AbstractA nickel‐catalyzed three‐component coupling reaction through cyanation of a carbon‐carbon triple bond is described. A nickel(0) complex effectively catalyzes a sequential coupling reaction between allenes, alkynes and hydrogen cyanide from acetone cyanohydrin in a highly regio‐ and stereoselective fashion. The trigger for this reaction is hydronickelation to allenes. The initial hydride attack predominantly occurs at the central carbon of the allene to give a π‐allylnickel(II) species. Subsequent syn‐carbometalation connects a β‐carbon of alkynoates and a less‐hindered carbon of the allylnickel(II) species, and the corresponding cyanoalkenes are obtained as a single stereoisomer without any another organometallic reagents as a coupling partner.magnified image
Packed with functionality: The key step in the title reactions with acetone cyanohydrin is a regioselective hydronickelation of allenes. Subsequent carbometalation of the alkyne followed by reductive elimination gave cyano‐functionalized tetrasubstituted alkenes in a regio‐ and stereoselective manner (see scheme; EWG=electron‐withdrawing group, Ts=p‐toluenesulfonyl).
The synthesis of regio- and stereoselective arylsubstitutedα,β-unsaturated aldehydes and ketones from activated allenes was achieved. This mild and non-metallic oxidation is exclusively driven by benign ambient air and triggered by visible light. The same starting materials under ideal anaerobic conditions led to the 2,3-diphenylselenation adduct with no trace of oxygenated products, demonstrating