3-(Benzimidazol-2-yl)- and 3-(benzothiazol-2-yl)thiochromones, 3-Di(indol-3-yl)methylthiochromones, 3-Formyl- and 3-cyanothiochromones, Anils and phenylhydrazones of 3-formyl- and 2-amino-3-formylthiochromones, Nucleophilic addition, Regioselectivity