Polyacrylonitrile Fiber-Immobilized Cobalt Catalyst for Controllable Divergent Transformations of Terminal Alkynes toward Highly E -Selective Hydroboration and Dimerization

The development of heterogeneous catalysts that can selectively drive divergent reaction pathways from identical feedstocks without altering the catalytic scaffold, remains a major challenge. Herein, we report a bis(imino)pyridine-cobalt functionalized polyacrylonitrile fiber (PAN BIP-Co F) that enables controlled divergent transformations of terminal alkynes. The fiber catalyst was synthesized by immobilization of Co(II) on bis(imino)pyridine modified polyacrylonitrile fiber and characterized by mechanical strength analysis, EA, FTIR, XRD, XPS, TGA, and SEM. Remarkably, subtle modulation of reaction conditions selectively triggered two distinct pathways using only 3 mol % of the same heterogeneous catalyst (PAN BIP-Co F). Under basic and nonpolar conditions at 80 °C, terminal alkynes underwent hydroboration with pinacolborane (HBpin) to afford E -alkenylboronate esters in yields of up to 91%. However, the introduction of 1,3-bis(diphenylphosphino)propane (dppp) and a polar solvent at 50 °C redirected the reaction toward alkyne dimerization, producing E -1,3-enynes in yields of up to 84% with >99% selectivity. Moreover, the fiber catalyst PAN BIP-Co F exhibited high stability and recyclability in these divergent reactions, highlighting its practical potential for sustainable and value-added alkyne transformations.