Preparation and reactivity of N-phenyl- and N-methyl-o-diazoacetyl-benzenesulphonamide. A novel synthesis of benzothiazine dioxides

Abstract

o-Diazoacetylbenzenesulphonyl chloride reacts with aniline and with methylamine to give the corresponding sulphonamides (VIII; R = Ph or Me). With formic acid the diazo-ketones cyclise to give, respectively, 2,3-dihydro-2-phenyl- and -2-methyl-4H-1,2-benzothiazin-4-one 1,1-dioxide (X; R = Ph or Me). Toluene-p-sulphonic acid effects a similar cyclisation but the thiazine dioxides are in this case accompanied by benzisothiazole derivatives (XIII; R = Ph or Me). Thermolysis of the diazo-ketones also provides the thiazine dioxides along with their 3-oxo-isomers (XIX) arising by cyclisation of the keten which is the product of Wolff rearrangement. Photolysis of o-diazoacetyl-N-methylbenzenesulphonamide leads only to the Wolff rearrangement product.