Porous Ligand Creates New Reaction Route: Bifunctional Single-Atom Palladium Catalyst for Selective Distannylation of Terminal Alkynes

Article abstract of DOI:10.1016/j.chempr.2020.06.020

We proposed a unique research concept of “mechanism-oriented catalyst design”: The structural elements of single-atom catalyst are designed according to the requirements of organic synthesis mechanism. This concept is totally different from the previous “electrocatalytic” single-atom-site research concept. This work suggests that single-atom-site catalysts not only afford an efficient platform for transforming homogeneous reactions into heterogeneous reactions, but also possess many interesting potentials in developing new synthetic reactions and solving homogeneous reaction problems. Single-atom-site (SAS) catalyst, as a highly reactive heterogeneous catalytic system, is one of the effective tools for complex organic synthesis. However, excessive attention on the catalysis and regulation of metal atoms has led to the neglect of the role of supports and ligands. Here, we employed a P-doped porous organic polymer as a support, as well as a ligand in the developed Pd SAS catalysts. The enrichment of the substrates by the pores, ligand action of the support, and high chemoselectivity and anti-agglomeration of SAS catalysts were the most striking features of this SAS catalyst. A highly selective distannylation of terminal alkynes with a new mechanism was achieved by using the multiple properties of SAS catalyst. This catalytic system offers an effective strategy to utilize the enrichment of the substrate by the pores to regulate the reaction mechanism, which opens a new frontier to use pores, ligands, and SASs for synergistic controlling reaction paths. Single-atom-site catalysts have many applications in organic synthesis. However, most of the research models related to organic synthesis still stay in the mode of “pursuing higher catalytic performance,” mainly based on electrocatalysis. This article provides a reasonable design of the catalyst in accordance with the characteristics and reaction requirements of organic synthesis and finally uses it for the development of a new reaction route. The distannylation of alkynes is very useful in the construction of complex molecules. In the past, only a few terminal alkynes could be achieved by selective distannylation. Based on the mechanism of the reaction, the porous organic polymer catalyst with triarylphosphonate as the backbone was designed and prepared with advantages including pore enrichment, ligand regulation, and single-atom selective regulation. This catalyst solved all the problems in this reaction, such as narrow substrate scope, poor selectivity, and low catalytic efficiency.