Synthesis of alkylated aminofluorenes by palladium-catalyzed substitution at halofluorenes

New N-substituted 2-amino-9,9-dialkylfluorenes optionally bearing electron-withdrawing substituents such as nitro or cyano in position 7 can be synthesized starting from 2-halo-9,9-dialkylfluorenes by Pd-catalyzed substitution with amines. Chiral amino groups can be introduced by this method too. 2-N,N-Dimethylamino-7-nitro-9H-fluorene was obtained in a convenient way by reductive amination. The N-substituted 2-amino-7-nitro-9H-fluorenes are promising candidates for fluorescence probes for femtosecond solvation dynamics.