Origin of Enantioselectivity in Palladium-Catalyzed Asymmetric Allylic Alkylation Reactions Using Aminophosphine Ligands

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• 作者：Michael Widhalm ; Ulrike Nettekoven ; Hermann Kalchhauser ; Kurt Mereiter ; Maria José ; Calhorda ; and Ví ; tor Fé ; lix
• 刊名：Organometallics
• 出版年：2002
• 出版时间：January 21, 2002
• 年：2002
• 卷：21
• 期：2
• 页码：315 - 325
• 全文大小：215K
• 年卷期：v.21,no.2(January 21, 2002)
• ISSN：1520-6041

文摘

The asymmetric induction observed in palladium-catalyzed allylic alkylation reactions withtypical substrates was investigated using three structurally related chiral PN ligands, whichall contain a binaphthyl unit and either a benzyl (1) or ferrocenylmethyl (2, 3) fragmentbridging phosphorus and nitrogen complexation sites. The intermediate allyl palladium(II)complexes of ligands 1-3 have been isolated and spectroscopically characterized. For two ofthem, 1K and 3K, the crystal structure has been determined. A rationalization of theexperimental findings on a molecular level is proposed based on the results of DFT (ADF)and molecular mechanics (CERIUS2) calculations. Studies on both the entire molecules andsimpler models indicate that the stereochemical outcome is not determined by electroniceffects, but mostly by a delicate balance of steric repulsions. In particular, the presence ofa benzyl or a ferrocenylmethyl group in the chelate chain has a strong effect on itsarrangement, thereby directly influencing asymmetric induction.