From conventional to dual Co/photoredox mediated reductive coupling of alkynes and alkenes

Metal-catalyzed reductive coupling reactions between alkenes and alkynes are a long-standing tradition as a way to create complex unsaturated building blocks of value in organic synthesis ventures. Here, we review the general synthetic approaches realized under Co-catalysis utilizing chemical reductants, albeit with some limitations in scope and user-friendliness. A more recent advancement shows that these reductive ene-yne coupling reactions can also be accommodated by photoredox catalysis marking a stepping stone in the area, and creating new incentives for this kind of carbon-carbon bond formation and beyond.