Microwave-promoted synthesis of 2-amino-4-aryl-4H-pyrans on soluble polymeric support

Article abstract of DOI:10.1081/SCC-200057285

2-Amino-4-aryl-4H-pyran derivatives could be prepared rapidly and smoothly in good to excellent yields by the microwave-assisted liquid-phase strategy of multicomponent synthesis on polyethylene glycol. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1081/SCC-200057285

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Microwave‐Promoted Synthesis
of 2‐Amino‐4‐aryl‐4H‐pyrans on
Soluble Polymeric Support
Min Xia a , Qiong Chen b & Yue‐dong Lu a
a Department of Applied Chemistry , Zhejiang
University of Sciences , Hangzhou, China
b Department of Biological and Chemical
Engineering , Jiaxing College , Jiaxing, China
Published online: 16 Aug 2006.
To cite this article: Min Xia , Qiong Chen & Yue‐dong Lu (2005) Microwave‐Promoted
Synthesis of 2‐Amino‐4‐aryl‐4H‐pyrans on Soluble Polymeric Support, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 35:10, 1381-1390, DOI: 10.1081/SCC-200057285
To link to this article: http://dx.doi.org/10.1081/SCC-200057285
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Synthetic Communicationsw, 35: 1381–1390, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200057285
Microwave-Promoted Synthesis of
2-Amino-4-aryl-4H-pyrans on Soluble
Polymeric Support
Min Xia
Department of Applied Chemistry, Zhejiang University of Sciences,
Hangzhou, China
Qiong Chen
Department of Biological and Chemical Engineering, Jiaxing College,
Jiaxing, China
Yue-dong Lu
Department of Applied Chemistry, Zhejiang University of Sciences,
Hangzhou, China
Abstract: 2-Amino-4-aryl-4H-pyran derivatives could be prepared rapidly and
smoothly in good to excellent yields by the microwave-assisted liquid-phase strategy
of multicomponent synthesis on polyethylene glycol.
Keywords: Liquid phase, microwave, multicomponent synthesis
The design of multicomponent reactions (MCR) is an important field of
research in combinatorial chemistry.[1] Because they are a one-pot reactions,
generally MCRs afford good yields and ready operations and are fundamen-
tally different from two-component reactions in several aspects.[2] Therefore,
great efforts have been and still are being made to find and develop new multi-
component reactions.[3] Usually, to drive the conversion of MCR, one or two
components are excessive and this always leads to the trouble of separating
Received in Japan December 8, 2004
Address correspondence to Min Xia, Department of Applied Chemistry, Zhejiang
University of Sciences, Hangzhou 310033, China. Tel.: þ 86 0511-86843224;
E-mail: xiamin@hzcnc.com
1381

1382
M. Xia, Q. Chen, and Y. Lu
and purifying the target products. In traditional solution-phase systems, it is
often the chief drawback of MCRs.
Recently, organic synthesis of small molecular compounds on soluble
polymers, that is, liquid-phase chemistry, has increasingly become an attrac-
tive research field.[4] It couples the advantages of homogeneous solution-
phase chemistry (high reactivity, lack of diffusion phenomena, and ease of
analysis without the complicated cleavage-and-check procedure) with those
of heterogeneous solid-phase chemistry (use of excessive reagents, ready
isolation, and purification of target products). Besides, it is convenient for
liquid-phase reactions being grafted from solution-phase systems without
apparent kinetic changes. Therefore, they are the optimum choice for MCRs.
Among various soluble polymers, polyethylene glycol (PEG) is the most
helpful and promising because of its low cost and outstanding chemical
stability.
It is well known that many reactions can be dramatically promoted by
microwave irradiation[5] and this technology can also be applied to soluble
polymer-supported reactions.[6] In this respect, solvent-involved and solvent-
free methods are both workable. Currently, 4H-pyrans derivatives have been
the intriguing focus in the field of medicinal chemistry because of their various
bioactivities and pharmaceutical activities.[7–12] In connection with our
interests in liquid-phase synthesis on soluble polymeric support,[13] we herein
report the efficiently microwave-assisted preparation of 2-amino-4-aryl-4H-
pyran derivatives on PEG support (Scheme 1).
The PEG 4000–bound acetoacetate 2 was prepared by the microwave-
promoted nucleophilic reaction of PEG 4000 with 2,2,6-trimethyl-4H-1,3-
dioxin-4-one (TKD). Because of the high toxicity and hazard operation of
diketene, TKD has increasingly become an effective alternative to diketen
as an acetoacetyl reagent.[14] Classically, the nucleophilic reaction involved
with TKD should be carried out at a high temperature for a prolonged
time.[15] In our case, however, the acetoacetylation was fulfilled smoothly
by microwave irradiation at 350 W within 3 min, affording the quantitative
1
conversion of terminal hydroxyl groups on PEG (determined by H NMR).
Scheme 1.

Synthesis of 2-Amino-4-aryl-4H-pyrans
1383
Traditionally, the preparation of 4-aryl-4H-pyrans has taken place in solutions
such as benzene, ethanol, acetonitrile, etc. for a long time (6–8 h) under
refluxing; b-dicarbonyl compounds, arylaldehydes, and active methylene
compounds were needed in this multicomponent synthesis.[16] To our
knowledge, however, there has been no literature about the microwave-
assisted multicomponent synthesis of 4-aryl-4H-pyran derivatives on soluble
polymer by liquid-phase methodology.
In ethanol solution, PEG-bound acetoacetate 2, molononitrile, and corre-
sponding arylaldehyde were mixed in the mole ratio of 1:4:4 with 1–2 drops
of piperidine as the catalyst. The resulted mixture was irradiated at 400 W.
Because the reaction took place on soluble polymeric support, excessive
reagents drove the condensation instead of requiring isolation and purification.
When microwave irradiation was over and the mixture was cooled to room
temperature, ether was poured to precipitate the PEG-linked intermediate 3.
After simple washing with ether, purified intermediate 3 could be applied to
the next step. In this procedure, the advantages of liquid-phase reaction were
displayed: one hand, the purity of PEG-bounded intermediate 3 could be con-
veniently determined by TLC analysis without the complicated cleavage-
and-check workup; the other hand, the homogenous reaction afforded
intermediate 3 in good to excellent yields (Table 1) in dramatically shorted
time (from several hours to several minutes).
During the experiment, we found the presence of a catalytic amount of
piperidine was indispensable. Although in our case some kinds of arylalde-
hydes such as 3-nitrobenzaldehyde could undergo the three-component con-
densation in moderate yields with the absence of piperidine, the majority of
other kinds of arylaldehydes could hardly afford the expected products
of 2-amino-4-aryl-3-cyano-4H-pyrans without the presence of piperidine.
Instead, almost quantitative amount of arylidene malononitriles were isolated.
Table 1. Microwave-promoted liquid-phase synthesis of 4-aryl-4H-pyran-5-
carboxylates
Comp.
Ar
Time (min)a
Mp (8C)
Yield (%)b
4a
4b
4c
4d
4e
4f
C6H5
2-ClC6H4
3.5
3.5
3.5
5.5
4.0
3.5
5.5
5.0
4.0
3.5
187–188
161–162
202–204
134–135
181–182
160–162
226–228
150–152
166–167
153–154
93
96
88
83
96
91
94
89
93
91
3-O2NC6H4
4-CH3OC6H4
4-HOC6H4
4-ClC6H4
4g
4h
4i
2,6-Cl2C6H3
2,4-Cl2C6H3
3,4-OCH2OC6H3
4-FC6H4
4j
aTime for condensations.
bIsolated yields.

1384
M. Xia, Q. Chen, and Y. Lu
Moreover, it was discovered the formation of arylidene malononitriles was
so ready that nearly quantitative conversion could be fulfilled in the absence
of piperidine. Apparently, the work of piperidine involved in the catalysis
of the nucleophilic addition of PEG-bound acetoacetate to C55C double
bonds on arylidene malononitriles. There was reported[17] that 4-(N,N-
dimethylamino)benzaldehyde could carry out the condensation with malono-
nitrile and 5,5-dimethylcyclohexane-1,3-dione to provide 2-amino-4-(4-N,N-
dimethylamino-phenyl)-3-cyano-4H-pyran in excellent yield. In our case,
however, even if in the presence of piperidine, the target product of
4H-pyran was not obtained from the microwave-irradiated condensation
with malononitrile, arylaldehyde, and PEG-linked acetoacetate 2. Similarly,
almost a quantitative amount of a-cyano-4-(N,N-dimethylamino)-cinnamoni-
trile was separated. We attributed the reason of the phenomena to the weaker
electron-withdrawing capacity of ester group on PEG-supported acetoacetate
than that of the ketone group on 5,5-dimethylcyclohexane-1,3-dione.
Therefore, the methylene on PEG-bound acetoacetate was unable to attack
the deactivated C55C double bonds, which were caused from the strong
electron-donating capacity of N, N-dimethylamino group on a-cyano-4-
(N,N-dimethylamino)cinnamonitrile. Based on this evidence, we assumed
the possible reaction route in this multicomponent protocol might be the
following (Scheme 2).
An arylaldehyde was firstly condensed with malononitrile to afford
a-cyanocinnamonitrile derivative 5, this step could be regarded as a fast
Knoevenagel addition without the help of piperidine. The key step took
place in the process that active methylene moiety on intermediate 2 reacted
with the C55C double bond to provide the intermediate 6, which was
cyclized by nucleophilic attack from the OH group to the cyano moiety.
Finally, the expected intermediate 3 was offered by intramolecular tautomer-
ization. Through the deprotection, the target 2-amino-4-aryl-3-cyano-4H-
pyran-5-carboxylate 4 was obtained.
Usually, it takes several hours or overnight for the cleavage step to be
completed in MeONa/MeOH system at room temperature. We had reported[18]
Scheme 2.

Synthesis of 2-Amino-4-aryl-4H-pyrans
1385
that microwave irradiation could be applied to accelerate the release of
products from PEG support. Moreover, the time and power of microwave
irradiation could be adjusted by simple determination on TLC analysis.
Therefore, when the mixture of intermediate 3 in 1N MeONa/MeOH
solution was irradiated at 460 W for only 2 min, the target products of
2-amino-4-aryl-3-cyano-4H-pyran-5-carboxylates
4
were completely
released from the polymer support. In the soluble polymer-supported synthesis,
the procedure for the decision on optimum reaction conditions could be largely
simplified by the convenient TLC method, avoiding those complicated
cleavage-and check workups that are necessary for solid-phase methodology.
In summary, we have demonstrated that soluble polymer-supported
acetocetate could be utilized as the versatile precursor for the multicomponent
construction of the pharmaceutically interesting 4H-pyran derivatives through
the use of commercially available building blocks and that the PEG-linked
intermediates could tolerate microwave reaction conditions. The soluble poly-
mer supported liquid-phase synthesis overcame the defect of troublesome
isolation in this three-component system while microwave irradiation
obviously promoted the efficiency of preparation in each step. The coupling
of microwave technology and liquid-phase synthesis strategy has constituted
a novel and attractive avenue for the rapid generation of structural diverse
libraries because of their inherent advantages.
EXPERIMENTAL SECTION
Mps were determined on X4 mp apparatus and the thermometer was
not corrected. 1H NMR spectra were obtained on a Bruker Avance
DMX400 MHz instrument. FT-IR spectra were recorded on Perkin-Elmer
298 spectrophotometer. Ms data were recorded on HP 5989B instrument.
MW experiments were performed in a 50-mL round-bottomed flask
(attached to a reflux condenser) on a Sanle WHL07S-01 microwave instru-
ment at 2450 Hz frequency (0–700 W).
General Procedure for the Preparation of PEG-bound
Acetoacetate 2
A mixture of PEG 4000 (1 g, 0.5 mmol) and TKD (1.5 mmol) in anhydrous
toluene (10 mL) was irradiated under microwave cavity at 350 W for 3 min.
After the completion of the reaction, ether (50 mL) was poured into the
cooled mixture to precipitate the PEG-linked acetoacetate 2, which was
1
washed with ether for several times and then dried over vacuum. H NMR
(400 MHz, CDCl3): d ¼ 2.27 (s, 3H, CH3), 3.49 (s, 2H, COCH2CO),
3.53–3.79 (m, PEG backbone, OCH2CH2O), 4.30 (t, 2H, J ¼ 5 Hz,
PEG-OCH2CH2OCO).

1386
M. Xia, Q. Chen, and Y. Lu
General Procedure for the Preparation of
2-Amino-4-aryl-3-cyano-4H-pyran-5-carboxylates 4
The mixture of PEG-linked acetoacetate 2 (0.5 g, 0.25 mmol), arylaldehyde
(1.0 mmol), malononitrile (1.0 mmol), and piperidine (1–2 drops) in ethanol
(20 mL) was heated under microwave irradiation at 400 W for the needed
time. Upon the finishing of the reaction, PEG-supported intermediate 3 was
separated by precipitation and rinsing from ether (100 mL). It should be
further purified by dissolution and precipitation for two or three times.
The solution of PEG-bound intermediate 3 (0.25 g) in 1N MeONa/MeOH
(10 mL) was irradiated at 460 W for 2 min. After cooling, water (15 mL) was
poured and then CH2Cl2 (10 mL) was added to extract the product, which
could be further purified by column chromatography using EtOAc/hexane
(1:3) as the eluent.
2-Amino-4-phenyl-3-cyano-4H-pyran-5-carboxylates (4a): White,
crystalline solid (recrystallized from 95% ethanol); mp 187–1888C;
Anal. C15H14N2O3 calcd.: C, 66.67; H, 5.18; N, 10.37. Found: C, 66.56; H,
5.09; N, 10.31. FT-IR (KBr): 3412, 3330, 3226, 3203, 2195, 1701, 1680,
1608, 1408, 1334, 1264, 1178, 1122, 1062, 696 cm21
;
1H NMR
(DMSO-d6): d ¼ 2.36 (s, 3H, CH3), 3.58 (s, 3H, OCH3), 4.43 (s, 1H, CH),
4.49 (s, 2H, NH2), 7.18–7.31 (m, 5H, ArH); MS: m/z (%) ¼ 270 (Mþ,
18.04), 255 (9.37), 238 (6.69), 223 (2.02), 211 (11.71), 193 (100.00),
176 (11.71), 161 (32.16), 133 (8.84), 105 (7.13), 77 (10.95), 67 (10.09),
43 (31.43).
2-Amino-4-(2-chlorophenyl)-3-cyano-4H-pyran-5-carboxylates (4b):
White, crystalline solid (recrystallized from 95% ethanol); mp 161–1628C;
Anal. C15H13ClN2O3 calcd.: C, 59.21; H, 4.27; N, 9.21. Found: C, 59.11; H,
4.19; N, 9.14. FT-IR (KBr): 3424, 3333, 3221, 3198, 2949, 2196, 1702,
1
1679, 1647, 1603, 1409, 1345, 1264, 1063, 746; H NMR (DMSO-d6): 2.39
(s, 3H, CH3), 3.56 (s, 3H, OCH3), 4.50 (br, s, 2H, NH2), 5.04 (s, 1H, CH),
7.14–7.16 (m, 2H, ArH), 7.21 (d, 1H, J ¼ 6.4 Hz, ArH), 7.34 (d, 1H,
J ¼ 8 Hz, ArH); MS: m/z (%) ¼ 304 (Mþ,5.49), 289 (5.33), 269 (22.21),
245 (6.13), 193 (100.00), 176 (11.20), 161 (26.84), 133 (7.07), 105 (4.83),
67 (17.77), 43 (43.42).
2-Amino-4-(3-nitrophenyl)-3-cyano-4H-pyran-5-carboxylates (4c):
Pale red, crystalline solid (recrystallized from 95% ethanol); mp 202–
2048C; Anal. C15H13N3O5 calcd.: C, 57.14; H, 4.12; N, 13.33. Found: C,
57.03; H, 4.05; N, 13.31. FT-IR (KBr): 3400, 3330, 3266, 3223, 2192,
1699, 1675, 1607, 1530, 1416, 1345, 1270, 1115, 1064, 791; 1H NMR
(DMSO-d6): d ¼ 2.42 (s, 3H, CH3), 3.61 (s, 3H, OCH3), 4.58 (s, 1H, CH),
4.67 (s, 2H, NH2), 7.49 (t, J ¼ 8 Hz, 1H, ArH), 7.57 (d, J ¼ 8 Hz, 1H,
ArH), 8.04 (s, 1H, ArH), 8.13 (d, J ¼ 8 Hz, 1H, ArH); MS: m/z (%) ¼ 316
([M þ 1]þ, 21.08), 298 (35.69), 284 (9.27), 268 (5.38), 256 (2.81), 210
(1.91), 193 (100.00), 176 (9.14), 161 (23.00), 133 (7.13), 105 (4.54), 76
(6.87), 67 (7.66), 43 (14.99).

Synthesis of 2-Amino-4-aryl-4H-pyrans
1387
2-Amino-4-(4-methoxylphenyl)-3-cyano-4H-pyran-5-carboxylates
(4d): White, crystalline solid (recrystallized from 95% ethanol); mp 134–
1358C; Anal. C16H16N2O4 calcd.: C, 64.00; H, 5.33; N, 9.33. Found: C,
63.88; H, 5.27; N, 9.39. FT-IR (KBr): 3406, 3333, 3205, 2194, 1701, 1676,
1
1649, 1607, 1511, 1402, 1342, 1265, 1176, 1123, 1060; H NMR (DMSO-
d6): d ¼ 2.04 (s, 3H, CH3), 3.59 (s, 3H, OCH3), 3.77 (s, 3H, OCH3), 4.39
(s, 1H, CH), 4.42 (br, s, 2H, NH2), 6.83 (d, 2H, J ¼ 8 Hz, ArH), 7.12
(d, 2H, J ¼ 8 Hz, ArH); MS: m/z (%) ¼ 300 (Mþ, 22.37), 285 (7.31), 268
(11.50), 241 (11.73), 225 (6.59), 193 (55.43), 184 (25.77), 176 (4.20), 161
(15.23), 133 (9.02), 114 (17.42), 105 (4.67), 67 (11.54), 63 (19.49), 43
(100.00).
2-Amino-4-(4-hydroxylphenyl)-3-cyano-4H-pyran-5-carboxylates
(4e): White, crystalline solid (recrystallized from 95% ethanol); mp 181–
1828C; Anal. C15H14N2O4 calcd.: C, 62.94; H, 4.90; N, 9.80. Found: C,
63.08; H, 4.96; N, 9.71. FT-IR (KBr): 3440, 3317, 3026, 2958, 2193, 1710,
1672, 1594, 1513, 1410, 1338, 1247, 1068, 821; 1H NMR (DMSO-d6):
d ¼ 2.26 (s, 3H, CH3), 3.53 (s, 3H. OCH3), 4.17 (s, 1H, CH), 6.66
(d, J ¼ 8.2 Hz, 2H, ArH), 6.82 (s, 2H, NH2), 6.92 (d, J ¼ 8.2 Hz, 2H, ArH),
9.28 (s, 1H, OH); MS: m/z (%) ¼ 286 (Mþ, 28.87), 271 (16.84), 254
(15.15), 239 (6.42), 227 (25.78), 21 (15.55), 193 (100.00), 176 (14.27), 161
(40.97), 133 (13.89), 105 (10.54), 89 (12.47), 77 (11.78), 67 (21.45), 43
(70.50).
2-Amino-4-(4-chlorophenyl)-3-cyano-4H-pyran-5-carboxylates (4f):
White, crystalline solid (recrystallized from 95% ethanol); mp 160–1628C;
Anal. C15H13ClN2O3 calcd.: C, 59.21; H, 4.27; N, 9.21. Found: C, 59.33; H,
4.32; N, 9.16. FT-IR (KBr): 3410, 3332, 3227, 3204, 2193, 1700, 1676,
1647, 1607, 1409, 1342, 1267, 1064, 838, 764; 1H NMR (DMSO-d6):
d ¼ 2.31 (s, 3H, CH3), 3.52 (s, 3H. OCH3), 4.30 (s, 1H, CH), 6.97 (s, 2H,
NH2), 7.15 (d, J ¼ 8.4 Hz, 2H, ArH), 7.38 (d, J ¼ 8.4 Hz, 2H, ArH); MS:
m/z (%) ¼ 304 (Mþ, 15.32), 289 (10.42), 269 (4.80), 245 (13.56), 193
(100.00), 176 (12.77), 161 (31.97), 149 (20.12), 133 (8.72), 105 (7.06), 67
(11.19), 43 (80.43).
2-Amino-4-(2,6-dichlorophenyl)-3-cyano-4H-pyran-5-carboxylates
(4g): Yellow, crystalline solid (recrystallized from 95% ethanol); mp 226–
2288C; Anal. C15H12Cl2N2O3 calcd.: C, 53.10; H, 3.54; N, 8.26. Found: C,
53.01; H, 3.49; N, 8.31. FT-IR (KBr): 3457, 3400, 3332, 3262, 3205, 2195,
1709, 1671, 1608, 1434, 1403, 1372, 1267, 1227, 1125, 1083, 772, 734;
1H NMR (DMSO-d6): d ¼ 2.26 (s, 3H, CH3), 3.46 (s, 3H, OCH3), 5.36
(s, 1H, CH), 7.00 (s, 2H, NH2), 7.27 (t, 1H, J ¼ 8 Hz, ArH), 7.33 (d, 1H,
J ¼ 8 Hz, ArH), 7.38 (d, 1H, J ¼ 8 Hz, ArH); MS: m/z (%) ¼ 338 ([M-1]þ,
14.84), 323 (14.90), 279 (10.37), 193 (100.00), 176 (10.90), 161 (29.34),
133 (8.94), 67 (13.34), 43 (42.91).
2-Amino-4-(2,4-dichlorophenyl)-3-cyano-4H-pyran-5-carboxylates
(4h): White, crystalline solid (recrystallized from 95% ethanol); mp 150–
1528C; Anal. C15H12Cl2N2O3 calcd.: C, 53.10; H, 3.54; N, 8.26. Found: C,

1388
M. Xia, Q. Chen, and Y. Lu
53.19; H, 3.61; N, 8.21. FT-IR (KBr): 3447, 3324, 3292, 3260, 3197, 2208,
1
1714, 1683, 1604, 1380, 1254, 1074, 845; H NMR (DMSO-d6): d ¼ 2.33
(s, 3H, CH3), 3.49 (s, 3H, OCH3), 4.84 (s, 1H, CH), 7.01 (s, 2H, NH2), 7.23
(d, J ¼ 8.2 Hz, 1H, ArH), 7.38–7.40 (dd, J ¼ 8.2 Hz, J ¼ 2.1 Hz, 1H, ArH),
7.55 (d, J ¼ 2.1 Hz, 1H, ArH); MS: m/z (%) ¼ 339 (Mþ, 29.97), 323
(8.19), 303 (35.07), 279 (5.96), 243 (3.68), 193 (100.00), 176 (7.09), 161
(18.95), 133 (5.54), 105 (3.47), 67 (11.96), 43 (44.71).
2-Amino-4-(3,4-dimethyleneoxylphenyl)-3-cyano-4H-pyran-5-carb-
oxylates (4i): White, crystalline solid (recrystallized from 95% ethanol); mp
166–1678C; Anal. C17H16N2O4 calcd.: C, 65.38; H, 5.13; N, 8.97. Found: C,
65.49; H, 5.18; N, 8.88. FT-IR (KBr): 3416, 3332, 3209, 2949, 2870, 2195,
1
1699, 1683, 1609, 1502, 1430, 1344, 1254, 1060, 943, 810, 763; H NMR
(DMSO-d6): d ¼ 2.28 (s, 3H, CH3), 3.54 (s, 3H, OCH3), 4.22 (s, 1H, CH),
5.98 (d, J ¼ 1.7 Hz, 2H, OCH2O), 6.58 (dd, J ¼ 1.7 Hz, J ¼ 8 Hz, 1H, ArH),
6.64 (d, J ¼ 1.7 Hz, 1H, ArH), 6.83 (d, J ¼ 8 Hz, 1H, ArH), 6.88 (s, 2H,
NH2); MS: m/z (%) ¼ 314 (Mþ, 43.14), 299 (10.28), 282 (8.98), 254
(16.17), 239 (13.80), 193 (100.00), 176 (12.81), 161 (36.82), 133 (13.25),
105 (10.02), 63 (30.62), 43 (61.73).
2-Amino-4-(4-fluorophenyl)-3-cyano-4H-pyran-5-carboxylates (4j):
White, crystalline solid (recrystallized from 95% ethanol); mp 153–1548C;
Anal. C15H14FN2O3 calcd.: C, 62.28; H, 4.84; N, 9.68. Found: C, 62.38; H,
4.90; N, 9.59. FT-IR (KBr): 3410, 3332, 3272, 3205, 2197, 1700, 1680,
1649, 1611, 1507, 1408, 1380, 1341, 1269, 1064, 850, 766; 1H NMR
(DMSO-d6): d ¼ 2.36 (s, 3H, CH3), 3.59 (s, 3H, OCH3), 4.43 (s, 1H, CH),
4.48 (br, s, 2H, NH2), 6.98 (t, 2H, J ¼ 8.4 Hz, ArH), 7.14–7.18 (m, 2H,
ArH); MS: m/z (%) ¼ 288 (Mþ, 23.59), 273 (17.51), 257 (4.55), 229
(22.33), 213 (8.13), 193 (100.00), 176 (13.57), 161 (37.89), 149 (28.63),
133 (14.39), 105 (7.69), 67 (14.98), 43 (48.07).
ACKNOWLEDGMENT
We are thankful for the financial support from Natural Science Fund of
Zhejiang Province (202031) and the Natural Science Fund of China
(20401013).
REFERENCES
1. (a) Weber, L.; Illegen, K.; Almstetter, M. Discovery of new multi component
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