title: Lithium diisopropylamide-mediated ortholithiation and anionic fries rearrangement of aryl carbamates: role of aggregates and mixed aggregates.
abstract: Structural and mechanistic studies of the lithium diisopropylamide (LDA)-mediated anionic Fries rearrangements of aryl carbamates are described. Substituents at the meta position of the arene (H, OMe, F) and the dialkylamino moiety of the carbamate (Me(2)N, Et(2)N, and i-Pr(2)N) markedly influence the relative rates of ortholithiation and subsequent Fries rearrangement. Structural studies using (6)Li and (15)N NMR spectroscopies on samples derived from [(6)Li,(15)N]LDA reveal an LDA dimer, LDA dimer-arene complexes, an aryllithium monomer, LDA-aryllithium mixed dimers, an LDA-lithium phenolate mixed dimer, and homoaggregated lithium phenolates. The highly insoluble phenolate was characterized as a dimer by X-ray crystallography. Rate studies show monomer- and dimer-based ortholithiations as well as monomer- and mixed dimer-based Fries rearrangements. Density functional theory computational studies probe experimentally elusive structural and mechanistic details.
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
authors.forename: Kanwal Jit
authors.initials: KJ
authors.lastname: Singh
authors.forename: David B
authors.initials: DB
authors.lastname: Collum
mesh_terms: D000838:Anions / Q000737:chemistry*; D002219:Carbamates / Q000737:chemistry*; D018360:Crystallography, X-Ray; D019281:Dimerization; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D007700:Kinetics; D008094:Lithium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D009942:Organometallic Compounds / Q000737:chemistry*; D011437:Propylamines / Q000737:chemistry*
chemical_list: D000838:Anions; D002219:Carbamates; D006841:Hydrocarbons, Aromatic; D009942:Organometallic Compounds; D011437:Propylamines; D008094:Lithium; C007442:diisopropylamine