Alkali metal counterion control of enolate protonation stereoselectivity.

ABSTRACT

[reaction see text] Generation of the lithium salt of the norbornenol shown (M = H) followed by quenching with aqueous NH(4)Cl solution gives predominantly the beta-epimeric ketone 6. Similar production of the potassium alkoxide leads instead to the alpha-epimer (991). These results reveal the potential importance of alkali metal counterions as stereocontrol elements.