AbstractThe reaction of thionylaniline with dicyclopentadiene has afforded the Diels–Alder adduct which has been oxidized into the corresponding sulfonamide bearing a benzothiazine moiety. Molecular and crystal structure of the sulfonamide has been elucidated via single-crystal X-ray diffraction analysis. Higher reactivity of the olefin functionality of the norbornene fragment has been found; the formation of two structural isomers has been revealed.