sulfuric acid) at 60 °C for 12 hours. The two stirred solutions were extracted with dichloromethane and washed with aqueous sodium bicarbonate, and then analyzed by HPLC. As shown in Figure , the vicinal diamine 2a was almost completely converted into the imine 4a whereas the rearrangement benzofused Nheterocycle 3a was intact. In addition, we also detected aniline by using HR-MS (Figure ) when vicinal diamine 2a was transformed into the imine 4a. This control result indicated that the imine 4a was produced from the small amount of vicinal diamine 2a in the presence of sulfuric acid under thermal irradiation in the bulk phase.