In 1997 we have described the first example of the acid-catalyzed intramolecular reaction of an isothiocyano group with the furan moiety. We found that treatment of 2-[bis(2-furyl)methyl] aryl isothiocyanates with perchloric acid in 1,4-dioxane led to the formation of 2,4-difuryl-4H-3 ,1-benzothiazines derivatives (Scheme [1] ). [14] In this case the intramolecular ipso substitution followed by furan ring migration occurred instead of cyclic thioamide formation which is ...