium complex [26], iodine [27], and
an ion-exchange resin [28] are recent developments in the
hydroarylation of alkenes. However, these methods require
use of stoichiometric or excess amounts of strong acids/
bases and air/moisture-sensitive organometallic reagents.
In most studies, the halide salts obtained as byproducts are
drawbacks of these reactions.
Keywords KHSO4 Á Heterogeneous catalysis Á
Hydroarylation Á Styrenes Á Aromatics
Introduction
Results and discussion
Functionalization of arenes and heteroarenes is of great
importance in synthesis of pharmaceuticals, and agro- and
fine chemicals; therefore, various procedures for their
acylation and alkylation have been reported. Transition-
metal-catalyzed hydroarylation of alkenes is of particular
importance due to its high selectivity, synthetic efficiency,
and environmental friendliness. Traditionally, these trans-
formations are performed by Friedel–Crafts reactions with
acyl or alkyl halides in combination with at least equimolar
quantities of a Lewis acid. Recently, promising transition-
In view of our ongoing quest for green and sustainable
processes for functionalization of alkenes [29–33] and
alkynes [34] for diverse applications, we envisioned a
metal-free catalyst system for hydroarylation of styrenes
with aromatic compounds in the presence of KHSO4
(10 mol%) as an efficient catalyst under mild conditions
(Scheme 1).
These reactions are particularly interesting from the
viewpoint of green chemistry because hydroarylation
exhibits perfect atom efficiency and relies on the use of
simple arene reactants and safe catalysts, no production of
toxic waste material, applicability of various substrates,
and heterogeneous catalysis, allowing facile catalyst/
product separation. Careful choice of inorganic acid, sol-
vent, and reaction conditions enabled us to develop a
R. D. Patil Á G. Joshi Á S. Adimurthy (&)
Analytical Science Discipline, Central Salt and Marine
Chemicals Research Institute (CSIR), G. B. Marg,
Bhavnagar 364002, India
e-mail: sadimurthy@yahoo.com
123

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R. D. Patil et al.
R
Table 1 Screening of various catalysts and solvents for hydroaryla-
tion of styrene with b-naphthol
OH
KHSO4 (10 mol%)
+
OH
DCE, Reflux
8 h
R
OH
OH
Cat (mol%)
55-96%
+
Solvent, Reflux
8 h
1
2
Scheme 1
3a
convenient protocol, which allows for efficient reaction of
various alkenes with various arene functionalities to give
the corresponding regioselectively alkylated product in a
number of cases.
Entry Cat. (mol%) Solvent
Conv. (%)a Yield (%)b Sel.c
1
KHSO4 (10) DCE
KHSO4 (12.5) DCE
KHSO4 (50) DCE
KHSO4 (100) DCE
KHSO4 (10) Neat
98
93
85
84
63
65
100
100
95
[99:1
[99:1
97:3
93:7
100
2
3
Initially, to determine the optimum reaction conditions,
the reaction of b-naphthol (1) with styrene (2) using a
catalytic amount of KHSO4 and in different solvent media
was investigated, and the reaction progress and yield
were monitored by gas chromatography (GC) (Table 1).
The reaction of equimolar amount of 1 with 2 in 5 cm3
1,2-dichloroethane at reflux for 8 h in presence of 10 mol%
KHSO4 resulted in complete conversion to 3 (Table 1,
entry 1). GC and GC-mass spectrometry (GC–MS) analy-
ses of the reaction mixture revealed 98% conversion of 1
to yield the arylated product 3 with more than 99%
selectivity. Use of excess amount of KHSO4 under the
same conditions resulted in less conversion and the for-
mation of undesired products (Table 1, entries 2–4). When
neat reaction was carried out, it indeed gave [99% selec-
tive product 3, but led to less conversion (Table 1, entry 5).
Use of 10 mol% KHSO4 showed the highest catalytic
activity and selectivity for hydroarylation of styrene with
b-naphthol (Table 1, entry 1). Switching to other solvents
led to lower conversion and yields under these conditions
(Table 1, entries 6–10). Various other catalysts were also
applied to the hydroarylation reaction, but showed lower
catalytic activity and lower yield of the desired product
(Table 1, entries 11–17) than that of KHSO4.
4
100
100
98
5
6
KHSO4(10)
DCM
94:6
99:1
–
7
KHSO4 (10) Cyclohexane 91
100
–
8
KHSO4 (10) CH3CN
KHSO4 (10) CH3OH
KHSO4 (10) THF
NaHSO4 (10) DCE
–
9
61
–
81
62:38
–
10
11
12
13
14
15
16
17
–
88
77
91
56
30
68
28
99
98:2
98:2
89:11
11:89
–
HCl (10)
HCl (10)
H2SO4 (10)
HNO3 (10)
PTS
DCE
Neat
DCE
DCE
DCE
Neat
95
100
97
78
99
1:99
31:69
PTS
84
Reaction conditions: 3.5 mmol of 1, 3.5 mmol of 2, cat, 5 cm3 sol-
vent/neat, reflux, 8 h
DCE 1,2-dichloroethane, DCM dichloromethane, PTS p-toluenesul-
fonic acid
a
GC conversions based on 1
b
GC yields of arylated products based on conversion
c
Selectivity determined by GC of 3a to others
The effect of temperature on the formation of 3 under
the conditions of Table 1 was also studied. This study
showed that, at room temperature and at 40 °C, there is no
conversion by GC analysis even when the reaction con-
tinued up to 15 h (Table 2, entries 1 and 2). However, at
60 °C, 9% conversion and 100% selectivity of the desired
product were observed (entry 3). At reflux temperature of
1,2-dichloroethane the best conversion and selectivity were
observed (entry 4). Therefore the rest of the experiments
were carried out under these optimized conditions.
arylated products in good to high yields with high
selectivity ([99:1) (Table 3, entries 1–3). However, hydro-
arylation reaction of b-naphthol with styrenes having elec-
tron-withdrawing substituents also offered high yields and
high selectivity (Table 3, entries 4 and 5), except with
4-acetoxystyrene (Table 3, entry 6) for which it gave product
3f with 93% selectivity, which may be due to the strong
electron-withdrawing property of the acetoxy group. All
products of Table 3 were formed with high selectivity
(except entry 6) of the desired product 3a–3f as determined
1
The scope of the KHSO4-catalyzed hydroarylation
reactions of various styrenes with b-naphthol was exam-
ined under the optimized conditions, and results are
indicated in Table 3. The hydroarylation reaction of vari-
ous styrenes having electron-donating substituents with
b-naphthol proceeded efficiently to give the corresponding
by H nuclear magnetic resonance (NMR) of the purified
products. Note that hydroarylation of various styrenes with
b-naphthol provided the desired product as major isomer with
all styrenes in excellent yields compared with the reported
procedures [33–35]. These facts indicate the efficiency,
selectivity, and catalytic activity of the present system.
123

KHSO4: a highly efficient and reusable heterogeneous catalyst
1095
Table 2 Effect of temperature on hydroarylation of styrene with
b-naphthol
98
100
80
60
40
20
0
85
83
82
OH
OH
KHSO4 (10 mol%)
+
DCE, Reflux
1
2
3a
Entry Temp. (°C) Time (h) Conv. (%)a Yield (%)b Sel.c
1
2
3
4
a
RT
15
15
15
8
0
0
–
–
40
–
–
60
9
9
100
[99:1
Fresh
1
2
3
Reflux
98
98
No of Cycles
GC conversions based on 1
Fig. 1 KHSO4 recyclability chart
b
GC yields of arylated products
c
Selectivity determined by GC of 3a to others
transformation. Although a small amount of water was
beneficial for recycling the catalyst (KHSO4), when the
reaction was tested without KHSO4, on the addition of a
drop of water no product was detected by GC–MS analysis.
This fact helps to rule out the contribution of H2O alone
to promote the hydroarylation reactions. In another set of
recycling of KHSO4, when D2O was added instead of H2O,
no deuterated product was detected, however the desired
hydroarylated product was obtained. We reasoned that a
trace amount of water could help to disperse the KHSO4 to
facilitate the hydroarylation reaction [35].
Table 3 Hydroarylation of different styrenes with b-naphthol
R
OH
OH
KHSO4 (10 mol%)
+
DCE, Reflux
8 h
R
1
2a-2f
3a-3f
Entry
R
Time Product Yield Selectivityb Referencec
(h)
(%)a
As can be evidenced from the scanning electron
microscope (SEM) images (Fig. 2) of fresh and recovered
KHSO4, the fresh KHSO4 is surrounded by a number of
H2O molecules, which is not the case for the recovered
KHSO4. The surrounding water molecules help the dis-
persion of the catalyst, and thus activate the hydroarylation
reaction.
1
2
3
4
5
6
–H
8.0
7.0
6.0
5.0
8.0
3a
3b
3c
3d
3e
3f
96
93
88
93
94
73
[99:1
99:1
99:1
98:2
96:4
93:7
–CH3
–t-Bu
–Br
[28]
–Cl
–OCOCH3 8.0
Reaction conditions: 3.5 mmol of 1, 3.5 mmol of 2a–2f, 5 cm3 DCE
a
As evident from the recyclability chart of KHSO4
(Fig. 1), the catalyst could be easily recovered and reused
for up to three consecutive cycles with good conver-
sions. Therefore a reaction mechanism for electrophilic
substitution of styrenes with 2-naphthol is proposed in
Scheme 2.
Isolated yields
1
Determined by H NMR of desired product to other isomer
b
c
Identity confirmed by comparison of spectroscopic data
To assess the reusability of KHSO4, after completion of
To explore the scope and limitations of the present cat-
alytic procedure, representative examples of functionalized
aromatic and heteroaromatic compounds were treated with
styrene and substituted styrenes, and the results are sum-
marized in Table 4.
the reaction, the KHSO4 was retrieved from the reaction
mixture by simple filtration, dried, and recycled under
the same experimental conditions, but GC analysis showed
no formation of hydroarylated product. Furthermore, to
corroborate the reusability of the catalyst, another reaction
was carried out by the addition of a trace amount of water
(through a syringe) to the recovered catalyst under the
same conditions; GC analysis showed 85% conversion with
97% selectivity of the desired product (Fig. 1). This sug-
gests that the hydrated form of the catalyst is active for this
As shown in Table 4, various substituted styrenes
reacted smoothly with a-naphthol to give corresponding
hydroarylated products in 48–72% isolated yields with
90–98% selectivity (Table 4, entries 1–3). The reaction of
phenol with t-butylstyrene (Table 4, entry 4) and styrene
(Table 4, entry 5) gave moderate yields (43% and 42%) of
123

1096
R. D. Patil et al.
Fig. 2 Scanning electron
microscope (SEM) images
of KHSO4 catalyst
conversion under the conditions studied. The present cata-
lytic system has remarkable advantages such as: good
activity and selectivity in a number of cases, no need to
maintain dry or inert atmospheric conditions, ready avail-
ability, low cost, and recoverable and reusable catalyst, and
importantly, it does not generate any toxic waste. This
simple procedure offers a very attractive alternative for
synthesis of motifs that are found in various bioactive
molecules.
K2SO4 + HSO4- + H+
2 KHSO4
+
H+
O-H
R
R
OH
OH
H
-H+
Experimental
All products from Table 1 were analyzed by GC–MS using
a Shimadzu GCMS-QP2010. Gas chromatograms of com-
pounds listed in Table 1 were recorded on a Thermo Trace
R
R
Scheme 2
1
GC Ultra using HP-5 column. H and 13C NMR spectra
were recorded on a spectrometer operating at 500 and
125 MHz, respectively, in CDCl3 unless otherwise stated.
Chemical shifts are reported in ppm relative to the appro-
priate standard tetramethylsilane (TMS). Fourier-transform
infrared (FT-IR) spectra were recorded on a Perkin Elmer
GX-2000 spectrometer. Mass spectra were recorded on a
micromass Q-Tof microTM in ES? mode. Analytical thin-
layer chromatography (TLC) was performed on Aluchro-
sep Silica Gel 60/UV254 plates. Purification of compounds
(Tables 3, 4) was carried out by column chromatography
using 100–200 mesh silica gel. All reactions were carried
out in air without any special precautions. Unless otherwise
stated, all reactions were carried out in an oil bath with
magnetic stirring, and yield refers to isolated yields in
Tables 3 and 4. Scanning electron microscope (SEM, LEO
1430 UP model) was used to observe the morphology of
KHSO4 before and after reaction.
hydroarylated product with high selectivity ([99:1) in the
former case. The same trend is observed in the reaction of
p-cresol with methylstyrene and t-butylstyrene (Table 4,
entries 6 and 7), but with good yields. The relatively low
yield of thiophene with styrene is due its lower reactivity
compared with naphthols and phenols under the present
conditions (Table 4, entry 8). However, the reaction of 2-
methythiophene with t-butylstyrene gave the corresponding
hydroarylated product in good yield with high selectivity
(Table 4, entry 9).
Conclusions
Herein we describe a general, mild, and efficient method for
hydroarylation of styrenes with various aromatics and het-
eroaromatics using KHSO4 (10 mol%) as a highly efficient
and selective heterogeneous catalyst. Styrenes with elec-
tron-donating substituents showed higher selectivity for the
hydroarylation reaction than those with electron-withdraw-
ing substituents. KHSO4 could be recovered and reused up
to a minimum of three consecutive cycles with good
General procedure for hydroarylation of styrenes
All reactions were carried out in air without any special
precautions. To a stirred solution of 1 or 4 (3.5 mmol) and
substituted styrene (3.5 mmol) in 5 cm3 1,2-dichloroethane
123

KHSO4: a highly efficient and reusable heterogeneous catalyst
1097
Table 4 Hydroarylation of styrenes with arenes and heteroarenes
R
KHSO4 (10 mol%)
Ar(Hetero)H +
R
DCE, Reflux
8-24 h
Ar(Hetero)
4a-4e
2a-2e
5a-5i
4a = 1-Naphthol
4b = Phenol
4c = 4-Me-phenol
4d = Thiophene
4e = 2-Me-thiophene
2a R = H
5a Ar = 1-HO-2-naphthyl, R = H 5f Ar = 2-HO-5-Me-phenyl, R = CH3
5b Ar = 1-HO-2-naphthyl, R = Cl 5g Ar = 2-HO-5-Me-phenyl, R = t-Bu
5c Ar = 1-HO-2-naphthyl, R = Br 5h Ar = 2-Thienyl, R = CH3
5d Ar = 2-HO-phenyl, R = t-Bu
5e Ar = 2-HO-phenyl, R = H
2b R = CH3
2c R = t-Bu
2d R = Br
2e R = Cl
5i Ar = 5-Me-2-thienyl, R = t-Bu
Entry
4
2
Time (h)
5
Yield (%)a
Selectivityb
Referencec
[28]
1
2
3
4
5
6
7
8
9
4a
4a
4a
4b
4b
4c
4c
4d
4e
2a
2e
2d
2c
2a
2b
2c
2b
2c
8
12
24
14
15
10
10
15
14
5a
5b
5c
5d
5e
5f
72
67
48
43
42
72
73
33
53
91:9
90:10
98:2
[99:1
77:23
68:32
70:30
73:27
[99:1
[27]
[27]
5g
5h
5i
Reaction conditions: 3.5 mmol of 4a–4e, 3.5 mmol of 2a–2e, 10 mol% KHSO4, 5 cm3 DCE, 80 °C, 8 h
a
Isolated yield
Determined by 1H NMR of purified main product to other isomer
b
c
Identity confirmed by comparison of spectroscopic data
1-[1-(4-tert-Butylphenyl)ethyl]-2-naphthol
(3c, C22H24O)
(DCE), 47.0 mg commercially available KHSO4 (10 mol%)
was added. The mixture was allowed to reflux at 80 °C for
8 h. The progress of the reaction was monitored by TLC.
The reaction mixture was cooled to room temperature
and filtered to remove KHSO4. The KHSO4 was washed
with 5 cm3 DCE, and the filtrate was concentrated in vacuo.
The residue was subjected to column chromatography on
silica gel (hexane–ethyl acetate) to obtain pure hydroary-
lated products.
Reddish-brown viscous liquid. 1H NMR (500 MHz,
CDCl3): d = 1.21 (s, 9H), 1.67 (d, J = 7.0 Hz, 3H), 4.88
(s, 1H), 5.03 (q, J = 7.0 Hz, 1H), 6.90 (d, J = 8.5 Hz,
1H), 7.25 (m, 5H), 7.38 (t, J = 8.0 Hz, 1H), 7.57 (d,
J = 8.5 Hz, 1H), 7.70 (d, J = 8.0 Hz 1H), 7.98 (d,
J = 5.0 Hz, 1H) ppm; 13C NMR (125 MHz, CDCl3):
d = 17.2, 31.3, 34.5, 119.5, 122.5, 123.1, 123.8, 126.1,
126.6, 126.9, 128.7, 128.9, 129.7, 132.9, 140.1, 149.9,
151.7 ppm; IR (neat): m = 3,452, 3,056, 2,959, 2,872,
1,664, 1,602, 1,511, 1,463, 1,393, 1,366, 1,261, 1,206,
1,148, 1,019, 932, 813, 749, 687, 559, 429 cm-1; GC–MS:
m/z (%) = 304 (100) [M?], 289 (95), 247 (40), 233 (30),
215 (25), 170 (60), 161 (15), 144 (27), 130 (15), 123 (38),
103 (18), 91 (12), 77 (8), 65 (3); LRMS: calcd 304.18,
found 304.28.
1-(1-Phenylethyl)-2-naphthol (3a, C18H16O)
Brown viscous liquid. 1H NMR (500 MHz, CDCl3):
d = 1.91 (s, 3H), 5.23 (s, 1H), 5.31 (q, J = 7.0 Hz, 1H),
7.1 (d, J = 9.0 Hz, 1H), 7.35 (t, J = 7.5 Hz, 1H), 7.44
(q, J = 8.0 Hz, 3H), 7.51 (d, J = 7.51 Hz, 2H), 7.56
(t, J = 8.0 Hz, 1H), 7.77 (d, J = 8.5 Hz, 1H), 7.91 (d,
J = 8.0 Hz, 1H), 8.14 (d, J = 9.0 Hz, 1H) ppm; 13C NMR
(125 MHz, CDCl3): d = 18.9, 36.5, 121.0, 124.6, 124.8,
125.6, 128.3, 128.4, 128.9, 130.4, 130.6, 130.7, 131.5,
134.6, 145.6, 153.2 ppm; IR (neat): m = 3,499, 3,059,
3,026, 2,969, 2,934, 2,876, 1,661, 1,623, 1,601, 1,512,
1,448, 1,374, 1,260, 1,210, 1,147, 1,075, 1,025, 933, 855,
813, 751, 701, 587, 529, 504, 450 cm-1; GC–MS:
m/z (%) = 248 (100) [M?], 233 (92), 215 (72), 203 (20),
189 (10), 115 (28), 77 (18), 63 (7); LRMS: calcd 248.12,
found 248.15.
1-[1-(4-Bromophenyl)ethyl]-2-naphthol
(3d, C18H15BrO)
1
Dark-brown viscous liquid. H NMR (500 MHz, CDCl3):
d = 1.68 (d, J = 7.0 Hz, 3H), 4.85 (s, 1H), 5.07 (q,
J = 7.0 Hz, 1H), 6.88 (d, J = 8.5 Hz, 1H), 7.13 (t, J = 7.0
Hz, 1H), 7.22 (q, J = 7.5 Hz, 3H), 7.27 (d, J = 7.5 Hz, 2H),
7.34 (t, J = 8.0 Hz, 1H), 7.55 (d, J = 8.5 Hz, 1H), 7.68 (d,
J = 8.0 Hz 1H), 7.92 (d, J = 8.5 Hz, 1H) ppm; 13C NMR
123

1098
R. D. Patil et al.
(125 MHz, CDCl3): d = 17.2, 34.9, 119.4, 122.7, 123.1,
123.9, 126.6, 126.8, 127.2, 128.7, 128.9, 129.1, 129.7,
132.9, 143.8, 151.5 ppm; IR (neat): m = 3,397, 3,028, 2,998,
2,922, 2,837, 1,610, 1,510, 1,457, 1,369, 1,298, 1,246,
1,176, 1,109, 1,034, 827, 742, 688, 547, 419 cm-1; GC–MS:
m/z (%) = 326 (56) [M?], 311 (52), 293 (3), 231 (55), 215
(12.5), 202 (25), 170 (100), 141 (15), 128 (2.5), 116 (27),
101 (35), 89 (12.5), 77 (13); LRMS: calcd for C18H15BrO
[K?] 364.99, found 364.33.
125.2, 125.6, 125.7, 125.9, 127.8, 128.9, 132.4, 133.5,
143.7, 148.1 ppm; IR (neat): m = 3,538, 3,059, 2,970,
2,932, 2,875, 1,659, 1,576, 1,490, 1,389, 1,262, 1,198,
1,090, 1,055, 1,016, 895, 820, 784, 749, 566, 542 cm-1
;
GC–MS: m/z (%) = 282 (86) [M?], 267 (90), 249 (10),
231 (32), 215 (8), 202 (28), 170 (100), 141 (23), 115 (25),
101 (33), 89 (10), 77 (15); LRMS: calcd 282.08, found
282.85.
2-[1-(4-Bromophenyl)ethyl]-1-naphthol
(5c, C18H15BrO)
1
Dark-brown viscous liquid. H NMR (500 MHz, CDCl3):
1-[1-(4-Chlorophenyl)ethyl]-2-naphthol
(3e, C18H15ClO)
1
Dark-brown viscous liquid. H NMR (500 MHz, CDCl3):
d = 1.6 (d, J = 7.5 Hz, 1H), 4.4 (q, J = 7 Hz, 1H), 5.1 (s,
1H), 7.1 (d, J = 8.0 Hz, 2H), 7.3 (d, J = 8.5 Hz, 1H), 7.3
(d, J = 8.5 Hz, 2H), 7.4 (m, 2H), 7.7 (m, 1H), 8.0 (t,
J = 9.5 Hz, 1H) ppm; 13C NMR (125 MHz, CDCl3):
d = 21.0, 38.4, 120.6, 120.9, 121.0, 124.9, 125.1, 125.71,
125.75, 126.0, 127.9, 129.4, 132.0, 133.5, 144.2,
148.1 ppm; IR (neat): m = 3,504, 3,059, 2,969, 2,871,
1,657, 1,573, 1,491, 1,352, 1,150, 1,016, 811, 786, 618,
450, 422 cm-1; GC–MS: m/z (%) = 326 (55) [M?], 311
(53), 293 (3), 231 (55), 215 (13), 202 (25), 170 (100), 141
(15), 128 (3), 116 (28), 101 (35), 89 (13), 77 (13); LRMS:
calcd 326.03, found 326.75.
d = 1.69 (d, J = 7.0 Hz, 3H), 4.86 (s, 1H), 5.03 (q,
J = 7.5 Hz, 1H), 6.90 (d, J = 9.0 Hz, 1H), 7.17 (m, 4H),
7.23 (t, J = 7.5 Hz, 1H) 7.32 (t, J = 7.5 Hz, 1H), 7.57 (d,
J = 8.5 Hz, 1H), 7.69 (d, J = 8.0 Hz, 1H), 7.84 (d,
J = 8.0 Hz, 1H) ppm; 13C NMR (125 MHz, CDCl3):
d = 17.4, 34.3, 119.0, 123.0, 123.2, 123.4, 126.6, 128.5,
128.82, 128.88, 128.9, 129.8, 132.1, 132.7, 142.8,
151.2 ppm; IR (neat): m = 3,487, 3,058, 2,962, 2,873,
1,622, 1,511, 1,462, 1,395, 1,365, 1,260, 1,205, 1,149,
1,018, 932, 812, 745, 689, 592, 468 cm-1; GC–MS:
m/z (%) = 282 (98) [M?], 267 (100), 249 (18), 231 (47),
215 (15), 170 (19), 139 (20), 116 (27), 101 (35), 88 (12), 77
(13), 63 (7); LRMS: calcd for C18H15ClO [Na?] 305.07,
found 305.20.
2-[1-(4-tert-Butylphenyl)ethyl]phenol (5d, C18H22O)
1
Dark-brown viscous liquid. H NMR (500 MHz, CDCl3):
d = 1.3 (s, 9H), 1.4 (d, J = 7 Hz, 2H), 3.6 (t, J = 6.5 Hz,
1H), 6.3 (m, 1H), 6.4 (d, J = 15.5 Hz, 2H), 7.2 (m, 2H),
7.3 (m, 3H) ppm; 13C NMR (125 MHz, CDCl3): d = 22.8,
32.9, 43.6, 126.9, 127.0, 127.4, 128.5, 129.6, 136.3, 136.5,
144.3, 151.6 ppm; IR (neat): m = 3,413, 3,059, 3,019,
2,958, 2,869, 1,583, 1,511, 1,474, 1,447, 1,364, 1,270,
4-[1-(2-Hydroxy-1-naphthyl)ethyl]phenyl acetate
(3f, C20H18O3)
1
Dark-brown viscous liquid. H NMR (500 MHz, CDCl3):
d = 1.77 (d, J = 7.0 Hz, 3H), 2.25 (s, 3H), 5.12 (q,
J = 7.5 Hz, 1H), 5.20 (s, 1H), 6.95 (d, J = 9.0 Hz, 1H),
7.0 (d, J = 8.5 Hz, 2H), 7.31 (m, 3H), 7.40 (t, J = 7.0 Hz,
1H), 7.62 (d, J = 8.5 Hz, 1H), 7.76 (d, J = 8.0 Hz, 1H),
7.96 (d, J = 8.0 Hz, 1H) ppm; 13C NMR (125 MHz,
CDCl3): d = 17.5, 21.1, 34.3, 119.1, 121.7, 123.0, 123.6,
126.5, 128.2, 128.7, 128.8, 129.7, 132.8, 141.9, 149.0,
151.4, 169.9 ppm; IR (neat): m = 3,434, 3,057, 2,966,
2,930, 1,739, 1,666, 1,625, 1,506, 1,436, 1,369, 1,199,
1,201, 1,098, 1,022, 820, 739, 693, 563, 479 cm-1
;
GC–MS: m/z (%) = 254 (38) [M?], 239 (100), 223 (8),
197 (25), 181 (8), 165 (5), 121 (20), 98 (25), 91 (13), 77
(8); LRMS: calcd for C18H22O [–1] 253.17, found 252.83.
4-Methyl-2-[1-(4-methylphenyl)ethyl]phenol
(5f, C16H18O)
Colorless viscous liquid. 1H NMR (500 MHz, CDCl3):
d = 1.58 (d, J = 7.0 Hz, 3H), 2.27 (s, 3H), 2.29 (s, 3H),
4.27 (q, J = 7.0 Hz, 1H), 4.61 (s, 1H), 6.61 (d, J = 8.0 Hz,
1H), 6.88 (d, J = 8.0 Hz, 1H), 7.02 (s, 1H), 7.08 (d,
J = 8.0 Hz, 2H), 7.13 (d, J = 8.0 Hz, 2H) ppm; 13C NMR
(125 MHz, CDCl3): d = 20.9, 21.1, 21.2, 38.5, 116.0,
127.5, 127.9, 128.6, 129.5, 130.0, 131.9, 136.1, 142.4,
151.2 ppm; IR (neat): m = 3,502, 3,433, 3,021, 2,968,
2,926, 2,870, 1,611, 1,503, 1,457, 1,372, 1,328, 1,257,
1,167, 1,017, 913, 848, 814, 744, 522, 463, 422 cm-1
;
GC–MS: m/z (%) = 306 (5) [M?], 264 (100), 249 (89), 231
(52), 171 (85), 115 (48), 101 (29), 94 (13), 77 (18), 65 (12);
LRMS: calcd for C20H18O3 [Na?] 329.12, found 329.13.
2-[1-(4-Chlorophenyl)ethyl]-1-naphthol
(5b, C18H15ClO)
1
Dark-brown viscous liquid. H NMR (500 MHz, CDCl3):
d = 1.6 (d, J = 7.0 Hz, 3H), 4.0 (q, J = 7.0 Hz, 1H), 5.1
(s, 1H), 7.1 (d, J = 8.5 Hz, 2H), 7.2 (d, J = 8.0 Hz, 2H),
7.3 (d, J = 8.0 Hz, 2H), 7.4 (t, J = 4.5 Hz, 2H), 7.7 (t,
J = 5.5 Hz, 2H), 8.0 (d, J = 8.5 Hz, 2H) ppm; 13C NMR
(125 MHz, CDCl3): d = 21.0, 38.2, 120.8, 121.0, 124.9,
1,190, 1,117, 1,047, 815, 781, 730, 511, 469, 419 cm-1
;
GC–MS: m/z (%) = 226 (65) [M?], 211 (100), 196 (18),
134 (50), 105 (8), 91 (18), 77 (12), 65 (7); LRMS: calcd
226.14, found 226.24.
123

KHSO4: a highly efficient and reusable heterogeneous catalyst
1099
4. Sezen B, Sames D (2003) J Am Chem Soc 125:5274
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gew Chem Int Ed 44:3125
2-[1-(4-tert-Butylphenyl)ethyl]-4-methylphenol
(5g, C19H24O)
Colorless viscous liquid. 1H NMR (500 MHz, CDCl3):
d = 1.28 (s, 9H), 1.60 (d, J = 7.0 Hz, 3H), 2.28 (s, 3H),
4.28 (q, J = 6.5 Hz, 1H), 4.56 (s, 1H), 6.64 (d, J = 7.5 Hz,
1H), 6.90 (d, J = 8.0 Hz, 1H), 7.04 (s, 1H), 7.17 (d,
J = 8.0 Hz, 2H), 7.30 (d, J = 8.0 Hz, 2H) ppm; 13C NMR
(125 MHz, CDCl3): d = 22.4, 22.6, 33.0, 36.0, 40.0,
127.2, 128.7, 129.4, 130.1, 131.5, 133.4, 143.6, 150.8,
152.7 ppm; IR (neat): m = 3,438, 2,963, 2,927, 1,632,
1,507, 1,383, 1,264, 1,114, 1,020, 669, 620, 421 cm-1
;
GC–MS: m/z (%) = 268 (42) [M?], 253 (100), 211 (15),
197 (14), 134 (9), 105, 91 (15), 77 (11), 65 (8); LRMS:
calcd 268.18, found 268.24.
13. Kimura M, Futamata M, Mukai R, Tamaru Y (2005) J Am Chem
Soc 127:4592
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2-[1-(4-tert-Butylphenyl)ethyl]-5-methylthiophene
(5i, C17H22S)
Colorless viscous liquid. 1H NMR (500 MHz, CDCl3):
d = 1.2 (s, 9H), 1.5 (d, J = 7.0 Hz, 3H), 2.3 (s, 3H), 4.1
(q, J = 7 Hz, 1H), 6.5 (d, J = 3 Hz, 1H), 7.1 (d, J = 8 Hz,
2H), 7.2 (d, J = 8 Hz, 2H) ppm; 13C NMR (125 MHz,
CDCl3): d = 15.3, 23.2, 31.3, 31.4, 40.4, 42.0, 123.1,
124.4, 125.3, 125.8, 126.8, 126.9, 128.0, 134.7, 137.8,
143.1 ppm; IR (neat): m = 3,055, 3,024, 2,964, 2,870,
1,656, 1,511, 1,456, 1,405, 1,365, 1,266, 1,109, 1,018, 831,
800, 671, 572, 463, 419 cm-1; GC–MS: m/z (%) = 258
(48) [M?], 243 (100), 228 (18), 213 (13), 201 (8), 187 (3),
152 (3), 125 (8), 100 (25), 91 (5), 77 (3); LRMS: calcd for
C17H22S [-1] 257.14, found 256.91.
Acknowledgments We thank DST, New Delhi, India for the financial
support of this project under the Green Chemistry Task Force Scheme
(no. SR/S5/GC-02A/2006). We would like to acknowledge Mr. Hitesh,
Mr.V. K. Aggrawal, Mr. Harshad/Miss. Daksha, Mr. A. K. Das and Mr.
Jayesh of this institute for their help inanalyzing NMR, IR, GC/GC-MS,
LC-MS and SEM, respectively. R. D. Patil and G. Joshi are thankful to
CSIR, New Delhi, India for the award of their Senior Research
Fellowships.
28. Das B, Krishnaiah M, Laxminarayana K, Damodar K, Kumar DN
(2009) Chem Lett 38:42
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Lett 50:2529
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