Enantioselective protonation of achiral lithium enolates using a chiral amine in the presence of lithium bromide

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Abstract Asymmetric synthesis of 2-alkyl-1-tetralones ( 2 ) was achieved in up to 91% e.e. by enantioselective protonation of their corresponding achiral lithium enolates ( 4 ) using a chiral amine (( R )- 1 ) as a chiral source in the presence of lithium bromide. Enantioselective alkylation using ( R )- 1 was also carried out, and it is found that the alkyl halide prefers the si -face of the lithium enolate 6 as oppose to the re -face preference of 4a in case of protonation.