Amberlyst-15 in ionic liquid: An efficient and recyclable reagent for nucleophilic substitution of alcohols and hydroamination of alkenes

Article abstract of DOI:10.1002/ejoc.201000456

The nucleophilic substitution reaction of secondary alcohols and hydroamination of alkenes with amides, sulfonamides, carbamates, and amines using Amberlyst-15 immobilized in [Bmim][BF₄] (1-butyl-3- methylimidazolium tetrafluoroborate) ionic liquid as an efficient recyclable reagent is described. The solvent effect is prominent in the reaction, and the desired substitution products are obtained in good to excellent yield. The protocol is advantageous due to the ease of handling of the reagents, the simple work-up procedure, and the environmentally benign conditions that allow effective recyclability. A facile protocol involving Amberlyst-15 in the ionic liquid [Bmim][BF₄] (= 1-butyl-3-methylimidazolium tetrafluoroborate) has been developed for nucleophilic substitution of alcohols and hydroamination of alkenes.

Full text of DOI:10.1002/ejoc.201000456

FULL PAPER
DOI: 10.1002/ejoc.201000456
Amberlyst-15 in Ionic Liquid: An Efficient and Recyclable Reagent for
Nucleophilic Substitution of Alcohols and Hydroamination of Alkenes
Ziyauddin S. Qureshi,[a] Krishna M. Deshmukh,[a] Pawan J. Tambade,[a] Kishor P. Dhake,[a]
and Bhalchandra M. Bhanage*[a]
Keywords: Hydroamination / Heterogeneous catalysis / Ionic liquids / Nucleophilic substitution / Amidation
The nucleophilic substitution reaction of secondary alcohols
and hydroamination of alkenes with amides, sulfonamides,
carbamates, and amines using Amberlyst-15 immobilized in
[Bmim][BF4] (1-butyl-3-methylimidazolium tetrafluorobor-
ate) ionic liquid as an efficient recyclable reagent is de-
scribed. The solvent effect is prominent in the reaction, and
the desired substitution products are obtained in good to ex-
cellent yield. The protocol is advantageous due to the ease
of handling of the reagents, the simple work-up procedure,
and the environmentally benign conditions that allow effec-
tive recyclability.
for the direct substitution of alcohols and hydroamination
of alkenes with various nucleophiles by using Amberlyst-15
immobilized in ionic liquid.[6]
Introduction
Carbon–nitrogen bond-forming reactions are one of the
most important types of reactions in organic chemistry.[1]
Usually, amines are prepared either by amination of halides
or by reduction of compounds such as nitriles, oximes, or
amides. Hydroamination of alkenes is one of the most ef-
ficient approaches to the synthesis of higher substituted
amines and their derivatives. Amination of alcohols results
in the formation of very important intermediates that are
relevant to the synthesis of various pharmaceuticals and
fine chemicals.[2] Substitution of the hydroxyl group in
alcohols by a nucleophile generally necessitates preacti-
vation of the hydroxyl group, because of its poor leaving
ability. This can be achieved by using high temperature or
by adding suitable promoters. Because the latter approach
leads to the formation stoichiometric amounts of salt waste,
the development of an efficient, more atom-economic and
environmentally viable method for the direct substitution of
alcohols with a nitrogen nucleophile is highly desirable.
Several transition-metal-complex catalysts based on pal-
ladium and ruthenium have been developed for the direct
substitution of alcohols with various nitrogen nucleophiles,
such as amides, sulfonamides, carboxamides, carbamates,
and amines,[3] and, recently, various Lewis and Brønsted
The importance of green reactions in organic synthesis
has led us to explore the use of ionic liquids as novel sol-
vents, catalysts, reagents, and also in separation processes.[7]
Features that make ionic liquids attractive include their lack
of vapor pressure, nonvolatility, nonflammability and their
wide liquid-state temperature range. Besides the possibility
of recycling the catalytic system, interest in using ionic li-
quids comes from the unique interactions of these media
with the active species and from the possibility of modifying
the reaction activity and selectivity.[8] This prompted us to
initiate a systematic exploration of the amination reaction
of alcohols and alkenes.
In a continuation of our work on the application of ionic
liquids in several organic transformations,[6,9] we report
herein a simple, facile, and highly efficient protocol for
nucleophilic substitution of alcohols, and hydroamination
of alkenes by Amberlyst-15 in the ionic liquid [Bmim][BF4]
(= 1-butyl-3-methylimidazolium tetrafluoroborate); see
Scheme 1. The reagent, Amberlyst-15, and solvent,
acid
catalysts
(NaAuCl4,[4a]
H-Montmorillonite,[4b]
MoCl5,[4c] FeCl3,[4d] Cu(OAc)2,[4e] triflate salts,[4f–4i] hetero-
poly acid,[4j] and Brønsted acid[4k]) have been employed for
the amidation of alcohols. In contrast, hydroaminations are
generally catalyzed by transition and alkali metals.[5] Re-
cently, we reported a very efficient and economical method
[a] Department of Chemistry, Institute of Chemical Technology,
N. Parekh Marg, Matunga, Mumbai 400019, India
Fax: +91-22-24145614
Scheme 1. Nucleophilic substitution of alcohols and hydroamin-
ation of alkenes.
E-mail: bhalchandra_bhanage@yahoo.com
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[Bmim][BF4], are both air-stable and the system is appli- Table 2. Substitution of alcohols with nitrogen-containing nucleo-
philes.[a]
cable to a wide range of substrates.
Results and Discussion
Initial studies were conducted using Amberlyst-15 as the
choice of reagent for the nucleophilic substitution reaction
of benzamide (2) with benzhydrol (1) as a prototype reac-
tion. Various reaction conditions for this transformation
were investigated, and the results obtained are summarized
in Table 1. Initially, screening of different solvents showed
that the ionic liquid [Bmim][BF4] was superior to organic
solvents and to other ionic liquids (Table 1, entries 1–7). By
varying the reaction temperature from room temperature to
100 °C, a gradual improvement in yield was observed
(Table 1, entries 2 and 8–10). However, prolonging the reac-
tion time did not offer any significant advantage (Table 1,
entry 11). Several solid acid reagents were also screened
(Table 1, entries 2 and 12–15), among which, Amberlyst-15
was found to be the most effective reagent under the present
reaction conditions. Amberlyst-15 is a sulfonic acid type
styrene/divinylbenzene copolymer, and the probable reason
for its higher activity can be explained on the basis of its
physical properties, such as H+ capacity (4.2 meq/g) and
high surface area (42 m2/g). Furthermore, it was observed
that lowering the Amberlyst-15 concentration decreased the
yield of the substituted product (Table 1, entry 16). Hence,
the optimum reaction conditions for the transformation of
1 and 2 into 3 is the use of Amberlyst-15 (0.75 g) as reagent
with solvent [Bmim][BF4] at 80 °C for 2 h.
Table 1. Reaction parameters for the addition of benzamide (2) to
benzhydrol (1).[a]
Entry Reagent
Solvent
Temp. [°C] Yield [%][b]
1
2
3
4
5
6
7
8
9
10
Amberlyst-15
[Bmim][PF6]
[Bmim][BF4]
[Omim][BF4]
[Bmim][Cl]
1,4-dioxane
toluene
80
80
80
80
80
80
80
r.t.
60
100
80
80
80
80
80
80
76
88
55
n.r.
39
59
n.r.
n.r.
62
90
90
n.r.
80
trace
n.r.
65
Amberlyst-15
Amberlyst-15
Amberlyst-15
Amberlyst-15
Amberlyst-15
Amberlyst-15
Amberlyst-15
Amberlyst-15
Amberlyst-15
CH3CN
[Bmim][BF4]
[Bmim][BF4]
[Bmim][BF4]
[Bmim][BF4]
[Bmim][BF4]
[Bmim][BF4]
11[c] Amberlyst-15
12
13
14
15
Amberlite-IR-120
Indion-225H
Montmorillonite K-10 [Bmim][BF4]
Lewatit K-2620
[Bmim][BF4]
[Bmim][BF4]
16[d] Amberlyst-15
[a] Reagents and conditions: benzhydrol (1 mmol), benzamide
(1 mmol), solvent (2 mL), reagent (0.75 g), 2 h. [b] GC yield; n.r.:
no reaction. [c] Reaction was carried out for 3 h. [d] Reagent
(0.32 g).
To explore the scope of the reaction, we performed a set
of experiments with a range of secondary benzylic alcohols
and various types of nitrogen nucleophiles, including amide,
sulfonamide, carbamates, and amines, using Amberlyst-15
immobilized in ionic liquid [Bmim][BF4]; the good to excel-
lent yields obtained are summarized in Table 2. After com-
[a] Reagents and conditions: alcohol 1 (1 mmol), nucleophile 2
(1 mmol), Amberlyst-15 (0.75 g), [Bmim][BF4] (2 mL), 80 °C. [b]
GC yield. n.r. (no reaction). [c] Nucleophile 2 (3 mmol).
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Uses of Amberlyst-15 in Ionic Liquid
pletion of the reaction, the ionic liquid phase containing electron-donating groups reacted effectively with benz-
[Bmim][BF4] and reagent Amberlyst-15 were almost quanti- amide, providing the corresponding products with excellent
tatively recovered by simple extraction of the product with 88–90% yields (Table 2, entries 10 and 13). The reaction is
ethyl acetate.
highly efficient and proceeds smoothly with primary amides
Firstly, when amides (benzamide, acetamide, and acryl- within a short reaction time. The secondary amide phthala-
amide) were used for the nucleophilic substitution with mide did not react under these reaction conditions, even
benzydric alcohol (1a), excellent yields of the desired substi- after prolonged reaction time (Table 2, entry 7).
tuted products were obtained (Table 2, entries 1–3).
The reaction of 1-phenylethanol (1d) with 2a or 2c af-
Benzhydric alcohols possessing electron-withdrawing and forded the desired benzylated products 3da and 3dc in 70–
Table 3. Hydroamination of alkenes with nitrogen-containing nucleophiles.[a]
[a] Reagents and conditions: alkene 4 (1 mmol), nucleophile 2 (3 mmol), Amberlyst-15 (0.75 g), [Bmim][BF4] (2 mL), 80 °C. [b] GC yield.
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B. M. Bhanage et al.
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71% yield (Table 2, entries 17 and 18) as the coupling prod- bornene also underwent nucleophilic substitution with
ucts, indicating the influence of the phenyl ring on the benzamide to provide the hydroaminated product 5da
benzhydric alcohol. It was noticed that the yield remained (Table 3, entry 10).
relatively constant with sulfonamide nucleophiles of varying
electronic and steric properties, because electron-rich 4-
Conclusions
methyl- and 2-methylbenzenesulfonamide yielded the corre-
sponding amidation products in 92–90% yield (Table 2, en-
tries 5 and 6). The sulfonamide nucleophile also smoothly
underwent substitution with a range of alcohols, giving
overall good to excellent yields of the expected products
(Table 2, entries 4, 11, 14, 15, 19, and 20). Ethyl carbamate
was found to react excellently with benzylic alcohols pos-
sessing either electron-withdrawing or electron-donating
substituents, and the reaction reached completion within 1–
2 h; the corresponding substituted carbamates were ob-
tained with 90–97% yield (Table 2, entries 8, 12, 16, and
21). We then conducted the reaction of benzhydrol 1a with
amines such as p-nitroaniline (2i), which gave a moderate
yield of the product 3ai (Table 2, entry 9). Unfortunately,
other benzylic, cyclic, and allylic alcohols were not compat-
ible with this nucleophilic substitution protocol (Table 2,
entries 22–24).
Amberlyst-15 in the ionic liquid [Bmim][BF4] was found
to be an efficient, recyclable system for nucleophilic substi-
tution reactions of alcohols and for hydroamination reac-
tions of alkenes with several amides, sulfonamides, carba-
mates, and amines as nitrogen nucleophiles. Substitution of
alcohols with nucleophiles generally provides higher yields
of benzylated amides than the corresponding hydroamin-
ation of alkenes due to the formation of dimeric by-prod-
ucts. Notable advantages offered by this metal-free reaction
system are the use of an ionic liquid as a greener solvent,
higher yields of desired products, greater substrate compati-
bility, and simple workup procedures, making this approach
an important supplement to existing methods.
Experimental Section
To explore the generality of the protocol, we then ex-
tended this methodology to the hydroamination of alkenes,
whereby initial reaction of styrene (4a) with benzamide (2a)
using Amberlyst-15 in ionic liquid [Bmim][BF4] afforded a
mixture of the desired intermolecular hydroaminated prod-
uct 5aa and 1,3-diphenylbut-1-ene (6). Formation of the lat-
ter might be due to reaction of styrene with the intermedi-
ate phenylethyl cation, which, on subsequent elimination of
a proton, gives alkene 6. Therefore, to increase the yield of
the desired hydroaminated product, an excess of nucleo-
phile (amide) was added (3 equiv.); under these conditions,
a 60% yield of product was obtained. Further increases in
the amount of nucleophile had no profound effect on the
product yield.
With the optimized conditions in hand, we further inves-
tigated a range of nitrogen nucleophile substrates 2 in the
hydroamination reaction of alkenes 4. The results are sum-
marized in Table 3. The reaction of styrene with nitrogen-
containing nucleophiles, namely benzamide, acrylamide,
sulfonamide, p-toluenesulfonamide, and ethyl carbamates,
gave the corresponding hydroaminated derivatives in mod-
erate to good yields (Table 3, entries 1–5). Similarly, 3-meth-
ylstyrene (4b) also underwent hydroamination with both
benzamide (2a) and p-toluenesulfonamide (2e) (Table 3, en-
tries 6 and 7). When α-methyl styrene (4c) was treated with
p-toluenesulfonamide (2e) it was observed that, instead of
expected product 5ce, under the acidic conditions α-methyl-
styrene itself underwent dimerization to form 4-methyl-2,4-
diphenyl-2-pentene and 4-methyl-2,4-diphenyl-1-pentene in
55% combined yield (1:1) (Table 3 entry 8). Previously, Shi-
rakawa and co-workers demonstrated the palladium-cata-
lyzed dimerization of vinylarenes using indium triflates as
a cocatalyst.[10] Herewith, under the same reaction condi-
tions, we carried out the self-dimerization of styrene to gen-
erate the dimerized alkene 6 in more than 90% yield
General: All chemicals and reagents were purchased from commer-
cial suppliers and were used without further purification. Products
were characterized by their respective melting points and by using
1
IR (Perkin–Elmer FTIR), H and 13C NMR (Varian Mercury 300
NMR Spectrometer) spectroscopic analyses. The reactions
were monitored by GC analysis (Perkin–Elmer/Chemito,
30 mϫ0.32 mm, 1D-0.25 µm BP10) and by TLC analysis. The
identities of the products were further confirmed by GC–MS analy-
sis (Shimadzu GC–MS QP 2010). The various ionic liquids used
were prepared as previously reported.[11]
Typical Procedure for Nucleophilic Substitution of Benzylic Alcohols
with Nitrogen Nucleophiles: To a well-stirred mixture of Amberlyst-
15 (opaque beads, 0.75 g) in [Bmim][BF4] (2 mL), nucleophile 2a–i
(1 mmol) and alcohol 1a–g (1 mmol) were added. The resulting re-
action mass (homogeneous substrate) was further stirred at 80 °C
and the progress of the reaction was monitored by GC/TLC. After
completion of the reaction, the mixture was cooled to r.t., which
led to the precipitation of a solid product. To this was added water
(15 mL), which resulted in the separation of the ionic liquid phase
as [Bmim][BF4] is soluble in water. Ethyl acetate (2ϫ 5 mL) was
then added, which separated the Amberlyst-15 resin beads from the
reaction mass. This was then filtered off. The aqueous phase was
further extracted with ethyl acetate (2ϫ 5 mL) to leave behind the
residual product with the organic extract. This was dried with
Na2SO4, and the solvent was evaporated in vacuo to yield the prod-
uct. The crude product was subjected to further purification by
column chromatography (silica gel; mesh size 60–120; petroleum
ether/ethyl acetate, 90:10).
Typical Procedure for Hydroamination of Alkenes with Nitrogen Nu-
cleophiles: To a well-stirred mixture of Amberlyst-15 (opaque be-
ads, 0.75 g) in [Bmim][BF4] (2 mL), nucleophile 2a–h (3 mmol) and
alkenes 4a–d (1 mmol) were added. The resulting reaction mass
(homogeneous substrate) was then stirred at 80 °C in a sealed tube
and the reaction was monitored by GC/TLC until completion. Af-
ter completion of the reaction, the mixture was cooled to r.t., which
led to the precipitation of a solid product. To this was added water
(15 mL), which resulted in the separation of the ionic liquid phase
(Table 3, entry 9). Furthermore, it was observed that nor- as [Bmim][BF4] is soluble in water. Ethyl acetate (2ϫ 5 mL) was
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Uses of Amberlyst-15 in Ionic Liquid
then added, which separated the Amberlyst-15 resin beads from the
reaction mass. This was then filtered off. The aqueous phase was
further extracted with ethyl acetate (2ϫ 5 mL) to leave behind the
residual product with the organic extract. This was dried with
Na2SO4, and the solvent was evaporated in vacuo to yield the prod-
uct. The crude product was subjected to further purification by
column chromatography (silica gel; mesh size 60–120; petroleum
ether/ethyl acetate, 90:10).
(%) = 255 (42), 226 (16), 225 (99), 182 (100), 152 (17), 134 (6), 104
(96), 77 (43), 51 (14). MS–MS (ESI–): m/z calcd. for [M – 1] 254.31;
found 253.93.
N-[(4-Chlorophenyl)phenylmethyl]-4-methylbenzenesulfonamide
(3be): Yield 94% (349 mg), white solid, m.p. 115 °C. IR (KBr):
3240, 3057, 3032, 2866, 1914, 1598, 1489, 1433, 1321, 1161, 1092,
1049, 935, 904, 871, 836, 804, 745, 701, 670, 629, 573, 539,
483 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.55–7.52 (d, J =
8.2 Hz, 2 H), 7.25–7.03 (m, 11 H), 5.54–5.51 (d, J = 7.6 Hz, 1 H),
5.47–5.45 (d, J = 7 Hz, 1 H), 2.38 (s, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 143.46 (C), 140.06 (C), 138.99 (C), 137.17
(C), 133.46 (C), 129.42 (2ϫCH), 128.78 (2ϫCH), 128.73 (2ϫCH),
Typical Procedure for Recycling the Ionic Liquid and Reagent for
the Nucleophilic Substitution of Benzhydrol with Benzamide: After
completion of reaction, the reaction mixture was cooled to r.t. and
diluted with water (15 mL). The aqueous solution was then ex-
tracted with ethyl acetate (2ϫ5 mL). The aqueous layer consisting 128.62 (2ϫCH), 127.86 (2ϫCH), 127.27 (CH), 127.18 (2ϫCH),
of the ionic liquid was distilled for 2 h to remove water, leaving
behind the ionic liquid [Bmim][BF4] (recovery 96%). Filtered Am-
berlyst-15 and recovered ionic liquid were dried under vacuum for
1 h and then charged with benzhydrol and benzamide again for the
recyclability study. It was observed that recovered ionic liquid and
reagent could be reused for three consecutive cycles for the amid-
ation of benzhydrol with only a slight decrease in yield (88, 86,
then 84%).
60.75 (CH), 21.50 (CH3) ppm. MS–MS (ESI–): m/z calcd. for [M –
1] 370.88; found 370.20.
Ethyl [(4-Chlorophenyl)phenylmethyl]carbamate (3bh): Yield 95%
(274 mg), white solid, m.p. 117 °C; (KBr): 3283, 3027, 2983, 2763,
1909, 1711, 1684, 1531, 1491, 1367, 1278, 1238, 1171, 1089, 1041,
894, 848, 755, 700, 609, 504, 482 cm–1. 1H NMR (300 MHz,
CDCl3): δ = 7.35–7.16 (m, 9 H), 5.94–5.91 (d, J = 7.6 Hz, 1 H),
5.33 (br., 1 H), 4.16–4.08 (q, J = 7 Hz, 2 H), 1.25–121 (t, J =
6.45 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 155.74
(C=O), 141.20 (C), 140.34 (C), 133.16 (C), 128.76 (2ϫCH), 128.71
(2ϫCH), 128.53 (2ϫCH), 127.69 (2ϫCH), 127.23 (CH), 61.19
N-Benzhydrylbenzamide (3aa): Yield 88% (252 mg), white solid,
m.p. 168 °C. IR (KBr): ν = 3313, 3056, 3027, 1638, 1520, 1495,
˜
1359, 1314, 1262, 1245, 1088, 1028, 940, 853, 799, 754, 738, 706,
692, 600, 577, 464 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.83– (CH2), 58.14 (CH), 14.51 (CH3) ppm. MS (EI): m/z (%) = 289 (34),
7.80 (d, J = 7.6 Hz, 2 H), 7.53–7.25 (m, 13 H), 6.68 (br., 1 H), 6.45
260 (97), 216 (100), 201 (23), 180 (14), 165 (50), 152 (5), 165 (50),
(d, J = 7.6 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 166.48 138 (46), 127 (2), 104 (75), 79 (12), 77 (35), 51 (12). MS–MS
(C=O), 141.47 (C), 134.26 (C), 131.70 (C), 128.76 (4ϫCH), 128.64 (ESI–): m/z calcd. for [M – 1] 288.76; found 288.07.
(2ϫCH), 127.6 (3ϫCH), 127.51 (4ϫCH), 127.1 (2ϫCH), 57.46
N-[Phenyl(p-tolyl)methyl]benzamide (3ca): Yield 88% (264 mg),
(CH) ppm. MS (EI): m/z (%) = 287 (62), 210 (11), 182 (25), 165
white solid, m.p. 162 °C. IR (KBr): 3313, 3060, 3032, 2917, 1908,
(24), 105 (100), 77 (58), 45 (31).
1638, 1579, 1523, 1489, 1353, 1321, 1246, 1178, 1084, 1053, 929,
N-Benzhydryl-4-methylbenzenesulfonamide (3ae): Yield 92%
856, 796, 775, 741, 703, 577, 478 cm–1. 1H NMR (300 MHz,
CDCl3): δ = 7.81–7.79 (d, J = 7 Hz, 2 H), 7.52–7.42 (t, J = 7.05 Hz,
1 H), 7.44–7.41 (t, J = 7.35 Hz, 2 H), 7.36–7.27 (m, 5 H), 7.19–
7.17 (d, J = 8.2 Hz, 2 H), 7.13–7.15 (d, J = 7.6 Hz, 2 H), 6.70–6.68
(d, J = 7 Hz, 1 H), 6.42–6.39 (d, J = 7.6 Hz, 1 H), 2.33 (s, 3 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 166.44 (C=O), 141.62 (C), 138.55
(310 mg), white solid, m.p. 156 °C. IR (KBr): ν = 3249, 2656, 2358,
˜
1599, 1495, 1451, 1315, 1161, 1096, 1059, 1029, 941, 811, 751, 700,
1
677, 572, 488 cm–1. H NMR (300 MHz, CDCl3): δ = 7.5–7.54 (d,
J = 8.2 Hz, 2 H), 7.25–7.09 (m, 12 H), 5.57–5.55 (d, J = 7.1 Hz, 1
H), 5.4–5.37 (d, J = 7.0 Hz, 1 H), 2.35 (s, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 143.22 (C), 140.53 (C), 137.38 (2ϫC), (C), 137.30 (C), 134.31 (C), 131.65 (CH), 129.44 (2ϫCH), 128.70
129.37 (2ϫCH), 128.57 (4ϫCH), 127.61 (2ϫCH), 127.38 (2ϫCH), 128.62 (2ϫCH), 127.46 (3ϫCH), 127.41 (2ϫCH),
(4ϫCH), 127.22 (2ϫCH), 61.35 (CH), 21.50 (CH3) ppm. MS (EI): 127.04 (2ϫCH), 57.2 (CH), 21.1 (CH3) ppm. MS–MS (ESI–): m/z
m/z (%) = 337 (1), 322 (1), 260 (2), 183 (15), 167 (17), 155 (16), 104 calcd. for [M – 1] 300.38; found 300.20.
(27), 91 (40), 77 (23), 45 (53).
N-[Phenyl(p-tolyl)methyl]benzenesulfonamide (3cd): Yield 87%
N-Benzhydryl-2-methylbenzenesulfonamide (3af): Yield 90%
(293 mg), white solid, m.p. 148 °C. IR (KBr): 3248, 3054, 2873,
(303 mg), white solid, m.p. 159–161 °C. IR (KBr): ν = 3423, 3297, 1508, 1435, 1317, 1159, 1092, 1052, 929, 845, 757, 723, 699, 593,
˜
1
3080, 2961, 2879, 1571, 1455, 1314, 1163, 1042, 832, 763, 703, 612, 555, 480 cm–1. H NMR (300 MHz, CDCl3): δ = 7.68–7.65 (d, J =
562 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.83–7.81 (d, J =
7.6 Hz, 2 H), 7.38–7.07 (m, 12 H), 5.51–5.49 (d, J = 7.1 Hz, 1 H),
5.09–5.07 (d, J = 6.3 Hz, 1 H), 2.43 (s, 3 H) ppm. 13C NMR
7.9 Hz, 2 H), 7.48–7.43 (t, J = 7.5 Hz, 1 H), 7.35–7.30 (t, J =
7.7 Hz, 2 H), 7.20–7.14 (m, 3 H), 7.11–7.07 (m, 2 H), 7.01–6.98 (d,
J = 8.5 Hz, 2 H), 6.97–6.94 (d, J = 8.5 Hz, 2 H), 5.56–5.54 (d, J =
(75 MHz, CDCl3): δ = 140.41 (C), 138.04 (C), 136.91 (C), 136.43 7.1 Hz, 1 H), 5.33–5.30 (d, J = 7.3 Hz, 1 H), 2.26 (s, 3 H) ppm. 13
C
(C), 132.69 (CH), 132.27 (CH), 129.68 (CH), 128.53 (4ϫCH),
127.65 (4ϫCH), 127.23 (CH), 125.99 (2ϫCH), 61.34 (CH), 20.09
(CH3) ppm. MS–MS (ESI–): m/z calcd. for [M – 1] 336.44; found
336.20.
NMR (75 MHz, CDCl3): δ = 140.48 (C), 140.37 (C), 137.5 (C),
137.46 (C), 132.35 (CH), 129.27 (2ϫCH), 128.75 (2ϫCH), 128.54
(2ϫCH), 127.57 (1ϫCH), 127.29 (2ϫCH), 127.27 (2ϫCH),
127.16 (2ϫCH), 61.17 (CH), 21.02 (CH3) ppm. MS–MS (ESI–):
m/z calcd. for [M – 1] 336.44; found 336.20.
Ethyl Benzhydrylcarbamate (3ah): Yield 97% (247 mg), white solid,
m.p. 127–130 °C. IR (KBr): 3286, 3027, 2989, 1712, 1686, 1530,
1492, 1443, 1366, 1273, 1239, 1179, 1130, 1078, 1041, 1026, 890,
Ethyl (Phenyl-p-tolylmethyl)carbamate (3ch): Yield 93% (250 mg),
white solid, m.p. 104 °C. IR (KBr): 3323, 3029, 2967, 2862, 2774,
1912, 1805, 1706, 1688, 1539, 1495, 1459, 1368, 1338, 1297, 1251,
1169, 1080, 1038, 919, 886, 814, 738, 701, 677, 617, 591, 507,
1
825, 760, 742, 698, 609, 582, 469, 496 cm–1. H NMR (300 MHz,
CDCl3): δ = 7.35–7.24 (m, 10 H), 5.99–5.96 (d, J = 7.6 Hz, 1 H),
5.37 (br., 1 H), 4.16–4.09 (q, J = 7 Hz, 2 H), 1.26–1.21 (t, J = 463 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.05–7.31 (m, 9 H),
6.75 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 155.83
(C=O), 141.84 (2ϫC), 128.64 (2ϫCH), 127.45 (2ϫCH), 127.26 7.2 Hz, 2 H), 2.29 (s, 3 H), 1.22–4.17 (t, J = 7 Hz, 3 H) ppm. 13C
(2ϫCH), 61.14 (CH2), 58.71 (CH), 14.56 (CH3) ppm. MS (EI): m/z NMR (75 MHz, CDCl3): δ = 155.80 (C=O), 141.97 (C), 138.87
5.90–5.88 (d, J = 6.5 Hz, 1 H), 5.24 (br., 1 H), 4.12–4.05 (q, J =
Eur. J. Org. Chem. 2010, 6233–6238
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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6237

B. M. Bhanage et al.
FULL PAPER
R. V. Ohri, A. T. Radosevich, K. J. Hrovat, C. Musich, D. Hu-
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f) D. Hollmann, A. Tillack, D. Michalik, R. Jackstell, M.
Beller, Chem. Asian J. 2007, 2, 403–410.
(C), 137.10 (C), 129.29 (2ϫCH), 128.56 (2ϫCH), 127.31 (2ϫCH),
127.14 (2ϫCH), 121.95 (CH), 61.02 (CH2), 58.43 (CH), 21.02
(CH3) ppm. MS (EI): m/z (%) = 269 (44), 254 (2), 240 (11), 223 (5),
208 (6), 196 (87), 192 (7), 181 (28), 165 (30), 152 (5), 141 (2), 134
(1), 120 (10), 118 (32), 104 (79), 91 (20), 77 (23), 65 (8), 51 (5), 45
(3). MS–MS (ESI–): m/z calcd. for [M – 1] 268.34; found 268.15.
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Int. Ed. 2006, 45, 1744–1747.
N-(1-Phenylethyl)-p-toluenesulfonamide (3de): Yield 86% (236 mg),
white solid, m.p. 82 °C. IR (KBr): 3253, 3068, 2970, 1597, 1494,
1451, 1430, 1323, 1303, 1209, 1156, 1121, 1083, 1018, 957, 869,
1
812, 766, 703, 673, 559, 539 cm–1. H NMR (300 MHz, CDCl3): δ
= 7.64–7.6 (d, J = 8.2 Hz, 2 H), 7.25–7.01 (m, 7 H), 5.34–5.32 (d,
J = 7.1 Hz, 1 H), 4.47–4.42 (qd, J = 7 Hz, 1 H), 2.37 (s, 3 H), 1.14–
1.39 (d, J = 7 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
143.02 (C), 142.15 (C), 137.65 (C), 129.4 (2ϫCH), 128.44
(2ϫCH), 127.30 (2ϫCH), 127.07 (CH), 126.13 (2ϫCH), 53.65
(CH), 23.57 (CH3), 21.46 (CH3) ppm. MS (EI): m/z (%) = 275 (1),
211 (2), 196 (12), 155 (63), 120 (66), 91 (100), 77 (22), 65 (26).
Ethyl (1-Phenylethyl)carbamate (3dh): Yield 94% (181 mg), pale
yellow oil. IR (KBr): 3325, 2979, 2928, 2361, 1704, 1534, 1450,
1383, 1331, 1248, 1098, 1070, 781, 763, 700, 618, 559 cm–1. 1H
NMR (300 MHz, CDCl3): δ = 7.35–7.24 (m, 5 H), 5.10–5.08 (d, J
= 5.9 Hz, 1 H), 4.83 (br., 1 H), 4.14–4.05 (q, J = 6 Hz, 2 H), 1.47–
1.45 (d, J = 6.5 Hz, 3 H), 1.33–1.18 (t, J = 8 Hz, 3 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 155.93 (C=O), 143.82 (C), 128.59
(2ϫCH), 127.22 (2ϫCH), 125.94 (1ϫCH), 60.78 (CH2), 50.54
(CH), 22.53 (CH3), 14.60 (CH3) ppm. MS (EI): m/z (%) = 193 (36),
178 (100), 164 (85), 150 (71), 134 (24), 120 (60), 106 (11), 103 (19),
91 (8), 79 (78), 51 (19), 42 (51). MS–MS (ESI–): m/z calcd. for [M –
1] 192.11; found 191.93.
1,3-Diphenylbut-1-ene (6): Yield 90% (187 mg), pale yellow oil. IR
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age, Tetrahedron Lett. 2010, 51, 724–729.
(KBr): 3026, 2963, 2854, 1687, 1600, 1493, 1451, 1384, 1264, 1113,
1
1017, 965, 909, 743, 698, 617, 539, 487 cm–1. H NMR (300 MHz,
[7] a) P. Wasserscheid, T. Welton, Ionic Liquids in Synthesis, 2nd
ed., Wiley-VCH, 2002; b) R. D. Rogers, K. R. Seddon (Eds.),
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CDCl3): δ = 7.35–7.15 (m, 10 H), 6.39–6.38 (m, 2 H), 3.67–3.59
(m, 1 H), 1.47–1.44 (d, J = 7 Hz, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 145.60 (Cipso), 137.6 (C-1), 128.5 (C-2), 128.4 (Cortho),
128.29 (C-3), 127.03 (Cmeta), 126.20 (C-4), 126.14 (Cpara), 42.60
(CH), 21.21 (CH3) ppm. MS (EI): m/z (%) = 208 (60), 193 (57),
178 (26), 179 (19), 152 (4), 115 (100), 91 (39), 77 (16), 44 (12).
[8] M. J. Earle, S. P. Katdare, K. R. Seddon, Org. Lett. 2004, 6,
707–710.
Acknowledgments
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Tetrahedron Lett. 2009, 50, 2811–2814; b) A. G. Panda, S. R.
Jagtap, N. S. Nandurkar, B. M. Bhanage, Ind. Eng. Chem. Res.
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Bhor, B. M. Bhanage, Catal. Commun. 2009, 10, 833–837; e)
K. M. Deshmukh, Z. S. Qureshi, N. S. Nandurkar, B. M.
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Received: April 5, 2010
The financial support from the Indira Gandhi Centre for Atomic
Research (IGCAR) Kalpakkam, India is gratefully acknowledged.
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Published Online: September 22, 2010
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Eur. J. Org. Chem. 2010, 6233–6238