The facile one-pot synthesis of N-imidoylbenzotriazoles via a Beckmann rearrangement of ketoximes

Article abstract of DOI:10.1016/j.tet.2010.06.001

N-Imidoylbenzotriazoles 2a-m were obtained in good to excellent yields (up to 97%) by the reaction of ketoximes 1a-m with MsCl and subsequently with benzotriazole as a one-pot process in Toluene/CH₃CN at reflux temperature via a Beckmann rearrangement.

Full text of DOI:10.1016/j.tet.2010.06.001

Tetrahedron 66 (2010) 6097e6100
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The facile one-pot synthesis of N-imidoylbenzotriazoles via a Beckmann
rearrangement of ketoximes
*
*
Hong-Jun Pi, Li-Feng Liu, Shan-Shan Jiang, Wenting Du , Wei-Ping Deng
School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
a r t i c l e i n f o
a b s t r a c t
Article history:
N-Imidoylbenzotriazoles 2aem were obtained in good to excellent yields (up to 97%) by the reaction of
ketoximes 1aem with MsCl and subsequently with benzotriazole as a one-pot process in Toluene/CH3CN
at reflux temperature via a Beckmann rearrangement.
Received 19 April 2010
Received in revised form 1 June 2010
Accepted 1 June 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Available online 8 June 2010
1. Introduction
benzotriazoles in the presence of BF3$Et2O and the reaction of
isocyanates8 with N-acylbenzotriazoles have also been reported to
Imidoylbenzotriazoles are chemically stable and versatile re-
agents, which have been employed as useful substitutes for imidoyl
chlorides1 in the synthesis biologically important functional groups
or compounds (shown in Fig. 1) such as enaminones,2
produce the imidoylbenzotriazoles.
In 1999, Katritzky9 reported a new synthesis of imidoylbenzo-
triazoles via BtTs mediated Beckmann Rearrangement of Ketox-
imes, in which a heterogeneous reaction system is required (t-BuOK
or K2CO3/crown ether 18C6) and the yields of corresponding
products are low to moderate in most cases. Considering the
availability of various ketoximes, this new synthetic methodology
obviously provides a potentially useful way to imidoylbenzo-
triazoles despite of the moderate yields and relatively harsh re-
action condition.
N-substituted
b
-enamino acid derivatives,3 polysubstituted ami-
dines,4 1,5-substituted tetrazoles,5 amidrazones,6 and triazoles.6
R1
R1
R2
HN
R1
R2
HN
R3
O
N
N
R3
N
N
R2
amidines
N
R4
As a part of research work in our group, we have developed
a series of catalytic systems for the Beckmann Rearrangement of
ketoximes including BOPCl,10 TsCl,11 TAPC,12 AlCl3. 13 According to
the traditional reaction mechanism, the Beckmann Rearrangement
of oxime sulfonates occurs smoothly to form a reactive imino-
carbocation intermediate, which could be attacked by benzo-
triazole to form imidoylbenzotriazole as an excellent electrophile.
In Katritzky’s report,9 the pre-prepared BtTs, containing both
nucleophilic moiety Bt and Ts part serving for the formation of
oxime sulfonates, was used for the synthesis of N-imidoylbenzo-
triazole. The relatively low yield of BtTs system is presumably
caused by the low reactivity of BtTs in the formation of oxime
sulfonates; therefore crown ether 18C6 and strong base t-BuOK
instead of organic base such as triethylamine were employed to
facilitate this process.
Based on above assumption, as depicted in Scheme 1, we further
envisaged that the formation of oxime sulfonates A in situ by
treating the oximes 1 with sulfonyl chloride in the presence of base,
followed by smooth Beckmann Rearrangement of oxime sulfonates
A to form the iminocarbocation species B, which is subjected to
simultaneous nucleophilic attack by benzotriazole to afford the
imidoylbenzotriazoles 2. As a consequence, we would like to
enaminones
tetrazoles
R1
N
R1
Bt
R2
HN
N
R3
R1
R2
R2
R1
R2
X
N
N
R3
HN
H
N
N
N
enamino acid
derivatives
R3
triazoles
amidrazones
Figure 1.
Due to its synthetical importance, many efforts have been made
to develop the synthetic methods by Katritzky1e6 including the
reaction of secondary amides under various reaction systems such
as BtH/POCl3/Et3N,1a Bt2SO,1b BtCl/PPh3,3 BtH/Pyridine/(COCl)2,4
and BtH/SOCl2.4 The reaction of isonitriles7 with N-(aminoalkyl)
* Corresponding authors. Tel./fax: þ86 021 64252431; e-mail addresses:
ddwwtt@163.com (W. Du), weiping_deng@ecust.edu.cn (W.-P. Deng).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.06.001

6098
H.-J. Pi et al. / Tetrahedron 66 (2010) 6097e6100
property of substituents on aromatic ring. The benzophenone ox-
O
S
O
O
S
O
ime also proceeded smoothly affording product in 82% yield. No-
tably, the bulky oxime 1m gave corresponding N-
imidoylbenzotriazole 2m as a 3:1 E/Z isomers in very good yield
(entry 13, 77% yield), which is much better than that of Katritzky’s
result (77% vs 35% in BtTs system9). Interestingly, oximes 1i, 1j, and
1l were not ideal for this process and afforded corresponding
N-imidoylbenzotriazoles in low to moderate yields (40%, 37%, and
17%, respectively). We also tested the reaction of all substrates in
acetonitrile, and found that the yields of N-imidoylbenzotriazoles
for most cases were lower than that in toluene. However, for the
cyclohexanone oxime 1j and 1l, the yields were increased to 53%
from 37%, 73% from 17%, respectively(Table 1).
Compounds 2ael were determined as single E-isomers not only
based on the NMR spectrum comparisons of our compounds to that
of reported one,9 but also the single crystal structure of X-ray dif-
fraction of compound 2f, the ORTEP plots with atom numbering
scheme was shown in Figure 2. Compound 2m was assigned as
a 3:1 E/Z isomers based on the NMR spectrum comparison of our
compound to that of reported one.9
Cl
CH3
O
CH3
OH
R2
N
N
R1
R2
R1
Et3N
Et3NHCl
1
A
N
N
N
R2
N R1
B
+ MsO
Et3N
N
R2
R1
MsOHNEt3
H
N
2
N
N
Scheme 1. Possible reaction pathway.
describe herein
a highly efficient one-pot synthesis of imi-
doylbenzotriazoles by the reaction of ketoximes with MsCl and
benzotriazoles in toluene or acetonitrile using triethylamine as
base at reflux temperature.
2. Results and discussion
Initially, MsCl was used to react with acetophenone oxime 1a in
CH3CN using Et3N as base at 0 ꢀC, without any workup, the
resulting oxime sulfonate was then treated with benzotriazole at
reflux temperature (Table 1). To our delight, as expected, the re-
action proceeded very smoothly and generated the desired N-
imidoylbenzotriazole in good yield (76% vs 60% in BtTs system,9
entry 1). A simple solvent screening found that toluene gave the
best result (95% yield, entry 1). Next, we examined the scope of
substrates by using diarylketoxime 1b, arylalkylketoximes 1a, ceh,
dialkylketoximes 1iem, and cyclohexanone oxime 1j. All the ary-
lalkylketoximes gave corresponding N-imidoylbenzotriazoles in
excellent yields (91e97%) in toluene, regardless the electronic
Figure 2. ORTEP view and atom numbering scheme for N-Imidoylbenzotriazole 2f,
and the thermal ellipsolids of the non-hydrogen atoms are drawn at the 50% proba-
bility level.
Table 1
The one-pot synthesis of N-imidoylbenzotriazolesa
N
N
N
N
3. Conclusion
OH
R2
N
H
MsCl, Et3N
Solvent, 0 oC
N
N
reflux
R1
N
In conclusion, a new one-pot method for the synthesis of
N-imidoylbenzotriazoles has been presented. This newly developed
procedure would definitely provide an attractive way to make such
compounds considering the excellent yields, simple operation, mild
reaction condition, and easily available reagents.
R2
R1
1a-m
2a-m
Entry
R1
R2
Yield(%)
CH3CN/Tol.
Yielde (%)
Toluene
1(2a)
Ph
Ph
Ph
Ph
Me
Me
Me
Ph
Me
Me
Me
Me
Et
76/95
46
Nd.
60
d
d
70
d
d
d
d
d
d
20
37
20
60
35
1(2a)b
1(2a)c
2(2b)
3(2c)
4. Experimental
79/82
81/97
67/91
81/92
82/95
81/90
85/94
31/40
53/37
25/47
73/17
46/77
4.1. General methods
p-MeC6H4
p-MeOC6H4
o-MeOC6H4
m-MeOC6H4
Ph
4(2d)
5(2e)d
6(2f)d
7(2g)
All solvents were distilled under standard procedures prior to
use under nitrogen atmosphere. (For example: CH3CN distilled
from CaH2; THF, dioxane, toluene distilled from Sodium). 1H
(400 MHz) and 13C (100 MHz) NMR chemical shifts were reported
in CDCl3 7.27 ppm for 1H, 77 ppm for 13C as standards and coupling
constants (J) are reported in hertz (Hz). The following abbreviations
are used to designate signal multiplicity: s¼singlet, d¼doublet,
t¼triplet, q¼quartet, m¼multiplet, br¼broad.
8(2h)d
9(2i)
p-ClC6H4
Me
Me
Me
10(2j)
11(2k)
12(2l)
13(2m)
(CH2)5
Bn
Bn
Me
iPr
tBu
iPr
a
Reaction condition: (i) ketoxime (1.0 equiv), Et3N (2.2 equiv), MsCl (1.1 equiv),
Toluene/CH3CN, ice bath, 30 min; (ii) benzotriazole (1.5 equiv), reflux, 2 h.
b
THF was used instead of CH3CN or toluene.
Dioxane was used instead of CH3CN or toluene, and no desired product was
4.2. General procedure
c
found.
d
To a solution of corresponding ketoxime (2 mmol) and trie-
thylamine (0.62 mL, 4.4 mmol) in 4 mL of anhydrous toluene or
New compounds.
e
Yields from Katritzky’s result using toluene as solvent in Ref. 9.

H.-J. Pi et al. / Tetrahedron 66 (2010) 6097e6100
6099
acetonitrile under
a
nitrogen atmosphere was added MsCl
146.7, 131.3, 130.1, 129.2, 125.4, 119.7, 115.7, 112.5, 109.8, 106.2, 55.3,
(2.2 mmol) in an ice bath. After stirring for 30 min, benzotriazole
(3 mmol) was then added and the resulting mixture was refluxed
for 2 h. After completion of the reaction as monitored by TLC, the
reaction was quenched with saturated aqueous sodium carbonate.
The organic layer was extracted with ethyl acetate, dried over an-
hydrous sodium sulfate, and concentrated on rotary vacuum
evaporator. The resulting crude product was purified by column
chromatography on silica gel to give the corresponding N-aryl
imidoylbenzotriazole in high yield with petroleum ether and ethyl
acetate used as eluent. Other than, petroleum ether and ethyl ac-
etate with triethylamine were chosen as eluent for N-alkyl
substituted imidoylbenzotriazoles.
16.3; HRMS (EI) calcd for C
15H14N4O [Mþ] 266.1168, found
266.1164; IR(KBr), cmꢁ1: 3096, 3073, 3017, 1674, 1485, 1449, 1390,
1283, 1083, 968. Crystals of 2f were triclinic, space group P-1;
empirical formula C15H14N4O, formula weight, 266.30; a¼9.5140
(11) Å, b¼12.7073(15) Å, c¼13.2828(15) Å,
a
¼62.272(2)ꢀ,
¼86.659
b
(2)ꢀ,
g
¼74.863(2)ꢀ, V¼1368.4(3) Å3; T¼293(2) K;
l
¼0.71073 Å;
Z¼4, Dcalc¼1.293 g cmꢁ3
;
F(000)¼560,
m
¼0.085 mmꢁ1
; crystal
size¼0.420ꢂ0.381ꢂ0.207 mm; reflections collected, 7267; unique
reflections (Rint¼0.0709), 5029; wR2¼0.1437(all data), R1¼0.0527
(I>2s(I)); Data in the q
range 1.87e25.50ꢀ were collected at 293(2)
K on a Bruker Apex CCD diffractometer. The structure was solved by
direct methods and refined by full-matrix least-squares using all F2
data. The hydrogen atoms were placed in calculated positions and
allowed to ride on the parent atom.
All products gave satisfactory analytical data, which were listed
as follows.
4.2.1. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)ethylidene)aniline
4.2.7. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)propylidene) aniline
(2a). Light yellow solid (EtOAc-n-hexane); mp 109e110 ꢀC,
(2g). White solid (EtOAc-n-hexane); mp 101e102 ꢀC, (lit.1a mp
(lit.4 mp 106e108 ꢀC); 1H NMR (400 MHz, CDCl3)
d
8.54 (d,
99 ꢀC); 1H NMR (400 MHz, CDCl3)
d
8.50 (d, J¼8.3 Hz, 1H), 8.11 (d,
J¼8.3 Hz, 1H), 8.13 (d, J¼8.3 Hz, 1H), 7.59 (t, J¼7.7 Hz, 1H), 7.48
J¼8.3 Hz, 1H), 7.55 (t, J¼7.6 Hz, 1H), 7.48e7.36 (m, 3H), 7.16
(t, J¼7.7 Hz, 1H), 7.42 (t, J¼7.8 Hz, 2H), 7.19 (t, J¼7.4 Hz, 1H), 6.95 (d,
(t, J¼7.4 Hz, 1H), 6.94 (d, J¼7.6 Hz, 2H), 3.14 (q, J¼7.5 Hz, 2H), 1.35 (t,
J¼7.4 Hz, 2H), 2.75 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
154.0, 147.4,
J¼7.5 Hz, 3H); 13C NMR (100 MHz, CDCl3)
d 158.5, 147.4, 146.6, 131.5,
146.6, 131.3, 129.3, 129.2, 125.4, 124.4, 120.3, 119.7, 115.7, 16.3.
129.3(2), 129.2(7), 125.4, 124.2, 119.9, 119.7, 115.8, 23.0, 12.9.
4.2.2. (E)-N-((1H-Benzo[d][1,2,3]triazol-1-yl)(phenyl)methylene)
4.2.8. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)ethylidene)-4-chlor-
aniline (2b). Yellow needles (EtOAc-n-hexane); mp 131e132 ꢀC,
oaniline(2h). Colorless needles (EtOAc-n-hexane); mp 148e149 ꢀC;
(lit.4 mp 129e131 ꢀC); 1H NMR (400 MHz, CDCl3)
d
8.49 (d,
1H NMR (400 MHz, CDCl3)
d
8.47 (d, J¼8.2 Hz, 1H), 8.10 (d, J¼8.2 Hz,
J¼8.4 Hz, 1H), 8.17 (d, J¼8.3 Hz, 1H), 7.65 (t, J¼7.7 Hz, 1H), 7.52
(t, J¼7.7 Hz, 1H), 7.45e7.35 (m, 5H), 7.23 (t, J¼7.8 Hz, 2H), 7.04 (t,
J¼7.4 Hz, 1H), 6.88 (dd, J¼8.4, 1.1 Hz, 2H); 13C NMR (100 MHz,
1H), 7.57 (t, J¼7.6 Hz, 1H), 7.46 (t, J¼7.6 Hz, 1H), 7.37 (d, J¼8.3 Hz,
2H), 6.89 (d, J¼8.5 Hz, 2H), 2.73 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
154.6, 146.6, 145.9, 131.2, 129.8, 129.4, 129.3, 125.5, 121.8, 119.8,
CDCl3)
d
153.9, 147.1, 146.5, 132.1, 130.4(4), 130.3(8), 130.2(8), 129.4,
115.6, 16.4; HRMS (EI) calcd for C14H1135ClN4 [Mþ] 270.0672, found
270.0671; IR(KBr), cmꢁ1: 3112, 3067, 2832, 1682, 1595, 1485, 1390,
1207, 1075, 1038, 977.
129.0, 128.3, 125.7, 124.3, 121.6, 120.1, 115.5.
4.2.3. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)ethylidene)-4-meth-
ylaniline (2c). Light yellow solid (EtOAc-n-hexane); mp 117e118 ꢀC,
4.2.9. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)ethylidene) methan-
(lit.4 mp 113e115 ꢀC); 1H NMR (400 MHz, CDCl3)
d
8.47 (d, J¼8.2 Hz,
amine (2i). Yellow needles (EtOAc-n-hexane); mp 64e65 ꢀC, (lit.9
1H), 8.05 (d, J¼8.2 Hz, 1H), 7.49 (t, J¼7.5 Hz, 1H), 7.38 (t, J¼7.5 Hz,
mp 52.0e53.0 ꢀC); 1H NMR (400 MHz, CDCl3)
1H), 8.10 (d, J¼8.2 Hz, 1H), 7.53 (t, J¼7.6 Hz, 1H), 7.42 (t, J¼7.5 Hz,
d
8.39 (d, J¼8.3 Hz,
1H), 7.17 (d, J¼7.8 Hz, 2H), 6.84 (d, J¼7.9 Hz, 2H), 2.70 (s, 3H), 2.34 (s,
3H); 13C NMR (100 MHz, CDCl3)
d
153.9, 146.6, 144.8, 133.8, 131.3,
1H), 3.38 (s, 3H), 2.68 (s, 3H); 13C NMR (100 MHz, CDCl3)
146.2, 131.0, 128.4, 124.7, 119.1, 115.4, 37.0, 13.5.
d 155.0,
129.8, 129.1, 125.3, 120.4, 119.7, 115.8, 21.0, 16.2.
4.2.4. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)ethylidene)-4-me-
thoxyaniline (2d). Light yellow solid (EtOAc-n-hexane); mp
135e136 ꢀC, (lit.2 mp 128e129 ꢀC); 1H NMR (400 MHz, CDCl3)
4.2.10. 1-(3,4,5,6-Tetrahydro-2H-azepin-7-yl)-1H-benzo[d][1,2,3] tri-
azole (2j). Colorless needles (EtOAc-n-hexane); mp 110e111 ꢀC,
(lit.9 mp 101.0 ꢀC); 1H NMR (400 MHz, CDCl3)
d
8.44 (d, J¼8.3 Hz,
d
8.55 (d, J¼8.3 Hz, 1H), 8.13 (d, J¼8.3 Hz, 1H), 7.60 (t, J¼7.5 Hz, 1H),
7.48 (t, J¼7.5 Hz, 1H), 6.99e6.90 (m, 4H), 3.85 (s, 3H), 2.78 (s, 3H);
13C NMR (100 MHz, CDCl3)
156.8, 154.0, 146.6, 140.5, 131.3, 129.1,
1H), 8.08 (d, J¼8.2 Hz, 1H), 7.55 (t, J¼7.6 Hz, 1H), 7.42 (t, J¼7.6 Hz,
1H), 3.91e3.88 (m, 2H), 3.53e3.50 (m, 2H), 1.99e1.90 (m, 2H),
d
1.81e1.71 (m, 4H); 13C NMR (100 MHz, CDCl3)
d 162.1, 146.8, 131.3,
125.3, 121.7, 119.7, 115.8, 114.5, 55.5, 16.2.
128.7, 125.0, 119.5, 115.8, 50.5, 31.1, 29.5, 26.5, 23.3.
4.2.5. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)ethylidene)-2-me-
4.2.11. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)-2-phenyl-
thoxyaniline (2e). Colorless needles (EtOAc-n-hexane); mp
ethylidene)-1-phenylmethanamine (2k)9. 1H NMR (400 MHz, CDCl3)
131e132 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.59 (d, J¼8.3 Hz, 1H), 8.12
d
8.49 (d, J¼8.2 Hz, 1H), 8.02 (d, J¼8.2 Hz, 1H), 7.47 (t, J¼7.5 Hz, 1H),
7.42e7.32 (m, 5H), 7.30e7.13 (m, 6H), 4.91 (s, 2H), 4.72 (s, 2H); 13C
NMR (100 MHz, CDCl3) 155.6,146.9,139.6,134.8,131.7,129.2,129.1,
(d, J¼8.3 Hz, 1H), 7.59 (t, J¼7.5 Hz,1H), 7.47 (t, J¼7.7 Hz, 1H), 7.17 (td,
J¼8.0, 1.6 Hz, 1H), 7.06e6.97 (m, 2H), 6.94 (dd, J¼7.6, 1.5 Hz, 1H),
d
3.83 (s, 3H), 2.67 (s, 3H); 13C NMR (100 MHz, CDCl3)
d
155.2, 149.3,
128.8, 128.7, 127.8, 127.2(2), 127.1(5), 125.4, 119.8, 115.9, 54.1, 34.1.
146.7, 136.4, 131.5, 129.2, 125.3, 121.6, 121.1, 119.7, 116.0, 111.8, 55.7,
16.8; HRMS (EI) calcd for C15H14N4O [Mþ] 266.1168, found
266.1166; IR(KBr), cmꢁ1: 3070, 2961, 2934, 2832, 1684, 1490, 1443,
1396, 1248, 1085, 1031, 972.
4.2.12. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)ethylidene)-2 meth-
ylpropan-2-amine (2l)9. 1H NMR (400 MHz, CDCl3)
d 8.45 (d,
J¼8.4 Hz, 1H), 8.06 (d, J¼8.3 Hz, 1H), 7.53 (t, J¼7.5 Hz, 1H), 7.41 (t,
J¼7.4 Hz, 1H), 2.86 (s, 3H), 1.50 (s, 9H); 13C NMR (100 MHz, CDCl3)
4.2.6. (E)-N-(1-(1H-Benzo[d][1,2,3]triazol-1-yl)ethylidene)-3-me-
d 150.4, 146.5, 131.3, 128.3, 124.6, 119.3, 116.0, 54.5, 30.5, 18.1.
thoxyaniline (2f). Colorless crystals (EtOAc-n-hexane); mp
84e85 ꢀC; 1H NMR (400 MHz, CDCl3)
d
8.53 (d, J¼8.3 Hz, 1H), 8.13
4.2.13. N-[(E,Z)-1-(1H-Benzo[d][1,2,3]triazol-1-yl)-2-methyl-
(d, J¼8.3 Hz, 1H), 7.60 (t, J¼7.7 Hz, 1H), 7.49 (t, J¼7.7 Hz, 1H), 7.33 (t,
propylidene]propan-2-amine(2m)9. 1H NMR (400 MHz, CDCl3)
J¼8.0 Hz, 1H), 6.75 (dd, J¼8.3, 1.8 Hz, 1H), 6.56e6.44 (m, 2H), 3.85
d
8.34 (d, J¼8.3 Hz, 1H), 8.13 (d, J¼8.6 Hz, 1H), 8.07 (d, J¼8.3 Hz, 1H),
(s, 3H), 2.76 (s, 3H); 13C NMR (100 MHz, CDCl3)
d 160.5, 154.2, 148.8,
7.57e7.49 (m, 2H), 7.46e7.37 (m, 3H), 4.19e4.09 (m, 1H), 3.87e3.76

6100
H.-J. Pi et al. / Tetrahedron 66 (2010) 6097e6100
(m, 1H), 3.26e3.02 (m, 2H), 1.53 (d, J¼7.1 Hz, 6H), 1.34 (d, J¼6.2 Hz,
6H),1.17 (d, J¼6.8 Hz, 6H),1.11 (d, J¼6.2 Hz, 6H); 13C NMR (100 MHz,
References and notes
1. (a) Katritzky, A. R.; Rachwal, S.; Offerman, R. J.; Zbiginew, N.; Yagoub, A. K.;
Zhang, Y. Chem. Ber. 1990, 123, 1545; (b) Katritzky, A. R.; Stevens, C. V.; Zhang,
G.-F.; Jiang, J. Heterocycles 1995, 40, 231; (c) Katritzky, A. R.; Yang, B.; Abonia, R.;
Insuasty, B. J. Chem. Res., Synop. 1996, 540.
2. Katritzky, A. R.; Hayden, A. E.; Kirichenko, K.; Pelphrey, P.; Ji, Y. J. Org. Chem.
2004, 69, 5108.
3. Katritzky, A. R.; Donkor, A.; Fang, Y. J. Org. Chem. 2001, 66, 4041.
4. Katritzky, A. R.; Cai, C.; Singh, S. K. J. Org. Chem. 2006, 71, 3375.
5. Katritzky, A. R.; Cai, C.; Meher, N. K. Synthesis 2007, 8, 1204.
6. (a) Modzelewska-Banachiewicz, B.; Matysiak, J.; Niewiadomy, A. Eur. J. Med.
Chem. 2002, 36, 75; (b) Katritzky, A. R.; Khashab, N. M.; Kirichenko, N.;
Singh, S. K. J. Org. Chem. 2006, 71, 9051.
7. Katritzky, A. R.; Button, M. A. C.; Busont, S. J. Org. Chem. 2001, 66, 2865.
8. Katritzky, A. R.; Huang, T. B.; Voronkov, M. V. J. Org. Chem. 2001, 66, 1043.
9. Katritzky, A. R.; Monteux, D. A.; Tymoshenko, D. O. Org. Lett. 1999, 1, 577.
10. Zhu, M.; Cha, C.; Deng, W.-P.; Shi, X.-X. Tetrahedron Lett. 2006, 47, 4861.
11. Pi, H.-J.; Dong, J.-D.; An, N.; Du, W.; Deng, W.-P. Tetrahedron 2009, 65, 7790.
12. (a) Zhu, M. Studies on Small Molecule Catalyzed Beckmann rearrangement.
A thesis for the degree of Master of Science, Jan 2007. (b) Hashimoto, M.; Obora,
Y.; Sakaguchi, S.; Ishii, Y. J. Org. Chem. 2008, 73, 2894.
CDCl3)
d 158.0, 151.7, 145.6, 144.6, 132.6, 132.1, 128.4, 128.3, 124.6,
124.2, 120.0, 119.2, 115.6, 109.5, 51.2, 49.6, 36.8, 29.0, 24.4, 23.7,
19.7, 19.4.
Acknowledgements
This work was financially supported by the Natural Science
Foundation of China (No. 20602011), the New Century Excellent
Talents in University, the Ministry of Education, China (No. NCET-
07-0283), and ‘111’ Project (No. B07023).
Supplementary data
Supplementary data for this article can be found in the online
version, at doi:10.1016/j.tet.2010.06.001. The 1H NMR and 13C NMR
copies of all compounds were attached as supplementary material.
These data include MOL files and InChIKeys of the most important
compounds described in this article.
13. Liu, L.-F.; Liu, H.; Pi, H.-J.; Yang, S.; Yao, M.; Du, W.; Deng, W.-P. Syn. Commun., in
press.