Deuterium as a Stereochemically Invisible Blocking Group for Chiral Ligand Synthesis.

Abstract

Highly diastereoselective lithiation (s-BuLi/TMEDA in Et2O, -78 °C, 2 h) of (S)-2-ferrocenyl-4-(substituted)oxazolines followed by addition of MeOH-d4 gave up to 95% D incorporation. Subsequent application of alternative lithiation conditions (n-BuLi in THF, -78 °C, 2 h), followed by addition of an electrophile, resulted in a reversal of diastereoselectivity controlled primarily by the high kH/kD value for lithiation (isomer ratio typically between 10:1 and 20:1).