Many enamines 3 from 9-formylfluorene (1) were easily prepared by the reaction of 1 with several aliphatic, aromatic, alicyclic and heterocyclic secondary amines 2 in aqueous ethanol at room temperature. The reaction of 9-morpholinomethylenefluorene (3i), a typical 3, with bromine in dichloroethane gave the corresponding iminium bromide (4). The hydrolysis of 4 with water afforded 9 -bromo- 9 -formylfluorene (6). 2,2-Biphenylene-1, 1-dialkoxyethylene 10 was obtained from 9 -bromo- 9 -formylfluorene dialkyl acetal which was derived from 6 with alkyl orthoformate in alcohols under acidic conditions. Compound 10 was also obtained from 4 via 2, 2-biphenylene-1, 1-dialkoxy- 1 -morpholinoethane. Furthermore, the reactions of 3i with ethyl azidoformate and with P-toluenesulfonyl azide were investigated.