Synthesis of novel Schiff's bases containing pyridine rings

Article abstract of DOI:10.1081/SCC-120034167

Synthesis and characterization of six new Schiff's bases, potential hexadentate ligands, containing amide groups and pyridine rings with shallow structures are described. The two step reactions involving ring opening of isatoic anhydride with diamines fol

Full text of DOI:10.1081/SCC-120034167

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Synthesis of Novel Schiff's Bases Containing Pyridine
Rings
S. J. Swamy a , K. Suresh a , P. Someshwar a & D. Nagaraju a
a Department of Chemistry , Kakatiya University , Warangal, 506 009, India
Published online: 20 Aug 2006.
To cite this article: S. J. Swamy , K. Suresh , P. Someshwar & D. Nagaraju (2004) Synthesis of Novel Schiff's Bases
Containing Pyridine Rings, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 34:10, 1847-1853, DOI: 10.1081/SCC-120034167
To link to this article: http://dx.doi.org/10.1081/SCC-120034167
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 10, pp. 1847–1853, 2004
Synthesis of Novel Schiff’s Bases Containing
Pyridine Rings
*
S. J. Swamy, K. Suresh, P. Someshwar, and D. Nagaraju
Department of Chemistry, Kakatiya University, Warangal, India
ABSTRACT
Synthesis and characterization of six new Schiff’s bases, potential hexa-
dentate ligands, containing amide groups and pyridine rings with shallow
structures are described. The two step reactions involving ring opening of
isatoic anhydride with diamines followed by condensation with pyridine
aldehydes proceed smoothly to give Schiff’s bases containing pyridine
rings in high purity and better yields.
Key Words: Schiff’s bases; Amide group; Pyridine rings; Proteins.
INTRODUCTION
We have been attempting to develop new chelators, both open and closed
(ring), with shallow structures.[1–3] The richest sources of concave surfaces
*
Correspondence: S. J. Swamy, Department of Chemistry, Kakatiya University,
Warangal 506 009, India; E-mail: sj_swamy@yahoo.com.
1847
DOI: 10.1081/SCC-120034167
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

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1848
Swamy et al.
are found in the binding and active sites of proteins and nucleic acids. The
amide group is an important functional group of biomolecules and also yields
useful information. The comparisons of the energies of the rotational barrier to
amide rotation provides a means of characterization.[4] In view of the interest
in the amide group [R2N–C55O] in the coordination chemistry and biochem-
istry we have developed a series of new compounds containing O55C–NR2
group along with –NH2, –COOH, and –OH groups[1–3] that can bind
metal ions in a better way. Further, we have recently reported the non-template
synthesis of di- and tetra-amide macrocyclic ligands using the diamine
diamide compounds.[5] We have also investigated the catalytic applications
of the 4f-metal complexes of these ligands in organic synthesis.[6–8] The
structures of the complexes were reported as shown in Fig. 1.
The ligands and their complexes, we have reported earlier deal with the
orientation of the donor molecules to coordinate to the metal ions more effec-
tively. In view of the interest and importance of polydentate ligands in devel-
oping macrocyclic ligands and supramolecular interactions between metal
cations and also anions we have attempted to develop new polydentate ligands
with donor groups, O55C–NH, –NH2, .C55N–, and pyridine rings with
probable shallow structures.
Isatoic anhydride 1 reacts with diamines 2, 3, or 4 at room temperature
in water with the ring opening to form compounds, 2-amino-N-f2-[(2-amino-
benzoyl)amino]-ethyl (5)/propyl (6)/phenyl (7)-benzamides, respect-
ively.[1–3] The course of the reaction can be monitored with the expulsion
of CO2 with effervescence.
Condensation of compounds 5, 6, and 7 with 2-aminonicotinaldehyde 8 or
pyridine-2-carbaldehyde 9 in the presence of p-toluene sulfonic acid (PTSA)
in DMF resulted in the products 10–15 (Sch. 1) in the yields ranging between
65% and 85%.
Figure 1. The structures of the complexes.

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Novel Schiff’s Bases Containing Pyridine Rings
1849
The compounds exhibit characteristic IR absorptions of the groups, amine
1
n(–NH2), amide [n(.C55O) and n(C–N) þ d(N–H)], and n(C55N). The H
NMR spectral absorptions of all the compounds recorded in DMSO-d6 indi-
cate unequivocally the formation of the title compounds. The mass spectra
of the compounds exhibit the molecular ion peak and other fragments confirm
the proposed formulas of the compounds. These compounds with an open
structure tend to orient to develop a concave surface for coordination to
metal ions. These compounds are found to modify the spectral and redox
properties of transition metal ions.[9] We have carried out ring closure reac-
tions on diamine compounds 5, 6, and 7 to obtain N4-tetraazamacrocycles.[5]
Scheme 1.

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Swamy et al.
The development of the compounds 10–15 is interesting as the search for
supramolecular interactions[10–12] between the solid complex species and
covalent molecules[13,14] and/or counter ions both in solid state and sol-
ution[15] is the field of current importance.
EXPERIMENTAL SECTION
Isatoic anhydride and pyridine-2-carbaldehyde were obtained from
Aldrich Chemical Company, USA and used as received. 2-Aminonicotinalde-
hyde was prepared as described elsewhere.[16] All the solvents were distilled
and stored over molecular sieves. Melting points (uncorrected) were deter-
mined in open capillary tubes using Cintex apparatus. Purity of the compounds
was checked by TLC using Merk 60F-254 silica gel plates. The micro analysis
was performed using Perkin Elmer Series II CHNS analyzer-2400. IR spectra
in KBr discs were recorded using a Perkin Elmer-BX series FT-IR spectropho-
1
tometer. H NMR spectra were recorded on Bruker ARX200 spectrometer.
Mass spectrum was recorded using Varian MAT 311 A/AMD mass spec-
trometer. The electronic spectra in methanol were recorded on Shimadzu
2401 PC spectrometer.
2-Amino-N-f2-[(2-aminobenzoyl)amino] ethyl (5)/propyl (6)/phenyl
(7)-benzamide. To a solution of 0.1 mol of the diamine (1,2-diaminoethane
2, 6 g; 1,3-diaminopropane 3, 7.4 g; or 1,2-diaminobenzene 4, 10.8 g) in hot
water and 0.2 mol (29.8 g) of powdered isatoic anhydride was added and stirred
for 3 hr. Heating on water bath was continued till the effervescence of CO2 gas
ceased. The reaction mixture was allowed to stand over night and the product
recrystallized from dioxane 5 or methanol 6 and 7.
5. (23.2 g, 85%), m.p. 2418C. IR (KBr): 3460, 3360, 3275, 1620,
1
1550cm21. H NMR (DMSO-d6) d: 8.2br, (2H, –CO–NH), 7.0–7.6m (8H,
ArH’s), 4.3–4.7 (4H, –NH–CH2–), 2.9 (4H, –NH2). EIMS m/z: 298 (Mþ).
Anal. calcd for C16H18N4O2: C, 64.41; H, 6.08; N, 18.78. Found: C, 64.22; H,
5.94; N, 18.71.
6. (24.8 g, 87%), m.p. 1688C, IR (KBr): 3460, 3360, 3275, 1665, 1615,
1
1535 cm21. H NMR (DMSO-d6) d: 8.3t (2H, –CO–NH–), 6.6–7.9 (8H,
ArH’s), 4.5br (4H, –NH2), 3.3m (4H, –HN–CH2–), 1.55m (2H, –CH2–).
EIMS m/z: 312 (Mþ). Anal. calcd for C17H20N4O2: C, 65.37; H, 6.45; N,
17.94. Found: C, 65.13; H, 6.28; N, 17.81.
7. (28.5 g, 90%), m.p. 2188C, IR (KBr): 3450, 3360, 1620, 1500 cm21
,
1H NMR (DMSO-d6) d: 8.5 (2H, –CO–NH–), 7.2–7.7m (12H, ArH’s),
3.15br (4H, –NH2). EIMS m/z: 346 (Mþ). Anal. calcd for C20H18N4O2: C,
69.35; H, 5.24; N, 16.17. Found: C, 68.87; H, 5.08; N, 15.85.

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Novel Schiff’s Bases Containing Pyridine Rings
1851
N,N0-bis-2-f(2-amino-pyridine-3-ylmethylene)amino benzoyl)g-1,2-
diaminoethane (8), 1,3-diaminopropane (11), and 1,2-diaminobenzene
(12). A solution of 0.03 mol each of 5 (7.67 g), 6 (8.52 g), or 7 (9.54 g) and
0.06 mol (6.5 g) of o-aminonicotinaldehyde 8 and PTSA (0.1 g) dissolved in
120 mL of DMF was refluxed for 5 hr, cooled and poured over crushed ice.
The solid was filtered and recrystallized from methanol.
10. (8.4 g, 66%), m.p. 1708C, IR (KBr): 3325, 1617, 1520, 1450 cm21
.
1
UV—347, 304, 217 nm. H NMR (DMSO-d6) d: 9.85, (2H,–CO–NH–),
6.6–8.3 (16H, ArH’s, and –N55CH–), 4.74br (4H, –NH2), 3.7m (4H, –
CH2–CH2–). EIMS m/z: 506.1 (Mþ), 402, 298, 239, 162, 120 (100%), 92,
78, 65. Anal. calcd for C28H26N8O2: C, 66.39; H, 5.17; N, 22.12. Found: C,
65.98; H, 5.74; N, 21.75.
11. (10.8 g, 73%), m.p. 1108C, IR (KBr): 3337, 1616, 1525, 1450 cm21
.
1
UV—307, 232 nm. H NMR (DMSO-d6) d: 9.45s (2H, –CO–NH–), 6.66–
8.16m (20H, ArH’s, and –N55CH–), 4.74br (4H, –NH2), 3.52m (4H, HN–
CH2–), 1.79m (2H, –CH2–). EIMS m/z: 520 (Mþ), 416, 312, 239, 173,
137, 120 (100%), 92, 65. Anal. calcd for C29H28N8O2 : C, 66.91; H, 5.42;
N, 21.52. Found: C, 66.38; H, 5.14; N, 21.15.
12. (12.5 g, 82%), m.p. 1208C, IR (KBr): 3354, 1670, 1612, 1500,
1450 cm21. UV—340, 301, 220, 206 nm. 1H NMR (DMSO-d6) d: 9.86s
(–CO–NH–), 6.66–8.16m (20H, ArH’s, and –N55CH–), 4.52br (4H, –NH2).
EIMS m/z: 554 (Mþ), 539, 450, 356, 328, 209, 120 (100%), 92, 65. Anal. calcd
for C32H26N8O2 : C, 69.30; H, 4.73; N, 20.20. Found: C, 68.88; H, 4.54; N, 20.43.
N,N0-bis-2-f(pyridine-2-ylmethylene) amino-bezoylg-1,2-diaminoethane
(13), 1,3-diaminopropane (14), and 1,2-diaminobenzene (15). A 0.03 mol
each of 5 (7.67 g), 6 (8.52 g), or 7 (9.54 g) was dissolved in 100 mL DMF.
To this 30-mL DMF solution of pyridine-2-carbaldehyde 9 (0.06 mol, 6.4 g)
was added separately. The mixture was refluxed for 5 hr in presence of 0.1 g
PTSA. Then, it was cooled and poured over crushed ice and stirred over
night. The products were filtered and washed with water and cold methanol.
Recrystallization from methanol in presence of activated charcoal yielded
TLC pure products.
13. (8.3 g, 65%), m.p. 1208C, IR (KBr): 3329, 1636, 1508, 1456 cm21
.
1
UV—331, 247, 239 nm. H NMR (DMSO-d6) d: 8.667t (2H, –CO–NH–),
6.78–8.35 (18H, ArH’s, and –N55CH), 3.55 (4H, –HN–CH2). EIMS m/z:
476.5 (Mþ), 387.4. 298.3, 224.2, 163.2, 150.2, 137.1, 120.2 (100%), 92.1,
78.1, 65.1, 39.1. Anal. calcd for C28H24N6O2: C, 70.57; H, 5.08; N, 17.64.
Found: C, 69.97; H, 5.17; N, 17.52.
14. (10.0 g, 72%), m.p. 908C, IR (KBr): 3341, 1636, 1512, 1466 cm21
UV—330, 235 nm. H NMR (DMSO-d6) d: 8.55t (2H, –OC–NH–), 6.52–
7.89m (18H, ArH’s, and –N55CH–), 3.50br (4H, –HN–CH2–), l.85qu
(2H, –CH2–). EIMS m/z: 490 (Mþ), 401, 312, 224, 163, 150, 137, 120
.
1

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Swamy et al.
(100%), 92, 65. Anal. calcd for C29H26N6O2: C, 71.00; H, 5.34; N, 17.13.
Found: C, 69.65; H, 5.51; N, 16.56.
15. (12.1 g, 81%), m.p. 988C, IR (KBr) 3432, 1636, 1499, 1450 cm21
.
1
UV—341, 249, 225 nm. H NMR (DMSO-d6) d: 9.87 (2H, –OC–NH–),
6.68–8.61 (22H, ArH’s, and –N55CH–). EIMS m/z: 524 (Mþ), 435, 346,
209, 181, 120 (100%), 92, 78, 65. Anal. calcd for C32H24N6O2: C, 73.27;
H, 4.61; N, 16.02. Found: C, 72.86; H, 4.88; N, 15.83.
ACKNOWLEDGMENT
The authors thank UGC, New Delhi for the financial assistance under
major research project 12-57/2001, and Prof. Dr. H. Schumann of TU Berlin,
Germany for the analytical and spectral data.
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Received in India December 31, 2003

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