Reversal of enantioselectivity on protonation of enol(ate)s derived from 2-methyl-1-tetralone using C2-symmetric sulfonamides

The synthesis of enantiomerically enriched (R)-2-methyl-1-tetralone 1 (64% e.e.) was achieved through protonation of its lithium enolate 3 using a C-2-symmetrical bis-sulfonamide 5d as an internal proton source. Access to the complementary (S)-enantiomer 1 (45% e.e.) can be achieved using an external quench strategy involving acetic acid as the external proton source. (C) 2004 Elsevier Ltd. All rights reserved.