Selective Cycloaddition Reactions of Sulfo-Biginelli Derived 1,2,6-Thiadiazines

Modified sulfo-Biginelli conditions were developed to access dihydro-1,2,6-thiadiazines that were further functionalized and oxidized to 1,2,6-thiadiazines. These electron-deficient heterocyclic building blocks were subjected to regio- and stereoselective [4+2] and [3+2] cycloadditions with an electron-rich methylene cyclopropane, non-stabilized azomethine ylides, and alleneoates to provided novel bridged and fused bicyclic thiadiazines. This study illustrates the versatility of cyclic sulfamides and demonstrates the potential for a broad range of new applications of this scaffold in heterocyclic chemistry.