title: Lithium Enolates Derived from Pyroglutaminol: Aggregation, Solvation, and Atropisomerism.
abstract: Lithium enolates derived from protected pyroglutaminols were characterized by using (6)Li, (13)C, and (19)F NMR spectroscopies in conjunction with the method of continuous variations. Mixtures of tetrasolvated dimers and tetrasolvated tetramers in different proportions depend on the steric demands of the hemiaminal protecting group, tetrahydrofuran concentration, and the presence or absence of an α-fluoro moiety. The high steric demands of the substituted bicyclo[3.3.0] ring system promote dimers to an unusual extent and allow solvents and atropisomers in cubic tetramers to be observed in the slow-exchange limit. Pyridine used as a (6)Li chemical shift reagent proved useful in assigning solvation numbers.
authors.affiliation: Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca , New York 14853-1301, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Houghton
authors.affiliation: Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca , New York 14853-1301, United States.
authors.forename: Naomi A
authors.initials: NA
authors.lastname: Biok
authors.affiliation: Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca , New York 14853-1301, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Huck
authors.affiliation: Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca , New York 14853-1301, United States.
authors.forename: Russell F
authors.initials: RF
authors.lastname: Algera
authors.affiliation: Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca , New York 14853-1301, United States.
authors.forename: Ivan
authors.initials: I
authors.lastname: Keresztes
authors.affiliation: Worldwide Medicinal Chemistry, Pfizer Global Research and Development , 445 Eastern Point Road, Groton, Connecticut 06340, United States.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Wright
authors.affiliation: Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca , New York 14853-1301, United States.
authors.forename: David B
authors.initials: DB
authors.lastname: Collum
mesh_terms: D001643:Bridged Bicyclo Compounds; D002247:Carbon Isotopes; D005461:Fluorine; D007554:Isotopes; D008094:Lithium; D018020:Lithium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D011758:Pyrroles / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001643:Bridged Bicyclo Compounds; D002247:Carbon Isotopes; D007554:Isotopes; D018020:Lithium Compounds; D011758:Pyrroles; C431590:pyroglutaminol; D005461:Fluorine; D008094:Lithium