Enantioselective glyoxylate-ene reaction using a novel spiro bis(isoxazoline) ligand in copper catalysis

Novel chiral spiro bis(isoxazoline) ligands 3 and 4 are synthesized from an optically active olefin. The Cu(II)-spiro bis(isoxazoline) complex prepared in situ from Cu(OTf)2 and 3 promoted the glyoxylate-ene reaction in high yield and moderate enantioselectivity (up to 70%).

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(P,5aR,5a′R,8aR,8a′R,8bR,8b′R)-4,4′,5,5′,5a,5′a,6,6′,7,7′,8,8′,8a,8′a,8b,8′b-Hexadecahydro-3,3′-spirobi[3H-naphtho[1,8-cd]isoxazole]C19H26N2O2Ee = >99%[α]D21=+95.7 (c 0.22, CHCl3)Absolute configuration: (P,R,R,R,R,R,R)

(M,5aR,5a′R,8aR,8a′R,8bR,8b′R)-4,4′,5,5′,5a,5′a,6,6′,7,7′,8,8′,8a,8′a,8b,8′b-Hexadecahydro-3,3′-spirobi[3H-naphtho[1,8-cd]isoxazole]C19H26N2O2Ee = >99%[α]D24=+40.4 (c 1.07, CHCl3)Absolute configuration: (M,R,R,R,R,R,R)