Intramolecular conjugate displacement: a general route to hexahydroquinolizines, hexahydroindolizines, and related [m,n,0]-bicyclic structures with nitrogen at a bridgehead.
N-Protected amino aldehydes can be converted into allylic alcohols by the classical Morita-Baylis-Hillman reaction (cf. 2 --> 3) or by condensation with selenium-stabilized carbanions, followed by oxidation (cf. 2 --> 8 --> 3). The derived acetates undergo cyclization when the nitrogen protecting group is removed, affording [m,n,0]-bicyclic structures with nitrogen at a bridgehead (cf. 4 --> 5 --> 6). Formation of bicyclic structures via the reactions of Schemes 1 and 2 is general, and the stereochemistry of the starting amino aldehyde is preserved.
Clive
Derrick L J
DL
Chemistry Department, University of Alberta, Edmonton, Alberta, Canada. derrick.clive@ualberta.ca
Li
Zhiyong
Z
Yu
Maolin
M