Copper-catalyzed asymmetric propargylic etherification of oximes promoted by chiral tridentate P,N,N-ligand

Chiral Tridentate-Based Ligands

“…The same complexes were also used for the asymmetric copper-catalyzed [3+3] cycloaddition of racemic propargylic esters with 5-pyrazolones, resulting in high yields and very high enantioselectivities (ee = 71-97% for 5.12), 82 as well as for the decarboxylative alkylation of propargyl -ketoesters (ee = 83-98% for 5.13 with R = Ph). 83 The same group also exploited the ability of copper complexes of ligands 5.12 and 5.13 to activate propargylic esters to develop various asymmetric substitution reactions of racemic propargylic esters with different nucleophiles: nitrogen nucleophiles such as primary and secondary anilines (the best ligand being 5.12 for aromatic substrates with ee = 87-97% and 5.13 (R=H) for aliphatic ones with ee = 78-95%, see Scheme 5.6 b), 84 oxygen nucleophiles such as oximes (ee = 77-92% with 5.13 (R=Ph)), 85 but also various carbon nucleophiles such as -ketoesters (ee = 77-97% with 5.13 (R=Ph)), 86 1,3-dicarbonyl compounds (ee = 94-99% with 5.13 (R=Ph)), 87 enamines (ee = 96-98% with 5.12 for acyclic enamines 88 and 80-97% with 5.13 (R=Ph) for cyclic enamines), 89 oxindoles (d.e. > 90%, ee = 95-99% with 5.12), 90 and coumarins (ee = 77-97% with 5.13 (R=Ph)).…”