4. Development of New Catalytic Processes and Green Chemistry.

We have also been pursuing mechanistic and synthetic studies on palladium-catalyzed carbon-phosphorus bond forming reactions. Our interest concerns the development of general methodologies for the synthesis of novel functional phosphinic acids that can be used as bone agents and as chelators for radiopharmaceuticals. We have discovered that novel phosphinic acids and phosphineoxides can be prepared in high yields with good regioselectivity via Pd-mediated processes (Scheme VIII). We are also currently extending this research to catalytic synthesis of chiral chelating phosphines for potential applications in asymmetric catalysis.

We have recently extended our research into developing catalytic asymmetric processes in novel reaction media. We have designed new ionic BINAP-derived catalysts that are highly active and enantioselective for the hydrogenation of keto esters and aromatic ketones in ionic liquids (Scheme IX). We have also demonstrated that ionic liquids are efficient for the immobilization of these asymmetric catalysts. We intend to focus more of our efforts in this area of Green Chemistry over the next few years.

Representative Publications:

1. “Highly enantioselective catalytic asymmetric hydrogenation of b-keto esters in room temperature ionic liquids.” Ngo, H.L.; Hu, A.; Lin, W. Chem. Commun. 2003, 1912-1913 [pdf].

2. “Facile Synthesis of Chelating Bisphosphine Oxides and Bisphosphines Via Palladium-Catalyzed Bishydrophosphinylation Reactions.” Allen, Jr., A.; Ma, L.; Lin, W. Tetrahedron Lett. 2002, 43, 3707-3710 [pdf].

3. “Synthesis of Functional Bisphosphonates via New Palladium-Catalyzed Bis-hydrophospho-rylation Reactions.” Allen, Jr., A, Manke, D.R.; Lin, W. Tetrahedron Lett. 2000, 41, 151-154 [pdf].

4. “Unprecedented Insertion of Alkynes into a Palladium-Phosphine Bond. A Facile Route to Palladium-Bound Alkenyl Phosphorus Ylides.” Allen, A.; Lin, W. Organometallics, 1999, 18, 2922-2925 [pdf].