[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.

Azetidine derivatives R 0045Reduction of 4-(Haloalkyl)azetidin-2-ones with LiAlH 4 as a Powerful Method for the Synthesis of Stereodefined Aziridines and Azetidines. -The reductive transformation of azetidine-2-ones under conditions A) affords stereodefined aziridines. The products can be further transformed to tetrahydrofurans. Attempts to prepare tetrahydropyrans from substrates of type (X) fail. In all cases, a small amount of azetidines like (III) is observed (up to 5%). -(VAN BRABANDT, W.; DEJAEGHER, Y.; VAN LANDEGHEM, R.; DE KIMPE*, N.; Org. Lett. 8 (2006) 6, 1101-1104; Dep. Org. Chem., Fac. Biosci. Eng., Univ. Gent, B-9000 Gent, Belg.; Eng.) -R. Steudel 30-102

Azetidine derivatives R 0045Ring Transformation of 2-(Haloalkyl)azetidines into 3,4-Disubstituted Pyrrolidines and Piperidines. -The substrates are reduced with chloroalane and the products transformed to cis-substituted alkoxy-pyrrolidines and piperidines. In this context, the possibility of introducing nucleophiles others than halide is demonstrated. -(VAN BRABANDT, W.; VAN LANDEGHEM, R.; DE KIMPE*, N.; Org. Lett. 8 (2006) 6, 1105-1108; Dep. Org. Chem., Fac. Biosci. Eng., Univ. Gent, B-9000 Gent, Belg.; Eng.) -R. Steudel 30-103