Stereoselective Reactions. XXVII. Solution Structures of a Chiral Tridentate Lithium Amide in Relation to Enantioselective Deprotonation of 4-tert-Butylcyclohexanone

Abstract

^6Li- and ¹⁵N-NMR spectroscopic studies on the solution structures of a chiral tridentate lithium amide have revealed that it exists as a chelated monomer in which the lithium is tri-coordinated, as a chelated dimer in which the lithium is tetra-coordinated, or as a mixture of these two species depending upon the solvent used. It is concluded that lower Lewis acidity of the tri- and tetra-coordinated lithium compared to the di-coordinated lithium makes tridentate lithium amides inferior to dibentate lithium amides as bases in enantioselective deprotonation reaction.