Study On The Condensation Reaction Of Imine Azabenzoin Containing Benzothiazole Structur

In the field of organic synthesis,benzoin condensation is a powerful synthetic strategy which various natural products and important intermediates can be rapidly constructed.In most cases,asymmetric benzoin condensation is accomplished under the catalysis of chiral catalysts,which is a particularly useful method for the preparation of linear or cyclic stereostructures of α-hydroxyketones.In addition,the reaction conditions for benzoin condensation are usually mild and the process is simple,but it also comes with many challenges.For example,from the point of the reaction substrate,it is difficult for ortho-substituted aromatic aldehydes to participate in the reaction;from the point of selectivity,the products the cross-coupling of aldehydes and aldehydes containing an acidic α-proton.Under these conditions,the structure is prone to enol interconversion,resulting in racemization of the product.Therefore,in order to prevent the racemization pathway,proper design of the catalyst is required.When different aromatic aldehydes are coupled,there is competition between the benzoin condensation reaction and the same aromatic aldehydes.In order to obtain a single selective product,it is necessary to synthesize appropriate substrates and catalysts in advance,so as to control the reaction direction to proceed through the designed way.This paper is mainly described in two parts: the first part describes the research and development status of nitrogen-heterocyclic carbene-catalyzed benzoin condensation reaction at home and abroad,mainly including the benzoin condensation reaction between the same substrate molecules,the benzoin condensation reaction of different substrate molecules,and the intramolecular benzoin condensation reaction.In the second part,we designed and synthesized a series of reaction substrates such as benzothiazole-2-carbaldehyde and Tos amine aromatic aldehyde,established a model reaction for the synthesis of α-aminoketone containing benzothiazole structure catalyzed by nitrogen heterocyclic carbene,and then to optimize catalyst,base,solvent,substrate equivalent ratio and other conditions of the reaction,and the optimal reaction conditions of the model reaction were obtained.On this basis,the universality of the substrates of the model reaction was explored,and a total of 21α-aminoketone compounds were synthesized with excellent yields.