Fig. 1: Background and our strategy.

a Previous arts on transition-metal-catalyzed 1,2-difunctionalization of alkynes (three-component reaction, well-studied). b Our design (four-component reaction, unknown). c Synthesis of polysubstituted 1,3-dienes via nickel-catalyzed four-component reaction with two alkynes (this work). 3-component = three-component reaction, ATRA = atom transfer radical addition reaction, RA = radical addition reaction, AI = alkyne insertion reaction.