Ring transformation of 2-(haloalkyl)azetidines into 3,4-disubstituted pyrrolidines and piperidines.
[reaction: see text] Reduction of 4-(haloalkyl)azetidin-2-ones with chloroalane (AlH(2)Cl) afforded new 2-(haloalkyl)azetidines in high yields. The latter compounds proved to be very useful starting materials for rearrangements toward stereospecifically defined five- and six-membered azaheterocycles, such as 3,4-cis-disubstituted pyrrolidines and piperidines. During these reactions, bicyclic azetidinium intermediates were formed which were ring opened by a variety of nucleophiles. Hereby, reactions proceeding via 1-azoniabicyclo[2.2.0]hexanes are reported for the first time.
Van Brabandt
Willem
W
Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium.
Van Landeghem
Robin
R
De Kimpe
Norbert
N