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

Nick Tomkinson, Achim Porzelle, Julie L. Cavill, Richard L. Elliott, Gareth Evans, Timothy J. K. Gibbs, Ian L. Jones, James A Platts

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)
84 Downloads (Pure)

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.
Original languageEnglish
Pages (from-to)9961
Number of pages9966
JournalTetrahedron
Volume65
DOIs
Publication statusPublished - 2009

Keywords

  • cyclic secondary amines
  • iminium ions
  • accelerated transformations

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