High enantioselectivity (up to 94% ee) has been achieved in the protonation of samarium enolates which were generated by SmI2-mediated reduction of 2-aryl-2-methoxycyclohexanones using a C2-symmetric chiral diol as a protonsource.
SmI2-mediated reductive cleavage of α-hetero substituents of α-alkyl or α-aryl ketones and lactone gave the corresponding “thermodynamic samarium enolates”. Enantioselective protonation of the samarium enolates with C2-symmetric chiral diols afforded the corresponding ketones and lactone in moderate to high enantioselectivities.