The alpha-effect in cyclic secondary amines: new scaffolds for iminium ion accelerated transformations

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Tomkinson, Nick and Porzelle, Achim and Cavill, Julie L. and Elliott, Richard L. and Evans, Gareth and Gibbs, Timothy J. K. and Jones, Ian L. and Platts, James A (2009) The alpha-effect in cyclic secondary amines: new scaffolds for iminium ion accelerated transformations. Tetrahedron, 65. p. 9961. ISSN 0040-4020 (https://doi.org/10.1016/j.tet.2009.10.009)

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Abstract

Five-membered secondary amine heterocycles containing an α-heteroatom were prepared and shown to be ineffective as catalysts for the iminium ion catalysed Diels–Alder reaction between cinnamaldehyde and cyclopentadiene. Their six-membered counterparts proved to be highly active catalysts. In stark contrast, the catalytic activity observed when comparing the non α-heteroatom cyclic amines proline methyl ester and methyl pipecolinate showed the five-membered ring amine was significantly more active. Concurrent density functional theoretical calculations suggest a rationale for the observed trends in reactivity, highlighting that LUMO activation through an iminium ion intermediate plays a key role in catalytic activity.

ORCID iDs

Tomkinson, Nick ORCID logoORCID: https://orcid.org/0000-0002-5509-0133, Porzelle, Achim, Cavill, Julie L., Elliott, Richard L., Evans, Gareth, Gibbs, Timothy J. K., Jones, Ian L. and Platts, James A;
CORE (COnnecting REpositories)