Some transition metal catalyzed highly enantioselective reactions

Complex molecules are known to affect every aspect of our lives, from agrochemicals, to pharmaceuticals, to dietary supplements, to perfumes and cosmetics. The effort to develop efficient, practical, environment friendly, and low cost approaches relies on the design of effective synthetic methodologies. Cycloisomerizations are considered as attractive methods to provide quick access to complex molecular frameworks in a single transformation.; A novel protocol of Rh-catalyzed enyne cycloisomerization has been developed by in situ generate cationic catalytic species. Varieties of five-membered heterocyclic and carbocyclic compounds, including functionalized gamma-lactones, lactams, tetrahydrofurans, cyclopentanes, and cyclopentanones, have been synthesized in high yields and excellent enantioselectivies (>99% ee). A symmetric synthesis studies of related five-membered hetero- and carbocyclic natural products, such as pilocarpine, kainic acid, and methyl dihydrojasmonate, have been performed to demonstrate the synthetic utilities of Rh-catalyzed cycloisomerization reaction. More efforts to elucidate the mechanism of cycloisomerization were conduct by NMR studies.; To further expand the utility of this reaction and to address issues related to regio- and stereoselectivity, attention was shifted to allylic substituted enynes. The first examples of kinetic resolution process of Rh-catalyzed intramolecular Alder-ene reaction are described along with the studies of the scopes and stereochemistry of this remarkably efficient and selective process. The formal asymmetric synthesis of blastmycinone, a degradation product of the macrocyclic dilactone (+)-antimycin, was reported to address the application of this methodology.; Phthalimide substituted dehydroamino acids were hydrogenated in the presence of Rh-TangPhos complex. The enantioselectivity was obtained in up to 99.9% ee. The alpha-phthalimide ketones are employed in a Ru-TunePhos catalysts system, in which excellent enantioselectivities (92.3 to 99.0% ee) were achieved. A dynamic kinetic resolution process was also investigated by using phthalimide substituted beta-ketoester in the presence of Ru-complex. Excellent and unusual trans-selectivity was observed, which is reversed to Noyori system's result.; An efficient method for preparation of chiral nipecotic acid derivatives by hydrogenation was developed. The whole process comprises of an efficient partial hydrogenation of nicotinate and a subsequent highly enantioselective Rh catalyzed homogeneous hydrogenation, setting an effective example of highly enantioselective hydrogenation of substituted pyridines.; A novel palladium-catalyzed aryl homocoupling reaction was established via double transmetallation between Pd(II)X(enolate) and arylzinc reagent. As the first case of zinc reagent involves in double transmetallation homocoupling, different substituted aryls were investigated and high chemical yield were achieved.