Helical-Shaped Bis-1,4-benzoxathiines through an Inverse-Electron-Demand Hetero-Diels-Alder Reaction of ortho-Thioquinones

The reaction of transient ortho-thioquinones, which act as electron-poor dienes, with properly designed bis-dienophiles leads to the formation of helical-shaped bis-benzoxathiine cycloadducts with complete control of the regiochemistry and the relative stereochemistry. Bis-benzoxathiines were the result of two consecutive inverse-electron-demand cycloaddition processes with stereospecific approach of the diene anti to the bis-dienophile. The helical-shaped structure of the final products was demonstrated spectroscopically and confirmed by single-crystal X-ray analysis.