Bidentate NHC-based chiral ligands for efficient Cu-catalyzed enantioselective allylic alkylations: structure and activity of an air-stable chiral Cu complex.
Cu-catalyzed addition of alkylzinc reagents to a range of allylic phosphates is promoted efficiently and with high enantioselectivity to afford tertiary as well as quaternary carbon centers (up to 98% ee). Reactions proceed to completion with 0.5-5 mol % catalyst loading and are best promoted by commercially available CuCl2.2H2O. The X-ray structure of the chiral NHC-Ag(I) complex used in the study as well as that of a catalytically active NHC-Cu(II) complex are also reported; both complexes are air-stable and are formed in >/=95% isolated yield. The isolated Cu complex, which can be handled in air, is catalytically active. The present report provides the first precedent for efficient Cu-catalyzed allylic alkylations with chiral NHC ligands.
Larsen
Andrew O
AO
Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Leu
Wenhao
W
Oberhuber
Christina Nieto
CN
Campbell
John E
JE
Hoveyda
Amir H
AH
D000478:Alkylation; D000498:Allyl Compounds / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry; D006838:Hydrocarbons; D008024:Ligands; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry; D013237:Stereoisomerism
D000498:Allyl Compounds; D006573:Heterocyclic Compounds, 1-Ring; D006838:Hydrocarbons; D008024:Ligands; D009942:Organometallic Compounds; C030011:carbene; D003300:Copper; D012428:Ruthenium; D008697:Methane