Heteroaromatic thioketones react with maleic anhydride, norbornene, acrylonitrile, and styrene to form the Diels-Alder adducts, respectively. The thioketones also undergo cycloaddition with 2-chloroacrylonitrile followed by elimination of hydrogen chloride to give heteroaromatic analogues of o-quinodimethan derivatives. In these reactions, the thioketones act as a heterodiene on the dienophiles to give [4+ 2] cycloadducts ...