Recyclable (PhSe)2-catalyzed selective oxidation of isatin by H2O2: a practical and waste-free access to isatoic anhydride under mild and neutral conditions

Article abstract of DOI:10.1039/c5cy01030f

After a series of careful conditional optimizations and catalyst screenings, a methodology to prepare isatoic anhydrides through organoselenium-catalyzed selective oxidation of isatins by H₂O₂ under mild and neutral conditions was developed. The reactions were very practical because of the recyclability of the catalyst and solvent and the convenient isolation procedures of the products. This work reports the organoselenium-catalyzed oxidation of heterocycles that greatly expands the application scopes of organoselenium catalysis. It also indicates that the organoselenium catalysts are robust enough to be recycled in industrial production if suitable isolation procedures are developed.

Full text of DOI:10.1039/c5cy01030f

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Recyclable (PhSe) -catalyzed selective oxidation
2
of isatin by H O : a practical and waste-free
2
2
Cite this: DOI: 10.1039/c5cy01030f
access to isatoic anhydride under mild and neutral
conditions†
Lei Yu,*ab Jianqing Ye, Xu Zhang, Yuanhua Ding and Qing Xu*b
a
ab
a
After a series of careful conditional optimizations and catalyst screenings, a methodology to prepare isatoic
2 2
anhydrides through organoselenium-catalyzed selective oxidation of isatins by H O under mild and neu-
Received 8th July 2015,
Accepted 21st July 2015
tral conditions was developed. The reactions were very practical because of the recyclability of the catalyst
and solvent and the convenient isolation procedures of the products. This work reports the
organoselenium-catalyzed oxidation of heterocycles that greatly expands the application scopes of
organoselenium catalysis. It also indicates that the organoselenium catalysts are robust enough to be
recycled in industrial production if suitable isolation procedures are developed.
DOI: 10.1039/c5cy01030f
www.rsc.org/catalysis
large amount of acids, which are harmful from the viewpoint
of industrial production due to corrosion of equipment. In
Introduction
6
Isatoic anhydrides IJ1H-benzoijd]ij1,3]oxazine-2,4-diones) are
2006, Deligeorgiev et al. reported a nice work on the
significant intermediates for the construction of many useful
ultrasound-promoted oxidation of isatin to prepare isatoic
1a,b
7
organic skeletons, such as quinolones,
2,3-dihydroquin-
2-aminobenzoic
anhydride using urea/H
2
O
2
. But since generation of ultrasound
1
c
1d
azolin-4IJ1H)-ones,
acid derivatives,
benzodiazepinones,
1,2-dihydro-2-thioxo-4H-3,1-benzothiazin-
requires special sonication equipment and consumes huge
power energy and the oxidant urea/H O inevitably leads to urea
1
e–g
2
2
1
h
1i
4
-ones and others. In addition, isatoic anhydrides are also
as the massive solid waste, this technology is still far away from
large scale production. In addition, the method also required
an acidic solvent such as acetic acid or formic acid along with
2
abundantly employed compounds in herbicide production,
3
natural product synthesis and medicinal chemistry for the
7
preparation of enzyme inhibitors, non-nucleoside inhibitors,
drops of sulfuric acid. Thus, developing practical and waste-
4
antagonists, etc. Therefore, synthesis of isatoic anhydrides is
free oxidation procedures of isatins in neutral media are not
only desirable but also timely for industrial applications.
On the other hand, selenium is an important and neces-
sary trace element for human beings and has very wide appli-
cations in biochemistry, medicinal chemistry, organic synthe-
an important topic in synthetic organic chemistry research.
Although isatoic anhydrides can be synthesized through a
series of methodologies from smaller building blocks such as
5
a
5b
N-methylbenzenamines,
2-isocyanophenyl
lithiums,
5c
5d–f
8
indoles, 2-aminobenzoic acids,
etc., the oxidation of
sis and materials science. Recently, the eco-friendly aspects
isatins should be a more concise and clean choice because
isatins are cheap and accessible starting materials and this
procedure does not require highly toxic and hazardous
chemicals for laboratory preparation. But the currently
reported oxidation procedures of isatins to isatoic anhydrides
always employ oxidants that generate wastes, and require a
of organoselenium chemistry have attracted much attention
9
of chemists
and among the reported studies,
organoselenium catalysis is an important topic because of its
clean procedures, transition metal-free conditions and the
metabolizable catalyst element that is safe to the environ-
1
0
ment, providing potential alternatives of transition metal
catalysts in drug synthesis. Also recently, researchers have
11–13
a
reported a series of organoselenium-catalyzed reactions
Jiangsu Co-innovation Center for Prevention and Control of Important Animal
Infectious Diseases and Zoonoses, School of Chemistry and Chemical Engineering,
Yangzhou University, Yangzhou, Jiangsu 225002, China. E-mail: yulei@yzu.edu.cn
and this field is still in rapid progress in recent years. During
our continuous investigations on green organic reactions
b
Zhejiang Key Laboratory of Carbon Materials, College of Chemistry and
12,14
with industrial potential,
we also found that the
Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035, China.
E-mail: qing-xu@wzu.ed.cn
organoselenium compounds were very good catalysts for the
1
2
reactions using H O as the clean oxidant. Thus, it is
†
Electronic supplementary information (ESI) available: Detailed conditional
2 2
optimization tables and product NMR spectra. See DOI: 10.1039/c5cy01030f
envisioned that isatoic anhydrides might be synthesized
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through organoselenium-catalyzed clean oxidations under
mild and neutral conditions as well. But this strategy faces
tremendous challenges because of the multiple reaction
6
f
points for the oxidation of the C–C bonds (paths a and b)
and the possible organoselenium-catalyzed oxidation of the
amidogen N–H (path c), as reported in the literature (Scheme
1
3
1
). Recently, after a series of careful conditional optimiza-
tions and catalyst screenings, we successfully overcame the
above difficulties and developed an organoselenium-
catalyzed selective oxidation procedure of isatins to prepare
isatoic anhydrides (Scheme 1, path b). Herein, we wish to
report our findings.
15
Fig. 1 Solvent effect test.
Results and discussion
the product yield reached its peak at 88% when 9 vol% DMF/
MeCN was employed (Fig. 2).
Then, with the optimized solvent, the reaction tempera-
ture effect was tested, showing that room temperature (25 °C)
should be the most suitable condition. The product yield
decreased gradually when higher temperature was employed,
1
2
Based on our previous reports, we initially stirred isatin 1a
and H in MeCN in the presence of (PhSe) at room tem-
2
O
2
2
perature (25 °C). After 24 h, the expected product isatoic
anhydride 2a could be obtained in 72% yield after purifica-
tion with column chromatography (eqn (1)).
probably due to the decomposition of H
dation of the product (Fig. 3).
2 2
O or the deep oxi-
Since the reactions could not be completed and traces of
the starting material were always observed by TLC even after
(
1)
24 h, a series of parallel experiments were carried out in 9
vol% DMF/MeCN at 25 °C and stopped at 4 h, 6 h, 8 h, 12 h
and 24 h to judge the termination of the reaction. Fig. 4
showed that the best reaction time should be 8 h and the
product yield did not increase any more after then.
We then tried to optimize the reaction conditions. The sol-
vent effect was first examined and parallel reactions were
performed in a series of solvents such as MeCN, alcohols,
water, DMF, NMP, DMSO and THF for comparison (Fig. 1). It
was shown that the alcohol solvents did not help to optimize
the reaction (Fig. 1, runs 2–5 vs. 1) and water as a solvent also
resulted in a very low product yield (run 6). The other polar
solvents, such as DMF, NMP and DMSO were also tested
The effect of H
2 2
O dosage was also examined. Using 50–
300 mol% of H O , five parallel reactions were performed
2
2
under the screened out conditions respectively and their
results are shown in Fig. 5. It was found that the product
yield reached its peak when 200 mol% of H O was employed
2
2
2 2
and decreased with more H O , probably due to the deep oxi-
dation of the product because a series of unidentified by-
products were observed by TLC.
The catalyst loading effects were also investigated. Fortu-
nately, the best catalyst loading is 5 mol% as employed ini-
tially. Lower catalyst loadings resulted in a reduced 2a yield
due to the slower reaction speed while a higher catalyst load-
ing also gradually pulled down the product yield, probably
(
runs 7–9) and DMF was found to be the best one among
them (run 7) while the other two led to reduced product yield
run 8) or even completely restrained the reaction (run 9). A
(
low polar solvent, THF, was also employed but gave 2a in a
very low yield (run 10).
It was noticed that although the reaction in DMF afforded
product 2a in lower yield than in MeCN, the starting material
1
a dissolved well in it. Therefore, for further optimizations,
we then tried to increase the starting material solubility by
employing composite solvents of MeCN with DMF. The
results of the reactions performed in solvents with different
DMF/MeCN ratios are shown in Fig. 2 and it was found that
15
Scheme 1 Possible oxidation sites of isatin.
Fig. 2 DMF concentration effect test.
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15
Fig. 3 Temperature effect test.
15
2
Fig. 6 (PhSe) loading effect test.
screenings showed that with most diselenides as catalysts,
the reaction proceeded smoothly and gave product 2a in
moderate to good yields (Fig. 7, runs 1–7). Diselenides with a
strong electron donating group {e.g. ijp-IJCH
or strong electron withdrawing group {e.g. ij3,5-
Se] , run 7} both led to 2a in reduced yields. The
3 2 6 4 2
) NC H Se] , run
3}
a
IJCF
3
)
2
C
6
H
3
2
former was probably due to the lower reaction speed while
the latter was because of the too strong catalytic activity that
caused over-oxidations because a series of unidentified by-
products were observed by TLC. Selenides, such as EtSePh, i-
PrSePh, c-C H SePh and PhSePh all resulted in decreased 2a
6
11
yields (runs 8–11). The first three were probably due to the
delay of the catalytic species PhSe(O)OH generation through
syn-selenoxide elimination with H O . For the PhSePh sam-
1
5
Fig. 4 Time effect test.
2
2
ple, although this compound cannot generate PhSe(O)OH via
syn-selenoxide elimination, its selenoxide oxidation product
also has some catalytic activities, as documented in the
1
1n
literature.
presence of H
two steps, showing that PhSe(O)OH was the real catalytic
Our previous studies have disclosed that in the
2
O
2
, (PhSe) was converted to PhSe(O)OH in
2
1
2c
species. However, when PhSe(O)OH was directly used (run
1
8
2), the 2a yield was slightly reduced (run 12, 80% vs. run 1,
8%). This was because of the loading differences between
these two catalysts, since 5 mol% of PhSe(O)OH was equiva-
lent to only 2.5 mol% of (PhSe) , resulting in a 2a yield simi-
2
lar to the case of 3 mol% (PhSe) (84%, in Fig. 6). Similarly,
2
15
Fig. 5
2 2
H O dosage effect test.
due to the side reactions of the catalytic organoselenium spe-
cies with the starting material or the product.
It was notable that unlike many reported organoselenium-
11–13
catalyzed oxidations,
this reaction did not require special
organoselenium catalysts and the cheapest and most avail-
able pre-catalyst (PhSe) was screened out to be the best one
2
(Fig. 7), probably due to the high activity of isatin which
bears two carboxyl groups on the ring and the insertion of an
oxygen atom releases a portion of the ring tension. These
phenomena were also observed during our previous research
1
2c
15
on the Baeyer–Villiger oxidation of 2-MCBones.
Catalyst
Fig. 7 Catalyst screenings.
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PhSeBr, which can rapidly generate PhSe(O)OH, also led to a
reduced 2a yield due to the half-cut of the real catalytic spe-
cies (run 13). The inorganic selenium compound, SeO , only
2
polarity solvent, pure MeCN, which gave higher product
yields than the isatins in DMF/MeCN (Table 1, entries 18–24
vs. 11–17).
resulted in traces of product 2a (run 14), showing that only
organoselenium compounds are catalytically active for this
On the basis of our previous studies as well as the
11–13
references,
a plausible mechanism of this reaction is
7
7
reaction. The other chalcogen compounds, such as (PhS)
2
given. As proved by the Se NMR studies in our previous
1
2c
and (PhTe) , also showed some catalytic activities, but the
reports,
(PhSe)2 was initially oxidized by H O to
2 2
2
yields of 2a were very low (runs 15–16). Finally, a blank reac-
tion confirmed that the reaction could not happen without a
catalyst (run 17).
organoselenium species ijPhSeIJO)O] O (A), which afforded
benzeneseleninoperoxoic acid (B) after hydrolysis. Nucleophilic
2
addition of isatin 1 with B afforded 3. Then, a ring breaking
12c
Under the optimized conditions, a series of isatins were
employed, giving isatoic anhydrides in good yields (Table 1).
This methodology has wide application scopes and isatins
with different kinds of substituents including electron
donating or electron withdrawing groups at different posi-
tions of the aromatic ring or nitrogen were all successfully
oxidized to give the corresponding isatoic anhydrides,
affording a convenient methodology for isatoic anhydride
preparation. It was noticed that for the reactions using 9
vol% DMF/MeCN, the nitrogen-unsubstituted isatins gener-
ally afforded a higher product yield than the substituted
ones (Table 1, entries 1–10 vs. 11–17), probably due to the
higher polarity of the substrates, which led to the higher sol-
ubility in DMF/MeCN. These phenomena inspired us to per-
form reactions of nitrogen-substituted isatins in a lower
reaction happened in 3 and due to the higher activity of the
C–C bond adjacent to the carboxyl group, path a was preferred,
giving the final product isatoic anhydride 2 and the selenium
species C. Oxidation of C by H O regenerated B, which took
2
2
part in the next cycle of reaction (Scheme 2).
To ensure that the methodology is practical for large-scale
preparation, a magnified experiment for the oxidation of
isatin 1a in 50 mmol scale was performed in a 250 mL round
bottom flask. It was noticed that the product precipitated at
the bottom of the flask (Fig. 8). Thus, different from the pre-
vious small-scale preparations, the product could be easily
isolated by simple filtration.
Because the organoselenium catalytic species were very
stable and could be recycled and reused many times in our
1
2a,b,d
previous studies,
we speculated that the mother liquid,
Table 1 Synthesis of isatoic anhydridesa
1
2
b
Entry
1: R , R
Solvent
2%
1
2
3
4
5
6
7
8
9
1a: H, H
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
9 vol% DMF/MeCN
MeCN
2a: 88
2b: 86
2c: 85
2d: 89
2e: 80
2f: 84
2g: 78
2h: 81
2i: 78
2j: 88
2k: 72
2l: 73
2m: 76
2n: 72
2o: 71
2p: 71
2q: 70
2k: 75
2l: 75
2m: 84
2n: 76
2o: 75
2p: 80
2q: 78
1b: 5-Me, H
1c: 5-MeO, H
1d: 5-F, H
1e: 5-Cl, H
1f: 7-Cl, H
1g: 4-Br, H
1h: 5-Br, H
1i: 6-Br, H
1j: 7-Br, H
1k: H, Bn
1l: 5-Me, Bn
1m: 5-Me, Bu
1n: 5-F, Bn
1o: 5-F, Bu
1p: 5-Cl, Bn
1q: 5-Cl, Bu
1k: H, Bn
1l: 5-Me, Bn
1m: 5-Me, Bu
1n: 5-F, Bn
1o: 5-F, Bu
1p: 5-Cl, Bn
1q: 5-Cl, Bu
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
n
n
n
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
n
n
n
a
b
1
2 2 2
mmol of 1, 2 equiv. H O , 0.05 mmol of (PhSe) , and 2.5 mL of solvent were stirred at rt (25 °C) for 8 h. Isolated yields.
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thus reduced the loss of the product caused by its partial dis-
solution in the next cycles. The product yield began to
decrease after recycling of the mother liquid three times, pos-
sibly because for each reaction, some water was introduced
from aqueous H O and the accumulated water finally
2
2
changed the solvent properties and thus reduced the product
yield. It was shown that the mother liquid could be reused
for at least seven times with satisfactory 2a yield (77–94%)
1
and high purity, which was confirmed by the H NMR spec-
trum (Fig. 10).
Conclusions
Scheme 2 Possible mechanisms.
In conclusion, we developed a concise method for the synthe-
sis of isatoic anhydrides from available isatins through
organoselenium-catalyzed oxidation. Compared with the
known methodologies, this method is waste-free and can be
performed under mild and neutral conditions, which are
more preferable for large-scale preparation. The reaction is
metal-free and the catalytic element selenium is eco-friendly.
In addition, the easily recyclable catalyst and solvent and the
convenient isolation procedures made this method more
practical than the previously reported studies on isatoic anhy-
dride synthesis and organoselenium catalysis. To the best of
our knowledge, this reaction is the first example of the
organoselenium-catalyzed Baeyer–Villiger oxidation of hetero-
cycles and expands the application scopes of organoselenium
catalysis. More research studies on the applications of
organoselenium catalysis are on the way in our laboratory.
Fig. 8 The round bottom flask after reaction.
Experimental section
General methods
which contained the organoselenium catalyst, could be
directly reused in the next turn of reaction by adding fresh
isatin 1a and H O (Fig. 9). It was shown that the recycled
2 2
mother liquid resulted in even higher 2a yield than its first
use, possibly because of the fact that part of the product 2a
of the first turn experiment saturated the mother liquid and
The isatins were purchased from reagent merchant with their
purities more than 98% and were directly used as received.
The organoselenium catalysts were commercially available or
1
2d
prepared according to the literature.
The solvents were
1
Fig. 10 Product H NMR spectrum of the 7th catalyst recycle & reuse
Fig. 9 Catalyst recycle & reuse.
reaction.
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analytically pure (AR) and directly used without any special
treatment. All reactions were carried out in open air in
Schlenk tubes and monitored by GC-MS and/or TLC. In
small-scale experiments (1 mmol), the products were all puri-
fied by column chromatography on silica gel using petroleum
ether and ethyl acetate (ratio 2/1) as the eluent. The melting
points were measured by a WRS-2A digital instrument. The
IR spectra were measured on a Bruker Tensor 27 infrared
6-Methyl-1H-benzoijd]ij1,3]oxazine-2,4-dione 2b. Yellow
solid. M.p. 248.6–249.8 °C (lit. 249–250 °C). IR (KBr): 3109,
2010, 1781, 1728, 1622, 1514, 1422, 1349, 1269, 1145, 1030,
−
1 1
1001,916, 825, 780, 728 cm . H NMR (600 MHz, DMSO-d ) δ
6
(ppm): 11.64 (s, 1H, NH), 7.71 (s, 1H, ArH), 7.56 (d, J = 8.4
Hz, 1H, ArH), 7.06 (d, J = 8.4 Hz, 1H, ArH), 2.33 (s, 3H, CH
3
).
1
3
CNMR (150 MHz, DMSO-d ) δ (ppm): 159.9, 147.1, 139.2,
6
137.9, 132.9, 128.3, 115.3, 110.0, 20.0. MS (EI, 70 eV): m/z (%)
1
13
+
spectrometer. The H and C NMR spectra were recorded on
177(20) [M ], 133(100), 104(58). Known compound (4692-99-
1
16a
a Bruker Avance 600/400 instrument (600 or 400 MHz for H
3).
1
3
and 150 MHz for C NMR spectroscopy) using CDCl as the
6-Methoxy-1H-benzoijd]ij1,3]oxazine-2,4-dione 2c. Yellow
solid. M.p. 242.5–243.3 °C (lit. 242–244 °C). IR (KBr): 3246,
3183, 1782, 1733, 1623, 1507, 1422, 1360, 1334, 1257, 1157,
3
4
solvent and Me Si as the internal standard. The chemical
1
13
shifts for H and C NMR were referenced to internal Me Si
4
−
1
1
(0 ppm) and the J-values were shown in Hz. The mass spectra
1016, 920, 838, 753 cm . H NMR (600 MHz, DMSO-d ) δ
6
were measured on a Shimadzu GCMS-QP2010 Ultra spectro-
meter (EI). HRMS (ESI) analysis was measured on a Bruker
microTOF-Q II instrument.
(ppm): 11.6 (s, 1H, NH), 7.38 (dd, J = 2.4 Hz, J = 9.0 Hz, 1H,
ArH), 7.33 (d, J = 2.4 Hz, 1H, ArH), 7.11 (d, J = 9.0 Hz, 1H,
1
3
ArH), 3.81 (s, 3H, OCH3); C NMR (150 MHz, CDCl ) δ
3
(
5
ppm): 159.8, 155.2, 146.9, 135.5, 125.7, 116.9, 110.6, 109.8,
+
5.7. MS (EI, 70 eV): m/z (%) 193(25) [M ], 149(88), 106(100).
Typical procedure for the synthesis of 2a
1
6b
Known compound (37795-77-0).
1
1
mmol of 1a (147.1 mg) and 0.05 mmol of (PhSe) (5 mol%,
2
5.6 mg) were added. A solution of 2 mmol of H O (30 w/
2 2
6
-Fluoro-1H-benzoijd]ij1,3]oxazine-2,4-dione 2d. Yellow
solid. M.p. 263.7–264.6 °C (lit. 265–268 °C). IR (KBr): 3188,
932, 1941, 1760, 1696, 1426, 1259, 1224, 1119, 1040, 1002,
33, 893 847, 735 cm . H NMR (600 MHz, DMSO-d ) δ
6
ppm): 11.80 (s, 1H, NH), 7.70–7.64 (m, 2H, ArH), 7.20–7.17
m, 1H, ArH). C NMR (150 MHz, DMSO-d
d, JC–F = 3.2 Hz), 157.5 (d, JC–F = 239.9 Hz), 146.8, 138.1,
24.8 (d, JC–F = 24.2 Hz), 117.5 (d, JC–F = 7.8 Hz), 114.0 (d, JC–F
w%, 226.0 mg) in 2.5 mL of 9 vol% DMF/MeCN was injected
by a syringe. The mixture was stirred at 25 °C for 8 h and the
solvent was evaporated by vacuum. The residue was purified
by column chromatography (eluent: petroleum ether/EtOAc
2
9
(
(
(
−1
1
13
6
) δ (ppm): 159.2
2
/1) to give 143.5 mg of 2a (yield 88%). Other isatoic anhy-
drides 2 were prepared in a similar way.
1
=
24.2 Hz), 111.4 (d, JC–F = 8.1 Hz). MS (EI, 70 eV): m/z (%)
+
Detailed procedure for the large scale synthesis and the
catalyst recycle and reuse
181(22) [M ], 137(100), 109(53). Known compound (321-69-
7).
6
f
6
-Chloro-1H-benzoijd]ij1,3]oxazine-2,4-dione 2e. Yellow
solid. M.p. 277.0–278.6 °C (lit. 278–281 °C). IR (KBr): 3098,
772, 1698, 1619, 1495, 1419, 1343, 1272, 1243, 1186, 1038,
To a 250 mL round bottom flask, 7.35 g of isatin 1a (50
mmol), 0.78 g of (PhSe) (2.5 mmol), 91 mL of MeCN and 9
2
1
2 2
mL of DMF were added in that order. 10.2 mL of H O (30 w/
−
1 1
−
1
999, 909 846, 811, 751 cm . H NMR (600 MHz, DMSO-d
6
)
w%, d = 1.11 g mL , 100 mmol) was then dropped into the
stirred solution. The mixture was stirred for 8 h at room tem-
perature. The precipitated product isatoic anhydride 2a and
the mother liquid were isolated by simple filtration. The
product 2a was washed with a small amount of EtOH and
dried in air. The mother liquid was directly reused both as a
solvent and a catalyst in the next cycle. The detailed results
are summarized in Fig. 9.
δ (ppm): 11.85 (s, 1H, NH), 7.86 (d, J = 8.4 Hz, 1H, ArH),
1
3
7
.80–7.78 (m, 1H, ArH), 7.16 (d, J = 8.4 Hz, 1H, ArH).
C
6
NMR (150 MHz, DMSO-d ) δ (ppm): 158.9, 146.7, 140.3,
1
1
1
36.6, 127.6, 127.1, 117.4, 112.0. MS (EI, 70 eV): m/z (%)
+
97(20) [M ], 153(100), 125(35). Known compound (4743-
1
6c
7-3).
-Chloro-1H-benzoijd]ij1,3]oxazine-2,4-dione
solid. M.p. 212.4–214.6 °C (lit. 210–215 °C). IR (KBr): 3482,
8
2f.
Yellow
3
1
368, 3058, 1796, 1670, 1608, 1586, 1548, 1455, 1420, 1338,
312, 1272, 1251, 1164, 1077, 1014, 892, 752 cm . H NMR
Characterization of the products
−1 1
1
H-Benzoijd]ij1,3]oxazine-2,4-dione 2a. Yellow solid. M.p.
(600 MHz, DMSO-d ) δ (ppm): 7.74 (dd, J = 1.2 Hz, J = 7.8 Hz,
6
2
1
1
31.3–232.2 °C (lit. 233–234 °C). IR (KBr): 3240, 3104, 2939,
1H, ArH), 7.48 (dd, J = 1.8 Hz, J = 7.2 Hz, 1H, ArH), 6.58 (t, J
= 7.8 Hz, 1H, ArH); C NMR (150 MHz, CDCl ) δ (ppm):
3
1
3
767, 1617, 1513, 1487, 1438, 1362, 1327, 1264, 1152,1121,
−
1
1
011, 904, 792, 763 cm . H NMR (600 MHz, DMSO-d ) δ
169.1, 146.9, 133.7, 130.3, 119.0, 115.1, 111.7. MS (EI, 70 eV):
6
+
(ppm): 11.73 (s, 1H, NH), 7.92 (dd, J = 1.2 Hz, J = 7.8 Hz, 1H,
m/z (%) 197(13) [M ], 153(88), 44(100). Known compound
6
f,16d
ArH), 7.74 (dt, J = 2.4 Hz, J = 7.2 Hz, 1H, ArH), 7.25 (dt, J =
(63497-60-9).
1
3
2
.4 Hz, J = 7.2 Hz, 1H, ArH), 7.16 (d, J = 7.8Hz, 1H, ArH).
C
5-Bromo-1H-benzoijd]ij1,3]oxazine-2,4-dione 2g. Yellow
solid. M.p. 218.3–220.6 °C. IR (KBr): 3182, 3102, 2995, 2916,
1771, 1700, 1608, 1588, 1506, 1465, 1428, 1362, 1305, 1257,
NMR (150 MHz, DMSO-d ) δ (ppm): 159.8, 147.1, 141.4,
1
1
6
36.9, 128.9, 123.5, 115.3, 110.2. MS (EI, 70 eV): m/z (%)
+
+
−1 1
63(22) [M ], 119(100) [M − CO ], 92(70). Known compound
1215, 1181, 1031, 801, 751 cm . H NMR (600 MHz, DMSO-
2
5
b
(118-48-9).
d
6
) δ (ppm): 11.82 (s, 1H), 7.57–7.50 (m, 2H), 7.14 (d, J = 7.8
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1
3
Hz, 1H); C NMR (150 MHz, CDCl ) δ (ppm): 156.8, 146.5,
1720, 1655, 1568,1512, 1476, 1440, 1406, 1383, 1221, 1162,
1126,801, 745 cm . H NMR (600 MHz, CDCl3) δ (ppm): 7.96
(s, 1H, ArH), 7.55 (dd, J = 1.2 Hz, J = 9.0 Hz, 1H, ArH), 7.06
3
−
1 1
1
(
(
44.0, 136.7, 129.3, 123.3, 115.1, 109.2. MS (EI, 70 eV): m/z
%) 241(18) [M ], 197(100), 170(50). Known compound
77603-45-3).
-Bromo-1H-benzoijd]ij1,3]oxazine-2,4-dione 2h. Yellow
solid. M.p. 233.6–234.9 °C (lit. 235 °C). IR (KBr): 3491, 3240,
+
5
e
(d, J = 8.4Hz, 1H, ArH), 4.04 (t, J = 7.8 Hz, 2H, NCH ), 2.41 (s,
2
6
3H, CH ), 1.76–1.71 (m, 2H, CH ), 1.48–1.45 (m, 2H, CH ),
3
2
2
1
3
1.0 (t, J = 7.5Hz, 3H, CH
3
). C NMR (150 MHz, CDCl
3
) δ
3
1
179, 3094, 1772, 1701, 1615, 1496, 1474, 1417, 1340, 1272,
(ppm): 158.8, 147.8, 139.2, 138.3, 133.9, 130.5, 113.9, 111.6,
−
1
1
184, 1138, 1035, 998, 907, 845, 764 cm . H NMR (600
) δ (ppm): 11.85 (s, 1H), 7.99 (d, J = 2.4 Hz,
H), 7.89 (dd, J = 2.4 Hz, J = 8.7 Hz, 1H), 7.10 (d, J = 9.0 Hz,
44.7, 28.9, 20.4, 19.9, 13.7. MS (EI, 70 eV): m/z (%) 233(22)
+
MHz, DMSO-d
6
[M ], 146(100), 133(78). HRMS calcd. for C13
H
16NO
3
([M +
+
1
1
1
2
2
H] ): 234.1125; found: 234.1130.
1
3
H); C NMR (150 MHz, CDCl ) δ (ppm): 158.8, 146.7, 140.6,
39.3, 130.6, 117.6, 114.6, 112.4. MS (EI, 70 eV): m/z (%)
41(19) [M ], 197(100), 170(26). Known compound (4692-98-
).
1-Benzyl-6-fluoro-1H-benzoijd]ij1,3]oxazine-2,4-dione
2n.
3
Yellow solid. M.p. 136.6–138.3 °C. IR (KBr): 2917, 2600, 1669,
+
1581, 1523, 1493, 1342, 1310, 1284, 1260, 1226, 1145, 1025,
1
6e
−1 1
938, 886, 753 cm . H NMR (600 MHz, CDCl ) δ (ppm): 7.83
3
7
-Bromo-1H-benzoijd]ij1,3]oxazine-2,4-dione
solid. M.p. 220.1–222.5 °C. IR (KBr): 3179, 3104, 1780, 1706,
612, 1485, 1403, 1341, 1246, 1072, 1025, 922, 892, 785, 760
2i.
Yellow
(dd, J = 3.0 Hz, J = 7.8 Hz, 1H, ArH), 7.37–7.28 (m, 6H, ArH),
7.10 (dd, J = 3.6 Hz, J = 9.0 Hz, 1H, ArH), 5.30 (s, 2H, NCH ).
2
1
3
1
C NMR (150 MHz, CDCl ) δ (ppm): 158.5 (d, J
= 245.9
C–F
3
−
1 1
cm . H NMR (600 MHz, DMSO-d
6
) δ (ppm): 11.81 (s, 1H),
Hz), 157.5 (d, JC–F = 2.9 Hz), 148.1, 137.9, 134.1, 129.3, 128.3,
126.6, 125.0 (d, JC–F = 23.7 Hz), 117.0 (d, JC–F = 7.7 Hz), 116.3
(d, JC–F = 24.2 Hz), 113.2 (d, JC–F = 8.0 Hz), 48.9. MS (EI, 70
7
7
.83 (d, J = 8.4 Hz, 1H), 7.42 (dd, J = 1.8 Hz, J = 8.4 Hz, 1H),
.30 (d, J = 1.8 Hz, 1H); C NMR (150 MHz, CDCl ) δ (ppm):
3
59.3, 146.8, 142.4, 130.7, 130.3, 126.5, 117.7, 109.7. MS (EI,
0 eV): m/z (%) 241(20) [M ], 197(100), 170(56). Known com-
1
3
+
1
7
eV): m/z (%) 271(20) [M ], 198(43), 91(100). Known compound
+
16h
(749865-71-2).
5
e
pound (76561-16-5).
1-Butyl-6-fluoro-1H-benzoijd]ij1,3]oxazine-2,4-dione 2o. Yel-
low solid. M.p.129.6–131.2 °C. IR (KBr): 2923, 2858, 2724,
2547, 1659, 1579, 1518, 1388, 1306, 1224, 1146, 1021, 935,
8
-Bromo-1H-benzoijd]ij1,3]oxazine-2,4-dione
2j.
Yellow
solid. M.p. 191.8–193.0 °C (lit. 192–194 °C). IR (KBr): 3243,
215, 3131, 1792, 1721, 1608, 1494, 1459, 1346, 1308, 1252,
213, 1136, 1023, 815, 788, 745 cm . H NMR (600 MHz,
DMSO-d ) δ (ppm): 11.07 (s, 1H), 8.02 (dd, J = 1.2 Hz, J = 8.4
Hz, 1H), 7.95 (dd, J = 1.2 Hz, J = 7.8 Hz, 1H), 7.19 (t, J = 7.8
Hz, 1H); C NMR (150 MHz, CDCl
40.1, 139.5, 128.6, 124.5, 112.9, 107.9. MS (EI, 70 eV): m/z
%) 241(17) [M ], 197(100), 169(13). Known compound
−
1 1
3
1
3
807 768 cm . H NMR (600 MHz, CDCl ) δ (ppm): 7.66–7.64
−
1
1
(m, 1H, ArH), 7.17–7.14 (m, 1H, ArH), 6.65–6.63 (m, 1H,
ArH), 3.19(t, J = 7.2 Hz, 2H, NCH ), 1.69–1.65 (m, 2H, CH ),
6
2
2
1
3
1.48–1.44 (m, 2H, CH
(150 MHz, CDCl
127.2, 122.3 (d, JC–F = 22.8 Hz), 116.4 (d, JC–F = 23.0), 111.5 (d,
C–F = 6.9 Hz), 107.3, 42.0, 30.2, 19.3, 12.9. MS (EI, 70 eV): m/z
2
), 0.98 (t, J = 7.5Hz, 3H, CH
3
). C NMR
1
3
3
) δ (ppm): 159.1, 146.5,
3
) δ (ppm): 151.8 (d, JC–F = 231.6 Hz), 147.8,
1
(
(
+
J
1
6f
+
331646-98-1).
-Benzyl-1H-benzoijd]ij1,3]oxazine-2,4-dione 2k. Yellow
solid, yield: 72%. M.p. 138.8–140.6 °C (lit. 139–141 °C). IR
(%) 237(19) [M ], 150(100), 137(79). HRMS calcd. for
C H FNNaO ([M + Na] ): 260.0693; found: 260.0699.
+
1
1
2
12
3
1-Benzyl-6-chloro-1H-benzoijd]ij1,3]oxazine-2,4-dione
2p.
(
1
KBr): 3028, 2921, 1662, 1575, 1516, 1440, 1410, 1362, 1324,
Yellow solid. M.p. 147.0–148.8 °C (lit. 147–149 °C). IR (KBr):
−
1
1
279,1250, 1160, 1108, 1075, 1028, 898 834, 789 cm .
) δ (ppm): 7.98 (d, J = 7.8Hz, 1H, ArH),
.36–7.32 (m, 5H, ArH), 7.28–7.26 (m, 1H, ArH), 6.64–6.61 (m,
H
2922, 2852, 2541, 1668, 1571, 1443, 1338, 1312, 1280, 1228,
−
1
1
NMR (600 MHz, CDCl
7
2
(
1
3
1158, 1117, 1024, 917, 894, 873 cm . H NMR (600 MHz,
CDCl ) δ (ppm): 7.94 (d, J = 2.4 Hz, 1H, ArH), 7.36–7.32 (m,
4H, ArH), 7.29 (d, J = 5.4 Hz, 1H, ArH), 7.24 (d, J = 2.4 Hz,
3
1
3
H, ArH), 4.49 (s, 2H, NCH2). C NMR (150 MHz, CDCl ) δ
3
1
3
ppm): 151.6, 138.7, 135.6, 132.6, 129.1, 128.7, 128.2, 127.2,
1H, ArH), 6.58 (d, J = 9.0 Hz, 1H, ArH), 4.47 (s, 2H,NCH
NMR (150 MHz, CDCl ) δ (ppm): 150.1, 138.2, 135.5, 131.7,
129.0, 128.8, 128.2, 127.4, 126.9, 119.7, 113.4, 109.7, 47.0. MS
2
).
C
+
27.0, 115.1, 111.9, 46,9. MS (EI, 70 eV): m/z (%) 253(35) [M ],
3
1
d
1
80(85), 91(100). Known compound (35710-05-5).
-Benzyl-6-methyl-1H-benzoijd]ij1,3]oxazine-2,4-dione
Yellow solid. M.p. 147.3–148.8 °C. IR (KBr): 2917, 2861, 1780,
+
+
1
2l.
(EI, 70 eV): m/z (%) 243 [(M − 44) , 100], 288 [(M + 1) , 30].
16i
Known compound (57384-84-6).
1
7
619, 1574, 1445, 1384, 1317, 1280, 1063, 1048,912, 892, 808,
75 cm . H NMR (600 MHz, CDCl ) δ (ppm): 7.96 (s, 1H,
3
1-Butyl-6-chloro-1H-benzoijd]ij1,3]oxazine-2,4-dione 2q. Yel-
low solid. M.p. 140.8–142.2 °C. IR (KBr): 2956, 2924, 2854,
2389, 2318, 1654, 1566, 1383, 1307, 1216, 1157, 1017, 907,
−
1 1
ArH), 7.43 (d, J = 9.0 Hz, 1H, ArH), 7.37–7.34 (m, 2H, ArH),
−
1 1
7
.31–7.28 (m, 3H, ArH), 7.00 (d, J = 8.4 Hz, 1H, ArH ), 5.29 (s,
871 772 cm . H NMR (600 MHz, CDCl ) δ (ppm): 8.12 (d, J =
3
1
3
2
H, NCH
2
), 2.37 (s, 3H, CH
3
). C NMR (150 MHz, CDCl
3
) δ
2.4 Hz, 1H, ArH), 7.70 (dd, J = 2.4 Hz, J = 9.0Hz, 1H, ArH),
(ppm): 158.5, 148.5, 139.2, 138.2, 134.6, 134.2, 130.5, 129.1,
2
7.13 (d, J = 9.0 Hz, 1H, ArH), 4.05 (t, J = 7.8 Hz, 2H, NCH ),
1
2
3
28.1, 126.6, 114.7, 111.7, 48.5, 20.4. MS (EI, 70 eV): m/z (%)
1.76–1.71 (m, 2H, CH ), 1.50–1.44 (m, 2H, CH ), 1.01 (t, J =
2
2
+
13
67(27) [M ], 194(59), 91(100). Known compound (35710-11-
7.2Hz, 3H, CH
3
). C NMR (150 MHz, CDCl
3
) δ (ppm): 157.6,
1
6g
).
147.3, 139.9, 137.3, 130.1, 129.6, 115.7, 113.0, 45.1, 28.9, 19.9,
+
1
-Butyl-6-methyl-1H-benzoijd]ij1,3]oxazine-2,4-dione
2m.
13.8. MS (EI, 70 eV): m/z (%) 253(24) [M ], 166(100), 111(40).
1
6j
Yellow solid. M.p. 142.1–143.3 °C. IR (KBr): 2957, 2862, 2370,
Known compound (144155-83-9).
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Acknowledgements
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This work was supported by the NNSFC (21202141,
2
1173182), the Priority Academic Program Development
(PAPD) of Jiangsu Higher Education Institutions and the
Yangzhou Nature Science Foundation (YZ2014040) and the
Opening Foundation of the Key Laboratory of Environmental
Materials and Engineering of Jiangsu Province (K14010). We
thank Prof. Mark Lautens for suggestions and Miss Hongyan
Li and the analysis centre of Yangzhou University for
assistance.
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