Functional diamines with cationically polymerizable groups were successfully prepared in one-step by the chemoselective reaction of 4,4′-diamino-3,3′-dicarboxydiphenylmethane (1) using 1,8-diazabicyclo-[5.4.0]-7-undecene (DBU). The reaction of 1 with propargyl bromide (2a), 2-chloroethyl vinyl ether (2b), and 2-bromomethyl-1,4,6-trioxa-spiro[4.4]nonane (2c) using DBU proceeded chemoselectively under mild conditions without any protection of the amino group to produce the corresponding diamines (3a-3c) in high yields.