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MADAwALI et al., Orient. J. Chem., Vol. 34(3), 1633-1637 (2018)
particular,bezimidazolo-pyrimidine derivatives were
found as strong antimicrobial agents10, 11
with aqueous ammonia (1:1).Then the solid product
filtered, washed with water and dried. The product
further recrystallized from ethyl acetate. m. p.
198-99oC16.
.
Antimicrobial agents are one of the most
important weapons in the resistance of infection
caused by bacterial strains. In the last few years,
increase the resistance of micro-organisms toward
antimicrobial agents is a serious health problem,
so there is a need for safe, effective and novel
antimicrobial agents12.
General procedure for the synthesis of chalcone
derivative of 6-chlorobenzimidazoles (Iva)
To a reaction mixture of 6-chloro-2-
acetylbenzimidazole(10 mmol, 1.94 g) in aqueous
NaOH (10%, 30 ml), respective 2-chloroquinoline-
3-carbaldehyde (10 mmol, 1.91 g) were added and
agitated for 30 min.at an ambient temperature. After
the conclusion of the reaction the solid product was
filtered, washed and dried with water.Further, it was
By seeing impressive biological profile of
benzimidazoles, quinolines and pyrimidines and also
with respect to our work in synthesis and evaluation
of biologically active new heterocycles, we planned
to synthesize the new series of pyrimidines of
6-chlorobenzimidazoles as potential antimicrobial
agents.
recrystallized from ethanol17, 18, 19
.
Chalcone derivatives of 6-chlorobenzimidazoles
(Iva-k)
Iva: Yellow solid, yield 76%, m.p. 252-
254oC; IR (KBr): 3300, 3050, 2800, 1700, 1600,
1522, 1475,1250, 875, 800,750 cm-1; 1H NMR(CDCl3,
400 MHz): δ 7.69-7.71 (d, 1H,CO-CH=CH), 7.71-
7.69 (d, J=8Hz), 7.27-8.29 (m, 8H, ArH), 8.01-7.99
(d, J=8Hz), 8.65 (s, 1H, NH).
MATERIALS ANd METHOdS
All the solvents and reagents were bought
and used as such. The fusion points are examined
by open capillary tube method and are uncorrected.
By the use of KBr pellet technology IR spectra of
compounds on Shimadzu FTIR spectrometer 8400
S were noted. NMR spectra were seized on Bruker
Avance II of 400 NMR spectrometer.
Ivb: Yellow solid, yield 68%, m.p. 242-
244oC; IR (KBr): 3350, 3100, 2800, 1700, 1600,
1550, 1475, 1350, 775, 700 cm-1; 1H NMR(CDCl3,
400 MHz):δ 2.76 (s, 3H, CH3), 7.48-7.50 (d, 1H,CO-
CH=CH), 7.50-7.48 (d, J=8Hz), 7.27-7.78 (m, 8H,
ArH), 7.70-7.68 (d, J=8Hz), 8.65 (s, 1H, NH).
Synthesis of 6-chloro-2-(a-hydroxyethyl)benzimidazole(II)
An equimolar amount of 4-chloro-O-
phenylenediamine (0.01 mole) and lactic acid
(0.01 mole), 4N HCl are refluxed in synthetic
microwave oven with the intensity of 65% (450
w) for a period of 190 minutes. The conclusion
of the reaction was supervised by TLC, and then
the reaction mixture was neutralized with sodium
bicarbonate. The filtered product was washed
and dried with water. Further, it was purified by
Ivc: Yellow solid, yield 72%, m.p. 248-
250oC; IR (KBr): 3300, 3050, 2800, 1700, 1600,
1500, 1450, 1250, 775, 700 cm-1; 1H NMR(CDCl3,
400 MHz): δ 3.91 (s, 3H, OCH3), 7.482-7.487
(d, 1H,CO-CH=CH), 7.487-7.481 (d, J=2.4Hz),
7.16-7.94 (m, 8H, ArH), 7.94-7.91 (d, J=12Hz), 8.59
(s, 1H, NH)
General procedure for the synthesis of
pyrimidines of 6-chlorobenzimidazoles(va)
To a refluxing mixture of chalcone(3.68 g,
recrystallization from ethanol. m. p. 194-95oC13, 14, 15
.
Synthesis of 6-chloro-2-acetylbenzimidazole(III)
To a reaction mixture of 6-chloro-2-(α-
0.01 mol) and guanidine nitrate (1.80 g, 0.01 mol) in
ethanol (25 ml) was added an aqueous solution of
sodium hydroxide (40%, 5 ml) portion wise during a
period of 3 hours.Refluxing was continued further for
7 hours. The solvent was made to half of its volume.
And on cooling, the solid product was separated out.
Further, it was filtered, washed with cold aqueous
ethanol followed by water and dried.Pure product was
obtained by recrystallization from absolute ethanol.
hydroxyethyl)benzimidazole (9.8g, 50 mmol) in
Dilute H2SO4 (5% ; 40 ml) with stirring, a solution
of K2Cr2O7 (44g, 150 mmol) in aqueous H2SO4
(25%, V/V; 80 ml) was taken up during a period of
20 minutes drop wise.Continuing the agitation for
2 h, at an ambient temperature, the solid (which is the
chromium complex) separates out, was suspended
in 50 ml of water. The pH up to 6-6.5 was adjusted