The synthesis of new asymmetric double Schiff bases containing a new o-amino benzoic acid derivative

Article abstract of DOI:10.1081/SCC-200028639

A new o-amino benzoic acid derivative, 2-amino-N-phenyl-benzamide, has been obtained by the reaction of o-amino benzoic acid and aniline. Twelve new asymmetric Schiff bases, which have both (Chemical Equation Presented) and (Chemical Equation Presented) functional groups containing 2-amino-N-phenyl- benzamide, have been synthesized and characterized.

Full text of DOI:10.1081/SCC-200028639

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The Synthesis of New
Asymmetric Double Schiff
Bases Containing a New
o‐Amino Benzoic Acid
Derivative
Yongqing Liang a , Biyun Su a , Jianshe Zhao a &
Wenhua Sun b
a Shaanxi Key Laboratory of Physico‐Inorganic
Chemistry, Department of Chemistry , Northwest
University , Xi'an, 710069, P.R. China
b State Key Laboratory of Engineering Plastics and
The Center for Molecular Science, Institute of
Chemistry , The Chinese Academy of Sciences ,
Beijing, P.R. China
Published online: 10 Jan 2011.
To cite this article: Yongqing Liang , Biyun Su , Jianshe Zhao & Wenhua Sun (2004)
The Synthesis of New Asymmetric Double Schiff Bases Containing a New o‐Amino
Benzoic Acid Derivative, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 34:17, 3235-3242, DOI:
10.1081/SCC-200028639
To link to this article: http://dx.doi.org/10.1081/SCC-200028639
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 17, pp. 3235–3242, 2004
The Synthesis of New Asymmetric Double
Schiff Bases Containing a New o-Amino
Benzoic Acid Derivative
Yongqing Liang,1 Biyun Su,1 Jianshe Zhao,1,
*
and Wenhua Sun2
1Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of
Chemistry, Northwest University, Xi’an, P.R. China
2State Key Laboratory of Engineering Plastics and The Center for
Molecular Science, Institute of Chemistry, The Chinese Academy of
Sciences, Beijing, P.R. China
ABSTRACT
A new o-amino benzoic acid derivative, 2-amino-N-phenyl-benzamide,
has been obtained by the reaction of o-amino benzoic acid and aniline.
Twelve new asymmetric Schiff bases, which have both
and
functional groups containing 2-amino-N-phenyl-benzamide,
have been synthesized and characterized.
*
Correspondence: Jianshe Zhao, Shaanxi Key Laboratory of Physico-Inorganic Chem-
istry, Department of Chemistry, Northwest University, Xi’an 710069, P.R. China.
3235
DOI: 10.1081/SCC-200028639
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

3236
Liang et al.
Scheme 1. R ¼ Salicyl, 2-hydroxy-naphaldehyl, p-N,N-dimethyl-benzaldehydehydyl,
respectively.
Schiff bases have been extensively studied for their interesting chem-
istry,[1–3] special physical properties,[4–6] and important biological
activity.[7,8] Studies on the synthesis of the asymmetric Schiff bases have
received more and more focus. Elder[9] has done some useful work to afford
a general route to synthesize unsymmetric Schiff bases as has Atkins.[10]
Here we present the design and synthesis of a series of asymmetric double
Schiff bases using the 2-amino-N-phenyl-benzamide as the key unit.
Schiff bases with thionyl dichloride were first employed as the route into
investigation (Sch. 1), which was eventually confirmed to be unsatisfactory.
We found that the unsteadiness of the carbon-nitrogen double bond under
reaction conditions was undesirable for further reaction.
Finally, we adopted another synthesis route to obtain the products (Sch. 2).
Consequently, the reaction was carried out smoothly, offering the expected
products. The preparation of the key intermediate, 2-amino-N-phenyl-
benzamide, involved three key steps: (1) the protection of the amido using
hydrochloric acid; (2) the preparation of acyl chloride; and (3) the reaction of
carboxylic acid halides with aniline. Furthermore, the unsymmetric double Schiff
Scheme 2.

Synthesis of New Asymmetric Double Schiff Bases
3237
bases were obtained by reaction between 2-amino-N-phenyl-benzamide and
aldehydes in presence of a catalytic amount of toluene-p-sulfonic acid in ethanol.
According to the experiments, it should be pointed out that the two reac-
tions—steps 1 and 2—could be substituted by the direct reaction between
o-amino benzoic acid reacted with thionyl dichloride, in which the original
acidification step using hydrogen chloride could be omitted. Therefore, the
reaction was highly accelerated.
EXPERIMENTAL SECTION
Infrared spectra were obtained on a Perkin-Elmer System 2000 FT-IR
1
spectrometer. H NMR spectra were recorded on a Bruker BMX-300MHz.
Chemical shifts are indicated in d values (ppm) downfield from internal TMS.
Multiplicities were recorded as s (singlet), d (doublet), t (triplet), br (broad),
and m (multiplet). Melting point was obtained with an electrical apparatus
and was uncorrected. Elemental analyses were carried out on HP-MOD
1106 microanalyzer. Commercial-grade solvents were used without further
purification. Starting materials were purchased from the Aldrich Chemical
Company.
Preparation of 2-Amino-N-phenyl-benzamide (1)
o-Amino benzoic acid (0.137 g, 1.0 mmol) in ether (10 mL) was added to
fresh thionyl dichloride (10 mL). The resulting mixture was refluxed at 608C
while stirring for 2 hr and then concentrated under reduced pressure to remove
solful dichloride. Then the remains were dissolved in ether (20 mL) and added
to a solution of aniline (0.186 g, 2.0 mmol) in pyridine (5 mL). The resulting
mixture was then refluxed for 3 hr to obtain a green solution. The resulting
solution was concentrated under reduced pressure to remove pyridine and
ether. Then the mixture was dissolved in 20 mL ethanol and 100 mL distil-
lated water added. The precipitated product, 2-amino-N-phenyl-benzamide
(1), was obtained. It was recrystallized from ethanol/water (1 : 5). Yield:
1
50.4%. m.p. 1218C–1238C. H NMR: d 7.7(s, 1H), 7.5(d, 2H), 7.4(d, 1H),
7.3(t, 2H), 7.1(t, 1H), 6.7(m, 3H), 5.3–5.8(br, 2H). IR (KBr): 3471, 3365,
3287, 1638, 1599, 1538, 1441, 1322, 1254, 1156, 943, 751, 692 cm21
.
Anal.: C13H12N2O (212.25): Calcd.: C 73.56, H 5.70, N 13.20. Found: C
73.23, H 5.60, N 13.28.

3238
Liang et al.
Preparation of 2-(Benzylideneamino)-N-phenyl-benzamide (2)
To a solution of 2-amino-N-phenyl-benzamide (0.212 g, 1.0 mmol) and a
catalysis amount of toluene-p-sulfonic acid in 10 mL ethanol, benzaldehyde
(0.116 g, 1.1 mmol) in 3 mL ethanol was added drop-wise at room tempera-
ture. After 2 min, the crude product appeared as white powder. The mixture
was then stirred for 30 min and filtered. The crude product was recrystallized
1
from CH3CN/ethanol (1 : 5). Yield: 60.4%. m.p. 2148C–2168C. H NMR: d
8.0(d, 1H), 7.3(m, 2H), 7.2(m, 7H), 7.1(t, 3H), 6.8(t, 1H), 6.6(d, 1H),
6.1(d, 1H). IR (KBr): 3296, 3061, 2830, 1635, 1613, 1510, 1490, 1455,
1392, 1334, 1250, 1160, 1027, 926, 753, 697, 622 cm21. Anal.: C20H16N2O
(300.35): Calcd.: C 78.98, H 5.37, N 9.33. Found: C 78.66, H 5.36, N 9.28.
Preparation of 2-(2-Methoxy-benzylideneamino)-N-
phenyl-benzamide (3)
The procedure was the same as that for 2 and a white powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
Yield: 77.1%. m.p. 2248C–2268C. 1H NMR: d 8.0(d, 1H), 7.8(m, 1H),
7.4(t, 2H), 7.2–7.3 (m, 6H), 6.9(t, 1H), 6.8(d, 1H), 6.6(d, 1H), 6.2(s, 1H),
3.8(m, 3H). IR (KBr): 3405, 3047, 2970, 2943, 2842, 1645, 1612, 1493,
1452, 1431, 1328, 1288, 1245, 1189, 1153, 1110, 1024, 950, 862, 831, 750,
695, 635, 583, 525 cm21. Anal.: C21H18N2O2 (330.38): Calcd.: C 76.34,
H 5.49, N 8.48. Found: C 76.02, H 5.39, N 8.35.
Preparation of 2-(2, 4-Dimethoxy-benzylideneamino)-N-
phenyl-benzamide (4)
The procedure was the same as that for 2 and a white powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
Yield: 48.1%. m.p. 1838C–1848C. 1H NMR: d 7.9(d, 1H), 7.7(m, 1H),
7.4(m, 2H), 7.3(m, 2H), 7.2(m, 3H), 7.0(m, 1H), 6.8(d, 1H), 6.6(s, 1H),
6.4(m, 1H), 3.9(m, 3H), 3.5(m, 3H). IR (KBr): 3363, 3058, 2936, 2839,
1655, 1612, 1589, 1500, 1459, 1400, 1409, 1291, 1256, 1209, 1158, 1121,
1034, 958, 922, 832, 753, 696, 639, 581 cm21. Anal.: C22H20N2O3 (360.41):
Calcd.: C 73.32, H 5.59, N 7.77. Found: C 73.21, H 5.40, N 7.75.

Synthesis of New Asymmetric Double Schiff Bases
3239
Preparation of 2-(3-Chloride-benzylideneamino)-N-
phenyl-benzamide (5)
The procedure was the same as that for 2 and a white powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
Yield: 48.1%. m.p. 2128C–2138C. 1H NMR: d 8.0(d, 1H), 7.5(m, 1H),
7.4(t, 2H), 7.3(t, 3H), 7.1–7.2(m, 4H), 7.0(t, 1H), 6.6(d, 1H), 6.0(s, 1H). IR
(KBr): 3304, 3060, 1636, 1613, 1510, 1487, 1446, 1397, 1294, 1242, 1190,
1116, 949, 911, 885, 858, 795, 697, 643, 593 cm21. Anal.: C20H15ClN2O
(334.80): Calcd.: C 71.75, H 4.52, Cl 10.59, N 8.37. Found: C 71.58, H
4.19, Cl 10.66, N 8.36.
Preparation of 2-(4-Chloride-benzylideneamino)-N-
phenyl-benzamide (6)
The procedure was the same as that for 2 and a white powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
Yield: 88.7%. m.p. 2328C–2348C. 1H NMR: d 8.0(d, 1H), 7.6(m, 1H),
7.4(m, 2H), 7.3(m, 4H), 7.2(t, 3H), 6.9(t, 1H), 6.7(d, 1H), 6.1(s, 1H). IR
(KBr): 3299, 3061, 2927, 1634, 1614, 1509, 1489, 1448, 1391, 1314, 1249,
1160, 1116, 1089, 1015, 908, 872, 833, 754, 695, 626, 588, 544 cm21
.
Anal.: C20H15ClN2O (334.80): Calcd.: C 71.75, H 4.52, Cl 10.59, N 8.37.
Found: C 71.42, H 4.19, Cl 10.70, N 8.31.
Preparation of 2-(4-Dimethylamino-benzylideneamino)-N-
phenyl-benzamide (7)
The procedure was the same as that for 2 and an orange powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
Yield: 45.8%. m.p. 1798C–1818C. 1H NMR: d 8.0(d, 1H), 7.7(d, 1H),
7.5(d, 2H), 7.4(m, 4H), 7.3(t, 3H), 7.1(t, 1H), 6.7(t, 1H), 6.0(s, 1H),
3.1(s, 6H). IR (KBr): 3299, 3057, 2889, 2807, 1634, 1612, 1503, 1444,
1395, 1351, 1251, 1228, 1188, 1162, 1118, 1055, 1024, 946, 908, 870, 821,
756, 695, 599, 582, 550 cm21. Anal.: C22H21N3O (343.42): Calcd.: C 76.94,
H 6.16, N 12.24. Found: C 76.52, H 6.09, N 12.35.

3240
Liang et al.
Preparation of 2-(2-Hydroxy-benzylideneamino)-N-
phenyl-benzamide (8)
The procedure was the same as that for 2 and a white powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
1
Yield: 71.4%. m.p. 2388C–2408C. H NMR: d 10.2(d, 1H), 10.0(s, 1H),
8.0(d, 1H), 7.7(t, 1H), 7.6(d, 1H), 7.5(m, 3H), 7.4(m, 4H), 6.7(m, 3H),
6.3(s, 1H). IR (KBr): 3375, 3147, 2868, 2726, 2594, 1630, 1487, 1458,
1432, 1410, 1320, 1285, 1235, 1191, 1156, 1120, 1099, 1076, 1035, 1001,
950, 918, 857, 755, 700, 656, 599, 583, 519 cm21. Anal.: C20H16N2O2
(316.35): Calcd.: C 75.93, H 5.10, N 8.86. Found: C 75.68, H 4.93, N 8.78.
Preparation of 2-(2-Hydroxy-3-methoxy-benzylideneamino)-
N-phenyl-benzamide (9)
The procedure was the same as that for 2 and a jacinthe powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
1
Yield: 69.2%. m.p. 2008C–2028C. H NMR: d 10.3(d, 1H), 10.0(s, 1H), d
8.0(d, 1H), 7.7(m, 1H), 7.5(m, 2H), 7.4(m, 2H), 7.2(m, 3H), 6.8(m, 2H),
6.6(s, 1H), 6.4(d, 1H), 3.9(m, 3H). IR (KBr): 3446, 3314, 3068, 3017, 2972,
2940, 2844, 1679, 1617, 1598, 1541, 1492, 1461, 1444, 1396, 1322, 1256,
1198, 1134, 1095, 1080, 1039, 972, 892, 859, 835, 784, 761, 736, 695, 589,
544, 505 cm21. Anal.: C21H18N2O3 (346.38): Calcd.: C 72.82, H 5.24, N
8.09. Found: C 72.64, H 5.29, N 8.13.
Preparation of 2-(2-Hydroxy-3, 5-dichloro-
benzylideneamino)-N-phenyl-benzamide (10)
The procedure was the same as that for 2 and an orange powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
1
Yield: 78.7%. m.p. 2498C–2518C. H NMR: d 10.2(d, 1H), 10.0(s, 1H),
8.0(d, 1H), 7.6(m, 1H), 7.4(t, 2H), 7.3(m, 2H), 7.2(t, 3H), 6.8(d, 1H),
6.6(s, 1H), 6.4(d, 1H). IR (KBr): 3391, 3196, 3083, 1641, 1611, 1490, 1463,
1430, 1402, 1314, 1257, 1229, 1193, 1125, 1091, 1031, 1001, 920, 854, 758,
703, 656, 617, 597, 526 cm21. Anal.: C20H14Cl2N2O2 (385.24): Calcd.: C
62.35, H 3.66, Cl 18.41, N 7.27. Found: C 62.34, H 3.29, Cl 18.79, N 7.30.

Synthesis of New Asymmetric Double Schiff Bases
3241
Preparation of 2-(2-Hydroxy-4-nitryl-benzylideneamino)-N-
phenyl-benzamide (11)
The procedure was the same as that for 2 and a yellow powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
1
Yield: 56.0%. m.p. 2538C–2548C. H NMR: d 10.2(d, 1H), 10.0(s, 1H),
7.9(d, 1H), 7.7(t, 1H), 7.5(m, 3H), 7.4(m, 2H), 7.2(m, 2H), 7.0(m, 1H),
6.7(m, 2H), 6.3(d, 1H). IR (KBr): 3361, 3034, 1633, 1526, 1492, 1450,
1415, 1333, 1280, 1228, 1155, 1122, 1077, 930, 839, 749, 693, 640,
509 cm21. Anal.: C20H15N3O4 (361.11): Calcd.: C 66.48, H 4.18, N 11.63.
Found: C 66.32, H 4.09, N 11.65.
Preparation of 2-((2-Hydroxy-naphthalen-yl)-
benzylideneamino)-N-phenyl-benzamide (12)
The procedure was the same as that for 2 and a white powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
1
Yield: 94.9%. m.p. 2388C–2408C. H NMR: d 10.2(d, 1H), 10.0(s, 1H),
8.1(d, 1H), 7.8(t, 2H), 7.6(m, 4H), 7.5(m, 2H), 7.4(m, 2H), 7.1(m, 2H),
6.8(m, 2H), 6.5(s, 1H). IR (KBr): 3745, 3255, 3193, 3033, 1670, 1620,
1544, 1486, 1442, 1408, 1351, 1319, 1287, 1263, 1210, 1159, 1073, 1040,
979, 895, 750, 691, 596, 511 cm21. Anal.: C24H18N2O2 (366.14): Calcd.: C
78.67, H 4.95, N 7.65. Found: C 78.46, H 4.69, N 7.63.
Preparation of 2-((Pyridin-2-yl)-methyleneamino)-N-
phenyl-benzamide (13)
The procedure was the same as that for 2 and a white powder was
obtained. The crude product was recrystallized from CH3CN/ethanol (1 : 5).
Yield: 63.6%. m.p. 1848C–1858C. 1H NMR: d 8.6(d, 1H), 8.2(d, 1H),
8.0(m, 2H), 7.6(m, 2H), 7.4(m, 2H), 7.3(m, 4H), 7.2(t, 2H), 7.0(s, 1H). IR
(KBr): 3748, 3288, 3059, 1647, 1613, 1508, 1491, 1446, 1402, 1325, 1297,
1246, 1174, 1118, 1080, 1050, 1026, 996, 913, 865, 846, 790, 755, 697,
661, 617, 581, 536, 512 cm21. Anal.: C19H15N3O (301.34): Calcd.: C 75.73,
H 5.02, N 13.94. Found: C 75.53, H 4.72, N 13.94.

3242
Liang et al.
ACKNOWLEDGMENT
We are grateful for the financial support from the National Natural
Science Foundation of China (No. 20371039 and No. 20071027), the State
Key Fundamental Research Development Program (the 973 Program, No.
2003CB214606), and the Key Laboratory Research and Establish Program
of Shaanxi Education Section (No. 03JS006).
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Received in Japan March 9, 2004