Synthesis and antimicrobial evaluation of ethoxyphthalimide derivatized spiro [indole-3,5′-(1,3)thiazolo(4,5-<i style="">c</i>)isoxazol]-2(1<i style="">H</i>)-ones <i style="">via</i> ring closure metathesis

Abstract

368-373The synthesis of 3′-{(4-substituted phenyl-1-N-ethoxy­phthali­mido-6′-pyridin-2-yl}-3,3a′-dihydro-6′H-spiro[indole-3,5′-[1,3]­thi­a­zolo­[4,5-c]­isoxazol]-2(1H)-ones 6a-d is carried out &nbsp;through a five step pathway starting from acid catalyzed condensation of 2-aminopyridine with isatin yielding 3-(pyridin-2-ylimino)-1,3-dihydro-2H-indol-2-one 1 which on reaction with thioacetic acid in the presence of anhydrous ZnCl2 give 3′-pyridin-2-yl-4′H-spiro[indole-3,2′-[1,3]­thiazolidine]-2,4′(1H)-dione 2. Reaction of 2 with various aralde­hydes 3a-d affords the corresponding 5′-[(4-substituted phenyl)­methylidene]-3′-pyridin-2-yl-4′H-spiro­[indole-3,2′-[1,3]­thiazoli­dine]-2,4′(1H)-diones 4a-d. These chal­cones are further cyclised with hydroxylamine hydrochloride to furnish 3′-(4-substituted phenyl)-6′-pyridin-2-yl-3,3a′-dihydro-6′H-spiro[indole-3,5′-[1,3]thia­zolo[4,5-c]isoxazol]-2(1H)-ones 5a-d which are subsequently condensed with ω-bromo­ethoxy­phthalimide to yield the targeted compounds 6a-d. Structural confirmation of the synthesized compounds has been accomplished by IR, 1H NMR, and mass spectral data. Final compounds have been screened for their antimicrobial activity.</b