Experimental Selection of Bases for Colloidal Gold‐Polymer Composite Catalyst in Homocoupling Reactions

Abstract

This work describes the empirical screening of base types and amounts on the catalytic property of gold‐polymer composite particles in the aerobic homocoupling of arylboronic acid. As these particles notably improve the yields of biaryl in the presence of bases, various bases and their amounts are systematically tested to experimentally identify an ideal base that can provide high reactivity and recyclability of the composite particles in mild and green conditions. Interestingly, the following conditions ‐ soluble strong bases at sub‐stoichiometric quantities (0.5 eq.) and insoluble weak bases at excess amounts (3.0 eq.) in EtOH ‐ significantly enhance the catalytic activities of the composite particles. Upon screening two ideal bases, overall catalytic properties of the composite particles including reaction rate at three different temperatures, activation energy (51–52 kJ/mole), and recyclability (7 cycles) were compared. Understanding the effect of bases and fine‐tuning reaction conditions can potentially improve overall reactivity and recyclability of the composite particles as a green quasi‐homogenous catalyst.

Light-enhanced catalytic activity of stable and large gold nanoparticles in homocoupling reactions

“…Particularly, a much faster rate of reaction was observed under light irradiation after the first 4 h (i.e., over 35% yields), presumably due to the initial concentration of abundant reactant. The rate of reaction gradually decreased (e.g., 5–12% yields) as this type of homocoupling generally follows the first order kinetic 61 – 63 . This on-and-off trend of the reaction yields clearly indicated the importance of plasmonic AuNPs that can induce both photothermal heating of the reaction medium and SPR-enhanced catalytic activity under light irradiation.…”