Stereoselective synthesis of 3,4-disubstituted and 3,4,5-trisubstituted piperidines by Lewis acid-catalysed ene cyclisation of 4-aza-1,7-dienes

Walker, S. M., Williams, J. T., Russell, A. G., Kariuki, Benson ORCID: https://orcid.org/0000-0002-8658-3897 and Snaith, J. S. 2007. Stereoselective synthesis of 3,4-disubstituted and 3,4,5-trisubstituted piperidines by Lewis acid-catalysed ene cyclisation of 4-aza-1,7-dienes. Organic & Biomolecular Chemistry 5 (18) , pp. 2925-2931. 10.1039/b708139a

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Abstract

The thermal or Lewis acid-catalysed ene cyclisation of a variety of 4-aza-1,7-dienes afforded 3,4-disubstituted or 3,4,5-trisubstituted piperidines. Activation of the enophile with a single ester facilitated a thermal ene cyclisation, although the reaction was not amenable to Lewis acid catalysis. With other activating groups on the enophile it was found that Lewis acid catalysis was facile, although there was a. ne balance between the desired ene cyclisation and the competing hetero-Diels-Alder reaction, with the product distribution being influenced by the activating group on the enophile, the nature of the ene component, and the Lewis acid used. Activation of the enophile with an oxazolidinone function facilitated Lewis acid-catalysed cyclisation to afford mixtures of ene and hetero-Diels-Alder products. Activating the enophile with two ester groups gave a substrate that underwent a very facile ene cyclisation catalysed by MeAlCl2 to give the corresponding trans 3,4-disubstituted piperidines with diastereomeric ratios of and gt; 200 : 1.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	RCS Publishing
ISSN:	1477-0520
Last Modified:	24 Oct 2022 11:10
URI:	https://orca.cardiff.ac.uk/id/eprint/47174

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