A facile synthesis of annulated azolo[c][1,2,4]thiadiazine S,S-dioxides

Condensations of o-halo-substituted benzenesulfonyl chlorides with 3-aminoazoles give the corresponding azolo[c][1,2,4]benzothiadiazine S,S-dioxides. o-Fluorobenzenesulfonyl chlorides and o-bromobenzenesulfonyl chlorides bearing a nitro group are reactive enough to give the desired azolo[c][1,2,4]benzothiadiazine S,S-dioxides in a one-pot, base-promoted reaction. In all other cases, open-chain sulfonylated 3-aminoazole intermediates are isolated. The latter are converted into the title compounds upon addition of a copper(I) catalyst.