Synthesis 2001(10): 1523-1531
DOI: 10.1055/s-2001-16074
PAPER
© Georg Thieme Verlag Stuttgart · New York

Stereoselective Synthesis of Pyrrolidines and Pyrrolizidines by Intramolecular Carbolithiation

Iain Coldham*, Richard Hufton, Kathy N. Price, Richard E. Rathmell, David J. Snowden, Graham P. Vennall
School of Chemistry, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
Fax: +44(1392)263434; e-Mail: I.Coldham@exeter.ac.uk;
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Publikationsverlauf

Received 21 November 2000
Publikationsdatum:
23. September 2004 (online)

Abstract

Methods for the preparation of substituted homoallylic amines and their conversion to pyrrolidines or pyrrolizidines are described. N-Alkylation of a variety of homoallylic secondary amines with (tributylstannyl)methyl methanesulfonate and subsequent tin-lithium exchange, generates organolithium species that undergo intramolecular carbolithiation (anionic cyclization). High stereoselectivities in the cyclization, particularly for the formation of 2,4-disubstituted pyrrolidines, are obtained.

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The ratio of diastereomers of the picrate salts of 15 and 16 in the crystals was 60:40 by 1H NMR and 54:46 by X-ray, such that confirmation of the major diastereomer by X-ray structure analysis was not certain.