£¸¡B Pyrolysis of 2-methoxy-2¡¦-methylthiostilbene (22a) and 2,2¡¦-di(methylthio)stilbene (22b) gave not only polycyclic aromatic hydrocarbons (PAH) 17¡B18¡B2, but also the products 33, 34. In addition, photolysis of 22a¡B22b¡B2,2¡¦-dimethoxy stilbene (13) gave photocyclic products 31¡B40¡B12¡B45¡B46. ¤G¡B Pyrolysis of 2-dimethylamino-N-(arenylidene)anilines (20a-f) gave not only 1-methyl-2-arylbenzimidazole (25a-f), but also gave 2-arylquinoxaline (26a-e). Furthermore, compound 20f gave 37 and 25f, but didn't give 26f. ¤T¡B Pyrolysis of benzoic 1,2-dimethyl-3-indolyl anhydride gave 1,2-dimethylindole (19) ¡B3-methylquinoline (30) ¡B4-methylquinoline (31).