Microporous Polymeric Networks Containing a Long-Term Stable Au^I Catalyst for Enyne Cyclization

Abstract

Two microporous polymer networks having a confined Au I carbene catalyst were obtained and tested for the skeletal rearrangement of enynes. These catalysts were obtained from precursor porous organic polymers (POPs), a type of microporous polymer network, synthesized by the reaction of isatin or a mixture of isatin/trifluoroacetophenone (1:1) with triptycene (POP1 and POP2, respectively) through an electrophilic aromatic substitution, EAS, reaction promoted by trifluoromethanesulfonic acid. These precursors could be easily functionalized through the lactam moiety to form Au I carbene catalysts (POP1-AuCarbene and POP2-AuCarbene). The confined carbenes proved to be very active for the skeletal rearrangement of dimethyl 2-(3-methyl-2-butenyl)-2propinylmalonate enyne. A large increase in the stability of the Au I catalysts was observed compared to those of most of the homogeneous catalysts described so far in the bibliography. This long-term stability was associated with the separation of Au I atoms, induced by their confinement in the microporous networks. In particular, POP2-AuCarbene exhibited outstanding long-term stability, maintaining catalytic activity even after several months.

Micropores in Hollow Organic Cage Nanocapsule as a Size Exclusion Gate: Cage Entrapped Pd(II)-Catalyst for Efficient Cross-Coupling Reaction

“…Methodologies based on transition metal-catalyzed various coupling reactions have played an important role in modern synthetic organic chemistry, and the commercialization of new APIs, drugs, pharmaceuticals, and agrochemicals (mainly insecticides, fungicides, and herbicides). − For efficient and sustainable methodologies, there has been an emphasis on combining the benefits of heterogeneous catalysis while maintaining the conditions conducive to homogeneous reactions. , Optimum loading of the Pd­(II)-catalyst, along with its recovery after each catalytic reaction for recycling are linked to a sustainable process. , Heterogenization of such catalysts through anchoring on appropriate solid supports having a high surface area has been argued as one of the key processes for addressing this issue. Different research groups have explored several solid supports like fibers, metal–organic frameworks (MOFs), magnetic nanoparticles, covalent organic frameworks (COFs), dendrimers, and microporous inorganic solids like silica. − In a few instances, the confinement effect in microporous solids has helped in improving the efficiencies in terms of the stability, recovery/recycling of the catalysts. , However, the use of such solids as support has limited application potential owing to inadequate dispersibility in the reaction system. The other option of using suitable surfactants for entrapping the catalysts may also hinder the diffusion of reactants to the active catalyst core and the conversion efficiency, apart from the loss of the entrapped catalyst through leaching. , …”