New Reactions of Ketene Silyl Acetals with Imines Promoted by Titanium(IV) and Zirconium(IV) Chlorides
作者： Iwao Ojima , Stephan M. Brandstadter
DOI: 10.1007/978-94-009-2464-2_3
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摘要: The reactions of vinylketene silyl acetals (VKSAs) (1) with non-activated imines (2) and vinylimines (3) promoted by TiCl4 or ZrCl4 were investigated. When the simple imine complexes are used, give 5,6-dihydro-2-pyridones (6) and/or 5-amino-2-alkenoates (7) in good to excellent yields through y-addition. It is suggested that an addition-cyclization mechanism operative for formation 6. VKSAs proceed γ-1, 2 addition afford corresponding pyridones (8) amino-alkadienoates (9) moderate yields. In contrast this, use as promoter leads 6-aminomethylidene-5-phenyl-2-cyclohexen-l-ones (12) exclusive predominant product 4 addition. Mechanisms which can accommodate observed substantial substituent effects on distribution clear differences reactivity between proposed.
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