Intramolecular cyanoboration of alkynes via activation of boron–cyanide bonds by transition metal catalysts

Cyano(dialkylamino)boryl ethers of homopropargylic alcohols undergo intramolecular addition of a B–CN bond across their carbon–carbon triple bonds (cyanoboration) in the presence of palladium and nickel catalysts, furnishing five-membered cyclic boryl ethers regioselectively in good yields via 5-exo cyclization. The products were transformed into highly substituted α,β-unsaturated nitriles via Suzuki–Miyaura coupling to aryl iodides, rhodium-catalyzed conjugative addition to methyl vinyl ketone, and rhodium-catalyzed protodeborylation.