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

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.