|Abstract: ||Condensation of aromatic aldehydes,
malononitrile and thioglycolic acid gives 5-amino-3-oxo-7-substitutedphenyl-2-substitutedarylidene-2,3-dihydro-7H-[1,3]thiazolo[3,2-a] pyridine-6,8-dicarbonitrile 1a-e.
This acts as key intermediate for two series of final compounds 4a-e and 7a-e. In the first route compounds 1a-e are refluxed with hydroxylamine hydrochloride to yield
tricyclic compound 8-amino-3,6-bis(substitutedphenyl)-1,3,3a,9a-tetrahydro-6H-isoxazolo[3',4':4,5][1,3]thiazolo[3,2-a]pyridin-5,7-dicarbonitrile 2a-e. These when condensed with isatin
give the corresponding Schiff bases 3a-e.
Condensation of 3a-e with
bromoethoxyphthalimide give the final products 8-[(1N-ethoxyphthalimido-2-oxo-1,2-dihydro-3H-indol-3-ylidene)amino]-3,6-bis(substitutedphenyl)-1,3,3a,9a-tetrahydro-6H-isoxazolo[3',4':4,5] [1,3]thiazolo[3,2-a]pyridine-5,7-dicarbonitrile 4a-e. In the second pathway NH2
group of compounds 1a-e is protected
by bezoylation to furnish 5a-e.
These ,-unsaturated compounds (ring chalcones) when treated with hydrazine
hydrate undergo cyclization to form N-(5,7-dicyano-3,6-diphenyl-2H,6H-pyrazolo[3',4':4,5][1,3]thiazolo[3,2-a] pyridine-8-yl)benz- amide 6a-e. Active hydrogen of their pyrazole
ring is replaced by ethoxyphthalimido moiety to afford the final compounds N-(5,7-dicyano-3,6-bis
(substitutedphenyl)-2N-ethoxyphthalimido-2H,6H-pyrazolo[3',4':4,5][1,3]thiazolo[3,2-a] pyridine-8-yl)benzamide 7a-e. The structures of synthesized
compounds have been assigned on the basis of elemental analysis and spectral