RESUMEN
Ionic metal-organic frameworks (MOFs) offer a new platform to design and construct complete heterogeneous bifunctional catalytic systems for the chemical fixation of CO2 with epoxides. Herein, we developed a series of bifunctional pyridinium ionic MOF heterogeneous catalysts (66Pym-RXs and 67BPym-MeI) by the postsynthetic N-alkylation of noncoordinated pyridine sites in porous MOFs. The synergetic catalytic effect of acidic sites with nucleophilic anions in the ionic MOF significantly enhanced the catalytic activity toward the cycloaddition of CO2 with epoxides to produce cyclic carbonates under cocatalyst-free and solvent-free mild conditions. The catalytic activity of ionic MOFs is easily tuned by the introduction of different alkyl groups into pyridinium cations and halide ions. The 66Pym-iPrI catalyst displayed the highest catalytic performance in terms of the turnover number value for the synthesis of cyclic carbonates. The proposed alternative method provides the means of developing functional N-heterocyclic groups for the new design of bifunctional ionic MOFs as potential heterogeneous catalysts for CO2 fixation applications.
RESUMEN
A Pd-catalyzed domino process involving a double norbornene insertion/annulation reaction was developed for the expeditious synthesis of overcrowded olefins. In this one-pot reaction, four new C-C bond formations were achieved by three consecutive Heck carbopalladations and C-H activation across the C≡C triple bond of 2-alkynyl bromobenzenes with two norbornene rings via a reactive vinylic-Pd(II) species. This protocol provides a step-economical synthetic system to access the structurally identical molecular machine motifs of overcrowded olefins with high yields.