P. Ramesh

Solid-supported synthesis of isoxazole-substituted 1,4-dihydropyridines by modified hantzsch method and their aromatization

Abstract The synthesis of isoxazole‐substituted Hantzsch 1,4‐dihydropyridines has been achieved by modified Hantzsch procedure for the first time by utilizing ketoamides in place of keto esters on a neutral alumina support in excellent yields. These 1,4‐dihydropyridines are aromatized to the corresponding pyridines in high yields by using bismuth subnitrate (BiONO3) adsorbed on acidic alumina at ambient temperature.

Synthesis of 2([Methyl-5-[(E)-2-aryl-1-ethenyl]-4-isoxazolyl]imino)-1,3-thiazolan-4-ones and Their Mannich Bases

Isoxazolyl chloroacetamides (2) were obtained from 4-amino-3-methyl-5-styrylisoxazoles (1) on reaction with chloroacetyl chloride. Cyclocondensation of 2 with NH4SCN yielded 2([-methyl-5-(E)-2-aryl-1-ethenyl]-4-isoxazolylimino)-1,3-thiazolan-4-ones(3). Mannich reaction of 3 with formaldehyde and secondary amines gave isoxazolyl thiazolidinone Mannich bases (4 and 5).

Synthesis of 3-[4-({Methyl-5-[(E)-2-phenyl-1-ethenyl]-4-isoxazolyl}amino)-1,3-thiazol-2-yl]-2-aryl-1,3-thiazolan-4-ones as Potential Biodynamic Agents

A series of isoxazolyl thiazolyl thiazolidinones ( 4a–h ) were synthesized starting from isoxazolyl chloroacetamide 1 . Compound 1 upon heating with thiourea in ethanol furnished N4-{3-methyl-5-[(E)-2-phenyl-1-ethenyl]-4-isoxazolyl]-1,3-thiazole-2,4-diamine 2 . Condensation of 2 with aromatic aldehydes afforded corresponding Schiff bases ( 3a–h ), which undergo cyclocondensation on treatment with mercaptoacetic acid to give 3-[4-({methyl-5-(E)-2-phenyl-1-ethenyl]-4-isoxazolyl] amino)-1,3-thiazol-2-yl]-2-aryl-1, 3-thiazolyl –4-ones ( 4a–h ) in excellent yields. Structures of all the synthesized compounds have been established by elemental analyses, IR, 1H NMR, and mass spectral data.