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|Title:||Facile synthesis of alkoxyphthalimide derivatized benzimidazole assembled pyrazoles, pyrimidines and isoxazoles, via common intermediate chalcone|
Talesara, G L
|Abstract:||In the present investigation, synthesis of 2-(3-aryl-2-phenyl-3,4-dihydropyrazol-5-yl)-1-N-alkoxyphthalimidobenzimidazole 9a-h, 4-(1-N-alkoxyphthalimidobenzimidazol-2-yl)-6-arylpyrimidin-2-amine 10a-h and 2-(5-aryl-4,5-dihydroisoxazol-3-yl)-1-N-alkoxyphthalimidobenzimidazole 11a-h are described. Mild dichromate oxidation of 1-benzimidazol-2-yl-ethanol 1 gives 1-benzimidazol-2-yl-ethanone 2 which on Clasien condensation with various aromatic aldehydes yields the corresponding 3-aryl-1-(benzimidazol-2-yl)-prop-2-en-1-one 3a-d derivatives. Compound 3a-d act as key intermediates for all the three series of final compounds. In one pathway 3a-d is converted to its alkoxyphthalimide derivatives 5a-h by condensation with ω-bromoalkoxyphthalimides 4a-b, which cyclize with PhNHNH2/pyridine, guanidine nitrate/10% NaOH and hydroxylamine hydrochloride/CH₃COOH to give 9a-h, 10a-h and 11a-h respectively. In an alternative route, reaction of 3a-d with all the three reagents affords 2-(3-aryl-2-phenyl-3,4-dihydropyrazol-5-yl)benzimidazole 6a-d, 4-(benzimidazol-2-yl)-6-arylpyrimidin-2-amine 7a-d and 2-(5-aryl-4,5-dihydroisoxazol-3-yl)benzimidazole 8a-d which on condensation with ω-bromoalkoxyphthalimides 4a-b give the final compounds 9a-h, 10a-h and 11a-h. Structure elucidations of all the compounds have been accomplished by elemental analysis, IR, ¹H NMR and mass spectral data.|
|Appears in Collections:||IJC-B Vol.47B(07) [July 2008]|
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