Design And Synthesis Of Chiral Diene Ligands And Applications For Rhodium-Catalyzed Asymmetric Reaction

Since their introduction in2003, chiral dienes have become important members of chiral ligand families. The advent of chiral diene ligands offers new opportunities for asymmetric transition-metal catalysis. Compared with phosphane ligands, chiral dienes have proven to be excellent ligands for transition-metal-catalyzed asymmetric reactions in terms of both catalytic activities and enantioselectivities in a variety of rhodium-catalyzed asymmetric reactions. This essay mainly focuses on the design and synthesis of a new series of chiral diene ligands and its application in asymmetric reactions.A new class of monosubstituted C1-symmetric diene ligands with a DCP backbone has been developed. With an efficient lipase-catalyzed resolution as the key step, the ligand synthesis is convenient and high yielding. These new ligands were successfully applied in the rhodiumcatalyzed asymmetric arylation of N-tosylarylimines. The reaction proceeded smoothly and resulted in the corresponding diarylmethyltosylamides with excellent yields (98-99%) and high enantioselectivities (90-96%). These new ligands were also successfully applied in the rhodium-catalyzed asymmetric1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds. Under mild reaction conditions, the desired addition products were generated in high yields (90-99%) with high enantioselectivities (up to97%ee).We have developed a rhodium-catalyzed asymmetric addition of arylboronic acids to α,β-unsaturated γ-lactams using chiral diene as ligands. Under optimal conditions, the reaction proceeded with excellent yields and enantioselectivities, affording a variety of synthetically useful chiral β-substituted γ-lactams. The power of this methodology is demonstrated by the concise synthesis of (R)-baclofen and (R)-rolipram.We have developed a method for the enantioselective synthesis of flavanones through the rhodium-catalyzed asymmetric1,4-addition of arylboronic reagents to commercially available chromone using chiral diene as ligand. After optimization, chiral flavanones could be obtained in moderate yield and good enantioselectivity. Further investigation is needed for obtaining better results.