Reaction of N-(5-R-furan-2-ylmethylidene)anilines with difluorocarbene, generated in CF 2 Br 2 /Pb*/Bu 4 NBr/ultrasound system proceeds via 1,5-electrocyclization of intermediate azomethine ylides to give 6,6-difluorocyclopropa[b]furo[2,3-c]pyrrol-4(5H)-one or/and 4,4,6,6-tetrafluorocyclopropa[b]furo[2,3-c]pyrrole derivatives. Thermolysis of these compounds under solvent-free conditions gives rise
                                    N-(5-R-
呋喃-2-基亚甲基)
苯胺与
二氟卡宾在CF 2 Br 2 /Pb*/Bu 4 NBr/超声系统中通过中间体偶氮甲碱叶立德的1,5-电环化反应生成6, 6-二
氟环丙[b]
呋喃[2,3-c]
吡咯-4(5H)-一或/和4,4,6,6-四
氟环丙[b]
呋喃[2,3-c]
吡咯衍
生物。这些化合物在无溶剂条件下的热解产生高产率的 2,5-二取代 7-
氟-4,5-二氢
呋喃 [3,2-c] 
吡啶-4(5H)-酮。