Phase selectively soluble polymer supports to facilitate homogeneous catalysis
Soluble polymers that have phase selective solubility are useful in synthesis because they simplify purification and separation. Such selectively soluble polymers simplify catalyst, reagent, and product recovery and enable the use of Green chemistry principles in homogeneous catalysis. However, while homopolymers have been reported that have excellent thermal and phase-dependent solubility, less is known about copolymers. Also, less is known about the phase selective solubility of polar aprotic N,N-dialkyl polyacrylamides. This work describes a library synthesis of dye-labeled poly(N-n-octadecylacrylamide-co-N-n-butylacrylamide) copolymers and study of the effects of polymer composition in phase selective solubility of these copolymers. To study the relative importance of n-octadecyl versus n-butyl groups, copolymers with different ratios of n-octadecylacrylamide and n-butylacrylamide but with similar degrees of polymerization and polydispersity were prepared by a split-pool synthesis using a highly soluble poly(N-acryloxy-2-dodecylsuccinimide) as the precursor. Polymer sequestrants were used to remove excess amines and the byproduct N-hydroxyl-2- dodecylsuccinimide without fractionation of the polyacrylamides. Results demonstrated that poly(N-n-octadecylacrylamide-co-N-n-butylacrylamide) copolymers? phase selective solubility is equally dependant of the polar n-butyl and nonpolar n-octadecyl groups on the copolymers. Dye-labeled poly(N,N-dialkylacrylamide)s prepared by the polymerization of N,N-dialkylacrylamides monomers with methyl, ethyl, propyl, butyl, hexyl, and dodecyl N-alkyl groups in a variety of thermomorphic or latent biphasic polar/nonpolar solvent mixtures were also prepared. Studies showed that poly(N,N-dialkylacrylamide)s have phase selective solubility that is highly dependent of the size of the N-alkyl group. Soluble polymers are known to be useful supports for catalysts. This thesis also describes approaches to immobilization of a variety of catalysts on polyisobutylene (PIB). The most effective of these catalysts were analogs of pyridyl N-oxides that have been used as organocatalysts for the catalytic allylation of a variety of aromatic aldehydes. PIB-supported N-oxide promoted the allylation of aldehydes in up to 99% isolated yield. The products were isolated in the polar phase of a thermomorphic system and the catalyst was recycled through five cycles.