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Studies on the Bisoxazoline and (-)-Sparteine Mediated Enantioselective Addition of Organolithium Reagents to Imines.

ABSTRACT: The enantioselective addition of organolithium reagents to N-anisyl aldimines promoted by chiral bisoxazolines and (-)-sparteine as external ligands is described. This reaction proceeds readily with a wide range of aldimine substrates (aliphatic, aromatic, olefinic) and organolithium nucleophiles (Me, n-Bu, Ph, vinyl) in excellent yields (81-99%) and with high enantioselectivities (up to 95.5:4.5 er). The external ligands can be used in substoichiometric amounts albeit with slightly attenuated enantioselectivities. A systematic evaluation of the structural features of the bisoxazolines revealed a primary contribution from the substituent at C(4) and a secondary influence from the bridging substituents. A computational analysis (PM3) provided a clear rationalization for the origin of enantioselectivity.

SUBMITTER: Denmark SE

PROVIDER: S-EPMC2756708 | biostudies-other | 2008 May

REPOSITORIES: biostudies-other

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Studies on the Bisoxazoline and (-)-Sparteine Mediated Enantioselective Addition of Organolithium Reagents to Imines.

Denmark Scott E SE Nakajima Noriyuki N Stiff Cory M CM Nicaise Olivier J-C OJ Kranz Michael M

Advanced synthesis & catalysis 20080501 7-8

The enantioselective addition of organolithium reagents to N-anisyl aldimines promoted by chiral bisoxazolines and (-)-sparteine as external ligands is described. This reaction proceeds readily with a wide range of aldimine substrates (aliphatic, aromatic, olefinic) and organolithium nucleophiles (Me, n-Bu, Ph, vinyl) in excellent yields (81-99%) and with high enantioselectivities (up to 95.5:4.5 er). The external ligands can be used in substoichiometric amounts albeit with slightly attenuated e ...[more]

PMID: 19809587

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