Phase selectively soluble polymers for homogeneously supported catalysts

Abstract

Soluble polymer supports that could be used in thermomorphic and latent biphasic systems have been prepared and analyzed for their potential application as supports for facilitated synthesis and catalysis. Phase selective solubilities were evaluated using polymers tagged with either visible dyes or fluorescent probes. Heptane/DMF, heptane/90% ethanol-water, heptane/ethyl acetate, heptane/ ethanol and heptane/tert-butanol solvent mixtures were all studied as examples of thermomorphic or latent biphasic systems. A range of polymers, including poly-(tert-butylstyrene) (PTBS), poly(alkylsiloxanes) (PAS), poly(dodecylvinylpyrrolidone) (PDVP), poly(didodecylvinylpyrrolidone (PDDVP), poly(isobutylene) (PIB), poly(octadecyl acrylate)s (PODA), and poly(octadecyl methacrylate)s (PODMA), were tested for hydrophobic phase selective solubility. The results of these studies were compared to prior work with polar and nonpolar poly(N-alkylacrylamide)s and polystyrene. Together with this prior work, these results have indicated that a wide range of polymers and solvent mixtures can be used for the recycling of soluble polymer-bound catalysts, reagents and sequestrants using either thermomorphic or latent biphasic separation strategies.Synthetic routes to terminally functionalized polyisobutylene oligomers, useful as supports in synthesis and catalysis, are also discussed and described. Such hydrocarbon polymers serve as highly soluble nonpolar analogs of well known poly(ethylene glycol) supports for synthesis and catalysis with the difference that the polymers are separated after a reaction by an extraction with alkane solvent. The synthesis of two polyisobutylene-supported phase transfer catalysts (PTC) are also described. These PTCs utilize the robust triazole functionality as a key synthetic step towards the preparation of the catalytic species. N alkylation of a PIB-supported triazole provides a direct route to the preparation of a PTC. Preparation of a tertiary phosphoninium salt containing a terminal alkyne allows simple attachment of the PTC to a PIB-supported azide via a triazole linker using Sharpless' Cu (I) [3 + 2] cycloaddition. These materials are active in catalyzing solid-liquid PTC and can be easily recycled by liquid-liquid extraction techniques.