Synthesis Of N-Heterocycles By Aldehydes And Ketones Under Transition-Metal-Free Conditions

N-Heterocycles are an indispensable part of organic compounds and widely exist in various biologically and pharmacologically active natural products and drug molecules,and have broad practical value and prospects in the field of medicine.This paper focuses on the theme of " the synthesis of N-heterocycles by aldehydes and ketones under transition-metal-free conditions".Functionalized carbazoles,maleimidefused carbazoles,pyrimidines,dibenzoxazepinamines and dibenzothiazepinamines were synthesized from simple and readily available aldehydes and ketones substrates under transition-metal-free conditions.The specific research contents are as follows:1.We have developed a new strategy for the preparation of functional carbazoles via [4 + 2] cycloaddition of mono-functionalized indoles and alkynes/alkenes catalyzed by Na I.The advantages of this strategy are metal-and solvent-free conditions,a wide range of substrates,and gram-level synthesis.In addition,the carbazole products synthesized by this method can be further converted into optoelectronic material molecules with potential application value.2.We have developed a metal-free and solvent-free strategy for preparation maleimide-fused carbazoles with mono-functionalized indoles and maleimides as substrates.This method has been synthesized a variety of maleimide-fused carbazoles in good to excellent yields under simple and mild conditions,providing a convenient,green and environmentally friendly route for the synthesis of maleimidocarbazoles.3.We have developed a new method for the synthesis of pyrimidine derivatives under metal-free and solvent-free conditions with ketones and N,N-dimethylformamide dimethyl acetal as substrates.This method has been used ammonium salts as nitrogen source,a variety of pyrimidine compounds can be synthesized with good yields under simple and mild condition.This synthetic route can avoid the use of expensive metal catalysts,stoichiometric metal oxidants,and harmful reaction solvents,meeting the requirements of green and sustainable chemistry.4.We have reported a new strategy promoted by base for the synthesis of dibenzoxazepinamines and dibenzothiazepinamines with 2-nitrobenzaldehyde,methoxyamine hydrochloride and 2-aminophenol/2-aminothiophenol as raw materials.Cheap substrates,simple and mild reaction conditions,this method has the advantage of transition-metal free,wide range of substrates,and gram-scale synthesis.This provided an efficient and practical strategy for the preparation of dibenzoxazepines and dibenzothiazepines with potential pharmaceutical activity.