Research And Synthesis Of Asymmetric Allylation Catalyzed By Chromium Complex

Carbon-carbon bond formation is one of the most important transformations in organic chemistry.The addition reaction of the halides to the carbonyl,called the Nozaki-Hiyama-Kishi reaction(NHK reaction),has been shown to be a very efficient method in the various carbon-carbon bond formation reactions.This method results in the formation of secondary or tertiary alcohols while efficiently obtaining new carbon-carbon bonds.Since it is discovered in 1983,by Professor Nozaki of Kyoto University in Japan,it has been widely used in organic synthesis and natural product synthesis due to its mild experimental conditions,extensive substrate range and efficient asymmetric reaction,especially in the synthesis of macromolecules,such as the synthesis of palytoxin was achieved by Kishi with readily available halides and aldehydes under mild conditions.It can be divided into asymmetric allylation,asymmetric propargylation,asymmetric alkynylation,asymmetric ethylation,asymmetric alkylation and intramolecular Nozaki-Hiyama-Kishi reaction.These characteristics make the NHK reaction one of the most reliable synthetic methods in the natural product and the key step in total synthesis.The discovery of numerous excellent chiral ligands enables the asymmetric transformation to further enhance the chromium-catalyzed synthesis chemistry.We developed a new mothod for the synthesis of bisoxazoline ligands based on the oxazoline ligand developed by Nakada.We synthesized the ligand by three steps and achieve grams of preparation.1,3-diol is an important structure in many natural products and organic compounds.In most cases,diastereoselective reduction of alpha-hydroxy ketones can give 1,3-diol.However,regional and diastereoselective control has proved to be challenging.That is why we have carried out this topic,based on cheap raw materials 1,4-butylene glycol,after 2 steps,substrate(the benzyl Based protecting groups)can be got,and we also tried other protecting groups such as TBDPS,MOMO,benzoyl.Under CrCl2 and ligand,it reacted for 24 hours.We developed an efficient,stereoselective asymmetric allylation of 1,3-diol.Natural plants and marine animals contain a large number of compounds containing five-remebered lactones.Through the continuous efforts of chemists,many synthetic method of five-remembered lactone are developed.In recent years,the efficient asymmetric methods,especially the asymmetric cyclization within the molecule,especially asymmetric cyclization,has become the focus of many chemists.Combined with the bimetallic catalytic strategy,we have further developed the NHK reaction,the NHK reaction is derived to build a new method of chiral lactone,under conditions of m-CPBA as oxidant,MsOH,(4-CF3Ph)3PAuCl,AgNTf2,DCE as the solution.The reaction mixture was stirred at room temperature for 6 hours to construct a new strategy for the synthesis of chiral five-membered lactones.