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Keywords:Diastereoselective cyclisation / Pyrrolin-1-ium salts / Pyrrolidines / Heterocycles / Synthetic methods A number of new chiral 2-(α-bromoalkyl)pyrrolinium salts and 2-(α-selenoalkyl)pyrrolidines were synthesized by the halocyclisation and selenocyclisation, respectively, of N-(alkenylidene)alkylamines and subsequent reduction. These cyclisations were implemented in a diastereomeric fashion for the first time. Substrate control (starting imines possessing chirality in the N-alkyl or the N-alkenyl substituent) and re-

Diastereoselective Cyclization of N-Alkenylideneamines into 3,4-Dihydro--2H-pyrrol-1-ium Halides. -Novel approaches towards the diastereoselective electrophile-induced cyclization of N-alkenylidene alkylamines are presented. The halocyclization of chiral N-alkenylidene alkylamines (I) proceeds with only low to moderate diastereoselectivity. Similar results are achieved with the selenocyclization of related N-alkenylidene alkylamines (V), and the introduction of additional prochiral substituents into the imines does not give improved stereoselectivities. Diastereoselectivities of up to 68% d.e. are achieved when a chiral imine (XII) is reacted with a chiral selenium bromide (XV) as well as by application of N-alkenylidene alkylamines bearing stereocenters at the alkenylidene chain (XVII). -(SCHLEY, D.; LIEBSCHER*, J.; Eur.

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