Research For Gold Catalysed Tandem Claisen Rearrangement Reaction

Claisen rearrangement is one kind of[3,3]-σ type rearranging reactions with some features such as high efficiency,high atom economy and stereo specificity so that it is widely used in organic synthesis.Claisen rearrangement is a method to construct C-C bond efficiently,which is widely used in accessing orth-substituted phenol.In addition,chemists have designed various substrates favourable for rearrangement or utilised diverse catalysts to realise tandem Claisen rearrangement reactions of two components under mild conditions,synthesising plenty of compounds bearing complicated rings and natural products,and there is great value for this reaction in synthesising anti-cancer medicine molecules.Intermolecular alkoxylation/Claisen rearrangement cascade can access complicated cyclo compounds in high bond-construction efficiency which receives wide concerns by chemists in recent years.In this article,the gold catalyst which posses π acid property was chosen to catalyse the reaction,thus the intermolecular tandem alkoxylation/Claisen rearrangement of quinol and alkynyl carboxylic ester to synthesise benzofuran derivates was realised,followed by primary research for the asymmetric intermolecular Claisen rearrangement of N-alkynyl indole and allyl alcohol or quinol.This academic dissertation is divided into the following several sections:Section 1.Summarising systematically the research process of Claisen rearrangement involved or catalyzed by nonmetals.gold and other transition metal catalysts according to diverse reaction types of Claisen rearrangement.Section 2.In terms of π acid property to active unsaturated C-C bond of gold catalyst,an intermolecular alkoxylation/Claisen rearrangement/condensation cascade of quinol and alkynyl carboxylic ester catalysed by JohnPhosAuCl/AgNTf2 under mild conditions had been involved,which resulted in a series of benzofuran derivates in highest 86%yield.Additionally,some experiments to verify the mechanism were conducted,followed by the proposition of plausible reaction mechanism according to the experimental phenomenons and results.In the end.the scale-up experiment and chemical transformations had been conducted.In conclusion,the method is a new efficient pathway leading to benzofurans.Section 3.The intermolecular asymmetric Claisen rearrangement of N-alkynyl indole and allyl alcohol catalyzed by gold had been developed by keeping on taking advantages of the ability of the gold catalyst to active alkyne efficiently as well as introducing the chiral ligands.By conducting experiments,we had found that the alkoxylation of the two reactants could transform them into the intermediate product containing C-N axial chirality which can undergo the next stereospecific Claisen rearrangement at a heating condition,elementarily realising the transformation from axial chirality into central chirality.Moreover,the intermolcular tandem Claisen rearrangement of N-alkynyl indole and quinol was also studied,for which we found it is an alokoxylation/Claisen rearrangement cascade so that farther condition optimisation may avoid racemisation of products in theory.Despite the productivity of product is moderate and the enantioselectivity is not well up to now,our preliminary exploration has laid a foundation for increasing ee value and yield further.