Stereoselective Cyclopropanation of 1,1-Diborylalkenes via Palladium-Catalyzed (Trimethylsilyl)diazomethane Insertion

Palladium catalyzes the cydclopropanation of 2-substituted 1,1-diborylalkenes with (trimethylsilyl)diazomethane. The relative stereoselectivity is controlled via a carbene insertion sequence generating an exclusive anti conformation between the R and SiMe3 substituents. Mixed 1,1-diborylalkenes also contributed to the formation of stereoselective B, B, Si-cyclopropanes. Orthogonal activation with (NaOBu)-Bu-t gives protodeborylation preferentially on the boron moiety syn to the aryl group. Further oxidation gives access to polyfunctional cycloopropyl alcohols with controlled enantioselectivity when chiral boryl motifs are involved.

Automated summary

Palladium catalysis enables the cyclopropanation of 2-substituted 1,1-diborylalkenes with (trimethylsilyl)diazomethane, controlling the relative stereoselectivity. Furthermore, further reactions involving chiral boryl motifs lead to the formation of polyfunctional cycloopropyl alcohols with controlled enantioselectivity.