Zinc-Mediated Hydroxyallylation of Aldehydes with Cyclopropanols: Direct Access to Vicinal anti-sec,tert-Diols via Enolized Homoenolate

Direct and diastereoselective synthesis of vicinal anti-sec,tert-diols has been achieved by zinc-mediated α- hydroxyallylation of aldehydes with cyclopropanols. The reaction features the action of zinc enolized homoenolate, formed via ring opening of zinc cyclopropoxide and enolization of the resulting homoenolate, as γ-oxyallyl nucleophile toward the carbonyl electrophile, which stands in contrast to the previously described enolate mode of the same species. A bicyclic chairlike transition state wherein the aldehyde substituent favorably occupies the psuedoaxial position is proposed to account for the anti selectivity.