An efficient and eco-friendly protocol for the chemoselective N-benzyloxycarbonylation of amines was described. The reaction of amines with benzyl chloroformate (Cbz-Cl) in the presence of PEG-600 at room temperature afforded the corresponding N-Cbz derivatives in excellent yields. The method is applicable to the N-Cbz protection of aliphatic (acyclic and cyclic) and aromatic amines.
[Griffin, Roger J.; Evers, Elaine; Davison, Richard; Gibson, Ashleigh E.; Layton, Deborah; Irwin, William J. Journal of the Chemical Society - Perkin Transactions 1, 1996 , # 11 p. 1205 - 1211]