Microwave-assisted Synthesis and antifungal activity of coumarin[8,7-e][1,3]oxazine derivatives

Article abstract of DOI:10.1007/s11030-016-9662-2

The synthesis of novel coumarin[8,7-e][1,3]oxazine derivatives through a microwave-assisted three-component one-pot Mannich reaction is described in this study. All the target compounds were evaluated in vitro for their antifungal activity against Botryti

Full text of DOI:10.1007/s11030-016-9662-2

Mol Divers
DOI 10.1007/s11030-016-9662-2
ORIGINAL ARTICLE
Microwave-assisted Synthesis and antifungal activity
of coumarin[8,7-e][1,3]oxazine derivatives
Ming-Zhi Zhang1 · Rong-Rong Zhang1 · Wen-Zheng Yin1 · Xiang Yu1 ·
Ya-Ling Zhang1 · Pin Liu1 · Yu-Cheng Gu2 · Wei-Hua Zhang1
Received: 17 October 2015 / Accepted: 31 January 2016
© Springer International Publishing Switzerland 2016
Abstract The synthesis of novel coumarin[8,7-e][1,3]
oxazine derivatives through a microwave-assisted three-
component one-pot Mannich reaction is described in this
study. All the target compounds were evaluated in vitro
for their antifungal activity against Botrytis cinerea, Col-
letotrichum capsici, Alternaria solani, Gibberella zeae,
Rhizoctonia solani, and Alternaria mali. The preliminary
bioassays showed that 5e, 5m, and 5s exhibited good anti-
fungal activity and the most active compound was 5m with
an EC50 value as low as 2.1 nM against Botrytis cinerea.
and Acenocoumarol (Fig. 1), are anticoagulant agents that
function as vitamin K antagonists used in the prevention of
thrombosis and thromboembolism [4–6]. Osthole (Fig. 1), a
natural O-methylated coumarin found in many plants, shows
antifungal activity against Rhizoctonia solani and a broad
spectrum of other phytopathogenic fungi [7–9], and has a
long history of use in China as a fungicide. The recently intro-
duced strobilurin fungicide Coumoxystrobin (Fig. 1) is also
a coumarin derivative. It contains an (E)-methyl 3-methoxy-
2-phenylacrylate substructure and displays a broad spectrum
of antifungal activity [10–12].
Keywords Coumarin · Oxazine · Microwave-assisted
synthesis · Mannich reaction · Antifungal activity · SAR
In our previous work, Osthole was used as the lead
structure to carry out structural optimization [13–15], as
the 2H-pyran-2-one substructure in Osthole can be con-
sidered as configuration ring-closed analog of (E)-methyl
3-methoxy-2-phenylacrylate (shown in Fig. 2), which is the
pharmacophore of the strobilurin fungicides. In our lab we
observed that designed compounds containing the coumarin
scaffold exhibited high potency against phytopathogenic
fungi (unpublished results). In this paper, we focus not
only on the side-chain cyclization, but also on the introduc-
tion of an oxazine ring to the coumarin structure through a
microwave-assisted three-component one-pot Mannich reac-
tion (as shown in Fig. 2), as compounds containing an
oxazine subunit usually demonstrate favorable drug-like
properties, including good solubility and balanced lipophilic-
ity [16–19]. Some coumarin[8,7-e][1,3]oxazine derivatives
havealsobeenreportedtoexhibitanti-inflammatoryandanti-
tumour properties [20–24]. Aside from this, further structural
optimization and antifungal activity of novel coumarin[8,7-
e][1,3]oxazine derivatives have not been reported before.
Aiming to discover promising compounds for their use
as antifungal agents with a broad spectrum of activity
and a new mode of action, several 7-hydroxycoumarins
were used as the parent structure to generate a series of
Introduction
Coumarins, an important class of heterocyclic compounds,
are widely distributed throughout nature as secondary
metabolites from plants. They are frequently associated with
a wide range of biological activities, such as anticoagulant,
anticancer, and antifungal activities [1–3]. As the structural
core, coumarin is used regularly as a scaffold in medici-
nal and agricultural chemistry. Examples, such as Warfarin
Electronic supplementary material The online version of this
article (doi:10.1007/s11030-016-9662-2) contains supplementary
material, which is available to authorized users.
Wei-Hua Zhang
njzhangwh@126.com
B
1
Jiangsu Key Laboratory of Pesticide Science, College of
Sciences, Nanjing Agricultural University, Nanjing 210095,
People’s Republic of China
2
Syngenta Jealott’s Hill International Research Centre,
Bracknell, Berkshire RG42 6EY, UK
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Fig. 1 Structures of coumarin-containing drugs and agrochemicals
Fig. 2 Design strategy for the
target molecules
Scheme 1 Synthetic route to
coumarin[8,7-e][1,3]oxazine
derivatives
coumarin[8,7-e][1,3]oxazine derivatives. Herein, we report
the novel and efficient microwave-assisted synthesis of
coumarin[8,7-e][1,3]oxazine derivatives from readily avail-
able starting materials and their in vitro antifungal activity
against six phytopathogenic fungi.
(Table 1). The reaction of 7-hydroxycoumarins (3a–3e)
with different amines using catalytic amounts of 4-N,N-
dimethylaminopyridine (DMAP) to make 5a was chosen
as the model reaction to optimize the reaction conditions
(shown in Scheme 2). 1,4-Dioxane was found to be the
best solvent for this reaction (Entries a − d) under a
microwave power of 400 W, with the yields increasing con-
sistently with time, from 17 % (10 min) to a maximum
of 65 % (30 min) (Entries f , h, and i). Increasing the
microwave power and reaction time did not lead to a sig-
nificant improvement in yield. The results are summarized
in Table 1.
Results and discussion
Synthetic chemistry [25]
The coumarin ring was prepared via a Pechmann condensa-
tion using ZrCl4 as catalyst, and the 1,3-oxazine ring was
introduced through a microwave-assisted Mannich reaction.
Aniline, 4-methylaniline, 4-chloroaniline, and benzylamine
were used as the amine input in the condensation step for the
construction of the oxazine unit (Scheme 1).
Biological assays
The materials and methods used in the biological assays are
the same as those reported in the literature [26]. The antifun-
gal activity of the synthesized compounds was assessed using
solutions at a concentration of 50 ppm and Osthole as posi-
tive control. The biological results for the compounds tested
against six phytopathogenic fungi are reported in Table 2. In
In our initial study, we utilized microwave irradiation
to
synthesize
the
designed
coumarin[8,7-e]
[1,3]oxazines, as opposed to using the conventional heating
(Entries l − o). Reaction times can be reduced from about 6
hours to 30 min, and isolated yields increased up to 65 %
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Table 1 Optimization
parameters for formation of the
oxazine ring (5a)
Entry
Solvent
MW power
Temperature
Time
Yield (%)a
a
b
c
d
e
f
THF
320W
320 W
320 W
320 W
240 W
400 W
480 W
400 W
400 W
400 W
400 W
r.t.
30 min
30 min
30 min
30 min
30 min
30 min
30 min
10 min
20 min
35 min
40 min
6 h
32
41
16
58
24
65
59
17
35
63
62
26
41
43
60
Ethanol
r.t.
Toluene
r.t.
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
Toluene
r.t.
r.t.
r.t.
g
h
i
r.t.
r.t.
r.t.
j
r.t.
k
l
r.t.
b
–
80 ◦C
Reflux
80 ◦C
100 ◦C
b
m
n
o
Ethanol
–
6 h
b
1,4-dioxane
1,4-dioxane
–
6 h
b
–
6 h
aYields after purification by recrystallization
bConventional heating, no microwave irradiation
commonly against Botrytis cinerea, Colletotrichum cap-
sici, Gibberella zeae and Rhizoctonia solani, but lacking
potency against Alternaria solani and Alternaria mali, as
illustrated by the absence of activity against theses two
kinds of fungi, shown in Table 2. Nonetheless, compound 5p
showed equivalent activity with the positive control Osthole
against Alternaria mali. Second, the spectrum of antifungal
activity is generally improved by introducing a Cl to the 6-
position of the coumarin ring. Indeed, compounds 5e, 5i, and
5m displayed a broader spectrum of activity compared with
compound 5a. Thirdly, compounds exhibited better activ-
ity against Botrytis cinerea and Rhizoctonia solani when R4
was a phenyl group rather than substituted benzene or benzyl
groups, for example, compounds 5a, 5e, 5i, 5m, and 5q were
much more active against Botrytis cinerea and Rhizoctonia
solani than the other R4 compounds. Analogs 5e and 5m
even showed improved activity compared with the positive
control. However, for the other substituents of the coumarin
ring, the SAR was rather flat, i.e., marginally affected by
structural alterations.
In addition, as shown in Table 3, the EC50 values of these
active compounds were measured. The EC50 values of 5m
against Botrytis cinerea, Colletotrichum capsici and Rhizoc-
tonia solani were 2.1, 19, and 5.8 nM, respectively, more
potent than Osthole. Compound 5g displayed similar activ-
ity to Osthole against Colletotrichum capsici. Compounds 5e
and 5o showed weaker inhibition than Osthole against Rhi-
zoctonia solani. It is worth mentioning that the most active
compound 5m was identified as the most promising candi-
date for further study with a broad-spectrum of antifungal
activity.
Scheme 2 Synthesis of 5a
addition, the EC50 values of the most active compounds were
obtained and are shown in Table 3.
Antifungal activity and the structure-activity
relationships (SAR)
As shown in Table 2, these target compounds exhibited dif-
ferent rates of growth inhibition against the six fungi, and
some showed strong activity against Botrytis cinerea and
Rhizoctonia solani. Compounds 5e, 5m, 5s, and Osthole
showed 88.2, 98.7, 78.6, and 86.8 % inhibition, respec-
tively, against Botrytis cinerea. Compounds 5g and 5m
displayed 66.7 and 79.6 % inhibition, respectively, against
Colletotrichum capsici, and were more active than the posi-
tive control Osthole. Compounds 5e, 5m, 5o exhibited 73.3,
88.2, and 81.5 % inhibition, respectively, against Rhizoctonia
solani.
Although the antifungal activity of most of the coumarin
derivatives proved to be quite poor, making it difficult to
elucidate a detailed structure-activity relationship analysis,
some broad observations can still be drawn. First, it was
noticeable that where compounds were active it was most
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Table 2 Antifungal activity of
compounds 5a–5t (Inhibition
rates %, at 50 ppm)
Compd.
Botrytis
cinerea
Colletotrichum
capsici
Alternaria
solani
Gibberella
zeae
Rhizoctonia
solani
Alternaria
mali
5a
5b
5c
63.9
33.4
76.2
30.4
88.2
28.6
27.1
62.0
76.9
37.8
23.9
16.5
98.7
53.9
69.7
57.8
62.6
54.5
78.6
28.1
86.8
14.1
18.2
33.3
14.1
34.4
16.7
66.7
41.7
22.4
31.3
37.5
37.5
79.6
47.2
45.3
25.5
37.2
16.6
28.9
14.3
66.4
31.4
17.5
19.4
5.6
7.1
17.9
16.9
69.8
26.8
17.1
34.1
31.8
19.5
74.5
29.2
41.5
69.8
19.5
34.1
40.6
30.8
15.3
47.4
27.5
41.7
61.5
48.8
57.5
14.9
73.3
60.3
51.4
28.6
40.4
29.3
45.7
28.0
88.2
62.4
81.5
31.0
62.7
38.2
64.3
22.9
66.7
55.4
7.8
29.8
16.1
45.3
7.1
5d
5e
21.3
3.4
5f
5g
5h
5i
14.5
3.5
42.3
61.9
9.5
3.9
5j
11.3
12.1
4.5
16.7
22.0
42.3
44.6
10.1
20.3
78.6
49.1
8.6
5k
5l
5m
5n
5o
5p
5q
5r
37.5
26.7
18.1
10.6
13.8
9.4
5s
21.5
6.2
25.2
34.7
72.3
5t
Osthole
62.5
Bold means better activity than the control Osthole
Table 3 EC50 of the most active compounds
Pathogen
Compound
Toxic regression
R
EC50(nM)
95 % Confidence
interval
Botrytis cinrea
5e
Y = 4.1882 + 1.1207X
Y = 5.0878 + 1.2236X
Y = 3.7502 + 1.1866X
Y = 4.3172 + 0.8435X
Y = 4.4428 + 0.5918X
Y = 4.1642 + 0.9702X
Y = 3.9221 + 0.8790X
Y = 2.9245 + 1.5630X
Y = 4.2009 + 0.8875X
Y = 3.3057 + 1.4442X
Y = 4.5097 + 0.5854X
0.9864
0.9939
0.9987
0.9629
0.9815
0.9952
0.9886
0.9797
0.9983
0.9835
0.9899
16
2.1
3.0
26
24
19
69
65
5.8
36
28
13–20
1.6–3.2
2.8–3.2
18–38
19–30
17–22
58–82
50–84
5.0–6.5
29–44
23–34
Botrytis cinrea
5m
Botrytis cinrea
5s
Botrytis cinrea
Osthole
5g
Collecterichum capsica
Collecterichum capsica
Collecterichum capsica
Rhizoctonia solani
Rhizoctonia solani
Rhizoctonia solani
Rhizoctonia solani
5m
Osthole
5e
5m
5o
Osthole
Bold means better activity than the control Osthole
Conclusion
good antifungal activity against Botrytis cinerea and Rhi-
zoctonia solani, better than or similar to the positive control
Osthole. The EC50 values of 5m against Botrytis cinerea,
Colletotrichum capsici and Rhizoctonia solani were 2.1, 19,
and 5.8 nM, respectively, much lower than that of Osthole,
and compound 5m was identified as the most promising can-
didate for further study.
In summary, we have developed a microwave-assisted
synthetic method for the preparation of coumarin[8,7-
e][1,3]oxazine derivatives which proceeds in acceptable
yields and short reaction times. The in vitro antifungal activ-
ity of these compounds was evaluated. The preliminary
bioassay showed that compounds 5e, 5m and 5s exhibit
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Experimental
6-Chloro-7-hydroxy-3,4-dimethyl-2H-chromen-2-one (3e)
◦
1
All materials were obtained from commercial sources and
were used as received. Melting points were obtained on a
WRS-1B melting-point apparatus and are uncorrected. NMR
spectra were recorded on a Bruker DRX-400 instrument in
CDCl3 or DMSO-d6 using TMS as the internal reference
(400 and 100 MHz for 1NMR and 13C NMR, respectively).
Infrared (IR) spectra were recorded on a Bruker Tensor 27
spectrometer, and samples were prepared as KBr plates.
High-resolution mass spectra (HRMS) were acquired in pos-
itive mode on a JMS-AX505HA (JEOL, Japan). Microwave
irradiation was carried out using a microwave oven (WBFY-
201, Gongyi Yuhua Instrument Co., Ltd.) with an emission
frequency of 2450 MHz and a maximum output power of 800
W. The course of reactions and the purity of products were
monitored by TLC using silica gel GF/UV 254. Reaction
yields were not optimized.
Yield: 68 %, m.p. 263.7–264.2 C. H NMR (400 MHz,
DMSO-d6)δ: 11.17 (s, 1H), 7.71 (s, 1H), 6.85 (s, 1H), 2.31
(s, 3H), 2.04 (s, 3H).
Synthesis of coumarin[8,7-e][1,3]oxazine 5a–5t
A solution of primary amine 4 (5 mmol) in dioxane (15 mL)
was treated with formalin solution (35 %, 10 mmol). The
resulting mixture was held at room temperature and stirred
vigorously for 1 hour, then treated with 7-hydroxycoumarin
analogs 3a–3e (5 mmol) and a catalytic amount of DMAP
(20 mg), and irradiated at 400 W for 30 min in the microwave
synthesizer. The solvent was evaporated, and the residue was
crystallized from ethanol to give the title compounds 5a–5t.
4 -Methyl -9 -phenyl - 9,10-dihydrochromeno[8,7 -e][1,3]
oxazin -2(8H)- one (5a)
Synthesis of 7-hydroxycoumarin analogs 3a–3e [27,28]
◦
Yield: 65 %, m.p. 149.7–150.0 C. IR (KBr) cm−1: 3071,
A mixture of resorcinol 1 (or 4-chlororesorcinol) (0.1 mol)
and β-keto-ester 2 (0.12 mol) was cooled to 0◦C, and concen-
tratedsulfuricacid(40mL)wasaddeddropwise. Themixture
was held at room temperature for 12 hours with mechanical
stirring. Then the mixture was poured into 250 mL ice water
to give a precipitate, which was filtered off and crystallized
from ethanol to give compounds 3a–3e.
2915, 1727, 1595, 1495, 1449. 1H NMR (400 MHz, CDCl3):
δ: 7.37 (d, J = 8.8 Hz, 1H), 7.32–7.23 (m, 2H), 7.18–
7.11 (m,2H), 6.96 (t, J = 7.3 Hz, 1H), 6.78 (d, J= 8.8
Hz, 1H), 6.13 (s, 1H), 5.44 (s, 2H), 4.83 (s, 2H), 2.37 (s,
3H). 13C NMR (100 MHz, CDCl3): 161.02, 157.61, 153.12,
151.16, 147.92, 129.40, 123.59, 122.03, 118.52, 113.64,
113.25, 111.71, 108.89, 79.83, 46.36, 18.77. HRMS calcd
for C18H16O3N[M+H]+ 294.1125, found 294.1122.
7-Hydroxy-4-methyl-2H-chromen-2-one (3a)
4-Methyl-9-p-tolyl-9,10-dihydrochromeno[8,7-e][1,3]
oxazin-2(8H)-one (5b)
◦
1
Yield: 68 %, m.p. 187.6–187.8 C. H NMR (400 MHz,
DMSO-d6) δ: 10.55 (s, 1H), 7.60 (d, J = 8.7 Hz, 1H), 6.81
(d, J = 11.0 Hz, 1H), 6.71 (s, 1H), 6.14 (s, 1H), 2.37 (s, 3H).
◦
Yield: 63 %, m.p. 160.1–161.2 C. IR (KBr) cm−1: 3023,
2883, 1713, 1596, 1512, 1493.1H NMR (400 MHz, CDCl3):
δ: 7.36 (d, J = 8.8 Hz, 1H), 7.12–7.01(m, 4H), 6.77 (d, J = 8.8
Hz, 1H), 6.12 (s, 1H), 5.41 (s, 2H), 4.79 (s, 2H), 2.37 (s, 3H),
2.26 (s, 3H). 13C NMR (100 MHz, CDCl3): 161.05, 157.54,
153.13, 151.18, 145.58, 131.66, 129.91, 123.54, 118.78,
113.60, 113.21, 111.63, 108.85, 80.26, 46.46, 20.59, 18.76.
HRMS calcd for C19H18O3N[M+H]+308.1281, found
308.1279.
6-Chloro-7-hydroxy-4-methyl-2H-chromen-2-one (3b)
◦
1
Yield: 76 %, m.p. 285.3–285.4 C. H NMR (400 MHz,
DMSO-d6)δ: 11.34 (s, 1H), 7.74 (s, 1H), 6.88 (s, 1H), 6.19
(s, 1H), 2.37 (s, 3H).
7-Hydroxy-4-phenyl-2H-chromen-2-one (3c)
◦
1
Yield: 80 %, m.p. 250.2–250.5 C. H NMR (400 MHz,
DMSO-d6) δ: 10.71 (s, 1H), 7.66–7.46 (m, 5H), 7.29 (d, J
= 8.6 Hz, 1H), 6.88-6.69 (m, 2H), 6.17 (s, 1H).
9-(4-Chlorophenyl)-4-methyl-9,10-dihydrochromeno[8,7-
e][1,3]oxazin-2(8H)-one (5c)
◦
Yield: 57 %, m.p. 137.4–137.8 C. IR (KBr) cm−1: 3071,
7-Hydroxy-4-(trifluoromethyl)-2H-chromen-2-one (3d)
2955, 1724, 1593, 1492, 1437. 1H NMR (400 MHz, DMSO-
d6): δ: 7.52 (d, J = 8.8 Hz, 1H), 7.34–7.14 (m, 4H), 6.80 (d,
J = 10.3 Hz, 1H), 6.21 (s, 1H), 5.54 (s, 2H), 4.74 (s, 2H),
2.36 (s, 3H). 13C NMR (100 MHz, CDCl3): 160.92, 157.28,
153.12, 151.10, 146.55, 129.32, 127.10, 123.77, 119.86,
◦
1
Yield: 33 %, m.p. 185.5–185.5 C. H NMR (400 MHz,
DMSO-d6) δ: 10.99 (s, 1H), 7.56 (d, J = 10.5 Hz, 1H), 6.91
(d, J = 8.9 Hz, 1H), 6.84 (s, 1H), 6.77 (s, 1H).
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113.62, 113.39, 111.81, 108.54, 79.67, 46.50, 18.79. HRMS
calcd for C18H15O3NCl[M+H]+ 328.0735, found 328.0729.
9-Benzyl-6-chloro-4-methyl-9,10-dihydrochromeno[8,7-
e][1,3]oxazin-2(8H)-one (5h)
◦
9-Benzyl-4-methyl-9,10-dihydrochromeno[8,7-e][1,3]
oxazin-2(8H)-one (5d)
Yield: 71 %, m.p. 153.5–154.4 C. IR (KBr) cm−1: 3051,
2955, 1707, 1598, 1485, 1441. 1H NMR (400 MHz,
DMSO-d6): δ: 7.76 (s, 1H), 7.46–7.16 (m, 5H), 6.26 (s,
1H), 5.16 (s, 2H), 4.04 (s, 2H), 3.90 (s, 2H), 2.40 (s, 3H).
13C NMR (100 MHz, CDCl3): 159.86, 153.60, 152.67,
150.37, 138.25, 128.97, 127.87, 124.06, 116.82, 113.36,
112.26, 109.55, 84.41, 55.34, 43.87, 18.60. HRMS calcd for
C19H17O3NCl[M+H]+ 342.0891, found 342.0891.
◦
Yield: 62 %, m.p. 133.5–133.5 C. IR (KBr) cm−1: 3071,
2947, 1717, 1596, 1489, 1437. 1H NMR (400 MHz,
DMSO-d6): δ: 7.56 (d, J = 10.4 Hz, 1H), 7.43–7.22 (m, 5H),
6.85 (d, J = 10.2 Hz, 1H), 6.18 (s, 1H), 4.99 (s, 2H), 4.02 (s,
2H), 3.88 (s, 2H), 2.38 (s, 3H). 13C NMR (100 MHz, CDCl3):
161.12, 157.51, 153.09, 152.06, 137.49, 128.88, 128.62,
127.67, 123.34, 113.31, 113.26,111.61, 108.04, 82.63, 55.95,
45.12, 18.77. HRMS calcd for C19H18O3N[M+H]+
308.1281, found 308.1281.
4,9-Diphenyl-9,10-dihydrochromeno[8,7-e][1,3]oxazin-
2(8H)-one (5i)
◦
Yield: 75 %, m.p. 183.1–183.1 C. IR (KBr) cm−1: 3067,
6-Chloro-4-methyl-9-phenyl-9,10-dihydrochromeno[8,7-
e][1,3]oxazin-2(8H)-one (5e)
2959, 1716, 1589, 1488, 1445. 1H NMR (400 MHz,
DMSO-d6): δ: 7.64–7.44 (m, 5H), 7.35–7.14 (m, 5H), 6.92
(t, J= 7.2 Hz, 1H), 6.79 (d, J = 8.9 Hz, 1H), 6.25 (s,
1H), 5.60 (s, 2H), 4.83 (s, 2H). 13C NMR (100 MHz,
CDCl3): 129.69, 129.44, 128.86, 128.42, 126.13, 122.20,
118.64, 113.69, 111.62, 109.06, 79.90, 46.50. HRMS calcd
for C23H18O3N[M+H]+ 356.1281, found 356.1277.
◦
Yield: 75 %, m.p. 173.7–174.1 C. IR (KBr) cm−1: 3007,
2871, 1715, 1598, 1569, 1493. 1H NMR (400 MHz,
DMSO-d6): δ: 7.72 (s, 1H), 7.34–7.32 (m,2H), 7.21–7.11 (m,
2H), 6.93 (t, J = 7.2 Hz, 1H), 6.29 (s, 1H), 5.69 (s, 2H), 4.79
(s, 2H), 2.37 (s, 3H). 13C NMR (100 MHz, CDCl3): 160.35,
152.88, 152.08, 149.43, 147.52, 129.49, 123.51, 122.42,
118.67, 118.10, 113.34, 112.82, 110.35, 80.74, 46.43, 18.70.
HRMS calcd for C18H15O3NCl[M+H]+ 328.0735, found
328.0732.
4-Phenyl-9-p-tolyl-9,10-dihydrochromeno[8,7-e][1,3]
oxazin-2(8H)-one (5j)
◦
Yield: 68 %, m.p. 152.9–153.0 C. IR (KBr) cm−1: 3071,
1
2915, 1718, 1609, 1585, 1515, 1441. H NMR (400 MHz,
6-Chloro-4-methyl-9-p-tolyl-9,10-dihydrochromeno[8,7-
DMSO-d6): δ: 7.68–7.43 (m, 5H), 7.18 (d, J = 8.9 Hz,
1H), 7.14–6.93 (m, 4H), 6.76 (d, J= 8.9 Hz, 1H), 6.24 (s,
1H), 5.54 (s, 2H), 4.77 (s, 2H), 2.19 (s, 3H). 13C NMR
(100 MHz, CDCl3): 161.04, 157.70, 156.39, 151.87, 145.57,
135.56, 131.77, 129.95, 129.64, 128.87, 128.43, 126.08,
118.86, 113.67, 112.20, 111.52, 109.06,80.32,46.64, 20.62.
HRMS calcd for C24H20O3N[M+H]+ 370.1438, found
370.1435.
e][1,3]oxazin-2(8H)-one (5f)
Yield: 68 %, m.p. 199.6–199.9 C. IR (KBr) cm−1: 3055,
2971, 1725, 1596, 1565, 1510, 1485. H NMR (400 MHz,
◦
1
DMSO-d6): δ: 7.72 (s, 1H), 7.33–6.80 (m, 4H), 6.29 (s, 1H),
5.65 (s, 2H), 4.74 (s, 2H), 2.38 (s, 3H), 2.19 (s, 3H). 13C
NMR (100 MHz, CDCl3): 160.40, 152.87, 152.13, 149.46,
145.18, 132.09, 129.98, 123.45, 118.91, 118.06, 113.27,
112.71, 110.33, 81.17, 46.62, 20.59, 18.69. HRMS calcd for
C19H17O3NCl[M+H]+ 342.0891, found 342.0888.
9-(4-Chlorophenyl)-4-phenyl-9,10-dihydrochromeno[8,7-e
][1,3]oxazin-2(8H)-one (5k)
6-Chloro-9-(4-chlorophenyl)-4-methyl-9,10-
dihydrochromeno[8,7-e][1,3]oxazin-2(8H)-one (5g)
◦
Yield: 74 %, m.p. 186.5–187.3 C. IR (KBr) cm−1: 3075,
2887, 1717, 1614, 1585, 1492. 1H NMR (400 MHz,
DMSO-d6): δ: 7.61–7.52 (m, 3H), 7.52–7.44 (m, 2H),
7.35–7.26 (m, 2H), 7.26–7.15 (m, 3H), 6.79 (d, J = 8.9
Hz, 1H), 6.25 (s, 1H), 5.58 (s, 2H), 4.82 (s, 2H). 13C
NMR (100 MHz, CDCl3): 160.90, 157.45, 156.35, 151.79,
146.57, 135.46, 129.70, 129.36, 128.89, 128.42, 127.21,
126.28, 119.95, 113.67, 112.38, 111.70, 108.77, 79.74,
46.68. HRMS calcd for C23H17O3NCl[M+H]+ 390.0892,
found 390.0888.
◦
Yield: 78 %, m.p. 198.5–198.8 C. IR (KBr) cm−1: 3063,
2923, 1717, 1591, 1493, 1421. 1H NMR (400 MHz,
DMSO-d6): δ: 7.74 (s, 1H), 7.35–7.16 (m, 4H), 6.30 (s, 1H),
5.68 (s, 2H), 4.78 (s, 2H), 2.38 (s, 3H). 13CNMR (100 MHz,
CDCl3): 152.65, 152.10, 146.16, 129.43, 127.59, 123.68,
120.04, 118.12, 113.48, 112.90, 110.03, 80.60, 46.62, 18.71.
HRMS calcd for C18H14O3NCl2[M+H]+ 362.0345, found
362.0341.
123

Mol Divers
9-Benzyl-4-phenyl-9,10-dihydrochromeno[8,7-e][1,3]oxa
9-Benzyl-6-chloro-4-(trifluoromethyl)-9,10-dihydrochrome
zin-2(8H)-one (5l)
no[8,7-e][1,3]oxazin-2(8H)-one (5p)
◦
Yield: 62 %, m.p. 66.3–66.6 ◦C. IR (KBr) cm−1: 3059, 2959,
1720, 1592, 1553, 1493. H NMR (400 MHz, DMSO-d6):
Yield: 69 %, m.p. 150.6–151.0 C. IR (KBr) cm−1: 3003,
1
1
2859, 1737, 1593, 1485, 1445, 1405. H NMR (400 MHz,
δ: 7.69–7.47 (m, 5H), 7.43–7.28 (m, 5H), 7.23 (d, J =
8.9 Hz, 1H), 6.84 (d, J= 8.8 Hz, 1H), 6.22 (s, 1H),
5.03 (s, 2H), 4.08 (s, 2H), 3.91 (s, 2H). 13C NMR (100
MHz, CDCl3): 160.15, 157.74, 156.02, 152.61, 138.40,
135.47, 130.11, 129.31, 129.01, 128.90, 127.83, 125.93,
113.71, 111.84, 111.35, 108.35, 83.15, 55.36, 44.13, 31.17.
HRMS calcd for C24H20O3N[M+H]+ 370.1438, found
370.1434.
DMSO-d6): δ: 7.55 (s, 1H), 7.43–7.20 (m, 5H), 6.93 (s, 1H),
5.26 (s, 2H), 4.07 (s, 2H), 3.91 (s, 2H). 13C NMR (100 MHz,
CDCl3): 158.60, 154.09, 151.24, 141.35, 141.02, 136.83,
128.80, 128.77, 127.95, 123.84, 119.07, 112.98 (q, J = 5.6
Hz), 110.00, 106.68, 84.28, 56.10, 44.73. HRMS calcd for
C19H14O3NClF3[M+H]+ 396.0609, found 396.0605.
6-Chloro-3,4-dimethyl-9-phenyl-9,10-dihydrochromeno[8,
7-e][1,3]oxazin-2(8H)-one (5q)
6-Chloro-9-phenyl-4-(trifluoromethyl)-9,10-dihydrochrome
no[8,7-e[1,3]oxazin-2(8H)-one (5m)
◦
Yield: 66 %, m.p. 187.5–188.0 C. IR (KBr) cm−1: 3051,
2908, 1701, 1596, 1496, 1453. 1H NMR (400 MHz,
DMSO-d6): δ: 7.73 (s, 1H), 7.40–7.10 (m, 4H), 6.93 (t, J=
7.2 Hz, 1H), 5.69 (s, 2H), 4.79 (s, 2H), 2.34 (s, 3H), 2.08 (s,
3H). 13C NMR (100 MHz, CDCl3): 161.57, 151.69, 147.75,
147.60, 145.70, 129.45, 123.28, 122.30, 120.03, 118.63,
117.80, 113.98, 110.00, 80.60, 46.40, 15.15, 13.38. HRMS
calcd for C19H17O3NCl[M+H]+ 342.0892, found 342.0886.
◦
Yield: 72 %, m.p. 152.9–153.3 C. IR (KBr) cm−1: 3075,
2975, 1732, 1595, 1557, 1485. 1H NMR (400 MHz,
DMSO-d6): δ: 7.52 (s, 1H), 7.36–7.13 (m, 4H), 7.02–
6.88 (m, 2H), 5.75 (s, 2H), 4.81 (s, 2H). 13C NMR (100
MHz, CDCl3): 158.35, 153.95, 150.18, 147.15, 141.20,
140.87, 129.43, 123.97, 122.65, 119.27, 118.71, 112.93 (q,
J=5.7Hz), 110.68, 106.57, 80.98, 46.37. HRMS calcd for
C18H12O3NClF3[M+H]+ 382.0452, found 382.0450.
6-Chloro-3,4-dimethyl-9-p-tolyl-9,10-dihydrochromeno[8,7
-e][1,3]oxazin-2(8H)-one (5r)
◦
Yield: 58 %, m.p. 212.7–214.1 C. IR (KBr) cm−1: 3030,
6-Chloro-9-p-tolyl-4-(trifluoromethyl)-9,10-dihydrochrome
no[8,7-e[1,3]oxazin-2(8H)-one (5n)
2915, 1704, 1593, 1510, 1483.1H NMR (400 MHz,
DMSO-d6): δ: 7.73 (s, 1H), 7.25–6.91(m, 4H), 5.64 (s, 2H),
4.74 (s, 2H), 2.35 (s, 3H), 2.19 (s, 3H), 2.09 (s, 3H). 13C
NMR (100 MHz, CDCl3):161.62, 151.69, 147.78, 145.72,
145.26, 131.96, 129.95, 123.23, 119.96, 118.87, 117.76,
113.92, 109.98, 81.02, 46.58, 20.60, 15.14, 13.37. HRMS
calcd for C20H19O3NCl[M+H]+ 356.1048, found 356.1042.
◦
Yield: 80 %, m.p. 178.7–179.7 C. IR (KBr) cm−1: 3083,
2963, 1745, 1589, 1509, 1481. 1H NMR (400 MHz,
DMSO-d6): δ: 7.51 (s, 1H), 7.14–7.02 (m, 4H), 6.96 (s,
1H), 5.70 (s, 2H), 4.76 (s, 2H), 2.20 (s, 3H). 13C NMR
(100 MHz, CDCl3): 158.55, 154.10, 150.37, 144.95, 141.35,
141.02, 132.52, 130.07, 124.09, 119.37, 119.07, 113.00
(q, J = 5.7 Hz), 110.80, 106.65, 81.55, 46.70, 20.61.
HRMS calcd for C19H14O3NClF3[M+H]+ 396.0609, found
396.0607.
6-Chloro-9-(4-chlorophenyl)-3,4-dimethyl-9,10-dihydro
chromeno[8,7-e][1,3]oxazin-2(8H)-one (5s)
◦
Yield: 63 %, m.p. 213.7–214.1 C. IR (KBr) cm−1: 2924,
1707, 1586, 1487, 1428, 1328. 1H NMR (400 MHz,
DMSO-d6): δ: 7.75 (s, 1H), 7.39–7.10 (m, 4H), 5.68 (s, 2H),
4.78 (s, 2H), 2.35 (s, 3H), 2.09 (s, 3H). 13C NMR (100 MHz,
CDCl3):147.73, 146.25, 145.68, 129.39, 127.45, 123.47,
120.21, 120.00, 117.83, 114.14, 109.68, 80.47, 46.59, 15.18,
13.40. HRMS calcd for C19H16O3NCl2[M+H]+ 376.0502,
found 376.0496.
6-Chloro-9-(4-chlorophenyl)-4-(trifluoromethyl)-9,10-dihy
drochromeno[8,7-e][1,3]oxazin-2(8H)-one (5o)
◦
Yield: 61 %, m.p. 203.3–204.4 C. IR (KBr) cm−1: 3091,
2955, 1739, 1601, 1497, 1485. 1H NMR (400 MHz,
DMSO-d6): δ: 7.52 (s, 1H), 7.35–7.27 (m, 2H), 7.26–
7.17 (m, 2H), 6.98 (s, 1H), 5.73 (s, 2H), 4.80 (s, 2H).
13C NMR (100 MHz, CDCl3): 158.41, 153.56, 150.76,
146.38, 142.99, 129.42, 126.06, 123.15, 120.35, 117.76,
115.22 (q, J= 4.9 Hz), 111.59, 106.94, 99.97, 81.23, 45.18.
HRMScalcdforC18H11O3NCl2F3[M+H]+ 416.0063, found
416.0060.
9-Benzyl-6-chloro-3,4-dimethyl-9,10-dihydrochromeno[8,7
-e][1,3]oxazin-2(8H)-one (5t)
◦
Yield: 76 %, m.p. 178.0–178.5 C. IR (KBr) cm−1: 3030,
2902, 1700, 1620, 1591, 14788. 1H NMR (400 MHz,
123

Mol Divers
DMSO-d6): δ: 7.76 (s, 1H), 7.50–7.22 (m, 5H), 5.15 (s,
2H), 4.03 (s, 2H), 3.89 (s, 2H), 2.36 (s, 3H), 2.06 (s, 3H).
13C NMR (100 MHz, CDCl3): 161.67, 151.61, 148.66,
145.67, 137.25, 128.81, 128.65, 127.76, 123.00, 119.95,
117.44, 113.96, 109.17, 83.86, 56.03, 44.85, 15.16, 13.37.
HRMS calcd for C20H19O3NCl[M+H]+ 356.1048, found
356.1044.
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Science Foundation of China (No. 21272116) and the “Fundamen-
tal Research Funds for the Central Universities” (KYZ201426). We
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