Substitution of the benzotriazolyl group in N-(α -amidoalkyl)benzotriazoles and N-(α-sulfonamidoalkyl)benzotriazoles with allylsamarium bromide

Article abstract of DOI:10.1081/SCC-120024744

The nucleophilic substitution of the benzotriazolyl group in the N-(α-benzotriazol-1-ylalkyl)amides and N-(α-benzotriazol-1-ylalkyl) sulfonamides with allylsamarium bromide was investigated, and the corresponding homoallylamides or homoallylsulfonamides w

Full text of DOI:10.1081/SCC-120024744

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Substitution of the Benzotriazolyl Group in
N -(α-Amidoalkyl)benzotriazoles and N -(α-
Sulfonamidoalkyl)benzotriazoles with Allylsamarium
Bromide
Xiaoxia Wang a , Jian Li a & Professor Yongmin Zhang a b
a Department of Chemistry, Zhejiang University (Campus Xixi), Hangzhou, P.R. China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai, P.R. China
Version of record first published: 15 Aug 2006.
To cite this article: Xiaoxia Wang, Jian Li & Professor Yongmin Zhang (2003): Substitution of the Benzotriazolyl Group
in N -(α-Amidoalkyl)benzotriazoles and N -(α-Sulfonamidoalkyl)benzotriazoles with Allylsamarium Bromide, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 33:20, 3575-3581
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 20, pp. 3575–3581, 2003
Substitution of the Benzotriazolyl Group in
N-(a-Amidoalkyl)benzotriazoles and
N-(a-Sulfonamidoalkyl)benzotriazoles with
Allylsamarium Bromide
Xiaoxia Wang,1 Jian Li,1 and Yongmin Zhang1,2,
*
1Department of Chemistry,
Zhejiang University (Campus Xixi),
Hangzhou, P.R. China
2State Key Laboratory of Organometallic Chemistry,
Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai, P.R. China
ABSTRACT
The nucleophilic substitution of the benzotriazolyl group in the
N-(a-benzotriazol-1-ylalkyl)amides and N-(a-benzotriazol-1-ylalkyl)
sulfonamides with allylsamarium bromide was investigated, and the
*Correspondence: Yongmin Zhang, Professor, Department of Chemistry,
Zhejiang University (Campus Xixi), Tianmu-Shan Road, Hangzhou, 310028,
P.R. China; State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, 200032,
P.R. China; Fax: 86-571-8807077; E-mail: yminzhang@mail.hz.zj.cn.
3575
DOI: 10.1081/SCC-120024744
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
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3576
Wang, Li, and Zhang
corresponding homoallylamides or homoallylsulfonamides were
obtained in good to excellent yields.
Key Words: N-(a-Amidoalkyl)benzotriazoles; N-(a-Sulfonamido-
alkyl)benzotriazoles; Allylsamarium bromide; Homoallylamide;
Homoallylsulfonamide.
Benzotriazole is a very useful synthetic auxiliary[1] and its application
in organic chemistry has been extensively investigated. Elimination of the
benzotriazolyl group at an appropriate stage is an important aspect in
benzotriazole chemistry. Of the various methods available for the
removal of benzotriazolyl group, replacement of the benzotriazolyl
group with nucleophilic reagents has afforded many kinds of useful
and interesting compounds.[1e]
Organosamarium reagent allylsamarium bromide is an excellent
allylation reagent due to its advantageous properties already exploited
in organic synthesis. The nucleophilic addition reactions promoted by
allylsamarium bromide with nitriles,[2] oximes,[3] lactames, lactones and
acyclic amides[4] to give the corresponding diallylation products has been
well investigated. Herein we wish to report the nucleophilic substitution
reaction promoted by allylsamarium bromide.
Allylsamarium bromide has been reported to substitute the benzo-
triazolyl group in N-aminoalkylbenzotriazoles, thus providing a useful
method for the preparation of a variety of secondary and tertiary homo-
allylamines.[5] The similarity between N-(a-amidoalkyl)benzotriazoles
(readily obtained from amides, aldehydes, and benzotriazole) and
N-aminoalkylbenzotriazoles (easily available from amines, aldehydes
and benzotriazole) prompted us to investigate the possibility of preparing
homoallylamides via the nucleophilic substitution of the benzotriazolyl
group in the N-(a-amidoalkyl)benzotriazoles with allylsamarium bromide
(Sch. 1).
The study initiated with substrate la (R1¼R2 ¼C6H5). When 1a was
treated with allylsamarium bromide, the characteristic purple color of
Bt
NHCR2
SmBr
R1
R1
+
BtH
NHCR2
O
THF, RT
O
1
2
N
N
N
Bt =
Scheme 1.

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Substitution of the Benzotriazolyl Group
3577
Table 1. Replacement of the benzotriazolyl group in the N-(a-amidoalkyl)-
benzotriazoles and N-(a-sulfonamidoalkyl)benzotriazoles with allylsamarium
bromide.
Entry
1
Substrate
Product
Yieldsa (%)
74
Bt
2a
1a
NHCPh
O
NHCPh
O
Bt
2
3
69
76
1b
2b
MeO
MeO
NHCPh
O
H3C NHCPh
NHCPh
O
Bt
NHCPh
1c
H
O
O
Bt
4
5
6
82
96
96
1d
CH2NHCMe
O
NHCMe
O
Bt
O
O
3a
4a
NHS
O
CH3
NHS
O
CH3
Bt
O
O
3b
H3C
4b
H3
C
NHS
O
CH3
3c
NHS
O
CH3
4c
Bt
7
95
O
O
n-Pr
n-Pr
NHS
O
CH3
NHS
O
CH3
Bt
O
NHS
O
8
9
93
92
97
O
NHS
O
3d
3e
i-Pr
4d
i-Pr
CH3
CH3
CH3
Bt
O
NHS
O
O
NHS
O
i-Bu
4e
i-Bu
CH3
Bt
10
O
NHS
O
3f
4f
NHS
O
O
aYields of isolated products.
allylsamarium bromide faded immediately. Routine work-up afforded a
new compound, which was characterized as product 2a via its IR,
1H-NMR and MS spectral data. However, it was found that when either
R1 or R2 in substrate 1 is an alkyl, product 2 could not be afforded and
the only product obtained was that resulting from the reductive elimi-
nation of benzotriazole (Table 1, Entries 3 and 4). The formation of the
reduction product may be attributed to the reductive ability inherent of
the two-valent samarium in the allylsamarium bromide.
To further explore the generality of the reaction, it is reasonable to
extend the substrates to N-(a-sulfonamidoalkyl)benzotriazoles, which are
the analogues of N-(a-amidoalkyl)benzotriazoles and are easily prepared
from sulfonamides, aldehydes, and benzotriazole. As shown in Sch. 2, the
benzotriazolyl group in the N-(a-sulfonamidoalkyl)benzotriazoles can

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3578
Wang, Li, and Zhang
Bt
N
N
O
SmBr
R3
O
NHS
O
R3
+
NHS Ar
O
Ar
N
H
THF, RT
3
4
Scheme 2.
be replaced by allylsamarium bromide and give the corresponding
homoallylsulfonamides smoothly.
It is satisfying to note that no matter R3 in compound 3 is an aryl or
alkyl, products 4 can always be obtained in almost quantitative yields
(Table 1).
In conclusion, the benzotriazolyl group in the N-(a-amidoalkyl)-
benzotriazoles and N-(a-sulfonamidoalkyl)benzotriazoles can be replaced
by allylsamarium bromide. The readily available starting materials, the
mild reaction conditions and the excellent yields make the reaction
reported here an attractive one for the preparation of homoallylamides
and homoallylsulfonamides.
EXPERIMENTAL
Tetrahydrofuran was distilled from sodium-benzophenone immed-
iately prior to use. All reactions were conducted under a nitrogen
atomsphere. Melting points are uncorrected. 1H NMR spectra were
recorded on a Bruker 400 MHz instrument as CDCl3 solutions using
TMS as internal standard. Chemical shifts (ꢀ) are reported in ppm and
coupling constants J is given in Hz. IR spectra were recorded using KBr
disks with a Bruker Vector-22 infrared spectrometer. Elemental analyses
were performed on a EA-1110 instrument. Substrates 1a–1d[6] and
3a–3f [7] are prepared according to literature procedures.
General procedure for the replacement of the benzotriazolyl group with
allylsamarium bromide. Under an inert atmosphere of nitrogen, powdered
samarium (0.30 g, 2.0 mmol) was placed in a 50 mL two-necked flask and
allylbromide (0.27 g, 2.2 mmol) in 1 mL THF was added by syringe. After
subsequent addition of a catalytic amount of iodine, the mixture
was magnetically stirred for 1 h at room temperature to obtain a purple
suspension. Then a solution of N-(a-amidoalkyl)benzotriazoles or N-(a-
sulfonamidoalkyl)benzotriazoles (1 mmol) in 4–6 mL of THF was added
to the suspension in one portion by syringe. The purple color faded
immediately and the mixture was stirred for 5 min more. The reaction

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Substitution of the Benzotriazolyl Group
3579
was quenched with 0.1 M hydrochloric acid (5 mL) and extracted with
ether (3 ꢀ 10 mL). The organic layer was washed with brine and dried
over anhydrous Na2SO4. The solvent was removed by evaporation under
reduced pressure. The crude product was purified by preparative TLC on
silica gel (cyclohexane/ethyl acetate ¼ 3:1 as eluent).
Compound 2a. M.p.: 118–120ꢁC. ꢁmax (KBr)/cmꢂ1: 3349, 3054, 3030,
1635, 1603. ꢀH (CDCl3): 7.77 (2H, d, J 8.4 Hz), 7.28–7.52 (8H, m), 6.41
(1H, d, br, J 7.2 Hz), 5.74–5.81 (1H, m), 5.27–5.32 (1H, apparent q, J
6.8 Hz), 5.12–5.21 (2H, m), 2.70 (2H, apparent t, J. 6.8 Hz). m/z (%): 251
(Mþ, 0.61), 210 (30.96), 105 (100). Anal. calcd. for C17H17NO: C, 81.24;
H, 6.82; N, 5.57. Found: C, 81.33; H, 6.85; N, 5.52%.
Compound 2b. M.p.: 123–125ꢁC. ꢁmax (KBr)/cmꢂ1: 3340, 2959, 1633,
1532. ꢀH (CDCl3): 7.77–7.79 (2H, m), 7.43–7.54 (3H, m), 7.29–7.31 (2H,
m), 6.89–6.92 (2H, m), 6.37 (1H, d, br, J 6.8 Hz), 5.76–5.83 (1H, m),
5.12–5.27 (3H, m), 3.82 (3H, s), 2.68–2.73 (2H, m). m/z (%): 281 (Mþ,
0.52), 240 (32.26), 105 (100). Anal. calcd. for C18H19NO2: C, 76.84; H,
6.81; N, 4.98. Found: C, 76.89; H, 6.87; N, 4.91%.
Compound 4a. M.p.: 76–77ꢁC (Lit.[8] 76–77ꢁC). ꢁmax (KBr)/cmꢂ1
:
3259, 3062, 2897, 1642, 1600, 1497. ꢀH (CDCl3): 7.56–7.58 (2H, d, J
8.4 Hz), 7.08–7.34 (7H, m), 5.47–5.58 (1H, m), 4.92–5.09 (3H, m), 4.39
(1H, apparent q, J 6.8 Hz), 2.41–2.60 (5H, m).
Compound 4b. M.p.: 118–120ꢁC (Lit.[8] 116–117ꢁC). ꢁmax
(KBr)/cmꢂ1: 3253, 3063, 2921, 1644, 1597, 1496. ꢀH (CDCl3): 7.58 (2H,
d, J 8.4 Hz), 7.17 (2H, d, J 7.6 Hz), 6.96–7.02 (4H, m), 5.47–5.57 (1H, m),
5.04–5.09 (2H, m), 4.83 (1H, d, br, J 6.4 Hz), 4.34 (1H, apparent q, J
6.8 Hz), 2.44–2.53 (2H, m), 2.40 (3H, s), 2.30 (3H, s).
Compound 4c. M.p.: 87–88ꢁC. ꢁmax (KBr)/cmꢂ1: 3273, 3071, 2959,
2936, 2874, 1642, 1599, 1495. ꢀH (CDCl3): 7.76 (2H, d, J 8.4 Hz), 7.31
(2H, d, J 8.4 Hz), 5.56–5.61 (1H, m), 4.95–5.06 (2H, m), 4.33 (1H, d, br, J
7.6 Hz), 3.30–3.33 (1H, m), 2.47 (3H, s), 2.11 (2H, apparent t, J 6.4 Hz),
1.22–1.46 (4H, m), 0.82 (3H, t, J 7.2 Hz). m/z (%): 268 (Mþ þ 1, 1.41),
226 (59.75), 155 (58.36), 91 (100). Anal. calcd. for C14H21NO2S: C, 62.89;
H, 7.92; N, 5.24. Found: C, 62.82; H, 8.03; N, 5.21%.
Compound 4d. M.p.: 67–69ꢁC. ꢁmax (KBr)/cmꢂ1: 3268, 3070, 2958,
2875, 1641, 1599, 1496. ꢀH (CDCl3): 7.76 (2H, d, J 8.0 Hz), 7.30 (2H, d, J
8.0 Hz), 5.46–5.54 (1H, m), 4.93–5.06 (2H, m), 4.42 (1H, d, br, J 8.0 Hz),
3.09–3.14 (1H, m), 2.44 (3H, s), 2.08 (2H, apparent t, J 6.4 Hz), 1.76–1.82
(1H, m), 0.84 (6H, d, J 7.2 Hz). m/z (%): 268 (Mþ þ 1, 0.62), 226 (52.79),
155 (62.58), 91 (100). Anal. calcd. for C14H21NO2S: C, 62.89; H, 7.92; N,
5.24. Found: C, 62.85; H, 7.99; N, 5.20%.
Compound 4e. M.p.: 70–71ꢁC. ꢁmax (KBr)/cmꢂ1: 3274, 3070, 2958,
2933, 2871, 1642, 1600, 1497. ꢀH (CDCl3): 7.77 (2H, d, J 8.4 Hz), 7.31

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3580
Wang, Li, and Zhang
(2H, d, J 8.4 Hz), 5.56–5.63 (1H, m), 4.94–5.07 (2H, m), 4.28 (1H, br),
3.34–3.40 (1H, m), 2.45 (3H, s), 2.11 (2H, m), 1.22–1.30 (2H, m),
0.75–0.92 (7H, m). m/z (%): 282 (Mþ þ 1, 1.52), 240 (61.12), 155
(55.56), 91 (100). Anal. calcd. for C15H23NO2S: C, 64.02; H, 8.24; N,
4.98. Found: C, 64.12; H, 8.27; N, 4.92%.
Compound 4f. M.p.: 79–81ꢁC (Lit.[9] 80–81ꢁC). ꢁmax (KBr)/cmꢂ1
:
3251, 3060, 1641, 1600, 1496. ꢀH (CDCl3): 7.64–7.80 (2H, m), 7.28–7.53
(4H, m), 6.98–7.20 (4H, m), 5.48–5.62 (1H, m), 4.92–5.09 (3H, m), 4.39
(1H, apparent q, J 6.8 Hz), 2.41 (2H, apparent t, J 7.2 Hz).
ACKNOWLEDGMENT
We are grateful to the National Natural Science Foundation of
China (Project No. 20072033) and the Specialized Research Fund for
the Doctoral Program of Higher Education of China for financial
support.
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Substitution of the Benzotriazolyl Group
3581
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Received in Japan March 12, 2003

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