The Research Toward The Synthesis Of Isoindole And New Type Bisoxazoline Ligands

In this thesis,the main content is about the metal-catalyzed condensation reaction of a-diazo esters with organic azides,where the application of this conversion in the synthesis of isoindoles and the preparation of new type bisoxazoline ligands were explored.It includes the following three parts:1.A brief review of the synthetic methods of isoindole;2.preparation of isoindoles using the intramolecular interception strategy of a-diazo esters wint alkyl azides;3.preparation of new type bisoxazoline ligands.In the first part,the synthetic methods of isoindoles were briefly described.The isoindole is a very important organic substance,which is widely used in multiple fields.Many methods had been developed for its synthesis,and the key point is how to construct the pyrrole ring.The ring-forming strategies mainly include:Diels-Alder reaction,1,3-dipolar cycloaddition,oxidation reaction,reduction reaction,alkylation,phthalaldehyde condensation,ring formation from the phenylacetylene,etc..In the isoindole synthesis,the source of nitrogen atoms was mainly derived from amine or ammonia,and the nitro compounds were also involved in some strategies,while the azides were rarely employed.In the second part,the synthesis of isoindole by the intramolecular condensation of a-aryldiazo esters with alkyl azides was explored.13 diazo azides were successfully synthesized from the benzolactones as the substrate,where the preparation proceeded through the ring opening of benzolactones with the hydrogen bromide,azidation and Regtiz diazo transfer reaction.The catalyst,reaction temperature and solvent were studied with the standard substrate,then the reaction conditions were optimized as the following:substrate(0.2-0.4 mmol)in dichloromethane or chloroform with Rh2(oct)4(1%)could efficiently provided the corresponding isoindole in excellent yield.The substrates were also extended to investigate the effect of the aromatic ring and the ortho substituent of the azide group.Finally,13 isoindoles was obtained by this strategy.The experimental results showed that the intramolecular condensation reaction is very efficient,where the isolated yields of the isoindoles are determined by the product’s stabilities and the reaction times.In the third part,the preparation of the new type bisoxazoline ligands is studied.The chiral bisoxazolines and the compounds with binaphthyl skeletons are widely used as ligands in asymmetric catalysis reaction.In order to improve the enantioselective desymmetrization of the meso-alkyl bisazides developed by our group,we designed and synthesized seven bisoxazoline ligands connected with the binaphthyl units.Then the new type bisoxazolines were employed for desymmetrization of substrate 3-85,which was not effective in the previous report.Unfortunately,the enantioselectivity excess of the product could not be increased.We expect that the newly synthesized bisoxazolines with a binaphthyl unit could be employed as a powerful ligands for other organic transformations.