The α-thiocarbocation generated from the Pummerer reaction of an o-heteroaroyl- substituted sulfoxide is intercepted by the adjacent keto group to produce an α-thio- substituted heteroaromatic isobenzofuran. In the presence of a suitable dienophile, the reactive o-xylylene undergoes a Diels-Alder cycloaddition followed by an acid-catalyzed ring-opening and aromatization to give heteroaromatic naphthalene derivatives. This one- ...