TY - JOUR
T1 - Synthesis of new chiral terpyridine mono-N-oxide and di-N-oxide ligands and their applications in copper-catalyzed asymmetric cyclopropanation
AU - Wong, Wing-Leung
AU - Lee, Wing-Sze
AU - Kwong, Hoi-Lun
PY - 2002/8/1
Y1 - 2002/8/1
N2 - New families of chiral terpyridine mono-N-oxides L1-L3 and di-N-oxides L4-L6, were synthesized in moderate to good yields by simple oxidation of their corresponding terpyridines with m-CPBA. The copper(II) triflate complexes of these ligands were found to be highly effective catalysts for asymmetric cyclopropanation of styrene with ethyl diazoacetate. The isolated yields of cyclopropane were excellent and the enantiomeric excesses of up to 83% were observed. Competition experiments with substituted styrenes showed good σ+ correlations with ρ=-0.70 for mono-N-oxide L3 and ρ=-0.69 for di-N-oxide L6. © 2002 Elsevier Science Ltd. All rights reserved.
AB - New families of chiral terpyridine mono-N-oxides L1-L3 and di-N-oxides L4-L6, were synthesized in moderate to good yields by simple oxidation of their corresponding terpyridines with m-CPBA. The copper(II) triflate complexes of these ligands were found to be highly effective catalysts for asymmetric cyclopropanation of styrene with ethyl diazoacetate. The isolated yields of cyclopropane were excellent and the enantiomeric excesses of up to 83% were observed. Competition experiments with substituted styrenes showed good σ+ correlations with ρ=-0.70 for mono-N-oxide L3 and ρ=-0.69 for di-N-oxide L6. © 2002 Elsevier Science Ltd. All rights reserved.
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U2 - 10.1016/S0957-4166(02)00270-7
DO - 10.1016/S0957-4166(02)00270-7
M3 - RGC 21 - Publication in refereed journal
SN - 0957-4166
VL - 13
SP - 1485
EP - 1492
JO - Tetrahedron Asymmetry
JF - Tetrahedron Asymmetry
IS - 14
ER -