An investigation of the scope of the 1,7-electrocyclization of α,β:γ,δ-conjugated azomethine ylides

• Published in: Tetrahedron Vol. 70; no. 22; pp. 3621 - 3629
• Main Authors: Zhang, Weimin, Ning, Fuqiang, Váradi, Linda, Hibbs, David E., Platts, James A., Nyerges, Miklós, Anderson, Rosaleen J., Groundwater, Paul W.
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 03.06.2014; Elsevier
• Subjects: 1,5-Electrocyclization; 1,7-Electrocyclization; Azomethine ylides; Chemistry; Chemistry, Organic; Dienes; Olefins; Physical Sciences; PyrrolinesA azepines; Science & Technology; Tetrahedrons; Azomethine ylides; 1,5-Electrocyclization; 1,7-Electrocyclization; PyrrolinesA azepines; MECHANISM
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2014.03.078

Substituents on the diene component have little influence on the periselectivity of the cyclizations of α,β:γ,δ-conjugated azomethine ylides, with 1,7-electrocyclizations predominating. In some cases, subtle changes to these substituents can, however, influence the product formed, through their effect on the relative energies of the transition states for the 1,5- (6π) and 1,7-electrocyclization (8π) processes. The most striking changes in periselectivity occur for phenylethenyl-substituted azomethine ylides 3d–f, which can give either a pyrroline 4d,f or dihydrobenzazepine 6e, depending upon the alkene configuration. [Display omitted]