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 <i>N</i>‐Alkenyl‐2‐carbodiimidobenzenesulfonamides as Key Intermediates

Abstract

Abstract 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‐(R 2 ‐substituted amino)‐2 H ‐1,2,4‐benzothiadiazine 1,1‐dioxides by internal nucleophilic addition. Subsequent (tandem) cyclizations through iodoamination or hydroamination with Hg II /NaBH 4 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 &amp; Co. KGaA, 69451 Weinheim, Germany, 2008)