Stereoselective Synthesis of β-Hydroxyallenes with Multiple Contiguous Stereogenic Centers via Aldehyde Addition to α-Alkenyl-Substituted Zirconacyclopentenes

A highly stereoselective methodology for the synthesis of β-hydroxyallenes with multiple stereogenic centers including allenic axial chirality, as well as center chirality, via addition of α-alkenylzirconacyclopentenes to aldehyde is described. Remarkably, the reaction occurs with completely different chemoselectivity in comparison with the usual alkyl- or aryl-substituted zirconacyclopentenes; that means, the C−C bond formation occurred selectively at the alkenylic carbon substituted with phenyl or alkyl group, while in the latter cases, insertion of aldehydes into the alkyl−zirconium bond to afford seven-membered oxazirconacycles has usually been observed.