Synthesis of Diazaheterocyclic Ring‐Fused 1,2,4‐Benzothiadiazine 1,1‐Dioxides by a Sequential Aza‐Wittig/NH‐Addition Cyclization/Nucleophilic Ring‐Closure Methodology with N‐Alkenyl‐2‐carbodiimidobenzenesulfonamides as Key Intermediates.

Treatment of N-alkenyl-2-azidobenzenesulfonamides with triphenylphosphane and subsequent subjection of the resulting iminophosphoranes to aza-Wittig reactions with isocyanates generated functionalized carbodiimides, which spontaneously underwent cyclization to form 2-alkenyl-3-(R2-substituted amino)-2H-1,2,4-benzothiadiazine 1,1-dioxides by internal nucleophilic addition. Subsequent (tandem) cyclizations through iodoamination or hydroamination with HgII/NaBH4 produced a variety of diazaheterocyclic ring-fused benzothiadiazine dioxides. In one case a methano-bridged benzothiatriazabicyclotridecanone was obtained. The scope and limitations of these cyclizations are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)