Asymmetric Alkylation of Amide Enolates with Pseudoephedrine and Ephedrine as Chiral Auxiliaries—Unexpected Influence of Additives?

摘要

Asymmetric alkylation of carboxylic acid derivatives has been studied intensively for about 15 years. Numerous auxiliaries and tailor-made structures with high steric demands for effective Re/Si face differentiation have been synthesized and their efficiency tested. In recent years besides the preparative aspects of enolates, physico-chemical investigations into their structure-reactivity relationships have gained interest. Crystal structure analyses, osmometric measurements, and NMR studies in solution are helpful in the investigation of the factors that may control enolate reactions.