Cobalt-Catalyzed Regio- and Diastereoselective Formal [3 + 2] Cycloaddition between Cyclopropanols and Allenes

A cobalt–diphosphine
catalyst has been found to promote
a formal [3 + 2] cycloaddition reaction between a cyclopropanol and
an allene via cyclopropanol ring opening, which affords a 3-alkylidenecyclopentanol
derivative with high regio- and diastereoselectivities. The reaction
tolerates monosubstituted, 1,1-disubstituted, and 1,3-disubstituted
allenes and various functional groups. The reaction is proposed to
proceed through carbometalation of the allene with a cobalt homoenolate
followed by intramolecular carbonyl allylation of the resulting allylcobalt
species.