B ₂ pin ₂ ‐Assisted Nickel‐Catalyzed Z ‐Selective Semi‐Hydrogenation of Alkynes With Formic Acid

A nickel‐catalyzed, boron‐aided system enables highly stereoselective semi‐hydrogenation of alkynes to Z ‐alkenes, with formic acid employed as a benign hydrogen source to ensure operational safety. This protocol affords Z ‐alkenes in up to 95% yield and 96/4 stereoselectivity, displays excellent functional group tolerance, and gains further experimental validation via gram‐scale synthesis and facile product isolation. Mechanistic investigations confirm a homogeneous reaction pathway, with B 2 pin 2 facilitating the in situ generation of hydrogen from formic acid.