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Influence of Copper Salts, Solvents, and Ligands on the Structures of Precatalytic Phosphoramidite Copper Complexes for Conjugate Addition Reactions
Author(s) -
Zhang Hongxia,
Gschwind Ruth M.
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601857
Subject(s) - phosphoramidite , chemistry , copper , conjugate , reagent , amine gas treating , enantioselective synthesis , combinatorial chemistry , ligand (biochemistry) , polymer chemistry , organic chemistry , catalysis , dna , mathematical analysis , biochemistry , receptor , mathematics , oligonucleotide
For copper‐catalyzed enantioselective conjugate addition reactions of organozinc reagents, the available knowledge about the mechanism and the structures involved is still insufficient to understand in detail the strong influences of solvent, salt, and ligand size, or to enable a rational control of this reaction. Screening with three phosphoramidite ligands and four copper(I) salts using NMR spectroscopy has revealed a binuclear copper complex with mixed trigonal/tetrahedral stereochemistry as the basic structural motif of the ground state of precatalysts with highly stereoselective ligands. Ligands with smaller amine moieties allow higher coordination numbers and higher aggregation levels, leading to reduced ee values. Since the ESI mass spectra of several precatalytic copper halide complexes show a striking correlation with the structures observed in solution, ESI‐MS may be used as a fast tool to determine the maximum number of phosphoramidite ligands attached to copper.