Synthesis of new chiral terpyridine mono-N-oxide and di-N-oxide ligands and their applications in copper-catalyzed asymmetric cyclopropanation

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Original languageEnglish
Pages (from-to)1485-1492
Journal / PublicationTetrahedron Asymmetry
Volume13
Issue number14
Publication statusPublished - 1 Aug 2002
Externally publishedYes

Abstract

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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