Selective Long-Range Isomerization Carbonylation of a Complex Hyperbranched Polymer Substrate

作者：Ye Liu, Kaiwu Dong, Matthias Beller, Stefan Mecking · 发表于：ACS Catalysis · 年份：2018 · DOI：10.1021/acscatal.8b03117 · 被引用次数：33 · 研究领域：Synthetic Organic Chemistry Methods、Dendrimers and Hyperbranched Polymers、Organometallic Complex Synthesis and Catalysis

Hyperbranched oligoethylenes are rewarding and extremely challenging substrates for functionalization. They contain one double bond per molecule which offers itself for long-range isomerization carbonylation; however, these are present in various substitution patterns and high degrees of substitution render them unreactive, and furthermore different branch sites need to be passed in an isomerizing functionalization approach. Studies of Pd(II) catalysts with different bulky-substituted diphosphines on hyperbranched oligomers ( M n 1000–3000 g mol –1 ) amended by low-molecular-weight model substrates show that with 1,2-bis(4-phosphorinone)xylene alkoxycarbonylation occurs with high selectivity at the ends of branches to form primary esters with high conversions. The key to this is the retention of selectivity in long-range isomerization/carbonylation even at elevated temperatures that promote reaction rates. By a tandem cross-metathesis/long-range isomerization functionalization approach, difunctional esters were obtained. As a demonstration of their synthetic utility, these were polycondensed to semicrystalline all-aliphatic polyesters in which they serve as soft segments.