The [4 + 2]cycloaddition Reactions of Aromatic Thiones With Maleic Anhydride, Norbornene, and Norbornadiene

The reactions of aryl 1-naphthyl thiones and aryl 2-naphthyl thiones with maleic anhydride, norbornene, and norbornadiene gave the 1,4-cycloadducts containing 3,4-dihydro-2 H-thiopyran rings. 7H-Benz[de]anthracene-7-thione also reacted with norbornene and norbornadiene to give similar 1,4-cycloadducts. In the reaction of aryl phenyl thiones with norbornene, initially formed cycloadducts rearranged to aromatized compounds. In these reactions, the aromatic thiones reacted with the olefins as a heterodiene system.