Med Chem Res (2012) 21:1451–1470
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General procedure for the synthesis of N1-benzoylated
schiff bases of isoniazid
6.89–6.91 (s, 1H, OH), 7.06–7.08 (s, 1H, CH of C2 of
phenyl ring), 7.97 (d, 2H, CH of C5 and C6 of phenyl ring),
8.37 (d, 2H, CH of C2 and C6 of pyridine ring), 8.79 (d, 2H,
CH of C3 and C5 of pyridine ring), 11.71 (s, 1H, NH). IR
(KBr pellets) m cm-1: 3254.34 (NH str., amide), 3093.31
(CH str., aromatic), 2973.58 (CH str., aliphatic), 1644.86
(C=O str., amide), 1593.74 (C=C str., skeletal phenyl
nucleus), 1276.12 (C–O–C str., aralkyl ether), 1255.95 (OH
bending), 845.53 (CH out of plane bending, 4-substituted
pyridine).
The Schiff base (0.01 mol) obtained above was dissolved
in dichloromethane to which an equimolar amount of
benzoyl chloride, obtained by refluxing benzoic acid with
thionyl chloride, was added with stirring for 2 h. The crude
products were separated out by evaporating dichloro-
methane and recrystallized from ethanol to yield the pure
compounds.
Benzoic acid N0-(4-hydroxy-3-methoxy-benzylidene)-N-
(pyridine-4-carbonyl)-hydrazide (10)
Isonicotinic acid-3,4,5-trimethoxybenzylidene
hydrazide (4)
Mp (ꢁC) 230–233; Yield—57.8%; 1H NMR (400 MHz,
DMSO) d ppm: 3.70 (s, 3H, OCH3), 3.84 (s, 3H, OH),
7.28–7.38 (m, 5H, CH of phenyl ring), 7.46–7.50 (m, 3H, CH
of benzylidene ring), 7.70 (s, 1H, CH of N=CH), 7.91–7.94
(d, 2H, CH of C3 and C5 of pyridine ring), 8.77 (d, 2H, CH of
C2 and C6 of pyridine ring). IR (KBr pellets) m cm-1: 3414.15
(OH str.), 3036.09 (CH str., aromatic), 2904.92 (CH str.,
aliphatic), 1680.07 (C=O str., acyl group), 1597.13 (C=O
str., amide), 1513.22 (C=C str., skeletal phenyl nucleus),
1285.61 (C–O–C str., aralkyl ether), 814.96 (CH out of plane
bending, 4-substituted pyridine).
Mp (ꢁC) 205–208; Yield—80.7%; 1H NMR (400 MHz,
DMSO) d ppm: 3.36 (s, 9H, OCH3), 7.21–7.23 (s, 2H, CH
of C2 and C6 of trimethoxy phenyl ring), 7.83–7.84 (d, 2H,
CH of C3 and C5 of pyridine ring), 8.44 (s, 1H, CH of
N=CH), 8.73–8.76 (d, 2H, CH of C2 and C6 of pyridine
ring), 11.91 (s, 1H, NH). IR (KBr pellets) m cm-1: 3168.22
(NH str., amide), 2983.04 (CH str., aliphatic), 1682.00
(C=O str., amide), 1583.63 (C=C str., skeletal phenyl
nucleus), 1248.96 (C-O-C str., aralkyl ether), 858.36 (CH
out of plane bending, 4-substituted pyridine).
Isonicotinic acid-4-methylbenzylidene hydrazide (5)
Benzoic acid N0-(4-methylsulfanyl-benzylidene)-N-
(pyridine-4-carbonyl)-hydrazide (12)
Mp (ꢁC) 198–201; Yield—84.6%; 1H NMR (400 MHz,
DMSO) d ppm: 3.28 (s, 3H, CH3), 6.72–6.95 (m, 4H, CH
of phenyl ring), 7.76–7.77 (d, 2H, CH of C3 and C5 of
pyridine ring), 8.32 (s, 1H, CH of N=CH), 8.68–8.69 (d,
2H, CH of C2 and C6 of pyridine ring), 11.90 (s, 1H, NH).
IR (KBr pellets) m cm-1: 3177.86 (NH str., amide), 2935.78
(CH str., aliphatic), 1682.96 (C=O str., amide), 1583.63
(C=C str., skeletal phenyl nucleus), 1240.0 (C–O–C str.,
aralkyl ether), 835.21 (CH out of plane bending, 4-substi-
tuted pyridine).
Mp (ꢁC) 226–229; Yield—45.8%; 1H NMR (400 MHz,
DMSO) d ppm: 2.48 (s, 3H, SCH3), 7.11–7.20 (m, 3H, CH
of C3, C4 and C5 phenyl ring), 7.34–7.37 (d, 2H, CH of C2,
and C6 phenyl ring), 7.62–7.64 (d, 2H, CH of C3 and C5
of benzylidene ring), 7.91–7.93 (d, 2H, CH of C2 and C6 of
benzylidene ring), 8.21–8.23 (d, 2H, CH of C3 and C5 of
pyridine ring), 8.52 (s, 1H, CH of N=CH), 8.86–8.87 (d,
2H, CH of C2 and C6 of pyridine ring). IR (KBr pellets) m
cm-1: 3014.87 (CH str., aromatic), 1667.53 (C=O str., acyl
group), 1596.16 (C=O str., amide), 1497.79 (C=C str.,
skeletal phenyl nucleus), 609.53 (C–S str.), 732.98 (CH out
of plane bending, 4-substituted pyridine).
Isonicotinic acid-1-H-indol-3lmethylene hydrazide (8)
Mp (ꢁC) 225–228; Yield—61.9%; 1H NMR (400 MHz,
DMSO) d ppm: 7.07–7.16 (m, 2H, CH of C5 and C6 of
indole ring), 7.36–7.38 (m, 2H, CH of C4 and C7 of indole
ring), 7.53–7.54 (m, 2H, CH of C2 of indole ring),
7.80–7.81 (d, 2H, CH of C3 and C5 of pyridine ring), 8.60
(s, 1H, CH of N=CH), 8.68–8.71 (d, 2H, CH of C2 and C6
of pyridine ring), 11.24 (s, 1H, NH of indole), 11.57 (s, 1H,
NH of hydrazide). IR (KBr pellets) m cm-1: 3173.04 (NH
str., amide), 3052.48 (CH str., aromatic), 2940.61 (CH str.,
aliphatic), 1634.74 (C=O str., amide), 1428.35 (NH str.,
indole ring), 739.73 (CH out of plane bending, indole ring),
847.75 (CH out of plane bending, 4-substituted pyridine).
Benzoic acid N0-(4-methyl-benzylidene)-N-(pyridine-4-
carbonyl)-hydrazide (14)
Mp (ꢁC) 220–223; Yield—62.7%; 1H NMR (400 MHz,
DMSO) d ppm: 2.31 (s, 3H, CH3), 7.07–7.49 (m, 5H, CH
of phenyl ring), 7.59–7.61 (d, 2H, CH of C3 and C5
of benzylidene ring), 7.91–7.93 (d, 2H, CH of C2 and C6 of
benzylidene ring), 8.56–8.57 (d, 2H, CH of C3 and C5 of
pyridine ring), 8.68 (s, 1H, CH of N=CH), 8.93–8.94 (d,
2H, CH of C2 and C6 of pyridine ring). IR (KBr pellets)
123