Investigations into the enantioselective protonation of enolates derived from 2-methyl-1-tetralone using a chiral diamine ligand

The synthesis of enantiomerically enriched (+)-(R)-2-methyl-1-tetralone 1 (up to 47% e.e.) was achieved by enantioselective protonation of an achiral lithium enolate 3 using a chiral diamine additive in the presence of acetic acid. We discuss the factors (like salt effects and chelation) that are responsible for this observed enantioselectivity and comment on the role of the achiral acid.