Highly Enantioselective Desymmetrization of Anhydrides by Carbon Nucleophiles: Reactions of Grignard Reagents in the Presence of (−)-Sparteine

Authors


  • We thank Ivory D. Hills for X-ray crystallographic work. Support has been provided by Bristol-Myers Squibb, Novartis, Pfizer, and Pharmacia. Funding for the MIT Department of Chemistry Instrumentation Facility has been furnished in part by NSF CHE-9808061 and NSF DBI-9729592.

Abstract

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Where other common chiral ligands failed, (−)-sparteine can be employed to form complexes with Grignard reagents. These chirally modified reagents desymmetrize a range of anhydrides with good enantioselectivity (up to 92 % ee; see scheme). Whereas (−)-sparteine is well known to form complexes with organolithium reagents and to induce excellent enantioselection in their reactions with electrophiles, (−)-sparteine-controlled asymmetric processes that involve Grignard reagents are rare.

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