Boosting the feasibility of heterogeneous telomerization of 1,3-butadiene with methanol by low-surface-area N-heterocyclic carbene-functionalized hypercrosslinked polymers

Abstract

The main bottlenecks for the industrial application of existing heterogeneous telomerization catalysts are inferior activity, low stability, and poor selectivity. Herein, we develop a heterogeneous catalyst system to obstacle these issues. A low-surface-area hypercrosslinked polymer fabricated by 1,3-diary-imidazolium chlorides IXy·HCl (aryl = 1,6-dimethylphenyl) via the Scholl coupling method was prepared and utilized as solid ligand in pseudo-heterogeneous telomerization of 1,3-butadiene with methanol. Superior catalytic performance (high linear to branched regioselectivity up to 66:1, chemoselectivity up to 98.5%, and a recorded turnover number (TON) up to 3.1 × 105) for the linear product 1-methoxyocta-2,7-diene (1-MOD) was achieved. Moreover, the heterogeneous Pd catalyst could be in situ generated during the telomerization process, which could be reused at least 10 runs without catalytic activity and selectivity loss. Full characterization of catalysts and control experiments results demonstrated that the synergistic effect of low-surface-area hypercrosslinked skeleton and the coordination environment of Pd in heterogeneous catalyst modified by diene ligands such as 1,3-butadiene or 1-MOD was beneficial to boost the feasibility of heterogeneous telomerization. This innovation is a significant step toward the development of high-performance heterogeneous telomerization catalysts for industrial applications.