TY - JOUR T1 - On the intermediates in chiral bis(oxazoline)copper(II)-catalyzed enantioselective reactions--experimental and theoretical investigations. AU - Thorhauge,Jacob, AU - Roberson,Mark, AU - Hazell,Rita G, AU - Jørgensen,Karl Anker, PY - 2002/5/15/pubmed PY - 2002/5/15/medline PY - 2002/5/15/entrez SP - 1888 EP - 98 JF - Chemistry (Weinheim an der Bergstrasse, Germany) JO - Chemistry VL - 8 IS - 8 N2 - The intermediates in the chiral bis(oxazoline)copper(II)-catalyzed reactions have been investigated by means of experimental and theoretical investigations. It is shown that the absolute configuration of the hetero-Diels-Alder adduct obtained from the reaction of ethyl glyoxylate with 1,3-cyclohexadiene in the presence of the chiral bis(phenyloxazoline)copper(II) is dependent on the solvent. In this case, a linear relationship between the enantiomeric excess (ee) and the dielectric constant of the solvent was observed. However, the enantiomeric excess for the adduct obtained with the chiral bis(tert-butyloxazoline)copper(II) complex is independent of the solvent. The addition of different coordinating solvents to the chiral catalysts was investigated and no effect on the enantioselectivity of the reaction was observed. A series of chiral bis(tert-butyloxazoline)-, bis(phenyloxazoline)-, and bis(indaneoxazoline)copper(II) complexes has been prepared and characterized by X-ray analysis, and the similarity between the structures is discussed. For comparison, two related chiral bis(tert-butyloxazoline)- and bis(phenyloxazoline)zinc(II) complexes were also prepared and characterized. A series of chiral bis(oxazoline)copper(II)-substrate (the substrate being glyoxal or methyl glyoxylate) complexes was investigated by means of ab initio calculations. Calculation of the total energy of the optimized structure of 17-, 19-, and 21-electron bis(oxazoline)copper(II)-substrate complexes give the 17-electron complex as the most stable and the most reactive complex, while the 21-electron complex is less stable and also much less reactive. The optimized structures of both the 17-electron bis(tert-butyloxazoline)- and bis(phenyloxazoline)copper(II)-substrate complexes show that the plane of the substrate molecule is twisted by approximately 40-45 degrees out of the bis(oxazoline)copper(II) plane, in agreement with the X-ray structures. On the basis of the experimental results, X-ray structures, and ab initio calculations, the structure of the intermediate(s) and reactivity of the chiral bis(oxazoline)copper(II)-substrate complexes are discussed. SN - 0947-6539 UR - https://www.unboundmedicine.com/medline/citation/12007099/On_the_intermediates_in_chiral_bis_oxazoline_copper_II__catalyzed_enantioselective_reactions__experimental_and_theoretical_investigations_ L2 - https://doi.org/10.1002/1521-3765(20020415)8:8<1888::AID-CHEM1888>3.0.CO;2-9 DB - PRIME DP - Unbound Medicine ER -