Abstract 4-Lithio-Nt-butylpyridine-3-sulphonamide reacted with benzophenone and carbon dioxide respectively to give the corresponding intermediates which on appropriate treatment gave isothiazolo [5, 4-c] pyridin-3-one 1, 1-dioxides. Metalation of 2-and 4-(N, N- dialkylaminosulphonyl) pyridines with lithium diisopropylamide (LDA) gave anions which reacted with benzophenone to give carbinols which thermally cyclised to 1, 2-oxathiolo [3, ...