Halogen‐Atom Transfer Enabled <i>Z</i>‐Selective Styrene Synthesis via Dual Cobalt and Photocatalysis Through Coupling of Unactivated Alkyl Iodides With Terminal Arylalkynes

Abstract An efficient Z ‐selective cobalt‐catalyzed reductive hydroalkylation of terminal aryl alkynes with unactivated alkyl iodides has been achieved, providing a straightforward and modular route to access 1,2‐disubstituted Z ‐styrenes. This reaction operates under mild conditions without requiring over‐stoichiometric amounts of metal terminal reductants. Excellent Z/E ratios and good to excellent yields can be achieved for diverse and complex scaffolds with remarkable functional‐group compatibility. One potential utility of this reaction is demonstrated by the efficient synthesis of several syn homoallylic alcohols in a one‐pot two‐step sequence. Control experiments strongly support that the halogen‐atom transfer (XAT) process is the key to generating carbon radicals. DFT studies suggest that the catalytic system involves the Co(II)/Co(III) cycle and the steric repulsion between the Co(II) catalyst, and the alkenyl radical in radical capture by Co(II) is the dominant factor controlling the Z/E selectivity. This approach represents the first example of merging photo‐XAT with cobalt‐catalyzed reductive coupling of terminal aryl alkynes with unactivated alkyl iodides.