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Reversible 1,3-anti/syn-Stereochemical Courses in Copper-Catalyzed γ-Selective Allyl–Alkyl Coupling between Chiral Allylic Phosphates and Alkylboranes

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journal contribution
posted on 30.05.2012, 00:00 by Kazunori Nagao, Umi Yokobori, Yusuke Makida, Hirohisa Ohmiya, Masaya Sawamura
The stereochemical courses of the copper-catalyzed allyl–alkyl coupling between enantioenriched chiral allylic phosphates and alkylboranes were switchable between 1,3-anti and 1,3-syn selectivities by the choice of solvents and achiral alkoxide bases with different steric demands. The reactions with γ-silylated allylic phosphates allow efficient synthesis of enantioenriched chiral allylsilanes with tertiary or quaternary carbon stereogenic centers. Cyclic and acyclic bimodal participation of alkoxyborane species in an organocopper addition–elimination sequence is proposed to account for the phenomenon of the anti/syn-stereochemical reversal.

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