Azaaldol Condensation of a Lithium Enolate Solvated by N,N,N',N'-Tetramethylethylenediamine: Dimer-Based 1,2-Addition to Imines

作者：De Vries Timothy S; Bruneau Angela M; Liou Lara R; Subramanian Hariharaputhiran; Collum David B^*

来源：Journal of the American Chemical Society, 2013, 135(10): 4103-4109.

DOI：10.1021/ja400345c

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 beta-amino ester shown to be monomeric using Li-6 and N-15 NMR spectroscopies. Rate studies using F-19 NMR spectroscopy reveal reaction orders consistent with a transition structure of stoichiometry [(ROLi)(2)(TMEDA)(2)(imine)](double dagger). 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.

• 出版日期2013-3-13