Stereoselective reactions. 26. Solution structures of a chiral bidentate lithium amide in relation to the solvent-dependent enantioselectivities in deprotonation reaction

Article abstract of DOI:10.1016/S0040-4020(97)00422-5

⁶Li- and ¹⁵N-NMR spectroscopic analyses of a labeled chiral bidentate lithium amide ([⁶Li,¹⁵N₂]-(R)-1) have shown that it exists as a chelated monomer (5) in THF and in DME, as a chelated dimer (6) in toluene and in ether, while as a chelated monomer (5) in any of these solvents in the presence of 2 equivalents of HMPA. Solvent-dependent enantioselectivities in deprotonation of 4-tert-butylcyclohexanone (2) by (R)-1 appear to be correlated to these solution structures.