TY - JOUR
T1 - Studies on the bisoxazoline- and (-)-sparteine-mediated enantioselective addition of organolithium reagents to imines
AU - Denmark, Scott E.
AU - Nakajima, Noriyuki
AU - Stiff, Cory M.
AU - Nicaise, Olivier J.C.
AU - Kranz, Michael
PY - 2008/5/5
Y1 - 2008/5/5
N2 - The enantioselective addition of organolithium reagents to N-anisylaldimines promoted by chiral bisoxazolines and (-)-sparteine as external ligands is described. This reaction proceeds readily with a wide range of aldimine substrates (aliphatic, aromatic, olefinic) and organolithium nucleophiles (Me, n-Bu, Ph, vinyl) in excellent yields (81-99%) and with high enantioselectivities (up to 97:3.0 er). The external ligands can be used in substoichiometric amounts albeit with slightly attenuated enantioselectivities. A systematic evaluation of the structural features of the bisoxazolines revealed a primary contribution from the substituent at C(4) and a secondary influence from the bridging substituents. A computational analysis (PM3) provided a clear rationalization for the origin of enantioselectivity.
AB - The enantioselective addition of organolithium reagents to N-anisylaldimines promoted by chiral bisoxazolines and (-)-sparteine as external ligands is described. This reaction proceeds readily with a wide range of aldimine substrates (aliphatic, aromatic, olefinic) and organolithium nucleophiles (Me, n-Bu, Ph, vinyl) in excellent yields (81-99%) and with high enantioselectivities (up to 97:3.0 er). The external ligands can be used in substoichiometric amounts albeit with slightly attenuated enantioselectivities. A systematic evaluation of the structural features of the bisoxazolines revealed a primary contribution from the substituent at C(4) and a secondary influence from the bridging substituents. A computational analysis (PM3) provided a clear rationalization for the origin of enantioselectivity.
KW - Aldimines
KW - Bisoxazolines
KW - Catalysis
KW - Enantioselective addition
KW - Organolithium reagents
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U2 - 10.1002/adsc.200800017
DO - 10.1002/adsc.200800017
M3 - Article
C2 - 19809587
AN - SCOPUS:53849089248
SN - 1615-4150
VL - 350
SP - 1023
EP - 1045
JO - Advanced Synthesis and Catalysis
JF - Advanced Synthesis and Catalysis
IS - 7-8
ER -