Microenvironmental effect in polymer-supported reagents for organic chemistry

The microenvironment of a polymer-supported reagent consists of the polymer backbone, and the neighboring groups surrounding the active moieties. The interactions between the groups are not negligible due to a small confined volume within the macromolecule. The microenvironment can be tailored for maximized kinetics and yield in organic reactions.; Polymer-supported phosphine resins are synthesized and used to carry out the Mitsunobu reaction of benzyl alcohol with benzoic acid. Polymer-supported phosphine resins are compared with their small molecule analogues to quantify the electronic and microenvironmental effect. It is found that the choice of groups surrounding a ligand can be as important as the choice of the ligand. Increasing the hydrophobicity surrounding the phosphine ligands results in an increase in the reaction rate and the product yield. It is proposed that decreasing the polarity of the microenvironment surrounding the active sites increases the reactivity of the intermediate in the rate-determining step, resulting in an increase in the rate of product formation.; Polymer-supported sulfonic acid resins have been synthesized and used to catalyze the aldol condensation and the Prins reaction. The kinetics for the heterogeneous and homogeneous acid catalyzed reactions are studied and compared. Catalytic activity of the polymeric catalysts is influenced by matrix rigidity, porosity, particle size, and the microenvironment surrounding the acid ligands. The optimum reaction rate can be achieved by balancing the ligand density and the polarity of the microenvironment surrounding the active sites. Polymer-supported sulfonic acid resins outperform their small molecule analogue in reaction rate, product selectivity, and product yield.