Asymmetric Catalytic Intramolecular Hydroamination of Aminoallenes by Tantalum Amidoalkoxide Complexes

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• 作者：Michelle C. Hansen ; Carolyn A. Heusser ; Tarun C. Narayan ; Kristine E. Fong ; Nagiko Hara ; Alexander W. Kohn ; Alexander R. Venning ; Arnold L. Rheingold ; Adam R. Johnson
• 刊名：Organometallics
• 出版年：2011
• 出版时间：September 12, 2011
• 年：2011
• 卷：30
• 期：17
• 页码：4616-4623
• 全文大小：857K
• 年卷期：v.30,no.17(September 12, 2011)
• ISSN：1520-6041

文摘

A series of tantalum complexes of chiral bidentate amidoalkoxide ligands was prepared. The crystal structure of one complex, Ta(NMe₂)₃[-OCPh₂CH(CHMe₂)N(c-C₆H₁₁)-] was obtained. Unlike previously described titanium complexes with these ligands, which are dimeric with bridging oxygen atoms, this tantalum complex is monomeric with an approximate trigonal-bipyramidal geometry. The resulting complexes were examined for their in situ activity for catalytic asymmetric hydroamination/cyclization of an aminoallene. Enantioselectivities up to 80% ee were observed for the cyclization of 6-methylhepta-4,5-dienylamine to 2-(2-methylpropenyl)pyrrolidine at 135 掳C with 5 mol % catalyst loading.