Alternative tandem cyclisation pathways in the reaction between imines and enones,

Girling, P.R.; Batsanov, A.S.; Calow, A.D.J.; Shen, H.C.; Whiting, A.

Abstract

Dihydroisoquinoline reacts with Danishefsky's diene under Lewis acidic conditions or neat, to give low to moderate yields of the formal aza-Diels-Alder, [4+2]-cycloadduct. However, using methoxyvinyl methylketone with Lewis acid catalysis does not give the aza-Diels-Alder adduct, rather a formal [2+2+2]-cycloaddition occurs to provide access to a diacetyl dihydropyridine. Increased Lewis acid loading results in reduced dihydropyridine formation, and instead, a trimerisation reaction of the methoxyvinyl methyl ketone, to give 1,3,5-triacetylbenzene from a different formal [2+2+2]-cycloaddition. The formal [4+2]-cycloaddition reaction of methoxyvinyl methylketone requires a cyclic imine in order to form the dihydropyridine because the reaction with acyclic imines produced a dihydropyridine from a formal [1+2+1+2]-cycloaddition. Evidence resulting from the isolation of reaction intermediates and in situ spectroscopic studies, shows that the reaction between 3,4-dihydroisoquinoline and methyl vinyl ketone, catalysed by oxy-philic Lewis acids, proceeds via a Mannich-Michael pathway and an imminium ion species. All reactions occur by one-pot cascade routes.

Citation

Girling, P., Batsanov, A., Calow, A., Shen, H., & Whiting, A. (2016). Alternative tandem cyclisation pathways in the reaction between imines and enones,. Tetrahedron, 72(8), 1105-1113. https://doi.org/10.1016/j.tet.2016.01.006

• Journal Article Type: Article
• Acceptance Date: Jan 5, 2016
• Online Publication Date: Jan 7, 2016
• Publication Date: Feb 25, 2016
• Deposit Date: Jan 13, 2016
• Publicly Available Date: Jan 7, 2017
• Journal: Tetrahedron
• Print ISSN: 0040-4020
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 72
• Issue: 8
• Pages: 1105-1113
• DOI: https://doi.org/10.1016/j.tet.2016.01.006
• Keywords: Aza-Diels-Alder, Lewis-acid, Homogeneous catalysis, Cycloaddition, Dihydropyridine, Piperidenone.
• Public URL: https://durham-repository.worktribe.com/output/1394826