Cobalt(I)‐Catalyzed <i>E</i>‐Selective Hydroalkynylation of Terminal Alkynes or Internal Alkynes with Silyl‐Substituted Terminal Alkynes

A stereoselective cross‐dimerization between silyl‐substituted donor alkynes and aryl‐ or alkyl‐substituted terminal acceptor alkynes using an in situ generated Co(I)‐phosphine catalyst is reported. The reaction optimization for both classes of acceptor alkynes is conducted via Design of Experiments and showed high E ‐selectivities using different reaction conditions. Moreover, activated internal alkynes are successfully applied as acceptor alkynes in the cross‐hydroalkynylation, leading to highly substituted 1,3‐enynes in good regioselectivities and good to excellent yields.