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Synfacts 2007(6): 0619-0619  
DOI: 10.1055/s-2007-968500
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Gold(I)-Catalyzed Enantioselective Hydroamination of Allenes

Contributor(s): Hisashi Yamamoto, Joshua Payette
R. L. LaLonde, B. D. Sherry, E. J. Kang, F. D. Toste*
University of California, Berkeley, USA
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Publikationsdatum:
22. Mai 2007 (online)

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Significance

The authors report a gold(I)-xylyl-BINAP system whose catalytic as well as enantio­selective efficiency is highly dependent upon the coordinating counteranion. The isolable, bench-stable (R)-xylyl-BINAP(AuOPNB)2 (OPNB = p-nitro­benzoate) catalyzes the intramolecular hydroamination of a variety of alkyl- and aryl-substituted allenes in high yield and ee. The authors believe the electronic nature of the nitrobenzoate anion confers reactivity, favoring complex B, while its steric bulk induces asymmetry. Notably, when 3 mol% of AgBF4 are used, forming complex B with one chloride counteranion, product with only 51% ee is obtained, providing support for the role of the counteranion in chiral induction.