| Abstract
| - Three structurally similar series of 1,2,3,4-tetrahydro-β-carboline ligands, 4a−d, 6a−d and 7a−d, and two series of chiral oxazolidines, 8a−d and 9a−g, were synthesized and used as chiralcatalysts in the addition of diethylzinc to benzaldehyde. The enantioselectivities of the resulting1-phenyl-1-propanol were obtained in each case, and these ee values were, in most cases, relatedto the conformational populations of the free ligand as expressed by the calculated differences inthe energies of the ligand conformations formed by inversion at nitrogen. This suggested the possibleexistence of a linear free energy relationship. The effect on enantioselectivity of the carbon chainlength of the R group located (1) on the C-3 substituent of 4a−d, 6a−d, and 7a−d or (2) at C-5 in8a−d and 9a−g was studied in detail. On the basis of the correlations observed and the ligands'structural characterization, a structure was proposed for the transition state during ethyl grouptransfer when using ligands 8a−d. Furthermore, the change in enantioselectivity was successfullypredicted when diastereomeric ligands 11 and 12 were compared in this chiral addition.
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