M. David et al., STEREOCONTROLLED ADDITION OF PI-TYPE NUCLEOPHILES TO A BICYCLIC N-ACYLIMINIUM ION - NEW ACCESS TO TRANS-2,6-DISUBSTITUTED PIPERIDINE SUBSTRUCTURES, Synlett, (2), 1998, pp. 206
Bicyclic N-acyliminium ion I, generated in situ by treatment of aminoe
ther 4 with Lewis acids, smoothly reacted with pi-type nucleophiles, l
eading exclusively to the trans adducts.