Palladium nanoparticles embedded in improved mesoporous silica: a pH‐triggered phase transfer catalyst for Sonogashira reaction

Abstract

An efficient and reusable pH-responsive mesoporous silica nanocomposite shuttle-supported palladium catalyst was synthesized, which efficiently promotes the Sonogashira reaction in water-based biphasic systems. This catalyst of shell-embedded palladium nanoparticles is highly dispersed in organic phase in a pH range from 9 to 10 just like a homogeneous catalyst, and can be separated and reused like a heterogeneous one by adjusting the pH value of the aqueous medium. In addition, Sonogashira reactions can be performed without a copper co-catalyst.

Solid-Supported Palladium Catalysts in Sonogashira Reactions: Recent Developments

“…It is remarkable that the reaction using PdNPs@MMT or CuNPs@MMT independently barely worked, suggesting a synergistic effect of both metals. Unfunctionalized inorganic silicon-based materials can also act as support for PdNPs, which has been shown recently by the use of a pH-responsive mesoporous silica nanocomposite [130]. This kind of silica can be highly dispersed in an organic phase by adjusting pH (9-10) hence preserving the benefits of homogeneous catalysts.…”

Step‐by‐step synthesis of copper(I) complex supported on platinum nanoparticle‐decorated mesoporous silica hollow spheres and its remarkable catalytic performance in Sonogashira coupling reaction

“…Because of the need for very large quantities of the palladium catalyst, which is not economically viable, 13,14 many efforts have been focused on the development of heterogeneous catalysts to overcome the drawbacks associated with the recovery of the expensive catalyst in large‐scale industrial production 15–21 . Furthermore, to increase the specific surface area and reduce the content of active components, constructing a new heterogeneous catalyst on an appropriate support has been suggested 21–25 . The hollow mesoporous silica with unique advantages such as low density, high specific surface area, large pore volume, and mechanical stability is a suitable substrate for increasing the selectivity and improving catalyst stability 26–28 .…”

Functionalized Silica Matrices and Palladium: A Versatile Heterogeneous Catalyst for Suzuki, Heck, and Sonogashira Reactions

“…Encapsulation or immobilization of active nanometals on carbon-based materials, 13 metal−organic frameworks, 14 alumina, 15 polymers, 16 zeolites, 17 clays, 18 and inorganic matrices 19,20 have emanated as effective strategies that could enhance their recovery and reduce their tendency to undergo agglomeration. 21,22 Usually, immobilization is accomplished using covalent anchoring, 23 polymerizations, 24 encapsulations, 25 sol−gel condensation, 26 or the Stober method. 27 For versatile catalytic applications, PdNPs on supports can be protected with organic molecules to enhance their dispersity in solvents.…”