The Reaction of o-Aminoacetophenone N-Tosylhydrazone and CO2 toward 1,4-Dihydro-2H-3,1-benzoxazin-2-ones

Article abstract of DOI:10.1002/adsc.201900341

A transition-metal-free reaction of o-aminoacetophenone N-tosylhydrazone and CO₂ has been developed, leading to a series of 1,4-dihydro-2H-3,1-benzoxazin-2-ones in moderate to good yields. This procedure proceeds with the sequential fixation of CO₂ by amino leading to carbamic acid and the intra- molecular insertion of hydroxyl to carbene. (Figure presented.).

Full text of DOI:10.1002/adsc.201900341

Title: The Reaction of o-Aminoacetophenone N-Tosylhydrazone and
CO2 toward 1,4-Dihydro-2H-3,1-benzoxazin-2-ones
Authors: Hao Xiong, Xiaopeng Wu, Hepan Wang, Song Sun, Jin-Tao
Yu, and Jiang Cheng
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.201900341
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10.1002/adsc.201900341
Advanced Synthesis & Catalysis
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial sttaff))
The Reaction of o-Aminoacetophenone N-Tosylhydrazone and CO2
toward 1,4-Dihydro-2H-3,1-benzoxazin-2-ones
Hao Xiong, Xiaopeng Wu, Hepan Wang, Song Sun, Jin-Tao Yu, Jiang Cheng*
School of Petrochemical Engineering, Jiangsu Key Laboratory of Advanced Catalytic Materials & Technology, Jiangsu
Province Key Laboratory of Fine Petrochemical Engineering, Changzhou University, Changzhou, 213164, P. R. China.
Fax: (+86)519-8633-0257; E-mail: jiangcheng@cczu.edu.cn
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
1,4-Dihydro-2H-3,1-benzoxazin-2-one
shows
Abstract:
A
transition-metal-free reaction of o-
aminoacetophenone N-tosylhydrazone and CO2 has been abundant potential biological activities such as
developed, leading to a series of 1,4-dihydro-2H-3,1-
benzoxazin-2-ones in moderate to good yields. This
procedure proceeds with the sequential fixation of CO2
by amino leading to carbamic acid and the intra-
molecular insertion of hydroxyl to carbene.
progesterone
Keywords: metal-free; carbon dioxide; carbene
Carbon dioxide, which is believed responsible for
global warming, is now serving as a non-toxic,
abundant, and low-cost C1 source in organic
synthesis.[1] As such, the incorporation of CO2 into
organic compounds,[2] especially the heterocyclic
ones,[3-4] has drawn much attention. Carbon dioxide
inherently reacts with amines to produce carbamic
acids (eq. 1, Scheme 1).[5] Meanwhile, N-
tosylhydrazones were widely used in organic
synthesis,[6] and can also serve as carbene precursor to
undergo intermolecular insertion by hydroxyl in
carbamic acid[7,8] (eq. 2, Scheme 1). For example,
Jiang developed an elegant example on the base-
promoted reaction of CO2 (4 MPa), amines and
tosylhydrazones toward carbamates.[9] With this
regard, we envision to develop the sequential fixation
of atmosphere of CO2 by the amino in o-
aminoacetophenone N-tosylhydrazones and the intra-
molecular insertion of hydroxyl in the in situ formed
carbamic acid to N-tosylhydrazones as a carbene
precursor, leading to 1,4-dihydro-2H-3,1-benzoxazin-
2-ones (eq. 3, Scheme 1).
Scheme 1. The Synthetical Design and Representative 1,4-
Dihydro-2H-3,1-benzoxazin-2-ones.
1
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10.1002/adsc.201900341
Advanced Synthesis & Catalysis
receptor antagonist,[10] HIV-1 reverse transcriptase increased to 75% in DMSO (Table 1, entry 5).
inhibitor (Scheme 1).[11] Typical synthetical methods Reducing the amount of base resulted in lower yield.
includes the catalytic chlorocyclization of 2- The yield also decreased slightly under lower of
vinylphenylcarbamates,[12] the selenium-catalyzed elevated temperatures (Table 1, entry 5). The reaction
oxidative carbonylation of 2-aminobenzyl alcohol,[13] concentration has little effect on the efficiency of the
the
copper(I)/N-heterocyclic
carbene-catalyzed reaction (Table 1, entry 5). Other common bases, such
addition of terminal alkynes to trifluoromethyl as K2CO3, LiOtBu, KOtBu, and NaOtBu, were also
ketones,[14] and the intramolecular conversion of N,N- tested, and they were all inferior to Cs2CO3 (Table 1,
bis(2-picolyl)ureas to cyclic carbamates.[15] To the entries 6-9). Organic base DBU was totally
best of our knowledge, example on the application of ineffective for this transformation (Table 1, entry 10).
CO2 as a C1 source to access such frameworks has The reaction did not occur in the presence of O2 and it
never been reported so far.
was inhibited by water (Table 1, entry 5).
Table 1. Selected Results for Screening the Optimized
Table 2. The Scope of o-Aminoacetophenone N-
Reaction Conditionsa.[a]
Tosylhydrazones with Substitutents in Aryls. [a]
entry
base
solvent
DMF
yield (%)[b]
1
2
3
4
5
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
53
diglyme
THF
< 5
< 5
< 5
MeCN
DMSO
75, 63,c 68,d 65,e 70,f
72,g 0,h 57,i
6
7
8
9
K2CO3
LiOtBu
KOtBu
NaOtBu
DBU
DMSO
DMSO
DMSO
DMSO
DMSO
42
18
50
67
<5
10
[a]
Reaction conditions: o-aminoacetophenone N-
tosylhydrazone 1a (0.1 mmol), base (0.4 mmol), solvent
o
(1.5 mL), CO2 (1 atm.), at 100 C in a sealed Schlenk
tube for 12 h. [b] Isolated yield. [c] Base (0.2 mmol). [d] At
o
[e]
o
[f]
[g]
90 C. At 110 C. DMSO (1.0 mL). DMSO (2.0
[h]
[i]
mL).
mL).
under O2 (1 atm). DMSO/H2O (1.0 mL/0.5
[a]
Reaction conditions: o-aminoacetophenone N-
We initially tested the reaction of o-
aminoacetophenone N-tosylhydrazone 1a with
atmospheric pressure CO2 in DMF under 100 C in
tosylhydrazone 1 (0.1 mmol), Cs2CO3 (0.4 mmol), DMSO
(1.5 mL), CO2 (1 atm.), at 100 C in a sealed Schlenk tube
for 12 h.
o
o
the presence of Cs2CO3 (4 equiv.). To our delight,
1,4-dihydro-2H-3,1-benzoxazin-2-one
(3a)
was
isolated in 53% yield (Table 1, entry 1). The reaction
all failed to work in diglyme, THF and MeCN (Table
1, entries 2-4). Fortunately, the yield dramatically
With the optimized reaction conditions in hand, the
scope and limitation the reaction was tested using o-
aminoacetophenone N-tosylhydrazones with different
2
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10.1002/adsc.201900341
Advanced Synthesis & Catalysis
substitutents in aryls, as shown in Table 2. As
The application of this procedure was further
expected, this procedure was applicable for substrates studied and listed in Scheme 2. Racemic product 3t
with various substituents at para- or meta-positions was isolated in 47% yield under our procedure
(3b-3l, 50-76% yield). Some electron-withdrawing (Scheme 2, eqs 1). The S-isomer of 3t serves as a
groups, such as bromo, chloro and iodo (3c, 3e, 3f & nonpeptide oxytocin receptor agonist.[16] Meanwhile,
3l) were all compatible well, which provided handles progesterone receptor antagonist 3u was also
for potentially further functionalizations. Meanwhile, produced in 70% yield under the standard procedure
substrates with electron-donating substituents also (Scheme 2, eqs 2).[10] Moreover, this reaction in 2
worked well (3b, 3d, 3g & 3i). Notably, substrates mmol scale provided 3a in a comparable 70% yield
with heteroaryl ran smoothly to access product 3h in (Scheme 2, eqs 3).
67% yield. Unfortunately, N-substituted substrates,
such as 1v & 1w, failed to work under this procedure.
Scheme 2. Application of this procedure
So did the aliphatic amines, such as 3-amino-1-
phenylpropanone N-tosylhydrazone (1x).
Next, the scope of o-aminoacetophenone N-
tosylhydrazone possessing different substitutents
attached in carbonyl were investigated, as shown in
Table 3. Notably, o-amino benzaldehyde N-
tosylhydrazone worked well under the standard
procedure, providing 3m in 60% yield. Generally, this
procedure was applicable for many o-amino alkylaryl
ketone N-tosylhydrazone derivatives, allowing the
facile access to a series of 4-alkyl 1,4-dihydro-2H-
3,1-benzoxazin-2-ones in 75-92% yields (3n-3q). In
particular, o-amino diaryl ketone N-tosylhydrazone
worked well to afford 3r in 90% yield. Importantly,
the trifluoromethyl analogue ran smoothly under the
procedure, providing the corresponding product 3s in
66% yield.
Table 3. The Scope of o-Aminoacetophenone N-
Control experiment was conducted to get some
insights into this transformation. Firstly, the reaction
kinetic study showed zero-order for substrate 1a.[17]
Secondly, adduct 4 was detected by GC-MS after the
addition of styrene, indicating the involvement of
carbene intermediate (Scheme 3).[18]
Tosylhydrazone with Substitutents in Carbonyl.[a]
Scheme 3. Mechanism study
A proposed mechanism was outlined in Scheme 4.
First, Cs2CO3 binds with aniline and extracts a proton
from it.[19] Then the carboxylation of amine by CO2
takes place to produce intermediate C. Afterward,
intermediate C sequentially releases Ts- and N2 under
the assistance of base, leading to carbene intermediate
D. Finally, intramolecular insertion of carboxylic to
carbene delivers 1,4-dihydro-2H-3,1-benzoxazin-2-
ones (3a).
[a] Reaction conditions: 1 (0.1 mmol), Cs2CO3 (0.4 mmol),
DMSO (1.5 mL), CO2 (1 atm.), at 100 C in a sealed
Schlenk tube for 12 h.
o
3
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10.1002/adsc.201900341
Advanced Synthesis & Catalysis
Scheme 4. A Tentative Mechanism
Natural Science Foundation of Jiangsu Province (BK20150263)
for financial supports.
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In conclusion, we have developed a Cs2CO3-
promoted reaction of o-aminoacetophenone N-
tosylhydrazones and CO2, leading to 1,4-dihydro-2H-
3,1-benzoxazin-2-ones in moderate to good yields.
This procedure proceeds with the sequential fixation
of CO2 by amino and the intramolecular insertion of
hydroxyl in the in situ formed carbamic acid to
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Experimental Section
Annulation toward 5-Arylimidazo[1,2-c]quinazolines:
A 20 mL Schlenk tube equipped with a stir bar was
charged with 1a (0.10 mmol.), Cs2CO3 (0.40 mmol, 4
equiv.), and DMSO (1.5 mL), and sealed with a PTFE cap.
o
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CO2 (1 atm.) in an oil bath. After the completion of the
reaction, the mixture was cooled to room temperature and
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Acknowledgements
We thank the National Natural Science Foundation of China
(nos. 21572025, 21672028 and 21602019), “Innovation &
Entrepre-neurship Talents” Introduction Plan of Jiangsu
Province, Natural Science Foundation of Jiangsu Province
(BK20171193), the Key University Science Research Project of
Jiangsu Province (15KJA150001), Jiangsu Key Laboratory of
Advanced Catalytic Materials & Technology (BM2012110) and
Advanced Catalysis and Green Manufacturing Collaborative
Innovation Center for financial supports. Sun thanks Young
4
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Advanced Synthesis & Catalysis
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5
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10.1002/adsc.201900341
Advanced Synthesis & Catalysis
COMMUNICATION
The Reaction of o-Aminoacetophenone N-
Tosylhydrazone and CO2 toward 1,4-Dihydro-2H-
3,1-benzoxazin-2-ones
Adv. Synth. Catal. 2019, XX, Page – Page
Hao Xiong, Xiaopeng Wu, Hepan Wang, Song
Sun, Jin-Tao Yu, and Jiang Cheng*
6
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