title: Azaaldol condensation of a lithium enolate solvated by N,N,N',N'-tetramethylethylenediamine: dimer-based 1,2-addition to imines.
abstract: The lithium enolate of tert-amylacetate solvated by N,N,N',N'-tetramethylethylenediamine (TMEDA) is shown to be a doubly chelated dimer. Adding the dimeric enolate to 4-fluorobenzaldehyde-N-phenylimine affords an N-lithiated β-amino ester shown to be monomeric using (6)Li and (15)N NMR spectroscopies. Rate studies using (19)F NMR spectroscopy reveal reaction orders consistent with a transition structure of stoichiometry [(ROLi)2(TMEDA)2(imine)](‡). Density functional theory computations explore several possible dimer-based transition structures with monodentate and bidentate coordination of TMEDA. Supporting rate studies using trans-N,N,N',N'-1,2-tetramethylcyclohexanediamine showing analogous rates and rate law suggest that TMEDA is fully chelated.
authors: Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
authors: Timothy S
authors: TS
authors: De Vries
authors: Angela M
authors: AM
authors: Bruneau
authors: Lara R
authors: LR
authors: Liou
authors: Hariharaputhiran
authors: H
authors: Subramanian
authors: David B
authors: DB
authors: Collum
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis* / Q000737:chemistry; D001372:Aza Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D019281:Dimerization; D005029:Ethylenediamines / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012995:Solubility
chemical_list: D000447:Aldehydes; D001372:Aza Compounds; D005029:Ethylenediamines; D007097:Imines; D009942:Organometallic Compounds; C005798:N,N,N',N'-tetramethylethylenediamine; D008094:Lithium