Green synthesis of schiff bases derived from 4,5-diazafluorene-9-one in aqueous medium under microwave irradiation

Article abstract of DOI:10.14233/ajchem.2013.13848

A series of Schiff bases were successfully synthesized with satisfactory yield from various amines and 4,5-diazafluorene-9-one in water by using polystyrene sulfonic acid as a catalyst under microwave irradiation.

Full text of DOI:10.14233/ajchem.2013.13848

Asian Journal of Chemistry; Vol. 25, No. 6 (2013), 3390-3392
http://dx.doi.org/10.14233/ajchem.2013.13848
Green Synthesis of Schiff Bases Derived from 4,5-Diazafluorene-9-one in
Aqueous Medium Under Microwave Irradiation
*
HUI CANG , YU LU, WENYAN SHI, JINGLING SHAO and QI XU
Chemical and Biological Engineering College, Yancheng Institute of Technology, Yancheng 224051, Jiangsu Province, P.R. China
*Corresponding author: Fax: +86 515 88298618; Tel: +86 515 88298611; E-mail: canghui@ycit.edu.cn
(Received: 4 April 2012;
Accepted: 24 December 2012)
AJC-12595
A series of Schiff bases were successfully synthesized with satisfactory yield from various amines and 4,5-diazafluorene-9-one in water
by using polystyrene sulfonic acid as a catalyst under microwave irradiation.
Key Words: Schiff base, 4,5-Diazafluorene-9-one, Microwave irradiation, Aqueous medium.
INTRODUCTION
N
L
:
:
R =H
1
1
N
R1
L
R =NH
1
2
4,5-Diazafluoren-9-one and their derivatives are also
strong bidentate chelating and bridging agents1, which have
been widely explored due to their easy accessibility, easy
modification and relative air stability2. Synthesis of Schiff
bases containing a bipyridine type metal receptor3, has attracted
considerable attention due to their many applications in the
fields of catalyst4, conducting and photoresponsive materials5
and anion sensor6 etc. But, higher temperatures, increased
reaction times, plenty of organic solvent and the use of a cata-
lyst were generally required in previous synthesis of Schiff
bases from 4,5-diazafluorene-9-one7,8.
2
N
L
L
L
:
3
4
R =OH
1
R
R
R
R
=H
:
:
2
2
2
2
=CH
3
5
N
N
N
N
PSSA/H2O
MW
L
L
:
=OCH
=OH
3
6
N
R2
O
:
7
L
L
:
R
R
=COOH
8
2
2
=Cl
:
9
L
L
:
:
N
R
R
=R =H
4
10
3
N
NH
R3
=R =NO
4
11
3
2
N
R4
Scheme-I: Synthesis of schiff bases derived from 4,5-diazafluorene-9-one
In recent years, microwave irradiation was demonstrated
to be a valuable tool in organic synthesis resulting in faster
and cleaner reactions that sometimes exhibit different reacti-
vates due to specific microwave absorption9. From an environ-
mental view point, we report herein, for the first time, the
reaction (Scheme-I) can be successfully accomplished with
satisfactory yield in water by using polystyrene sulfonic acid
(PSSA) as a catalyst under microwave irradiation (MW), which
is a rapid and environmentally friendly preparation of schiff
bases from 4,5-diazafluorene-9-one compared to conventional
heating method.
with KMnO4 in a KOH solution following a literature method10.
The microwave reaction was carried out in the WF-4000M
closed type microwave synthesis system with the refluxing
equipment. Melting points were determined in open capillaries
and uncorrected. 1H NMR spectra were obtained using Bruker
DRX300 spectrometer with TMS. The IR spectra were deter-
mined as potassium bromide pellet on a Bruker Equinox55
FT-IR spectrophotometer. UV-VIS spectra were performed
with a UV-2501PC spectrophotometer. Mass spectra and
element analysis were done with LC-MSD-Trap-SL and
Elementar Vario EL III.
General procedure for preparation of L1-L11: All the
Schiff bases derived from 4,5-diazafluorene-9-one were
synthesized by modification of a literature procedure11. A
mixture of 4,5-diazafluorene-9-one (455 mg, 2.5 mmol) and
amines (3 mmol) were dissolved in 20 % polystyrene sulfonic
acid solution in water (5 mL) and then were exposed to
microwave irradiation (700 W, 100 ºC) for 7 min. The desired
EXPERIMENTAL
All reagents and solvents were purchased commercially
asAC grade and were used without further purification unless
noted. The molecular weight of polystyrene sulfonic acid is
70,000. Organic solvents were dried over 4 Å activated mole-
cular sieves prior to use. 4,5-diazafluoren-9-one was obtained
as light yellow needle by oxidation of 1,10-phenanthroline

Vol. 25, No. 6 (2013)
Green Synthesis of Schiff Bases Derived from 4,5-Diazafluorene-9-one 3391
precipitate was filtered after cooling, washed with ethanol 3
times and dried in vacuum oven at 50 ºC. The results of yield,
melt point and UV-visible spectra were listed in Table-1.
9-Imine-4,5-diazafluorene (L1): 1H NMR (CDCl3, 300
MHz): δ 8.82 (dd, 2H, J1 = 5.1, J2 = 1.5 Hz, pyridyl H ortho to
N), 8.05 (dd, 2H, J1 = 5.1, J2 = 1.5 Hz, pyridyl H para to N),
7.38 (t, 2H, J1 = 7.6, J2 = 5.1 Hz, pyridyl H meta to N), 5.45 (s,
1H, =NH). IR (KBr, νmax, cm-1): 3314, 3058, 1655, 1590, 1555,
1420, 1200, 801, 726. Elemental analysis calcd. (%) for
C11H7N3: C, 72.92; H, 3.89; N, 23.19. Found (%): C, 72.89; H,
3.92; N, 23.15. MS: m/z = 181.01 (Calcd.: 181.06).
Found (%): C, 79.30; H, 4.35; N, 16.36. MS: m/z = 257.13
(calcd.: 257.10).
1
9-(4-Methyanilino)-4,5-diazafluorene (L5): H NMR
(CDCl3, 300 MHz): δ 8.80 (dd, 1H, J1 = 5.0, J2 = 1.6Hz, pyridyl
H ortho to N), 8.64 (dd, 1H, J1 = 4.9, J2 = 1.6 Hz, pyridyl H
ortho to N), 8.25 (dd, 1H, J1 = 7.6, J2 = 1.5 Hz, pyridyl H para
to N), 7.39 (t, 1H, J1 = 7.6, J2 = 5.1 Hz, pyridyl H meta to N),
7.25 (m, 2H, pyridyl H meta to N and Ar-H), 6.98 (m, 2H,
pyridyl H para to N and Ar-H), 6.90 (d, 2H, J = 8.2Hz, Ar-H),
2.43 (s, 3H, -CH3). IR (KBr, νmax, cm-1): 3046, 2954, 2869,
1642, 1590, 1557, 1399, 752, 729. Elemental analysis calcd.
(%) for C18H13N3: C, 79.68; H, 4.83; N, 15.49. Found (%): C,
79.62; H, 4.85; N, 15.46. MS: m/z = 271.13 (calcd.: 271.11).
9-(4-Methoxyanilino)-4,5-diazafluorene (L6): 1H NMR
(CDCl3, 300 MHz): δ 8.80 (dd, 1H, J1 = 5.0, J2 = 1.6 Hz,
pyridyl H ortho to N), 8.65 (dd, 1H, J1 = 5.0, J2 = 1.6 Hz,
pyridyl H ortho to N), 8.23 (dd, 1H, J1 = 7.7, J2 = 1.5 Hz,
pyridyl H para to N), 7.38 (t, 1H, J1 = 7.7, J2 = 5.0 Hz, pyridyl
H meta to N), 7.09 (dd, 1H, J1 = 7.8, J2 = 1.7 Hz, pyridyl H
para to N), 6.98 (m, 5H, pyridyl H meta to N and Ar-H), 3.92
(s, 3H, -OCH3). IR (KBr, νmax, cm-1): 3043, 2999, 2837, 1634,
1590, 1559, 1497, 1400, 1234, 1023, 845, 757. Elemental
analysis calcd. (%) for C18H13N3O: C, 75.25; H, 4.56; N, 13.95.
Found (%): C, 75.20; H, 4.58; N, 13.97. MS: m/z = 287.07
(calcd.: 287.11).
9-Hydrazone-4,5-diazafluorene (L2): 1H NMR (CDCl3,
300 MHz): δ 8.75 (dd, 1H, J1 = 5.1, J2 = 1.6 Hz, pyridyl H
ortho to N), 8.65 (dd, 1H, J1 = 5.0, J2 = 1.6Hz, pyridyl H ortho
to N), 8.27 (dd, 1H, J1 = 7.7, J2 = 1.6 Hz, pyridyl H para to N),
8.16 (dd, 1H, J1 = 7.8, J2 = 1.6 Hz, pyridyl H para to N), 7.50
(t, 1H, J1 = 7.7, J2 = 5.1 Hz, pyridyl H meta to N), 7.39 (t, 1H,
J1 = 7.7, J2 = 5.0 Hz, pyridyl H meta to N), 6.65 (s, 2H, -NH2).
IR (KBr, νmax, cm-1): 3376, 3320, 3058, 1646, 1593, 1561,
1206, 799, 723. Elemental analysis calcd. (%) for C12H9N3: C,
67.34; H, 4.11; N, 28.55. Found (%): C, 67.30; H, 4.10; N,
28.52. MS: m/z = 196.01 (calcd.: 196.06).
9-Oxime-4,5-diazafluorene (L3): Sodium carbonate (0.016
g, 1.5 mmol) was used as a neutralizer in the reaction. 1H NMR
(CDCl3, 300 MHz): δ 13.14 (s, 1H, -OH), 8.73 (dd, 1H, J1 =
5.1, J2 = 1.6 Hz, pyridyl H ortho to N), 8.67 (dd, 1H, J1 = 5.0,
J2 = 1.6 Hz, pyridyl H ortho to N), 8.27 (dd, 1H, J1 = 7.7, J2 =
1.6 Hz, pyridyl H para to N), 8.17 (dd, 1H, J1 = 7.8, J2 = 1.6
Hz, pyridyl H para to N), 7.53 (t, 1H, J1 = 7.7, J2 = 5.1 Hz,
pyridyl H meta to N), 7.46 (t, 1H, J1 = 7.7, J2 = 5.0 Hz, pyridyl
H meta to N). IR (KBr, νmax, cm-1): 3141, 3036, 1627, 1593,
1564, 1495, 1399, 1008, 949, 748. Elemental analysis calcd.
(%) for C11H7N3O: C, 67.00; H, 3.58; N, 21.31. Found (%): C,
69.92.; H, 3.56; N, 21.36. MS: m/z = 197.10 (calcd.: 197.06).
9-Anilino-4,5-diazafluorene (L4): 1H NMR (CDCl3, 300
MHz): δ 8.81 (dd, 1H, J1 = 4.9, J2 = 1.5 Hz, pyridyl H ortho to
N), 8.65 (dd, 1H, J1 = 4.9, J2 = 1.6 Hz, pyridyl H ortho to N),
8.26 (dd, 1H, J1 = 7.8, J2 = 1.6 Hz, pyridyl H para to N), 7.43
(m, 3H, pyridyl H meta to N and Ar-H), 7.28 (t, 1H, J1 = 7.7,
J2 = 5.1 Hz, pyridyl H meta to N), 7.02 (m, 3H, Ar-H), 6.87
(dd, 1H, J1 = 7.8, J2 = 1.5 Hz, pyridyl H para to N). IR (KBr,
νmax, cm-1): 3045, 1656, 1592, 1561, 1401, 748, 710. Elemental
analysis calcd. (%) for C17H11N3: C, 79.36; H, 4.31; N, 16.33.
9-(4-Hydroxyanilino)-4,5-diazafluorene (L7): 1H NMR
(CDCl3, 300 MHz): δ 9.53 (s, 1H, -OH), 8.79 (dd, 1H, J1 =
4.9, J2 = 1.5 Hz, pyridyl H ortho to N), 8.67 (dd, 1H, J1 = 4.9,
J2 = 1.5 Hz, pyridyl H ortho to N), 8.27 (dd, 1H, J1 = 7.6, J2 =
1.5 Hz, pyridyl H para to N), 7.54 (t, 1H, J1 = 7.6, J2 = 4.9 Hz,
pyridyl H meta to N), 7.27 (t, 1H, J1 = 7.6, J2 = 4.9 Hz, pyridyl
H meta to N), 7.13 (dd, 1H, J1 = 7.6, J2 = 1.5 Hz, pyridyl H
para to N), 6.90 (m, 4H, Ar-H). IR (KBr, νmax, cm-1): 3144,
3037, 1638, 1592, 1561, 1504, 1401, 1276, 1230, 1165, 758,
708. Elemental analysis calcd. (%) for C17H11N3O: C, 74.71;
H, 4.06; N, 15.38. Found (%): C, 74.65; H, 4.00; N, 15.42.
MS: m/z = 272.85 (calcd.: 273.09).
9-(4-Carboxyanilino)-4,5-diazafluorene (L8): 1H NMR
(CDCl3, 300 MHz): δ 12.93 (s, 1H, -COOH), 8.82 (dd, 1H, J1
= 4.9, J2 = 1.5 Hz, pyridyl H ortho to N), 8.68 (dd, 1H, J1 =
4.9, J2 = 1.5 Hz, pyridyl H ortho to N), 8.29 (dd, 1H, J1 = 7.7,
J2 = 1.5 Hz, pyridyl H para to N), 8.02 (d, 2H, J = 8.6 Hz, Ar-
H), 7.56 (t, 1H, J1 = 7.7, J2 = 4.9 Hz, pyridyl H meta to N),
TABLE-1
RESULTS OF YIELD, MELTING POINT AND UV-VISIBLE SPECTRA OF L1-11
UV-VIS λmax (> 235 nm, ε × 104)a
No.
Yield (%)
m.p. (ºC)
78
82
80
87
89
85
90
81
93
85
83
195-196
208-210
>300
188-189
225-226
202-203.
>300
249 (2.40), 304 (0.99), 317 (1.01).
245 (2.45), 303 (0.98), 313 (1.13).
242 (2.41), 308 (1.00), 315 (0.96).
240 (2.40), 302 (0.95), 315 (1.02).
244 (2.56, 302 (0.98), 314 (1.13), 416 (0.20).
252 (3.80), 300 (1.44), 314 (1.04), 435 (0.29).
244 (2.69), 302 (1.15), 314 (0.97), 433 (0.26)
245 (2.73), 265 (2.51), 302 (1.01), 314 (0.91), 394 (0.16)
246 (3.24), 302 (1.15), 314 (1.01), 405 (0.20)
242 (2.03), 303 (1.22), 314 (1.18), 396 (2.50)
CH3CN: 303 (0.58), 385 (1.30), 406 (1.27), 562 (0.32)
L1
L2
L3
L4
L5
L6
L7
L8
L9
L10
L11
>300
216-217
188-189
>300
aL1-L10 in CHCl3 and L11 in CH3CN.

3392 Cang et al.
Asian J. Chem.
7.24 (t, 1H, J1 = 7.7, J2 = 4.9 Hz, pyridyl H meta to N), 7.17
(d, 2H, J = 8.6 Hz, Ar-H), 6.83 (dd, 1H, J1 = 7.7, J2 = 1.5 Hz,
pyridyl H para to N). IR (KBr, νmax, cm-1): 3098, 3032, 1702,
1702, 1663, 1598, 1566, 1398, 1259, 1164, 752, 723. Elemental
analysis: calcd. (%) for C18H11N3O2: C, 71.75; H, 3.68; N,
13.95. Found (%): C, 71.70; H, 3.63; N, 13.89. MS: m/z =
300.99 (calcd.: 301.09).
3100, 1616, 1594, 1557, 1496, 1404, 1334, 1095, 754, 740,
λmax (> 235 nm, ε): Elemental analysis: calcd. (%) for
C17H10N6O4: C, 56.36; H, 2.78; N, 23.20. Found. (%): C, 56.32;
H, 2.74; N, 23.25. MS: m/z = 362.14 (calcd.: 362.08).
Conclusion
This work has demonstrated an efficient and general
microwave irradiation protocol for the synthesis of schiff bases
derived from 4,5-diazafluorene-9-one under microwave irra-
diation using polystyrene sulfonic acid as a catalyst in aqueous
medium. The simple product isolation via filtration precludes
the use of a organic solvent thus culminating in an environ-
mentally benign aqueous protocol for the synthesis of schiff
bases derived from 4,5-diazafluorene-9-one.
1
9-(4-Chloroanilino)-4,5-diazafluorene (L9): H NMR
(CDCl3, 300 MHz): δ 8.83 (dd, 1H, J1 = 5.0, J2 = 1.5 Hz,
pyridyl H ortho to N), 8.70 (dd, 1H, J1 = 5.0, J2 = 1.5 Hz,
pyridyl H ortho to N), 8.26 (dd, 1H, J1 = 7.6, J2 = 1.5 Hz,
pyridyl H para to N), 7.43 (m, 3H, pyridyl H meta to N and
Ar-H), 7.07 (t, 1H, J1 = 7.7, J2 = 5.0 Hz, pyridyl H meta to N),
7.03 (dd, 1H, J1 = 7.8, J2 = 1.5 Hz, pyridyl H para to N), 6.95
(d, 2H, J = 8.2 Hz, Ar-H). IR (KBr, νmax, cm-1): 3046, 1656,
1592, 1561, 1400, 1087, 839, 749, 730. Elemental analysis
calcd. (%) for C18H10N3Cl: C, 69.99; H, 3.45; N, 14.40. Found
(%): C, 69.93; H, 3.46; N, 14.45. MS: m/z = 291.01 (calcd.:
291.06).
ACKNOWLEDGEMENTS
This work was funded by the Applied Basic Research
Project ofYancheng Institute of Technology of Chian, Jiangsu
(Grant No. XKR2011005).
1
9-Phenylhydrazone-4,5-diazafluorene (L10): H NMR
REFERENCES
(DMSO, 300 MHz): δ 10.72 (s, 1H, -NH), 8.90 (d, 1H, J = 7.7
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ortho to N), 8.29 (dd, 1H, J = 7.7Hz, pyridyl H para to N),
7.59 (m, 3H, pyridyl H meta to N and Ar-H), 7.45 (m, 3H,
pyridyl H meta to N and Ar-H), 7.10 (m, 1H, Ar-H). IR (KBr,
nmax, cm-1): 3385, 3047, 1652, 1591, 1560, 1404, 750, 713.
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N, 20.58. Found (%): C, 74.92; H, 4.41; N, 20.64. MS: m/z =
272.14 (calcd.: 272.11).
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9-(2,4-Dinitrophenylhydrazone)-4,5-diazafluorene
1
(L11): H NMR (DMSO, 300 MHz): δ 12.01 (s, 1H, -NH),
8.96 (s, 1H, Ar-H), 8.84 (d, 1H, J = 5.0Hz, pyridyl H ortho to
N), 8.76 (d, 1H, J = 4.9, Hz, pyridyl H ortho to N), 8.59 (d,
1H, J = 7.8Hz, pyridyl H para to N), 8.53 (d, 1H, J = 7.8 Hz,
pyridyl H para to N), 8.42 (m, 2H, Ar-H), 7.73 (t, 1H, J1 =
7.7, J2 = 5.0 Hz, pyridyl H meta to N), 7.56 (t, 1H, J1 = 7.8, J2
= 5.0 Hz, pyridyl H meta to N). IR (KBr, νmax, cm-1): 3414,
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