Cobalt‐Catalyzed Z‐Selective Hydrosilylation of Terminal Alkynes

A cobalt‐catalyzed Z ‐selective hydrosilylation of alkynes has been developed relying on catalysts generated from bench‐stable Co(OAc)₂ and pyridine‐2,6‐diimine (PDI) ligands. A variety of functionalized aromatic and aliphatic alkynes undergo this transformation, yielding Z ‐vinylsilanes in high yields with excellent selectivities (Z /E ratio ranges from 90:10 to >99:1). The addition of a catalytic amount of phenol effectively suppressed the Z /E ‐isomerization of the Z ‐vinylsilanes that formed under catalytic conditions.     

Catalytic Enantioselective Cyclopropenation of Internal Alkynes: Access to Difluoromethylated Three‐Membered Carbocycles

Herein we described an efficient Rh^II‐catalyzed enantioselective cyclopropenation reaction of internal alkynes with a masked difluorodiazoethane reagent (PhSO₂CF₂CHN₂, Ps‐DFA). This asymmetric transformation offers efficient access to a broad range of enantioenriched difluoromethylated cyclopropenes (40 examples, up to 99 % yield, 97 % ee). The synthetic utility of obtained strained carbocycles is demonstrated by subsequent stereodefined processes, including cross‐couplings, hydrogenation, Diels–Alder reaction, and Pauson–Khand reaction.