Unusual reagent control of diastereoselectivity in the 1,2-addition of hard carbon nucleophiles to C(6)-heteroatom substituted cyclohexenones.

[reaction: see text] A surprising and synthetically useful counterion-dependent reversal of diastereoselectivity was found in 1,2-additions of hard carbon nucleophiles to C(6)-heterosubstituted cyclohexenones. In general, Grignard reagents added syn to the C(6)-substituent and Li reagents added anti, although some exceptions were found. Selectivities could be increased in some cases by appropriate choice of solvent and/or cosolvent.