Molecular iodine-catalysed amidation reaction of secondary benzylic and allylic alcohols with carboxamides or sulfonamides

Article abstract of DOI:10.3184/030823409X12526892025900

A highly efficient method for the C-N bond formation via 2 mol% of molecular iodine-catalysed amidation reaction of benzylic and allylic alcohols with carboxamides or sulfonamides in MeCN is described, giving the corresponding substituted amides and allyl

Full text of DOI:10.3184/030823409X12526892025900

638 RESEARCH PAPER
OCTOBER, 638–641
JOURNAL OF CHEMICAL RESEARCH 2009
Molecular iodine-catalysed amidation reaction of secondary benzylic and
allylic alcohols with carboxamides or sulfonamides
Xufeng Lin*, Jun Wang, Fangxi Xu and Yanguang Wang
Department of Chemistry, Zhejiang University, Hangzhou 310027, P. R. China
A highly efficient method for the C–N bond formation via 2 mol% of molecular iodine-catalysed amidation reaction
of benzylic and allylic alcohols with carboxamides or sulfonamides in MeCN is described, giving the corresponding
substituted amides and allylic amides in moderate to excellent yields. The significan features of the procedure
include mild and metal-free reaction conditions, operational simplicity, inexpensive reagents, short reaction time,
and good yields.
Keywords: molecular iodine, amidation reaction, C–N bond formation
C–N Bond formation is a useful synthetic method for making
substituted amines.1 It is important to develop simple, efficient
and environmentally friendly C–N bond forming reactions.
Methods for the construction of C–N bond include transition
metal catalysed substitution reactions of alcohols or halides
with nitrogen nucleophiles,2,3 and transition metal catalysed C–
H amination reactions.4 Among the various strategies, the direct
catalytic substitution of alcohols with nitrogen nucleophiles is
a salt-free, highly atom-economic, environmentally friendly
synthetic method with water as the only byproduct. Although a
number of direct substitution reactions of alcohols with amines
catalysed by transition metals have been reported,5,6 the use
of weak nitrogen nucleophiles such as readily available
amides are uncommon and require harsh conditions.
catalysed amidation of secondary benzylic and allylic alcohols
with carboxamides and p-toluenesulfonamide.
The selected model reaction was carried out with
diphenylmethanol (1a) and benzamide (2a) (Scheme 1). We
examined several organic solvents. These were commercially
available and were used without further purification or drying
(Table 1). We found that a remarkable solvent effect existed
in our iodine-catalysed reaction. Only polar solvent such as
nitromethane and acetonitrile were good solvents giving a high
yield of the corresponding substituted amide (3a) (Table 1,
entries 3 and 4). Apolar solvents such as THF and dioxane did
not give a product (Table 1, entries 1 and 2). Furthermore, the
reaction time and the catalyst concentration were reduced to
2 h and 2 mol%, respectively (Table 1, entries 4–8).
A few Lewis acid catalysed amidation reactions of
alcohols with amides have been described using NaAuCl4,7
Table 1 Optimisation of reaction conditions
,10
H-Montmorillonite,8 MoCl5,9 Bi(OTf)3-KPF6
AgOTf11
and FeCl3.12 However, the use of expensive and toxic
metal catalysts and anhydrous reaction condition reduced
the practical application of these methods. Therefore,
development of a more practical and economical method for
direct substitution of benzylic or allylic alcohols by amides is
highly desirable for the synthesis of corresponding substituted
benzylic and allylic amides.
Entry Catalyst/mol% Solventb
Time/h Yield/%c
1
2
3
4
5
6
7
8
5
1, 4-dioxane
THF
5.0
5.0
1.0
1.0
5.0
2.0
1.5
1.0
No reaction
5
No reaction
5
MeNO2
MeCN
MeCN
MeCN
MeCN
MeCN
97
97
5
0
No reaction
2
98
98
98
10
20
Recently, molecular iodine has received considerable
attention as an inexpensive and readily available catalyst for
various organic transformations due to its moderate Lewis
acidity and water-tolerance.12-19 In continuation of our studies
of molecular iodine-catalysed organic reactions,20-22 we now
describe a C–N bond formation reaction via molecular iodine-
aReaction condition: diphenylmethanol 1a (1 mmol), benzamide
2a (1 mmol), I2 and solvent (4 mL), under reflux condition.
bSolvents were commercially available and used without
further purification or drying.
cIsolated yield.
O
OH
I2
NH2
HN
O
+
solvent, reflux
1a
2a
3a
Scheme 1
R2
R1
OH
R1
I2 (2 mol%)
MeCN
HN
R2 NH2
+
Ar
Ar
1
3
2
Scheme 2
* Correspondent. E-mail: lxfok@zju.edu.cn

JOURNAL OF CHEMICAL RESEARCH 2009 639
Using the optimised reaction conditions, we examined a
number of secondary benzylic alcohols 1a–e as well as amide
2a–d (Scheme 2). We obtained the corresponding substituted
amides 3a–k in 61–98% yields (Table 2). The reaction occurred
easily at room temperature when the benzylic alcohols
possessed electron-donating groups such as methoxy (Table 2,
entries 2, 4, 7, 8 and 10). Aliphatic primary amides such as
acrylamide and acetamide also underwent smooth amidation
with benzylic alcohols and gave the desired products (Table 2,
entries 9–11). Although this reaction was highly efficient for
secondary benzylic alcohols, benzyl alcohol itself did not
react under these conditions even on prolonged heating.
Furthermore, we carried out this reaction with allylic
alcohols and amides using the established procedure, to
Table 2 Iodine-catalysed amidation reaction of secondary benzylic alcohols with amidea
Entry
1
Alcohols
Amides
Products
Time/h
2.0
Yield/%c
98
O
Ph
O
OH
N
H
Ph
NH2
Ph
Ph
1a
2a
3a
O
Ph
OH
Ph
N
H
2
1.0
97
OMe
MeO
1b
3b
O
OH
N
H
Ph
3
4
4.0
2.0
61
1c
3c
OH
O
85d
N
H
MeO
OMe
Br
3d
1d
OH
O
N
5
6
5.0
2.0
65
98
H
Br
3e
1e
Ph
SO2NH
SO2NH2
2b
3f
Ph
SO2NH
7
8
1.0
2.0
97
2b
3g
OMe
OMe
SO2NH
88d
2b
3h
O
Ph
O
N
H
9
3.0
5.0
76
NH2
3i
2c
O
N
H
10
68d
2c
OMe
3j
O
O
Ph
NH2
2d
N
11
4.0
85
H
OMe
3k
aReaction condition: benzylic alcohol 1 (2 mmol), amide 2 (2 mmol), I2 (2 mol%) and MeCN (8 mL), under reflux condition.
b Using MeNO2 as solvent.
cIsolated yield.
dAt room temperature.

640 JOURNAL OF CHEMICAL RESEARCH 2009
Table 3 Iodine-catalysed amidation reaction of allylic and propargyl alcohols with amidea
Entry
Alcohols
Amides
Products
Time/h
1.0
Yield/%b
98
O
OH
HN
Ph
1
2a
Ph
3l
1f
O
HN
2
1f
2c
1.0
92
Ph
3m
O
HN
3
4
1f
2d
2b
2.0
3.0
90c
Ph
3n
NHTs
OH
55c
1g
3o
aReaction conditions: allylic or propargyl alcohols 1 (2 mmol), amide (2 mmol), I2 (2 mol%), MeCN (8 mL), r. t.
bIsolated yield.
Cunder reflux condition.
as internal standard. MS was obtained using ESI ionisation. Melting
points were obtained on a microscopical instrument and uncorrected.
All the products have been previously described.7, 12, 27-32
obtain the corresponding allylic amides (Table 3, entries 1–3).
All the reactions proceeded smoothly in the presence of 2
mol% iodine in acetonitrile in good yields. We also carried out
this reaction with propargyl alcohol 1g and amide, obtaining
the corresponding propargyl amide 3o in moderate yield
(Table 3, entry 4).
General procedure for preparation of 3a–o
A
mixture of benzylic or allylic alcohol (2 mmol), amide
(2 mmol) and I2 (2 mol%) in the MeCN (8 mL) was stirred at room
temperature or under reflux condition for the appropriate time. After
the reaction was completed, the reaction mixture was quenched by
10% aq Na2S2O3 solution (10 mL) and extracted with ethyl acetate
(2 ¥ 20 mL). The combined organic layers were dried over Na2SO4
and then concentrated in vacuo. The residure was purified by column
chromatography on silica gel column with hexane-EtOAc (4:1)
to obtain the corresponding amide product. The spectra data of the
compounds 3a–o are as follows.
Following literature precedent,23-26 we consider that iodine
catalyses the reaction as a mild Lewis acid via a possible
SN1 mechanism (Scheme 3). A benzyl carbocation might be
formed from benzyl alcohol in the presence of molecular
iodine, followed by nucleophilic attack by the amide to afford
the corresponding substituted amides.
In summary, we have developed a simple and efficient C–
N bond formation reaction via a molecular iodine-catalysed
amidation reaction of secondary benzylic and allylic alcohols
with carboxamides or p-toluenesulfonamide in acetonitrile.
Using this method, propargyl alcohols can also react with
amide, giving the corresponding propargyl amides. The
notable features of the procedure include mild and metal-free
reaction conditions, operational simplicity, use of a catalytic
amount of molecular iodine (2 mol%), short reaction time,
and good yields.
N-Benzhydrylbenzamide (3a): M.p. 168–169°C (lit.12 170°C);
1H NMR (400 MHz, CDCl3) d 6.44 (d, 1H, J = 7.6 Hz), 6.74 (d, 1 H,
J = 7.2 Hz), 7.24–7.35 (m, 10 H), 7.38–7.42 (m, 2 H), 7.47–7.52 (m,
1 H), 7.80 (d, 2 H, J = 7.6 Hz) ppm; 13C NMR (100 MHz, CDCl3)
d 57.66, 127.3 (2 C), 127.7 (4 C), 127.8 (2 C), 128.8 (2 C), 129.0
(4 C), 131.9, 134.4, 141.7 (2 C), 166.8 ppm; IR (KBr): 3312, 1638,
1521, 1496, 706 cm-1. MS (ESI): m/z = 288 ([M + H]+).
N-((4-Methoxyphenyl)(phenyl)methyl)benzamide (3b): M.p. 183–
184°C (lit.27 180–181°C); 1H NMR (400 MHz, CDCl3) d 3.77 (s, 3 H),
6.38 (d, 1 H, J = 8.0 Hz), 6.68 (brs, 1 H), 6.85 (d, 2H, J = 8.0 Hz), 7.19
(d, 2 H, J = 8.4 Hz), 7.24–7.49 (m, 8 H), 7.79 (d, 2 H, J = 7.2 Hz) ppm;
13C NMR (100 MHz, CDCl3) d 55.53, 57.13, 114.4 (2 C), 127.3 (2 C),
127.6 (2 C), 127.7, 128.8 (2 C), 128.9 (2 C), 129.0 (2 C), 131.9, 133.9
134.5, 141.9, 159.2, 166.8 ppm; IR (KBr): 3306, 1631, 1540, 1509,
1247, 1175, 1032, 700 cm-1. MS (ESI): m/z = 318 ([M + H]+).
Experimental
IR spectra were determined as KBr pellets on a Bruker model 470
spectrophotometer. 1H NMR and 13C NMR spectra were recorded
using a Bruker 400 MHz spectrometer in CDCl3 with tetramethylsilane
I2
R1
OH
R1
R1
OH
R1
H2N R2
R2
I2
N
H
Scheme 3

JOURNAL OF CHEMICAL RESEARCH 2009 641
N-(1-Phenylethyl)benzamide (3c): M.p. 118–120°C (lit.28 119–
120°C); H NMR (400 MHz, CDCl3) d 1.61 (d, 3 H, J = 6.4 Hz),
(E)-N-(1,3-Diphenylallyl)acrylamide (3m): M.p. 121–122°C (lit.12
123°C); H NMR (400 MHz, CDCl3) d 5.65 (d, 1 H, J = 10.4 Hz),
1
1
5.88 (m, 1 H), 6.15 (brs, 1 H), 6.20 (dd, 1 H, J = 16.0, 10.4 Hz), 6.32
(d, 1 H, J = 16.0 Hz), 6.35 (dd, 1 H, J = 16.0, 6.0 Hz), 6.54 (d, 1 H,
J = 16.0 Hz), 7.19–7.37 (m, 10 H) ppm; 13C NMR (100 MHz, CDCl3)
d 55.07, 126.8 (2 C), 127.3, 127.5 (2 C), 128.0, 128.1, 128.8 (2 C),
128.9, 129.1 (2 C), 130.9, 131.9, 136.6, 140.9, 164.9 ppm; IR (KBr):
3269, 3029, 1656, 1619, 1541, 1494, 1449, 1408, 1235, 954, 749,
695 cm-1. MS (ESI): m/z = 264 ([M + H]+).
5.34 (m, 1 H), 6.45 (brs, 1 H), 7.28 (m, 1 H), 7.33–7.43 (m, 6 H),
7.50 (m, 1 H), 7.77 (d, 2 H, J = 7.2 Hz) ppm; 13C NMR (100 MHz,
CDCl3) d 21.95, 49.47, 126.5 (2 C), 127.2 (2 C), 127.7, 128.8 (2 C),
129.0 (2 C), 131.7, 134.8, 143.4, 166.8 ppm; IR (KBr): 3357, 2974,
1634, 1518, 1489, 1323, 700 cm-1. MS (ESI): m/z = 226 ([M + H]+).
N-(1-(4-Methoxyphenyl)ethyl)benzamide (3d): M.p. 112–114°C
(lit.27 113–114°C); 1H NMR (400 MHz, CDCl3) d 1.59 (d, 3 H, J = 7.2),
3.80 (s, 3 H), 5.30 (m, 1 H), 6.42 (brs, 1 H), 6.89 (d, 2 H, J = 8.4 Hz),
7.32 (d, 2 H, J = 8.4 Hz), 7.41–7.50 (m, 3 H), 7.77 (d, 2 H, J = 7.6 Hz)
ppm; 13C NMR (100 MHz, CDCl3) d 21.82, 48.87, 55.52, 114.3
(2 C), 127.2 (2 C), 127.7 (2 C), 128.7 (2 C), 131.6, 134.9, 135.5,
159.1, 166.8 ppm; IR (KBr): 3309, 2974, 1635, 1545, 1515, 1253,
832, 695 cm-1. MS (ESI): m/z = 256 ([M + H]+).
(E)-N-(1,3-Diphenylallyl)acetamide (3n): 126–128°C (lit.27 126–
127°C); 1H NMR (400 MHz, CDCl3) d 2.05 (s, 3 H), 5.82 (m, 1 H),
6.03 (d, 1 H, J = 7.6 Hz), 6.34 (dd, 1 H, J = 16.0, 6.0 Hz), 6.54 (d,
1 H, J = 16.0 Hz), 7.20–7.38 (m, 10 H) ppm; 13C NMR (100 MHz,
CDCl3) d 23.68, 55.03, 126.8 (2 C), 127.4 (2 C), 127.9, 128.0, 128.8
(2 C), 129.1 (2 C), 129.2, 131.6, 136.7, 141.1, 169.3 ppm; IR (KBr):
3292, 3030, 1640, 1535, 1493, 1449, 1371, 1308, 971, 747, 695 cm-1.
MS (ESI): m/z = 252 ([M + H]+).
N-(1-(4-Bromophenyl)ethyl)benzamide(3e):M.p. 119–121°C(lit.27
1
123–124°C); H NMR (400 MHz, CDCl3) d 1.55 (d, 3 H, J = 6.8),
N-(1,3-Diphenylprop-2-ynyl)-4-methylbenzenesulfonamide (3o):
5.25 (dq, 1 H, J = 6.4, 6.8 Hz), 6.38 (d, 1 H, J = 6.4 Hz), 7.23 (d, 2 H,
1
184–185°C (lit.32 186–188°C); H NMR (400 MHz, CDCl3) d 2.32
J = 8.4 Hz), 7.38–7.48 (m, 5 H), 7.74 (d, 2 H, J = 7.6 Hz) ppm; 13
C
(s, 3 H), 4.97 (d, 1 H, J = 9.2 Hz), 5.56 (d, 1 H, J = 9.2 Hz), 7.12 (d, 2
H, J = 7.2 Hz), 7.22–7.38 (m, 8 H), 7.56 (d, 2 H, J = 6.8 Hz), 7.82 (d,
2 H, J = 8.0 Hz) ppm; 13C NMR (100 MHz, CDCl3) d 21.67, 50.04,
85.74, 86.95, 122.2, 127.6 (2 C), 127.8 (2 C), 128.4 (2 C), 128.7,
128.8, 129.0 (2 C), 129.8 (2 C), 131.8 (2 C), 137.65, 137.67, 143.8
ppm; IR (KBr): 3268, 1597, 1491, 1430, 1332, 1155, 1091, 1050,
760, 698 cm-1. MS (ESI): m/z = 362 ([M + H]+).
NMR (100 MHz, CDCl3) d 21.95, 48.96, 121.5, 127.2 (2 C), 128.2
(2 C), 128.8 (2 C), 131.8, 132.0 (2 C), 134.6, 142.6, 166.9 ppm; IR
(KBr): 3350, 2983, 1635, 1526, 1488, 1316, 1099, 1011, 827 cm-1.
MS (ESI): m/z = 304 ([M + H]+).
N-Benzhydryl-4-methylbenzenesulfonamide (3f): M.p. 155–156°C
1
(lit.7 157°C); H NMR (400 MHz, CDCl3) d 2.38 (s, 3 H), 5.28 (d,
1 H, J = 7.2 Hz), 5.58 (d, 2 H, J = 7.2 Hz), 7.10–7.15 (m, 6 H),
7.20–7.22 (m, 6 H), 7.57 (d, 2 H, J = 8.0 Hz) ppm; 13C NMR (100
MHz, CDCl3) d 21.70, 61.57, 127.4 (2 C), 127.6 (4 C), 127.8 (2 C),
128.8 (4 C), 129.6 (2 C), 137.6, 140.8 (2 C), 143.4 ppm; IR (KBr):
3249, 1599, 1495, 1452, 1315, 1161, 1096, 811, 752 cm-1. MS (ESI):
m/z = 338 ([M + H]+).
We thank the National Natural Science Foundation of China
(No. 20702047 and J0830413) and the Natural Science
Foundation of Zhejiang Province (R407106 and Y4090028)
for financial support.
N-((4-Methoxyphenyl)(phenyl)methyl)-4-methylbenzenesulfonamide
(3g):M.p.129–130°C(lit.27129–130°C);1HNMR(400MHz,CDCl3)d
2.38(s,3H),2.76(s,3H),5.22(d,1H,J=6.8Hz),5.53(d,2H,J=6.8Hz),
6.74 (d, 2 H, J = 8.8 Hz), 7.01 (d, 2 H, J = 8.0 Hz), 7.10–7.15 (m,
4 H), 7.19–7.22 (m, 3 H), 7.56 (d, 2 H, J = 8.0 Hz) ppm; 13C NMR
(100 MHz, CDCl3) d 21.70, 55.49, 61.07, 114.1 (2 C), 127.4 (2 C),
127.5 (2 C), 127.7, 128.7 (2 C), 128.9 (2 C), 129.6 (2 C), 133.0, 137.7,
141.0, 143.3, 159.2 ppm; IR (KBr): 3240, 1610, 1511, 1448, 1433,
1323, 1252, 1159, 1048 cm-1. MS (ESI): m/z = 368 ([M + H]+).
N-(1-(4-Methoxyphenyl)ethyl)-4-methylbenzenesulfonamide (3h):
Received 19 July 2009; accepted 29 August 2009
Paper 09/0689 doi: 10.3184/030823409X12526892025900
Published online: 9 October 2009
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2
3
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1
M.p. 88–89°C (lit.29 86–88°C); H NMR (400 MHz, CDCl3) d 1.40
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5
6
7
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(d, 3 H, J = 6.8 Hz), 2.40 (s, 3 H), 3.76 (s, 3 H), 4.42 (m, 1 H), 4.96 (d,
1 H, J = 7.2 Hz), 6.72 (d, 2 H, J = 8.4 Hz), 7.02 (d, 2 H, J = 8.4 Hz),
7.20 (d, 2 H, J = 8.4 Hz), 7.63 (d, 2 H, J = 8.4 Hz) ppm; 13C NMR
(100 MHz, CDCl3) d 21.69, 23.64, 55.33, 55.49, 114.1 (2 C), 127.4
(2 C), 127.6 (2 C), 129.7 (2 C), 134.4, 138.0, 143.3, 159.2 ppm; IR
(KBr): 3275, 2960, 1614, 1513, 1321, 1247, 1178, 1160, 1090, 1031,
957 cm-1. MS (ESI): m/z = 306 ([M + H]+).
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N-Benzhydrylacrylamide(3i):175–177°C(lit.30177–178°C);1HNMR
(400 MHz, CDCl3) d 5.65 (d, 1 H, J = 10.4 Hz), 6.16 (dd, 1 H, J = 16.8,
10.4 Hz), 6.23–6.26 (m, 3 H), 7.22–7.35 (m, 10 H) ppm; 13C NMR
(100 MHz, CDCl3) d 57.28, 127.4, 127.6 (4 C), 127.7 (2 C), 128.9
(4 C), 130.8, 141.2 (2 C), 164.8 ppm; IR (KBr): 3279, 3026, 1651, 1619,
1536, 1494, 1408, 1232, 987 cm-1. MS (ESI): m/z = 238 ([M + H]+).
N-(1-(4-Methoxyphenyl)ethyl)acrylamide (3j): 104–106°C (lit.31
1
107.5°C); H NMR (400 MHz, CDCl3) d 1.50 (d, 3 H, J = 7.2 Hz),
3.78 (s, 3 H), 5.15 (m, 1 H), 5.61 (d, 1 H, J = 10.0 Hz), 5.89 (brs, 1 H),
6.07 (dd, 1 H, J = 18.8, 10.0 Hz), 6.27 (d, 1 H, J = 16.8 Hz), 6.86 (d,
2 H, J = 8.4 Hz), 7.25 (d, 2 H, J = 8.8 Hz) ppm; 13C NMR (100 MHz,
CDCl3) d 21.70, 48.46, 55.53, 114.3 (2 C), 126.7, 127.7 (2 C), 131.2,
135.3, 159.1, 164.7 ppm; IR (KBr): 3286, 2970, 1655, 1625, 1546,
1515, 1411, 1246, 1180, 828 cm-1. MS (ESI): m/z = 206 ([M + H]+).
N-((4-Methoxyphenyl)(phenyl)methyl)acetamide (3k): 159–160°C
(lit.27 159–160°C); 1H NMR (400 MHz, CDCl3) d 2.03 (s, 3 H), 3.79 (s,
3H), 6.20 (m, 2 H), 6.85 (d, 2 H, J = 9.2 Hz), 7.14 (d, 2 H, J = 8.4 Hz),
7.23–7.32 (m, 5 H) ppm; 13C NMR (100 MHz, CDCl3) d 23.55, 55.51,
56.63, 114.2 (2 C), 127.5 (2 C), 127.6 (2 C), 128.8 (2 C), 128.9, 134.0,
142.0, 159.1, 169.3 ppm; IR (KBr): 3310, 3061, 1638, 1545, 1513,
1448, 1370, 1249, 1185, 1031 cm-1. MS (ESI): m/z = 256 ([M + H]+).
(E)-N-(1,3-Diphenylallyl)benzamide (3l): 156–157°C (lit.27 157–
158°C); 1H NMR (400 MHz, CDCl3) d 6.04 (m, 1 H), 6.46 (dd, 1 H,
J = 16.0, 6.4 Hz), 6.63 (d, 1 H, J = 16.0 Hz), 6.64 (brs, 1 H), 7.25–
7.52 (m, 14 H), 7.84 (d, 2 H, J = 7.6 Hz) ppm; 13C NMR (100 MHz,
CDCl3) d 55.47, 126.8 (2 C), 127.3 (2 C), 127.5 (2 C), 128.0, 128.1,
128.8 (2 C), 128.9 (2 C), 129.0, 129.1 (2 C), 131.9, 132.0, 134.6,
136.6, 141.1, 166.7 ppm; IR (KBr): 3351, 3031, 1633, 1516, 1488,
1314, 967, 749 cm-1. MS (ESI): m/z = 314 ([M + H]+).
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