Research On The Construction Of Pyridine,Ploy-substituted Benzene And Thiazole Derivatives By Multi-component Series Cyclization

Polysubstituted aromatic hydrocarbons and heteroaromatic hydrocarbons widely exist in various natural products,bioactive molecules,pharmaceutical pesticides and materials chemistry.They are also common synthetic materials for the preparation of many industrial chemicals and functional materials.They are widely used in organic synthetic chemistry,pharmaceutical chemistry,high molecular material science and many other fields.Therefore,the efficient and highly selective construction of aromatics and heteroaromatics has been a hot topic in recent years.Starting from the acyclic precursors with different substituent groups,aromatic and heteroaromatic hydrocarbons can be constructed by multi-component series reaction,which provides a general and simple method for the preparation of small organic molecules and complex natural products,and opens up a new way for the further study of this kind of functionalized polysubstituted aromatic and heteroaromatic hydrocarbons.In this paper,a new method for the synthesis of multi substituted pyridines,multi substituted benzenes,benzothiazoles and thiazoles from various nitrogen-containing compounds was developed,the main research contents are as follows:1.One pot synthesis of polysubstituted pyridine derivatives from oxime esters and acetylacetone,aromatic aldehydes,or oxime esters and aromatic aldehydes without transition metal catalysis was studied.The method of highly selective construction of six membered heterocyclic polysubstituted pyridines with oxime esters as nitrogen source was developed.The results show that the reaction has a wide range of substrate adaptability and is insensitive to the substituent groups of aryl groups and steric hindrance effect.It provides a new way to synthesize asymmetric2,4-diarylpyridine compounds.2.Palladium catalyzed one-step synthesis of polysubstituted benzenes from aromatic aldehydes,aromatic amines and acetylacetone was studied.A method of selective synthesis of polysubstituted benzenes from simple and common acyclic substrates catalyzed by palladium was reported.This method breaks the conventional way of forming Hantzsch pyridine and provides a new way for the synthesis of aromatic rings from acyclic precursors.The amino and active acyl groups in the target products provide the possibility for further conversion and application of these compounds.3.Using phenylacetic acid,aromatic amines and elemental sulfur as starting materials,the synthesis of 2-substituted benzothiazole derivatives by multi-component cyclization without transition metal catalysis was studied.A new method promoted by NH₄I was developed to obtain valuable benzo and naphtho[2,1-d]thiazole compounds from cheap and stable starting materials.In this reaction system,K₃PO₄,which is cheap and easy to obtain,is used as the base without special reaction atmosphere,and shows good functional group compatibility under simple and mild conditions.4.Based on amino acids and elemental sulfur,a new method of cyclization of benzyl or acyl substituted 2,5-disubstituted thiazole derivatives was developed.This method can be used to construct thiazole derivatives with specific substituted positions,which is a good supplement to the research on the synthesis of 2-substituted benzothiazoles and provides a new choice for the synthesis of a variety of thiazoles.