title: Lithium Enolates Derived from Weinreb Amides: Insights into Five-Membered Chelate Rings.
abstract: Enolization of O-methyl hydroxamic acids (Weinreb amides) in tetrahydrofuran solution with lithium diisopropylamide affords predominantly tetrameric enolates. Aryl substituents on the enolates promote deaggregation. The aggregation states are assigned by using the method of continuous variation in conjunction with6Li NMR spectroscopy. Decoalescence of the tetramer resonance below -100 °C shows considerable spectral complexity attributed to isomerism of the methoxy-based chelates. Density functional theory calculations were used to examine the consequences of the bite angle of five-membered chelates in cubic tetramers and resulting solvation numbers that were higher than anticipated.
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: David B
authors.initials: DB
authors.lastname: Collum
mesh_terms: D000577:Amides / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry*; D019281:Dimerization; D008094:Lithium / Q000737:chemistry*; D047028:Macrocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure
chemical_list: D000577:Amides; D002614:Chelating Agents; D047028:Macrocyclic Compounds; D008094:Lithium