Enantioselective protonation of a lithium enolate derived from 2-methyl-1-tetralone using chiral sulfonamides

The synthesis of enantiomerically enriched (R)-2-methyl-1-tetralone (1) with 77% e.e. was achieved through protonation of its lithium enolate (3) using a C-2-symmetric tris-sulfonamide (6) as an internal chiral proton source. Access to the complementary (S)-enantiomer 1 with 33% e.e. was achieved using a related C-2-symmetric bis-sulfonamide (9) as the chiral proton source.