Copper-Catalyzed Three-Component Borylstannylation of Alkynes

Regio- and stereoselective installation of boryl and stannyl moieties into a carboncarbon triple bond of various alkynes has been achieved based on a three-component coupling reaction by using a diboron and a tin alkoxide with the aid of a copper(II) acetatetricyclohexylphosphine complex, giving diverse vic-borylstannylalkenes in a straightforward manner. Carbontin and carbonboron bonds of the resulting borylstannylation product are successively transformed into carboncarbon bonds by a MigitaKosugiStille and a SuzukiMiyaura coupling, leading to the formation of (Z)-tamoxifen with anti-breast cancer activity.