David Bergbreiter

Although SN2 reactions have been thoroughly studied in polar aprotic and protic solvents, not many studies have been done to study the rate of SN2 reaction in nonpolar solvents like alkanes due to the insolubility of anionic nucleophiles in these solvents. In this study, we investigated the use of N,N-diethyl- N-methylammonium-terminated polyisobutylene oligomers as phase-solubilizing agents for nucleophilic anions that could react with hydrocarbon-soluble substrates in alkanes. The results of these kinetic studies showed alkanes were comparable to MeCN as solvents in many reactions. Based on these studies, we developed a solid/liquid catalytic process using insoluble alkali metal carboxylate salts and a recyclable soluble polyisobutylene-bound catalyst that can be used to carry out SN2 reactions both in heptane and in hydrocarbon oligomeric solvents known as poly(α-olefins) (PAOs).

The use of soluble polymers as supports for catalysts is discussed and reviewed. Strategies where immobilized catalysts on soluble polymers are used in a monophasic reaction, but where the immobilized catalyst is recovered as an insoluble polymer-supported species in a liquid/solid separation step, are discussed. Such strategies include temperature perturbation, pH perturbation, and solvent precipitation as a means of producing a solid/liquid mixture for separation after a homogeneous reaction. Strategies where immobilized catalysts on soluble polymers are used in a monophasic reaction, but where the immobilized catalyst is recovered in one phase of a biphasic liquid/liquid mixture, are also described. Examples where temperature perturbation or additive addition are used as a means of producing a solid/liquid mixture for separation after a homogeneous reaction are discussed. Finally, examples where soluble polymers are used as supports homogeneously or biphasically and separated from products by membrane filtration or biphasic extraction are described.

The polymer‐bound Pd(0) catalyst (VIII), generated as shown in the reaction scheme, is employed in the preparation of the tertiary allylamines (XI) and (XII) from the allylic esters (IX) or the decarboxylation of the allyl carboxylates (XIII), yielding the ketones (XIV) and (XV).

This study describes the use of polyisobutylene (PIB) to phase-anchor pyridine ligands that form a phase-separable Grubbs third-generation catalyst. We further show that this complex is useful in ring-opening metathesis polymerization (ROMP) reactions. These PIB-bound pyridine-ligated Grubbs catalysts provide the same benefits of control over polymer chain growth and polydispersity of the product as their low-molecular-weight analogs and reduce Ru leaching in ROMP products from approximately 16% (820 ppm residues) as seen with a similar pyridine-ligated catalyst to a value of approximately 3% (160 ppm residues). These labile ligands are shown to be as effective at generating separable metal complexes as less labile PIB-functionalized N-heterocyclic carbene catalyst ligands that are typically used for immobilization but that require a multistep synthesis.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Abstract The novel use of polymeric reagents as selective phosphine absorbers in a homogeneous catalysis is presented. Silver(I) p-toluene sulfonate (A) is shown to absorb tertiary phosphines from organic solution and to restore PPh3-inhibited homogeneous hydrogenation of alkenes by RhC1L3 (L[dbnd]PPh3) to a non-inhibited rate. Treatment of RhC1L3 with ethylene in presence of A followed by addition of a second alkene and removal of ethylene under reduced pressure leads to an increased rate of hydrogenation for several alkenes.

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Abstract The novel use of polymeric reagents as selective phosphine absorbers in a homogeneous catalysis is presented. Silver(I) p-toluene sulfonate (A) is shown to absorb tertiary phosphines from organic solution and to restore PPh3-inhibited homogeneous hydrogenation of alkenes by RhC1L3 (L[dbnd]PPh3) to a non-inhibited rate. Treatment of RhC1L3 with ethylene in presence of A followed by addition of a second alkene and removal of ethylene under reduced pressure leads to an increased rate of hydrogenation for several alkenes.