An improved synthesis of 4-chlorocoumarin-3-sulfonyl chloride and its reactions with different bidentate nucleophiles to give pyrido[1′,2′:2,3]- and thiazino[3′,2′:2,3]-1,2,4-thiadiazino[6,5-c] benzopyran-6-one 7,7-dioxides, - A. Jashari, E. Hey-Hawkins, B. Mikhova, G. Draeger, E. Popovski (My University, 2007)