As the benefits and importance of green chemistry become more apparent, interest in applying its philosophies across the entire spectrum of chemical industries has increased. At the heart of its appeal is the fact the green chemistry promotes processes that can be both environmentally friendly and economically efficient. The commercial benefits can be realized directly by increasing efficiency through the use of catalytic reagents or indirectly by reducing the costs of transporting, handling, and disposing of hazardous chemicals and solvents. Guided by the principles of green chemistry, we have immobilized palladium catalysts onto collagen mimetic peptides (CMPs) capable of performing dual, simultaneous transformations under ambient conditions in aqueous media. Due to their triple helical structure, the peptides form ridged-rod nanoparticles in aqueous solutions. This ridged structure allows for well-defined spatial control of two separate “active sites” by immobilizing palladium centers at specific residues. The first active site was achieved by substituting an arginine residue onto a generic CMP sequence. The second site was achieved by coupling a carboxylic acid-containing phosphine ligand to a lysine residue via amide bond formation. Both the gaunidinium group on the arginine side chain and the phosphine coupled to the lysine side chain, were capable of forming complexes with palladium precursors. These peptide-supported complexes were used as effective catalysts for Suzuki-Miyaura couplings and catalytic allylic substitution reactions in aqueous media under ambient conditions. Although the catalytic systems are still in the early stages of development, their fundamental design offers several advantages compared to traditional catalysts. For example, because the system provides control of spatial separation between catalytic sites, there is potential to promote synergistic effects between cooperative catalysts.
|Commitee:||Bu, Xianhui, Derakhshan, Shahab|
|School:||California State University, Long Beach|
|Department:||Chemistry and Biochemistry|
|School Location:||United States -- California|
|Source:||MAI 56/01M(E), Masters Abstracts International|
|Subjects:||Chemistry, Environmental science|
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