title: On the racemization of chiral imidazolines.
abstract: Racemization of chiral imidazolines with base has been studied for the first time following an unexpected finding in the synthesis of chiral imidazoline ligands. Amine bases do not cause racemization. Strong inorganic bases can induce racemization, yet this occurs only when the nitrogen is unsubstituted, in agreement with a symmetry-allowed thermal disrotatory ring opening and closure from a diazapentadienyl anion. Surprisingly, even with electron-withdrawing N-substituents, no racemization is observed. Conditions which allow for the racemization-free manipulations of this important compound class have been defined and developed.
authors.affiliation: Department of Chemical Development, Boehringer-Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Road, Ridgefield, Connecticut 06877, USA. carl.busacca@boehringer-ingelheim.com
authors.forename: Carl A
authors.initials: CA
authors.lastname: Busacca
authors.forename: Teresa
authors.initials: T
authors.lastname: Bartholomeyzik
authors.forename: Sreedhar
authors.initials: S
authors.lastname: Cheekoori
authors.forename: Nelu
authors.initials: N
authors.lastname: Grinberg
authors.forename: Heewon
authors.initials: H
authors.lastname: Lee
authors.forename: Shengli
authors.initials: S
authors.lastname: Ma
authors.forename: Anjan
authors.initials: A
authors.lastname: Saha
authors.forename: Sherry
authors.initials: S
authors.lastname: Shen
authors.forename: Chris H
authors.initials: CH
authors.lastname: Senanayake
mesh_terms: D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004121:Dimethyl Sulfoxide; D007093:Imidazoles / Q000138:chemical synthesis / Q000737:chemistry*; D007536:Isomerism; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008968:Molecular Conformation; D012997:Solvents; D013237:Stereoisomerism
chemical_list: D007093:Imidazoles; D008024:Ligands; D012997:Solvents; D004121:Dimethyl Sulfoxide