Cycloaddition Reactions of Sulfo-Biginelli Derived Thiadiazines

Modified Sulfo-Biginelli conditions, including a new one-pot process from sulfamide and α,β-unsaturated carbonyl compounds, were developed to access diverse 1,2,6-thiadiazine-1,1-dioxides. These electron-deficient heterocyclic building blocks underwent highly regio- and stereoselective [4 + 2] and [3 + 2] cycloadditions with azomethine ylides, alleneoates, and methylene cyclopropanes to provide fused, bridged and spirocyclic thiadiazines. Chiral phosphine catalysis can be used to generate enantiomerically enriched annulation products. This study illustrates the synthetic versatility of cyclic sulfamides and their potential for the discovery of novel heterocyclic scaffolds.