Regioselective Hydrophosphorylation of Alkynes by a Functionalized Heterogeneous Cu-chitosan Based Catalyst

The functionalized heterogeneous Cu-chitosan based catalyst was developed for the regioselective hydrophosphorylation of alkynes with secondary H-phosphine oxides. The functionalized chitosan framework was produced through a cross-coupling reaction between chitosan and 2,4,6-trichloro-1,3,5-triazine. Following this, the coordination of Cu(OAc)2 with the functionalized chitosan framework led to the synthesis of the heterogeneous Cu-chitosan based catalyst. Various techniques, such as powder FT-IR spectroscopy, X-ray diffraction (XRD), N2 physical adsorption, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), were employed to characterize the catalyst. Subsequently, the resulting Cu(OAc)2@chitosan@2,4,6-trichloro-1,3,5-triazine catalyst exhibited remarkable catalytic activity in the regioselective hydrophosphorylation of alkynes with the formation of P–C bonds, displaying exceptional E/Z selectivity. This successful catalysis led to the synthesis of a range of (E) anti-Markovnikov adducts with high yields. The catalyst shows high recyclability in this transformation. On the basis of step-by-step control experiments, a plausible mechanism is proposed.