An efficient and practical method for the synthesis of 1-(2,6- difluorobenzoyl)-3-(2-alkyl-3-oxopyridazin-4-yl)ureas as potential chitin synthesis inhibitors

Article abstract of DOI:10.1007/s00706-005-0476-7

A mild and efficient method for the synthesis of 4-amino-3(2H)- pyridazinones from their corresponding 4,5-dichloropyridazinones under microwave-assisted conditions is described. A series of novel chitin synthesis inhibitors, benzoylphenylureas containing

Full text of DOI:10.1007/s00706-005-0476-7

Monatshefte f €u r Chemie 137, 779–784 (2006)
DOI 10.1007/s00706-005-0476-7
An Efficient and Practical Method
for the Synthesis of 1-(2,6-Difluorobenzoyl)-
3-(2-alkyl-3-oxopyridazin-4-yl)ureas
as Potential Chitin Synthesis Inhibitors
ꢀ
Qing-Chun Huang, and Xu-Hong Qian
Song Cao , De-Li Lu, Chuan-Meng Zhao, Li-Na Li,
ꢀ
1
Institute of Pesticides and Pharmaceuticals, East China University of Science
and Technology, Shanghai, China
2
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai, China
Received August 24, 2005; accepted October 13, 2005
Published online May 22, 2006 # Springer-Verlag 2006
Summary. A mild and efficient method for the synthesis of 4-amino-3(2H)-pyridazinones from their
corresponding 4,5-dichloropyridazinones under microwave-assisted conditions is described. A series of
novel chitin synthesis inhibitors, benzoylphenylureas containing the 3(2H)-pyridazinone, were synthe-
sized. The biological activity of these target compounds was evaluated.
Keywords. Bioorganic chemistry; Heterocycles; Microwave; Insecticidal activity.
Introduction
In the past decades benzoylphenylureas have attracted considerable interest because
of their insecticidal and antitumor activities [1]. In pesticides chemistry, these
compounds are generally recognized as insect growth regulators that interfere with
chitin synthesis causing death or abortive development [2]. Results from structure-
activity relationship studies of benzoylphenylureas revealed that the basic 2,6-dihalo
configuration in the benzoylurea moiety is critical to the activity [3, 4] (Fig. 1).
Now, more than ten members of this class of commercial pesticides containing the
N-(2,6-difluorobenzoyl)urea moiety have been manufactured and are used widely
in crop protection [5].
On the other hand, the 3(2H)-pyridazinone core has been utilized as a key
template in the search of new medicines and agrochemicals [6, 7]. Canada et al.
ꢀ Corresponding authors. E-mail: scao@ecust.edu.cn, xhqian@ecust.edu.cn

7
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S. Cao et al.
Fig. 1. N-2,6-Difluorobenzoylurea moiety
Fig. 2. Some bioactive benzoyl oxopyridazin-4-yl ureas
have attached the 5-position of 3(2H)-pyridazinone core to the benzoylurea moiety
Fig. 2), and it has been found that these compounds exhibited a significant
insecticidal activity on the southern armyworm [8]. Although the key intermediate,
-amino-3(2H)-pyridazinone, has been prepared by a traditional method [8], the
(
5
synthesis of 4-amino-3(2H)-pyridazinone seems to be difficult [9], therefore, there
are no reports on the introduction of the 4-position of 3(2H)-pyridazinone to
benzoylurea to date.
In our research group, we have been interested in studying the design, synthesis,
and biological activity of compounds containing the 3(2H)-pyridazinone nucleus
[10, 11]. In our earlier research, we briefly reported for the first time a novel
approach to 4-amino-3(2H)-pyridazinone via an unusual direct amination of
4,5-dichloropyridazinones with hydrazine hydrate under mild conditions [12].
To extend our previous work, we developed as a first step a new microwave-
enhanced synthesis to obtain the key intermediates 4-amino-3(2H)-pyridazinones in
a short reaction time, and then in the second step we combined the bioactive units of
the N-(2,6-difluorobenzoyl)urea moiety and the 4-position of the 3(2H)-pyridazinone
core to synthesize novel 1-(2,6-difluorobenzoyl)-3-(2-alkyl-3-oxopyridazin-4-yl)
ureas in order to find new compounds with higher insecticidal activity.
Results and Discussion
The title compounds were prepared as shown in Scheme 1. The starting material
4
,5-dichloro-3(2H)-pyridazinones were prepared by treating mucochloric acid with
semicarbazide hydrochloric acid in 50% ethanol [13]. 2-tert-Butyl-4,5-dichloro-
(2H)-pyridazinone (1f) and 2-phenyl-4,5-dichloro-3(2H)-pyridazinone (1h) were
3
prepared by treating mucochloric acid with tert-butylhydrazine hydrochloride and
phenylhydrazine hydrochloride [13]. Because the alkylhydrazine hydrochlorides
were commercially unavailable, the other 2-alkyl-4,5-dichloro-3(2H)-pyridazinones
1a–1e and 1g were prepared by conventional alkylation [14]. The key intermediates

Potential Chitin Synthesis Inhibitors
781
Scheme 1
2
a–2h were prepared by the direct amination of 2-substituted 4,5-dichloropyrida-
ꢁ
zinones with hydrazine hydrate in ethanol under microwave irradiation at 80 C.
The reaction times were decreased from more than 6 hours to 18 minutes and the
yields were also improved a little compared to those obtained by the conventional
heating method, which was reported previously [12]. The final compounds 3a–3h
were obtained by condensation of the 2-substituted 4-amino-3(2H)-pyridazinones
with 2,6-difluorobenzoyl isocyanate in toluene at room temperature.
1
The lowest-field protons in the H NMR spectrum appear at ꢀ ¼ 6.22 and
7
.52 ppm (which are assigned to the H-5 and H-6 of the pyidazinone ring of
2a–2h) as a doublet with a coupling constant of 4.60 Hz, indicating ortho coupling,
whereas the H-5 and H-6 of the pyidazinone ring of 3a–3h appear at ꢀ ¼ 7.74 and
7.81 ppm. These values are downfield due to the stronger electron-withdrawing
benzoylurea.
Insecticidal Activities
We measured the biological activity of 3a–3h against the armyworm, Pseudaletia
separata Walker, according to the modified method described previously [11]. The
bioassay tests show that some compounds exhibit moderate activity. The mortality
ꢂ3
of 3b–3f was 72, 50, 43, 53, and 30 at 500 mg dm , while 3a, 3g, and 3h showed
no activity. The length of the aliphatic chain at N-2 of the pyidazinone ring affect
the activity. A shorter or longer carbon chain was unfavorable to activity, and a
bulky group, such as phenyl, also decreased the activity.
In conclusion, we report a rapid, mild, and efficient procedure under microwave
conditions for the synthesis of 2-substituted 4-amino-3(2H)-pyridazinones. The
intermediates were successfully extended to synthesize some analogs of chitin
synthesis inhibitors, 3a–3h, attaching the 4-position of the 3(2H)-pyridazinone
core to the benzoylurea moiety, which had been previously inaccessible by existing
procedures. The easy preparation of 2-substituted 4-amino-3(2H)-pyridazinones
should make it an ideal synthon for organic synthesis and potential application
in biological research.
Experimental
1
13
All mp were obtained with an electrothermal digital apparatus made in Shanghai. H and C NMR
spectra were recorded on a Bruker WP-500SY spectrometer with TMS as internal standard. Chemical
shifts are reported in ꢀ (ppm) values. High-resolution mass spectra were recorded under electron

7
82
S. Cao et al.
impact conditions using a MicroMass GCT CA 055 instrument. Infrared (IR) spectra were recorded in
ꢂ1
the range 4000–600 cm using a Nicolet 470 infrared spectrometer. Microwave-promoted reaction
was carried out on an Initiator (Biotage AB, Sweden). Analytical thin-layer chromatography (TLC)
was carried out on precoated plates (silica gel 60 F254), and spots were visualized with UV light.
Syntheses of 2-Alkyl-4-amino-3(2H)-pyridazinones 2a–2h
A mixture of the dichloropyridazinone (1, 2.26 mmol), 1.13g hydrazine hydrate (22.6 mmol), and
1
3
5cm ethanol was heated (microwave; 18 min, 85 C), then concentrated to dryness in vacuo and the
ꢁ
residue was purified via column chromatography (elution with 1=4 ethyl acetate=petroleum ether) to
give solids or oils.
2
-Methyl-4-amino-3(2H)-pyridazinone (2a, C H N O)
5 7 3
ꢁ
1
Yield 58%; brown solid; mp 175–176 C; H NMR (500MHz, CDCl ): ꢀ ¼ 3.82 (s, CH ), 4.98
3
3
(
(
s, NH ), 6.24 (d, J ¼ 4.83 Hz, PyH), 7.51 (d, J ¼ 4.76Hz, PyH) ppm; MS (70eV): m=z(%) ¼ 125
2
þ
M , 42), 96 (22), 69 (72), 54 (100), 40 (36).
2
-Ethyl-4-amino-3(2H)-pyridazinone (2b, C H N O)
6 9 3
ꢁ
1
Yield 64%; brown solid; mp 120–122 C; H NMR (500MHz, CDCl ): ꢀ ¼ 1.38 (t, J ¼ 7.25Hz, CH ),
3
3
4
.22 (q, J ¼ 7.25 Hz, CH N), 5.04 (s, NH ), 6.23 (d, J ¼ 4.76Hz, PyH), 7.51 (d, J ¼ 4.76 Hz, PyH) ppm;
2
2
þ
MS (70 eV): m=z(%) ¼ 139 (M , 96), 111 (100), 83 (30), 69 (46), 33 (28).
2
-Propyl-4-amino-3(2H)-pyridazinone (2c, C H N O)
7
11 3
1
Yield 62%; oil; H NMR (500MHz, CDCl ): ꢀ ¼ 0.96 (t, J ¼ 7.41 Hz, CH ), 1.85–1.89 (m, CH ), 4.12
3
3
2
(
t, J ¼ 7.36Hz, CH N), 5.02 (s, NH ), 6.23 (d, J ¼ 4.80Hz, PyH), 7.53 (d, J ¼ 4.76Hz, PyH) ppm;
2
2
þ
MS (70 eV): m=z(%) ¼ 153 (M , 63), 125 (22), 111 (100), 83 (12).
2
-n-Butyl-4-amino-3(2H)-pyridazinone (2d, C H N O)
8
13 3
1
Yield 68%; oil; H NMR (500MHz, CDCl ): ꢀ ¼ 0.95 (t, J ¼ 7.34 Hz, CH ), 1.37–1.39 (m, CH ),
3
3
2
1
.76–1.82 (m, CH ), 4.15 (t, J ¼ 7.41Hz, CH N), 5.03 (s, NH ), 6.23 (d, J ¼ 4.71 Hz, PyH), 7.53
2
2
2
þ
(d, J ¼ 4.71 Hz, PyH) ppm; MS (70 eV): m=z(%) ¼ 167 (M , 47), 139 (77), 111 (100), 83 (14), 69 (60).
2
-Pentyl-4-amino-3(2H)-pyridazinone (2e, C H N O)
9
15 3
1
Yield 65%; oil; H NMR (500MHz, CDCl ): ꢀ ¼ 0.90 (t, J ¼ 7.12 Hz, CH ), 1.32–1.38 (m, CH CH ),
3
3
2
2
1
.79–1.85 (m, CH ), 4.19 (t, J ¼ 7.36Hz, CH N), 5.02 (s, NH ), 6.22 (d, J ¼ 4.72 Hz, PyH), 7.52
2
2
2
þ
(d, J ¼ 4.72 Hz, PyH) ppm; MS (70 eV): m=z(%) ¼ 181 (M , 76), 153 (63), 111 (100), 83 (12), 69 (46).
2
-t-Butyl-4-amino-3(2H)-pyridazinone (2f, C H N O)
8
13 3
ꢁ
1
Yield 70%; solid; mp 109–111 C; H NMR (500MHz, CDCl ): ꢀ ¼ 1.69 (s, (CH ) ), 5.29 (s, NH ),
3
3 3
2
þ
6
.33 (d, J ¼ 4.72 Hz, PyH), 7.59 (d, J ¼ 4.72Hz, PyH) ppm; MS (70 eV): m=z(%) ¼ 167 (M , 62),
1
11 (100), 83 (30), 57 (20), 55 (35), 41 (47).
2
-Benzyl-4-amino-3(2H)-pyridazinone (2g, C H N O)
1
1 15 3
ꢁ
1
Yield 55%; brown solid; mp 90–91 C; H NMR (500MHz, CDCl ): ꢀ ¼ 4.99 (s, NH ), 5.22 (s, CH ),
3
2
2
6
.20 (d, J ¼ 4.78 Hz, PyH), 7.25–7.42 (m, ArH), 7.53 (d, J ¼ 4.75 Hz, PyH) ppm; MS (70 eV):
þ
m=z(%) ¼ 201 (M , 100), 91 (63), 69 (46).
2
-Phenyl-4-amino-3(2H)-pyridazinone (2h, C H N O)
10 9 3
ꢁ
1
Yield 64%; solid; mp 135–136 C; H NMR (500MHz, CDCl ): ꢀ ¼ 4.55 (s, NH ), 6.27 (d, J ¼ 4.80Hz,
3
2
þ
PyH), 7.38–7.62 (m, ArH), 7.66 (d, J ¼ 4.80Hz, PyH) ppm; MS (70 eV): m=z(%) ¼ 187 (M , 100),
52 (21), 92 (20), 76 (30), 53 (32).
1

Potential Chitin Synthesis Inhibitors
-(2,6-Difluorobenzoyl)-3-(2-alkyl-3-oxopyridazin-4-yl)ureas 3a–3h
783
1
3
A solution of 0.48 g 2,6-difluorobenzoyl isocyanate (2.6mmol) in 5 cm dry toluene was added to a
3
stirred solution of 2.5mmol 2-alkyl-4-amino-3(2H)-pyridazinones 2a–2h in 5 cm dry toluene. The
mixture was stirred overnight at room temperature, then the solvent was removed by evaporation under
ꢁ
reduced pressure. The residue was chromatographed on a silica-gel column (petroleum ether (60–90 C)
ethyl acetate 4=1 to 2=1) to afford the desired product.
1
-(2,6-Difluorobenzoyl)-3-(2-methyl-3-oxopyridazin-4-yl]urea (3a, C H F N O )
13 10 2 4 3
ꢁ
1
Yield 58%; light yellow solid; mp 198–200 C; H NMR (500MHz, CDCl ): ꢀ ¼ 3.83 (s, CH ),
3
3
7
8
.02–7.06 (m, ArH), 7.49–7.55 (m, ArH), 7.73 (d, J ¼ 4.68Hz, PyH), 7.86 (d, J ¼ 4.61 Hz, PyH),
ꢂ1
.70 (s, NH), 11.37 (s, NH) ppm; IR (KBr): ꢁꢀ ¼ 3400, 3120, 1730, 1710, 1650 cm ; MS (70eV):
þ
3
m=z(%) ¼ 308 (M , 6), 165 (13), 141 (100), 113 (19); HRMS: calcd for C H F N O 308.0720,
1
3 10 2 4 3
1
found 308.0731; C NMR (125 MHz, DMSO-d ): ꢀ ¼ 39.7, 111.9, 112.9, 113.2, 135.4, 137.7, 150.1,
6
1
55.5, 157.8, 159.8, 162.2 ppm.
1
-(2,6-Difluorobenzoyl)-3-(2-ethyl-3-oxopyridazin-4-yl)urea (3b, C H F N O )
4 12 2 4 3
1
ꢁ
1
Yield 63%; light yellow solid; mp 217–218 C; H NMR (500 MHz, CDCl ): ꢀ ¼ 1.39
3
(
(
t, J ¼ 7.12 Hz, CH ), 4.26 (q, J ¼ 7.02 Hz, CH ), 7.02–7.05 (m, ArH), 7.49–7.55 (m, ArH), 7.74
3
2
d, J ¼ 4.59 Hz, PyH), 7.78 (d, J ¼ 4.64 Hz, PyH), 9.09 (s, NH), 11.38 (s, NH) ppm; IR (KBr):
ꢂ1
þ
ꢁ
ꢀ¼ 3420, 3220, 1750, 1700, 1660 cm ; MS (70 eV): m=z(%) ¼ 322 (M , 11), 165 (24), 141 (100),
1
3
1
37 (40), 113 (27); HRMS: calcd for C H F N O 322.0877, found 322.0860; C NMR
14 12 2 4 3
(
125 MHz, DMSO-d ): ꢀ ¼ 13.4, 46.9, 111.7, 112.9, 113.1, 135.5, 138.0, 150.0, 155.1, 157.8,
6
1
59.8, 162.2 ppm.
1
-(2,6-Difluorobenzoyl)-3-(2-propyl-3-oxopyridazin-4-yl)urea (3c, C H F N O )
1
5 14 2 4 3
ꢁ
1
Yield 62%; white solid; mp 170–171 C; H NMR (500 MHz, CDCl ): ꢀ ¼ 0.96 (t, J ¼ 7.41 Hz,
3
CH ), 1.82–1.88 (m, CH ), 4.15 (q, J ¼ 7.34 Hz, CH ), 7.02–7.05 (m, ArH), 7.49–7.55 (m, ArH),
3
2
2
7
.74 (d, J ¼ 4.69 Hz, PyH), 7.81 (d, J ¼ 4.69 Hz, PyH), 8.81 (s, NH), 11.38 (s, NH) ppm; IR (KBr):
ꢂ1
þ
ꢁ
ꢀ¼ 3450, 3180, 1750, 1710, 1680 cm ; MS (70 eV): m=z(%) ¼ 336 (M , 3), 157 (13), 141 (100),
1
3
1
13 (20); HRMS: calcd for C H F N O 336.1034, found 336.1036; C NMR (125 MHz,
15 14 2 4 3
DMSO-d ): ꢀ ¼ 10.9, 21.3, 53.1, 111.7, 112.9, 113.1, 135.6, 137.8, 150.1, 155.3, 157.8, 159.8,
6
1
62.2 ppm.
1
-(2,6-Difluorobenzoyl)-3-(2-n-butyl-3-oxopyridazin-4-yl)urea (3d, C H F N O )
1
6 16 2 4 3
ꢁ
1
Yield 57%; white solid; mp 217–218 C; H NMR (500MHz, CDCl ): ꢀ ¼ 0.89 (t, J ¼ 7.33 Hz, CH ),
3
3
1
.24–1.88 (m, CH ), 1.67–1.73 (m, CH ), 4.11 (q, J ¼ 7.08 Hz, CH ), 7.24–7.28 (m, ArH), 7.61–7.67
2
2
2
(
(
(
(
m, ArH), 7.85 (d, J ¼ 4.56 Hz, PyH), 7.91 (d, J ¼ 4.72 Hz, PyH), 11.05 (s, NH), 11.84 (s, NH) ppm; IR
ꢂ1
þ
KBr): ꢁꢀ ¼ 3380, 3130, 1720, 1700, 1680cm ; MS (70 eV): m=z(%) ¼ 350 (M , 6), 271 (50), 165
1
37), 141 (100), 113 (20); HRMS: calcd for C H F N O 350.1190, found 350.1199; C NMR
3
1
6 16 2 4 3
125 MHz, DMSO-d ): ꢀ ¼ 13.6, 19.3, 29.9, 51.2, 111.6, 112.7, 113.2, 135.8, 138.3, 150.3, 155.6,
6
1
57.4, 159.4, 162.8ppm.
1
-(2,6-Difluorobenzoyl)-3-(2-pentyl-3-oxopyridazin-4-yl)urea (3e, C H F N O )
1
7 18 2 4 3
ꢁ
1
Yield 66%; light yellow solid; mp 159–160 C; H NMR (500MHz, CDCl ): ꢀ ¼ 0.90 (t, J ¼ 7.02 Hz,
3
CH ), 1.32–1.38 (m, 2CH ), 1.79–1.85 (m, CH ), 4.19 (q, J ¼ 7.41 Hz, CH ), 7.01–7.04 (m, ArH),
3
2
2
2
7
.49–7.54 (m, ArH), 7.72 (d, J ¼ 4.77 Hz, PyH), 7.75 (d, J ¼ 4.61Hz, PyH), 9.19 (s, NH), 11.40 (s, NH)
ꢂ1
þ
ppm; IR (KBr): ꢁꢀ ¼ 3380, 3210, 1730, 1710, 1660 cm ; MS (70 eV): m=z(%) ¼ 364 (M , 5), 179
1
3
C
(21), 157 (22), 141 (100), 113 (23); HRMS: calcd for C H F N O 364.1347, found 364.1370;
1
7 18 2 4 3
NMR (125 MHz, DMSO-d ): ꢀ ¼ 13.8, 21.7, 27.4, 28.2, 51.7, 111.7, 112.8, 113.5, 135.7, 137.9, 150.4,
6
1
55.8, 157.2, 160.1, 162.5 ppm.

7
84
S. Cao et al.: Potential Chitin Synthesis Inhibitors
1
-(2,6-Difluorobenzoyl)-3-(2-t-butyl-3-oxopyridazin-4-yl)urea (3f, C H F N O )
1
6 16 2 4 3
ꢁ
1
Yield 71%; white solid; mp 221–222 C; H NMR (500 MHz, CDCl ): ꢀ ¼ 0.97 (s, (CH ) ), 7.02–7.05
3
3 3
(
m, ArH), 7.49–7.55 (m, ArH), 7.68 (d, J ¼ 4.57 Hz, PyH), 7.71 (d, J ¼ 4.51Hz, PyH), 9.13 (s, NH),
ꢂ1
1
1.44 (s, NH) ppm; IR (KBr): ꢁꢀ ¼ 3410, 3280, 1740, 1690, 1630 cm ; MS (70 eV): m=z(%) ¼ 350
þ
(
M , 30), 295 (66), 165 (37), 141 (100), 138 (83), 113 (60); HRMS: calcd for C H F N O
1
6
16
2
4
3
1
3
3
50.1190, found 350.1185; C NMR (125MHz, DMSO-d ): ꢀ ¼ 28.6, 65.3, 111.6, 112.8, 113.5,
6
1
35.7, 137.5, 150.3, 155.6, 157.5, 159.6, 162.4 ppm.
1
-(2,6-Difluorobenzoyl)-3-(2-benzyl-3-oxopyridazin-4-yl)urea (3g, C H F N O )
1
9 14 2 4 3
ꢁ
1
Yield 64%; light yellow solid; mp 210–211 C; H NMR (500MHz, CDCl ): ꢀ ¼ 5.35 (s, CH ),
3
2
6
.99–7.02 (m, ArH), 7.26–7.34 (m, ArH), 7.43–7.51 (m, ArH and PyH), 7.72–7.74 (m, ArH and
ꢂ1
PyH), 9.10 (s, NH), 11.37 (s, NH) ppm; IR (KBr): ꢁꢀ ¼ 3410, 3330, 1730, 1710, 1640 cm ; MS
þ
(
70 eV): m=z(%) ¼ 384 (M , 17), 227 (46), 141 (98), 113 (20), 91 (100); HRMS: calcd for
1
3
C H F N O 384.1131, found 384.1124; C NMR (125MHz, DMSO-d ): ꢀ ¼ 54.5, 111.9, 113.2,
19
14
2
4
3
6
1
13.4, 122.4, 127.6, 127.9, 128.4, 135.7, 137.8, 150.2, 154.8, 157.5, 160.2, 162.4 ppm.
1
-(2,6-Difluorobenzoyl)-3-(2-phenyl-3-oxopyridazin-4-yl)urea (3h, C H F N O )
1
8 12 2 4 3
ꢁ
1
Yield 63%; white solid; mp 198–199 C; H NMR (500MHz, CDCl ): ꢀ ¼ 7.02–7.06 (m, ArH),
3
7
.40–7.66 (m, ArH), 7.89 (d, J ¼ 4.66 Hz, PyH), 7.93 (d, J ¼ 4.72 Hz, PyH), 8.66 (s, NH), 11.51
ꢂ1
þ
(
s, NH); IR (KBr): ꢁꢀ ¼ 3420, 3310, 1720, 1680, 1640 cm ; MS (70 eV): m=z(%) ¼ 370 (M , 6),
2
13 (39), 157 (13), 141 (100), 113 (32); HRMS: calcd for C H F N O 370.0956, found 370.0957;
1
8 12 2 4 3
1
3
C NMR (125 MHz, DMSO-d ): ꢀ ¼ 111.9, 113.2, 113.4, 125.7, 128.5, 128.8, 135.5, 138.0, 141.4,
6
1
50.0, 155.1, 157.8, 159.8, 162.2 ppm.
Acknowledgements
We thank the National Basic Research Program of China (2003CB114405), the National High Tech-
nology Research and Development Program of China (863 Program, 2004AA2350707), the Shanghai
Foundation of Science of Technology (034319250), and the Shanghai Education Commission for
financial support.
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