Ruthenium-Catalyzed Intermolecular Coupling of Vinylic 1,2-Bisboronates with Alkynes: Stereoselective Access to Boryl-Substituted Homoallylic Alcohols.

The ruthenium catalytic addition of alkenes to alkynes has been demonstrated as a powerful synthetic tool to form diene motifs and widely applied in the synthesis of complex molecules. However, except for the intramolecular coupling, trisubstituted alkenes are unsatisfactory coupling partners with alkynes, presumably due to the increased steric hindrance. Herein, we discovered that substituted vinyl 1,2-bisboronate derivatives can serve as the trisubstituted alkene equivalents to couple with alkynes, generating various boryl-substituted homoallylic alcohol motifs with good stereoselectivity through the sequential allylboration with aldehydes. In contrast to carbon substituents on the double bond, boron substituents accelerate the alkyne coupling.