The Synthesis Of New Chiral N, P Ligands And Their Applications In Asymmetric Hydrogenation And Allylic Alkylation

This thesis consists of two parts: Synthesis and applications of new chiral N, P ligands in the Pd-catalyzed enantioselective allylic alkylation and in the Ir-catalyzed asymmetric hydrogenation.The design and synthesis of effective chiral ligands play an important role in transition-metal catalyzed asymmetric reactions. Many efforts were focused on the improvement of activities and enantioselectivities of new chiral ligands, chiral N, P ligands were extensively developed in the past two decades. In chapter one, a series of new N, P ligands 52a-52g bearing tetrahydroquinoline ring, which were derived from chiralα-pinene were synthesized. Palladium complexes of these N, P-ligands were proved to be efficient catalysts for the enantioselective allylic substitution reaction. The affects of solvents, bases, Palladium complexes were test. The results showed that ligand 52d was the best catalyst for the alkylation. The best result was obtained in high yield (up to 99% yield) and enantioselectivity (up to 95% ee).In chapter two, six chiral Fc-PHOX and one P centre chirality oxazoline N, P ligands were developed. The seven ligands (33a-33f and 47) and 52a-52g were reacted with [Ir(COD)Cl]₂ and NaBArF to equipped chiral catalysts 34a-34f, 48 and 38a-38g. These Ir-complexes were effective catalysts in the hydrogenation of functional and unfunctional olefins. Good conversion and enantioselectivity were obtained. Catalysts 34a-34f provided better enantioselevtivities than catalysts 38a-38g and 48. Catalysts 34a-34f were applied in the hydrogenation of allyl acetate and up to 100% conversions and up to 99% enantioselectivies were obtained. Catalysts 38a-38g were checked in the hydrogenation of functional and unfunctional olefins, such as diphenylpropene, allylalcohols, allyl acetates unsaturated ester, dehydrogenation aminoacid esters and vinyl phosphinates. The best result (90% ee) were obtained in the hydrogenation of vinyl phosphinate 43 with 38c as catalyst. The results (moderate enantioselectivities) showed that these bulkier ligands are both less reactivity and less selectivity than that of similar ligands. Repulsion between the pinene moiety and a phosphorus phenyl group may result in a conformational change that produces a more crowded active site which may reduced the enantioselectivity of hydrogenation. In order to test the affect of P chirality, the catalyst 48 was synthesized. Catalyst 48 has a P centre chirality and the oxazoline is an achiral ring. The results showed that 48 had high activity in the hydrogenation of functional and unfunctional olefins (92-99% yields). The enantioselectivities was modest (6-33% ee).