Flow-mediated synthesis of Boc, Fmoc, and Ddiv monoprotected diamines.

A series of monoprotected aliphatic diamines (21 examples) were synthesized via continuous flow methods. The carbamates and enamines were obtained in 45-91% yields using a 0.5 mm diameter PTFE tubular flow reactor. Using readily accessible protecting group precursors, the procedure serves as an attractive alternative to existing batch-mode synthetic routes by providing direct, multigram access to N-Boc-, N-Fmoc-, and N-Ddiv-protected compounds with productivity indexes of 1.2-3.6 g/h.