@article{6282faaa03594f808249c99651317240,
title = "The alpha-effect in cyclic secondary amines: new scaffolds for iminium ion accelerated transformations",
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.",
keywords = "cyclic secondary amines , iminium ions, accelerated transformations",
author = "Nick Tomkinson and Achim Porzelle and Cavill, {Julie L.} and Elliott, {Richard L.} and Gareth Evans and Gibbs, {Timothy J. K.} and Jones, {Ian L.} and Platts, {James A}",
year = "2009",
doi = "10.1016/j.tet.2009.10.009",
language = "English",
volume = "65",
pages = "9961",
journal = "Tetrahedron",
issn = "0040-4020",
publisher = "Elsevier Limited",
}