Synthesis of 3a,4-Dihydro-8-substituted-3H-isoxazolo [c-4,3]thiapyrano[5,6-3,2]quinolines

Abstract

Condensation of 2-chloro-3-formylquinoline 1a-c with allylthiol 2 afforded 2-allysulfanyl-3-formylquinolines 3a-c. Oximation followed by oxidation of 3a-c with NaOCl or chloramine-T, in cold or mercuric acetate resulted in the formation of respective nitrile oxides, which underwent insituintramolecular 1,3-dipolar cycloaddition reaction and afforded the title compounds 5a-c in high yield.