o-Phthalic Anhydride/Zn(OTf)2 co-catalyzed Beckmann rearrangement under mild conditions

Article abstract of DOI:10.1016/j.tet.2019.04.056

o-Phthalic anhydride/Zn(OTf)₂ co-catalyzed Beckmann rearrangement was developed, producing the corresponding amide in up to 99% yield with acid-sensitive functionalities tolerated well, and the scale of the reaction could be enlarged to 77 mmol and the excellent yield was maintained. A successive procedure was developed. Moreover, the reaction was carried out at rt under nearly neutral conditions, and the workup was concise. These features illustrated the potential of the protocol in amide synthesis.

Full text of DOI:10.1016/j.tet.2019.04.056

Tetrahedron xxx (xxxx) xxx
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o-Phthalic Anhydride/Zn(OTf) co-catalyzed Beckmann rearrangement
2
under mild conditions
a
,
b
,
*
, Teng Zhang , Wenjun Hong a
a
Ze-Feng Xu
a
Department of Chemistry, Zhejiang Sci-Tech University, Xiasha West Higher Education District, Hangzhou, 310018, China
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032,
b
China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 March 2019
Received in revised form
o-Phthalic anhydride/Zn(OTf)2 co-catalyzed Beckmann rearrangement was developed, producing the
corresponding amide in up to 99% yield with acid-sensitive functionalities tolerated well, and the scale of
the reaction could be enlarged to 77 mmol and the excellent yield was maintained. A successive pro-
cedure was developed. Moreover, the reaction was carried out at rt under nearly neutral conditions, and
the workup was concise. These features illustrated the potential of the protocol in amide synthesis.
17 April 2019
Accepted 23 April 2019
Available online xxx
©
2019 Elsevier Ltd. All rights reserved.
Keywords:
Beckmann rearrangement
Oxime
Amide
Co-catalysis
1
. Introduction
phosphinic chloride (BOP-Cl) [6], 2,2-dichloroimidazolidine-4,5-
dione (DCID) [7], cyclopropenium salt [8], cyanuric chloride [9],
and so on [10]. Very recently, reported by Hall and coworkers, a true
organocatalytic Beckmann rearrangement was achieved at rt
Oxime (1) could be converted to the corresponding amide (2)
though Beckmann rearrangement, which was first discovered by
the German chemist Ernst Otto Beckmann in 1886 [1], and is now
the most important method to obtain ε-caprolactam which was
used as the monomer of nylon in industry [2], and the reaction was
also widely used in total synthesis of nature products and prepa-
ration of other bioactive molecules [3].
Traditionally, Beckmann rearrangement always occurred under
very harsh conditions (strong acids and high temperatures) or in
uneconomic manners (requirement of excess additives), addition-
ally, oxime would be hydrolyzed giving ketone (3) in some cases
employing
2-methoxycarbonylphenyl
boronic
acid/per-
fluoropinacol system, and a fully catalytic nonself-propagating
mechanism was confirmed [11].
Considering the significance of the Beckmann rearrangement in
amide synthesis, developing of Beckmann rearrangement under
mild conditions (room temperature, neutral conditions) with easily
available and low-cost catalytic system and concise workup is still
highly desirable. Thus, a cyclic anhydride 4 catalyzed Beckmann
rearrangement was designed as depicted in Scheme 1. The oxygen
atom of oxime would add to carbonyl in cyclic anhydride to pro-
duce intermediate A, which might fragment to cation B and acetate
C. Re-combination of B and C would yield intermediate D, and if a
recyclization of D occurs by addition of oxygen of the acid group to
the carbonyl of the acetic acetimidic anhydride part, intermediate E
might be generated after proton transfer. Elimination of E would
then produce the desired amide 2 and rebirth cyclic anhydride 4 to
close the catalytic cycle.
[
4]. These drawbacks limited its applications for oximes bearing
sensitive groups. Organocatalysis is a powerful strategy in organic
transformations with great compatibility. In 2002, Giacomelli
group revealed that cyanuric chloride could promote the Beckmann
rearrangement of both ketoximes and aldoximes under very mild
conditions, producing amides and nitriles respectively [5]. From
then on, many organic catalysts or promoters were developed for
Beckmann rearrangement, for instance, bis(2-oxo-3-oxazolidinyl)
It's clear from the proposed catalytic cycle that the reaction
conditions should be nearly neutral albeit catalytic amount of acid
would be generated during the reaction. If such design could be
realized, a very mild and low-cost catalytic system could be
*
Corresponding author. Department of Chemistry, Zhejiang Sci-Tech University,
Xiasha West Higher Education District, Hangzhou, 310018, China.
E-mail address: xuzefeng@zstu.edu.cn (Z.-F. Xu).
https://doi.org/10.1016/j.tet.2019.04.056
0
040-4020/© 2019 Elsevier Ltd. All rights reserved.
2
Please cite this article as: Z.-F. Xu et al., o-Phthalic Anhydride/Zn(OTf) co-catalyzed Beckmann rearrangement under mild conditions,
Tetrahedron, https://doi.org/10.1016/j.tet.2019.04.056

2
Z.-F. Xu et al. / Tetrahedron xxx (xxxx) xxx
Table 1
a
Optimization of the reactions.
entry 4 (mol%) LA (mol%)
solvent time (h)
yield (%)b note
c
1
2
3
4
5
6
7
8
9
1
1
1
4a (100)
4b (100)
4c (100)
4d (100)
4e (100)
4a (100) Zn(OTf)
4b (100) Zn(OTf)
4c (100) Zn(OTf)
4d (100) Zn(OTf)
4e (100) Zn(OTf)
4c (100) Zn(OTf)
4c (50)
4c (20)
4c (10)
4c (10)
4c (10)
4c (10)
4c (10)
e
e
e
e
e
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
3
3
3
3
3
CN
CN
CN
CN
CN
6
6
6
6
6
0
0
0
0
0
3a, complex
c
c
c
c
3a, complex
3a, complex
3a, complex
3a, complex
3a, complex
3a, complex
2
2
2
2
2
2
(20) CH
(20) CH
(20) CH
(20) CH
(20) CH
(10) CH
(20) CH
CN overnight trace
CN overnight trace
CN
CN
CN
CN
CN
6
6
6
6
6
6
6
6
6
6
6
93
63
57
32
99
85
88
45
61
50
27
Scheme 1. Initial design of cyclic anhydride catalyzed Beckmann rearrangement.
3a
3a
0
1
2
13
14
5
6
7
8
1a remained
established. The proposed transformation also features such chal-
lenge: for the formation of intermediate A, an active enough an-
hydride was required in order to facilitate the addition of hydroxyl
of oxime to the carbonyl, however, such reactive anhydride may be
deleterious to the formation of intermediate E. In order to resolve
the contradiction, it's envisioned that the reactivity of the anhy-
dride was necessary, and if the two carbonyls in D were located
closely enough to each other, the generation of E should be
possible.
With this consideration, several cyclic anhydrides were tested,
and fortunately, after a series of screening of reaction conditions,
such proposal was realized with the assistance of Lewis acid ad-
ditive. So herein, we report our achievement on the mild Beckmann
Zn(OTf)
2
Zn(OTf)2 (20) CH CN
3
Zn(OTf) (20) CH CN
2 3
Zn(OTf)
Zn(OTf)
Zn(OTf)
Zn(OTf)
1
1
1
1
2
(20) DCE
(20) DCM
(20) THF
3a
3a
3a
3a
2
2
2
(20) toluene
a
Oxime 1 (1.0 mmol, 1.0 equiv), anhydride 4 and Lewis acid were dissolved in
CN at rt under nitrogen atomesphere and stirred until the complete
1
.0 mL CH
3
consumption of the oxime monitored by TLC analysis.
b
Isolated yield.
The reaction was carried in refluxed CH CN.
3
c
more electron-deficient anhydride 4d or rigid six-membered cyclic
anhydride 4e provided only 57e63% yields of 2a (entries 9e10,
Table 1), indicating that the electronic effect and the size of the ring
in anhydride were both important for the reaction. Reducing the
2
rearrangement employing o-phthalic anhydride/Zn(OTf) catalytic
system.
2
dosage of Zn(OTf) from 20 mol% to 10 mol% caused a sluggish re-
2
. Results and discussion
Our investigation was initiated with the evaluation of the in-
action and remarkable decrease of the yield (32%, entry 11, Table 1).
Actually, the amount of 4c could be declined to 10 mol% and the
yield of 2a was reserved (88%, entry 14, Table 1). Although a
quantitative yield was obtained when 50 mol% 4c was utilized
fluences of various cyclic anhydrides 4 on the Beckmann rear-
rangement of diphenylmethanone oxime (1a). Unfortunately, none
of the tested anhydrides could promote the reaction even with
(
entry 12, Table 1), the catalytic process (entry 14, Table 1) was
selected for further investigation of solvent because of the conve-
nience in workup, low cost and reagent efficiency. CH CN was
identified as the most effective among those tested solvents
3
100 mol% dosages of 4 in refluxed CH CN, and in each case, complex
3
mixture was obtained and after purification, benzophenone (3a)
was acquired (entries 1e5, Table 1). According to Kalkhambkar and
coworkers [10f], equal-equivalent trifluoromethanesulfonic anhy-
dride could promote Beckmann rearrangement easily at rt, signi-
fying that the failure here might result from the low activities of the
evaluated anhydrides. At this point, a variety of Lewis acids (such as
triflates of Sc , In , Y , Cu , Cu , Ag , La , Yb and Zn , Zn(OAc)
ZnO, ZnCl ) were screened to promote the reactivity of the carbonyl
in 4. However, no positive results were obtained for most of the
tested Lewis acids, and 3a was isolated as the major side product.
Although only trace amount of amide 2a was generated when the
(27e61% yields, entries 15e18, Table 1).
As depicted in Scheme 2, the compatibility of the anhydride/
2
Zn(OTf) catalytic system was evaluated under the optimized
conditions by the Beckmann rearrangement of various oximes
generated from corresponding ketones [12]. In general, the reaction
was sensitive to the electronic effect of the oximes. For diaryl ox-
imes, Beckmann rearrangement went very well and up to 99% yield
was obtained. Electron-rich oximes reacted much faster than
electron-deficient ones, for instance, dimethoxy substituted amide
III
III
III
I
II
I
III
III
II
2
,
2
2c could be obtained in 99% yield within 20 min, whereas difluor-
reaction was carried out with the addition of 20 mol% Zn(OTf)
2
and
CN (entries 6e7, Table 1),
and more rigid anhydrides provided
and 100 mol%
c was used, still at rt, oxime 1a transferred to the desired amide 2a
oamide 2d was generated in 97% yield after stirred overnight. The
selectivity of the migration of phenyl and p-tolyl could not be
controlled, and 2g and 2g′ was produced as a 1:1 mixture in 84%
total yield after 6 h. Aryl alkyl oximes were less reactive than diaryl
oximes. N-phenylacetamide (2h) was produced in 71% yield after a
1
00 mol% 4a or 4b after stirred at rt in CH
3
the combinations of Zn(OTf)
much more dramatic results. When 20 ml% Zn(OTf)
4
2
2
in 93% yield after 6 h (entry 8, Table 1). Replacement of 4c with
2
Please cite this article as: Z.-F. Xu et al., o-Phthalic Anhydride/Zn(OTf) co-catalyzed Beckmann rearrangement under mild conditions,
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Z.-F. Xu et al. / Tetrahedron xxx (xxxx) xxx
3
Scheme 2. Reaction scope.
prolonged reaction time compared to 2a; and the electron-rich N-
4-methoxyphenyl)acetamide (2j) was obtained in 81% yield after
h, which was also slower than the formation of 2c. 2i was pro-
and 90% yield (69.3 mmol, 13.7 g) of amide 2a was obtained.
(
6
According to our observation, most of 2a would precipitate as a
white solid from the reaction mixture, it's envisioned that a suc-
cessive operation for the synthesis of 2a should be possible. So after
the reaction of 1a under standard conditions was completed, the
mixture was filtrated quickly, and the precipitation was collected as
product (washed with cold ethanol and no further purification was
needed); and to the filtrate, containing catalysts and some amount
of the dissolved product 2a, a stirring bar and oxime 1a was added
to continue the reaction under nitrogen atmosphere. After the
consumption of 1a, the same operation was repeated. As depicted
in Fig. 1, for the first cycle, the yield of 2a was 68%, which was lower
than that in eq (1) because some 2a was dissolved in the filtrate; the
second and third cycles provided the desired 2a in 81% and 79%
duced in 91% yield. Disappointingly, 4-bromophenyl methyl oxime
ꢀ
performed poorly, and after heated at 50 C overnight, only 33%
yield of N-(4-bromophenyl)acetamide (2k) was delivered. Steric
substituent at the alkyl could not influence the reaction and amide
2
l was generated smoothly in 87% yield. Vinyl group could also
migrate as well and N-vinyl acetamide 2m was generated in 58%
yield with the configuration retention of the carbon-carbon double
bond. Heteroaryl, such as 1H-pyrrol-2-yl, was not compatible and
no desired amide 2n was obtained. Dialkyl oxime, such as camphor
oxime (1o), was inert under the standard conditions, giving no
desired corresponding amides (2o).
In order to protrude the advantage of the mild conditions,
several acid-sensitive functionalities (such as silyloxy group, N-Boc
and acetal moiety) were introduced into oximes (1p-r), which were
then submitted to the standard conditions [13]. Gratifyingly, the
tested acid-sensitive groups were all well compatible and the cor-
responding amides 2p-r were obtained in excellent yields (91e99%)
within 2 h, depicting the same accelerating influence of electron-
donating groups on the reaction.
(1)
A scalable reaction was carried out with 77 mmol (15.2 g) 1a as
substrate under the catalysis of 10 mol% 4a and only 10 mol%
Zn(OTf) (eq (1)). The workup of the reaction was very concise [14]
2
Fig. 1. Yields of successive synthesis of 2a. The reactions were carried out in 10 mL
CH
3
CN under standard conditions with 10 mmol of 2a for each cycle.
Please cite this article as: Z.-F. Xu et al., o-Phthalic Anhydride/Zn(OTf)
2
co-catalyzed Beckmann rearrangement under mild conditions,
Tetrahedron, https://doi.org/10.1016/j.tet.2019.04.056

4
Z.-F. Xu et al. / Tetrahedron xxx (xxxx) xxx
yields respectively. As a whole, the developed successive procedure
provided a relative green protocol for the synthesis of 2a.
using a Brucker Avance II DMX 400 spectrometer at 100 MHz.
Chemical shift is reported in ppm relative to the carbon resonance
3 6
of CDCl (77.00 ppm) or DMSO‑d (39.52 ppm). High resolution
mass spectra (HRMS) were obtained by Center for Instrumental
Analysis of Zhejiang Sci-Tech University and a Waters TOFMS GCT
Premier instrument for HRMS. The results are reported as m/e
(
(
(
2)
3)
4)
(
(
relative ratio). Accurate masses are reported for the molecular ion
M ) or a suitable fragment ion.
þ
2
4.2. General procedure for o-phthalic anhydride/Zn(OTf) co-
catalyzed Beckmann rearrangement
2
Oxime 1 (1.0 mmol, 1.0 equiv), Zn(OTf) (73.7 mg, 0.2 mmol, 0.2
equiv) and o-phthalic anhydride (15.0 mg, 0.1 mmol, 0.1 equiv)
were dissolved in 1.0 mL CH CN at rt under nitrogen atomesphere
3
and stirred until the complete consumption of the oxime moni-
tored by TLC analysis. The mixture was evaporated and the residue
was purified on flash column chromatography with petroleum
ether/ethyl acetate (5:1e2:1) as eluent to afford the desired amide
2.
Several control experiments provided some insights into the
mechanism. 4c could not catalyze the Beckmann rearrangement at
4.3. Procedure for scalable reaction of 1a
rt (eq (2)). When 20 mol% Zn(OTf)
trace amide 2a was detected after stirred at rt overnight (eq (3)),
indicating that Zn(OTf) could not catalyze the reaction effectively
at rt neither. Replacing 4c and Zn(OTf) with 10 mol% acetic anhy-
dride under standard conditions could only produce 2b in 15%
yield, and it's reported that Tf O could promote the rearrangement
efficiently [10f]. These facts inferred that more reactive anhydrides
Ac O, Tf O) could promote Beckmann rearrangement, but 4c was
2
was used as single catalyst, only
Diphenyl oxime (1a) (15.2 g, 77 mmol, 1.0 equiv), Zn(OTf)2
2.71 g, 7.7 mmol, 0.1 equiv) and o-phthalic anhydride (1.14 g,
(
7
2
.7 mmol, 0.1 equiv) were dissolved in 150 mL CH CN at rt under
3
2
nitrogen atomesphere and stirred until the complete consumption
of the oxime monitored by TLC analysis. The white precipitation
was collected by filtration and the filtration was concentrated to
2
5
0 mL, and 1% NaOH solution was added, the mixture was extracted
(
2
2
with ethyl acetate (20 mL) for tree times and the combined organic
phase was washed with brine (20 mL), and then evaporated giving
white slide. Recrystallization of the combined solid in ethanol
providing pure N-phenylbenzamide (2a, 13.7 g, 69.3 mmol, 90%
yield).
too stable to facilitate the reaction. Accordingly, the role of Zn(OTf)
2
might be to activate the anhydride functionality in 4c.
3
. Conclusion
A mild and easily handled Beckmann rearrangement was ach-
ieved employing the combination of rigid cyclic anhydride and
Lewis acid. When o-phthalic anhydride and Zn(OTf) were used as
4
4
.4. Analytical data of 2
2
.4.1. N-phenylbenzamide (2a) [11]
co-catalyst, Beckmann rearrangement of various oximes could
produce the corresponding amide in up to 99% yield at rt under
nearly neutral conditions and acid-sensitive functionalities were
well compatible. Additionally, the reaction scale could be easily
enlarged to 77 mmol and the efficiency was maintained, and also, a
successive procedure was developed providing a promising pro-
tocol that could be utilized in large scale production of amide. In
view of the appealing effect that combination of two low-effective
catalysts produced a high effective catalytic system, the investiga-
tion of the detailed mechanism is still undergoing in our lab.
1
H NMR (400 MHz, DMSO‑d
6
)
d
10.27 (br, 1H), 7.98 (d, J ¼ 7.3 Hz,
2
2
H), 7.82 (d, J ¼ 7.9 Hz, 2H), 7.64e7.47 (m, 3H), 7.37 (t, J ¼ 7.6 Hz,
13
H), 7.11 (t, J ¼ 7.3 Hz, 1H). C NMR (101 MHz, DMSO‑d
6
) d 166.05,
139.68, 135.49, 131.99, 129.07, 128.84, 128.13, 124.12, 120.84. HRMS
þ
(ESI) calcd for C13
H12NO 198.0919, found 198.0921.
4.4.2. 4-Methyl-N-(4-methylphenyl)benzamide (2b) [15]
1
H NMR (400 MHz, CDCl
.56 (d, J ¼ 8.3 Hz, 2H), 7.30 (d, J ¼ 8.0 Hz, 2H), 7.20 (d, J ¼ 8.2 Hz,
H), 2.46 (s, 3H), 2.38 (s, 3H).
3
)
d
7.88 (br, 1H), 7.80 (d, J ¼ 8.1 Hz, 2H),
7
2
4
. Experimental section
4.4.3. 4-Methoxy-N-(4-methoxyphenyl)benzamide (2c) [7]
1
H NMR (400 MHz, DMSO‑d
6
)
d
9.98 (s, 1H), 7.97 (d, J ¼ 8.6 Hz,
4.1. General information
2H), 7.68 (d, J ¼ 8.8 Hz, 2H), 7.05 (d, J ¼ 8.6 Hz, 2H), 6.92 (d,
13
J ¼ 8.8 Hz, 2H), 3.84 (s, 3H), 3.75 (s, 3H). C NMR (101 MHz,
Analytical thin layer chromatography (TLC) was performed us-
DMSO‑d
6
)
d
164.98, 162.22, 155.87, 132.87, 129.91, 127.55, 122.44,
þ
ing Silica Gel HSGF254 pre-coated plates. Flash column chroma-
tography was performed using 200e300 Mesh Silica Gel. Proton
nuclear magnetic resonance ( H NMR) spectra were recorded using
114.14, 114.00, 55.84, 55.60. HRMS (ESI) calcd for C15
258.1130, found 258.1136.
H16NO
1
Brucker Avance IIDMX 400 MHz spectrometers. Chemical shift (
reported in parts per million (ppm) downfield relative to tetra-
methylsilane (TMS, 0.00 ppm) or CDCl (7.26 ppm) or DMSO‑d
2.50 ppm). Coupling constants (J) are reported in Hz. Multiplicities
d
) is
4.4.4. 4-Fluoro-N-(4-fluorophenyl)benzamide (2d) [10j]
1
H NMR (400 MHz, DMSO‑d
6
)
d
10.32 (s, 1H), 8.04 (dd, J ¼ 8.8,
3
6
5.6 Hz, 2H), 7.79 (dd, J ¼ 8.8, 5.0 Hz, 2H), 7.37 (t, J ¼ 8.8 Hz, 2H), 7.20
13
(
(t, J ¼ 8.8 Hz, 2H). C NMR (101 MHz, DMSO‑d
6
) d 164.81, 164.56 (d,
are reported using the following abbreviations: s, singlet; d,
doublet; t, triplet; q, quartet; m, multiplet; br, broad; Carbon-13
J ¼ 249.0 Hz), 158.79 (d, J ¼ 240.4 Hz), 135.88, 131.67, 130.82 (d,
J ¼ 9.0 Hz), 122.69 (d, J ¼ 7.8 Hz), 115.84 (d, J ¼ 15.1 Hz), 115.62 (d,
13
þ
nuclear magnetic resonance ( C NMR) spectra were recorded
J ¼ 15.6 Hz). HRMS (ESI) calcd for C13
H
10
F
2
NO 234.0734, found
2
Please cite this article as: Z.-F. Xu et al., o-Phthalic Anhydride/Zn(OTf) co-catalyzed Beckmann rearrangement under mild conditions,
Tetrahedron, https://doi.org/10.1016/j.tet.2019.04.056

Z.-F. Xu et al. / Tetrahedron xxx (xxxx) xxx
5
2
34.0730.
4.4.15. Tert-butyl (4-acetamidophenyl)carbamate (2q) [11]
1
H NMR (400 MHz, DMSO‑d
6
)
d
9.75 (s, 1H), 9.17 (s, 1H), 7.39 (d,
13
4.4.5. 4-Chloro-N-(4-chlorophenyl)benzamide (2e) [16]
J ¼ 8.3 Hz, 2H), 7.30 (d, J ¼ 8.3 Hz, 2H), 1.96 (s, 3H), 1.42 (s, 9H).
NMR (101 MHz, DMSO‑d 167.76, 152.79, 134.71, 133.85, 119.43,
118.44, 78.75, 28.12, 23.79.
C
1
H NMR (400 MHz, CDCl
3
)
d
7.81 (d, J ¼ 8.7 Hz, 2H), 7.75 (s, 1H),
6
) d
7
.58 (d, J ¼ 8.7 Hz, 2H), 7.48 (d, J ¼ 8.7 Hz, 2H), 7.34 (d, J ¼ 8.7 Hz,
2
H).
4
.4.16. N-(Benzo[d] [1,3]dioxol-5-yl)acetamide (2r)
4
.4.6. 4-Bromo-N-(4-bromophenyl)benzamide (2f) [16]
ꢀ
1
M.p.: 85e87 C. H NMR (400 MHz, CDCl
H), 6.78 (ABd, J ¼ 19.9, 8.3 Hz, 2H), 5.98 (s, 2H), 2.17 (s, 3H).
168.38, 147.75, 144.30, 132.10, 113.32,
3
) d 7.49 (s, 1H), 7.23 (s,
1
H NMR (400 MHz, CDCl
3
)
d
7.78 (s, 1H), 7.73 (d, J ¼ 8.4 Hz, 2H),
13
1
C
7.63 (d, J ¼ 8.7 Hz, 2H), 7.55e7.47 (m, 4H).
3
NMR (101 MHz, CDCl ) d
þ
107.99, 103.07, 101.23, 24.30. HRMS (ESI) calcd for C
H
9 9
NNaO
3
4
2
.4.7. 4-Methyl-N-phenylbenzamide & N-(p-tolyl)benzamide (2g &
2
02.0475, found 202.0472.
0
g )
1H NMR (400 MHz, DMSO‑d
)
d
8.02 (br, 1H), 7.88e7.86 (m, 1H)),
.79e7.77 (m, 1H), 7.67e7.65 (m, 1H), 7.54e7.52 (m, 2H), 7.48e7.44
m, 1H), 7.38e7.34 (m, 1H), 7.28e7.25 (m, 1H), 7.18e7.14 (m,
1
1
6
Acknowledgments
7
(
H),2.43&2.36 (3H). 13C NMR (101 MHz, DMSO‑d
165.98, 142.07,
38.06, 135.36, 134.90, 134.03, 131.96, 131.49, 129.36, 129.17, 128.82,
28.47, 127.06, 127.02, 124.25, 120.53, 120.37, 21.34, 20.79. HRMS
We are grateful for the support of this work by the National
Natural Science Foundation of China (21801224), the Natural Sci-
ence Foundation of Zhejiang Province (LQ18B020009), the Scien-
tific Research Foundation of Zhejiang Sci-Tech University
6
) d
1
þ
(
ESI) calcd for C14
H
14NO 212.1075, found 2212.1083.
(16062193-Y).
4
.4.8. N-phenylacetamide (2h) [11]
1
H NMR (400 MHz, DMSO‑d
6
)
d
9.92 (s, 1H), 7.59 (d, J ¼ 7.5 Hz,
Appendix A. Supplementary data
13
2
H), 7.28 (t, J ¼ 7.5 Hz, 2H), 7.03 (d, J ¼ 7.5 Hz, 1H), 2.05 (s, 3H).
C
NMR (101 MHz, DMSO‑d
6
)
d
168.73, 139.81, 129.10, 123.41, 119.44,
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2019.04.056.
þ
2
4
2
4.45. HRMS (ESI) calcd for C
8
H
10NO 136.0762, found 136.0762.
.4.9. N-(p-tolyl)acetamide (2i) [11]
References
1
H NMR (400 MHz, DMSO‑d
H), 7.08 (d, J ¼ 8.2 Hz, 2H), 2.24 (s, 3H), 2.02 (s, 3H). C NMR
168.48, 137.30, 132.27, 129.47, 119.46, 24.38,
6
)
d
9.82 (s, 1H), 7.46 (d, J ¼ 8.2 Hz,
13
[
1] E. Beckmann, Ber. Dtsch. Chem. Ges. 19 (1886) 988.
[2] (a) A.H. Blatt, Chem. Rev. 12 (1933) 215;
b) T. Tatsumi, in: R.A. Sheldon, H. van Bekkum (Eds.), Fine Chemicals Though
Heterogeneous Catalysis, Wiley-VCH, 2001, p. 185;
c) W.C. Li, A.H. Lu, R. Palkovits, W. Schmidt, B. Spliethoff, F. Schuth, J. Am.
(
101 MHz, DMSO‑d
6
)
d
(
2
0.86.
(
4
.4.10. N-(4-methoxyphenyl)acetamide (2j) [11]
Chem. Soc. 127 (2005) 12595.
1
[
[
3] (a) J.D. White, P. Hrnciar, F. Stappenbeck, J. Org. Chem. 64 (1999) 7871;
(b) J.D. White, Y. Choi, Org. Lett. 2 (2000) 2373.
4] (a) R.F. Brown, N.M. van Gulick, G.H. Schemidt, J. Am. Chem. Soc. 77 (1955)
1094;
H NMR (400 MHz, DMSO‑d
6
)
d
9.77 (s, 1H), 7.49 (d, J ¼ 8.7 Hz,
13
2
H), 6.86 (d, J ¼ 8.7 Hz, 2H), 3.71 (s, 3H), 2.01 (s, 3H). C NMR
(
101 MHz, DMSO‑d
6
)
d
168.18, 155.47, 133.00, 120.99, 114.22, 55.56,
þ
(
(
b) A.H. Fenselau, E.H. Hamamura, J.G. Moffatt, J. Org. Chem. 35 (1970) 3546;
c) F. Greer, D.E. Pearson, J. Am. Chem. Soc. 77 (1955) 6649.
2
4.24. HRMS (ESI) calcd for C
9
H12NO 166.0868, found 166.0868.
[
5] L.D. Luca, G. Giacomelli, A. Porcheddu, J. Org. Chem. 67 (2002) 6272.
4
.4.11. N-(4-bromophenyl)acetamide (2k) [11]
[6] M. Zhu, C. Cha, W.P. Deng, X.X. Shi, Tetrahedron Lett. 47 (2006) 4861.
[7] Y. Gao, J. Liu, Z. Li, T. Guo, S. Xu, H. Zhu, F. Wei, S. Chen, H. Gebru, K.J. Guo, Org.
Chem. 83 (2018) 2040.
[
[
1
H NMR (400 MHz, DMSO‑d
6
)
d
10.06 (s, 1H), 7.56 (d, J ¼ 8.5 Hz,
13
2
H), 7.46 (d, J ¼ 8.5 Hz, 2H), 2.04 (s, 3H). C NMR (101 MHz,
8] C.M. Vanos, T.H. Lambert, Chem. Sci. 1 (2010) 705.
9] Y. Furuya, K. Ishihara, H. Yamamoto, J. Am. Chem. Soc. 127 (2005) 11240.
DMSO‑d
calcd for C
6
)
d
168.92, 139.15, 131.92, 121.31, 114.94, 24.48. HRMS (ESI)
þ
8
H
9
BrNO 213.9868, found 213.9870.
[10] (a) M. Hashimoto, Y. Obora, S. Sakaguchi, Y. Ishii, J. Org. Chem. 73 (2008) 2894;
(
(
b) H.-J. Pi, J.-D. Dong, N. An, W. Du, W.-P. Deng, Tetrahedron 65 (2009) 7790;
c) N. An, B.-X. Tian, H.-J. Pi, L.A. Eriksson, W.-P.J. Deng, Org. Chem. 78 (2013)
4.4.12. N,2-diphenylacetamide (2l)
4
297;
(d) B.-X. Tian, N. An, W.-P. Deng, L.A. Eriksson, J. Org. Chem. 78 (2013) 6782;
e) L. Ronchi, A. Vavasori, M. Bortoluzzi, Catal. Commun. 10 (2008) 251;
(f) R.G. Kalkhambkar, H.M. Savanur, RSC Adv. 5 (2015) 60106;
g) R. Raja, G. Sankar, J.M. Thomas, J. Am. Chem. Soc. 123 (2001) 8153;
(h) A.B. Fernandez, M. Boronat, T. Blasco, A. Corna, Angew. Chem. Int. Ed. 44
ꢀ
1
6
M.p.: 85e87 C. H NMR (400 MHz, DMSO‑d ) d 10.18 (s, 1H),
(
7
3
1
.63 (d, J ¼ 8.0 Hz, 2H), 7.45e7.13 (m, 7H), 7.04 (t, J ¼ 7.3 Hz, 1H),
.66 (s, 2H). 13C NMR (101 MHz, DMSO‑d
169.56, 139.72, 136.50,
29.57, 129.17 (s, 3H), 128.77, 126.98, 123.66, 119.58, 43.83. HRMS
6
) d
(
þ
H14NO 212.1075, found 212.1082.
(
(
(
2005) 2370;
(
ESI) calcd for C14
i) K. Hyodo, G. Hasegawa, N. Oishi, K. Kuroda, K. Uchida, J. Org. Chem. 83
2018) 13080;
4.4.13. (E)-N-styrylacetamide (2m) [11]
(j) F. Xie, C. Du, Y. Pang, X. Lian, C. Xue, Y. Chen, X. Wang, M. Cheng, C. Guo,
B. Lin, Y. Liu, Tetrahedron Lett. 57 (2016) 5820;
1
H NMR (400 MHz, CDCl
0.8 Hz, 1H), 7.39e7.26 (m, 4H), 7.21 (t, J ¼ 7.0 Hz, 1H), 6.14 (d,
J ¼ 14.5 Hz, 1H), 2.16 (s, 3H).
3
)
d
7.69 (br, 1H), 7.56 (dd, J ¼ 14.5,
(
3
k) Z. Li, C. Fang, Y. Zheng, G. Qiu, X. Li, H. Zhou, Tetrahedron Lett. 59 (2018)
934;
(l) J.K. Augustine, R. Kumar, A. Bombrun, A.B. Mandal, Tetrahedron Lett. 52
2011) 1074.
1
(
[
[
[
11] X. Mo, T.D.R. Morgan, H.T. Ang, D.G. Hall, J. Am. Chem. Soc. 140 (2018) 5264.
12] See experimental section.
13] We are thankful for the kind and significant suggestion from reviewers on the
scope of the acid-sensitive substrates.
4
.4.14. N-(4-((Tert-butyldimethylsilyl)oxy)phenyl)acetamide (2p)
ꢀ
1
M.p.: 94e97 C. H NMR (400 MHz, CDCl
J ¼ 8.7 Hz, 2H), 6.81 (d, J ¼ 8.7 Hz, 2H), 2.17 (s, 3H), 1.01 (s, 9H), 0.21
s, 3H). 13C NMR (101 MHz, CDCl
168.23, 152.32, 131.56, 121.63,
3
) d 7.47 (br, 1H), 7.37 (d,
[14] See experimental section.
(
3
) d
[
[
15] C. Ramalingan, Y.-T. Park, J. Org. Chem. 72 (2007) 4536.
16] Y.-Y. Zhu, H.-P. Yi, C. Li, X.-K. Jiang, Z.-T. Li, Cryst. Growth Des. 8 (2008)
1294e1300.
1
C
20.25, 25.66, 24.31, 18.17, ꢁ4.48. HRMS (ESI) calcd for
þ
14 2
H23NNaO Si 288.1390, found 288.1392.
2
Please cite this article as: Z.-F. Xu et al., o-Phthalic Anhydride/Zn(OTf) co-catalyzed Beckmann rearrangement under mild conditions,
Tetrahedron, https://doi.org/10.1016/j.tet.2019.04.056