During the second year of this grant significant progress has been made in the study of bimolecular Heck reactions using polystyrene/divinylbenzene immobilized palladium catalyst. After extensive exploration of heteroaromatic assemblies the dipyridophenazine adduct emerged as the best, most reliable construct. Eight different phenazine resins have been prepared, and characterized and quantified by LCMS. Each resin was synthesized by a standardized five-step protocol (counting deprotection), and each resin formed in >92% overall substitution. This suite of resins provides a systematic range of hydrophobic to hydrophilic interior environments for studying the Heck reaction.

From the catalysis perspective, we found a simple catalytic procedure using immobilized palladium acetate and each experiment gave unambiguous data for the couple of naphthyl triflate and butylvinyl ether. All immobilized catalyses ran in parallel reactions with the homogenous 1,10-phenanthroline-palladium acetate catalyst. Data showed that the interior environment of the resin overwhelmed the bulk solvent effect of DMF, THF, and toluene. For example, in DMF solvent the homogenous 1,10-phenanthroline-palladium acetate catalyst gave the 1,1-substituted alkene product in 95% yield and the 1,2-alkene product (combined E and Z) in 5% yield (94% chemical yield). The parallel solid-phase catalysis prepared from 1,8-ocatandiol gave the same products but in a 70% :30% product ratio (37% chemical yield). In all cases studied the 1,1-product always dominates, but the ratio of 1,1- to 1,2-substitution varies with the resin. The lower chemical yield for immobilized catalysts follows specifically with the swelling characteristics of the bulk solvent. DMF is the best solvent for the homogenous reaction in terms of yield and selectivity, but is the poorest solvent for the immobilized variants. Systematic data collected in the project will provide a cautionary warning for the development of other types of solid-phase catalyses.µ