Cobalt-catalyzed stereodivergent semi-hydrogenation of internal alkynes to alkenes is developed.

The difluoroalkylation of alkynes and alkenes by direct photoexcitation of ethyl difluoroiodoacetate is described. Under catalyst- and oxidant-free conditions, iododifluoro­alkylation and hydrodifluoro­alkylation products were generated from alkynes, and difluoroalkylation products were prepared from alkenes. This methodology provides a streamlined access to difluoroalkylated organic compounds starting from simple alkynes or alkenes.

An anion controlled stereodivergent semi‐hydrogenation of alkynes is reported. The reactions are catalyzed by the low‐cost and stable nickel(II) salts, using water as environmental friendly hydrogen source with zinc powder as metal reductant. Interestingly, the stereoselectivity of the reaction is well controlled by the anion of the nickel(II) salt. The present methodology allowed a low‐cost and convenient preparation of trans‐ and cis‐alkenes under mild conditions. The reaction mechanism is proposed with water as the hydrogen donor on the basis of the control experiments.

Enantioselective [2+2] cycloaddition reaction of azabenzonorbornadienes and oxabenzonorbornadienes with internal alkynes has been enabled by a catalyst system comprising Ni(COD) and (R)-SIPHOS-Ph-Mor. This transformation represents the first asymmetric [2+2] cycloaddition reaction of azabenzonorbornadienes with internal alkynes, providing a straightforward method to prepare four-membered carbocycles.