Studies On The Synthesis Method Of Benzimidazole/Thiazole/Quinazolinone Catalyzed By Variable Valence Metal/Peroxide System

Variable-valence metals refer to metals with multiple valence states,such as Mo,Co,Ce,Fe,V,Cu,etc.,which are usually used as catalysts with redox properties.The variable-valence metal/peroxide catalytic system constructed with variable metal as catalyst and peroxide as oxidant plays an important role in the art of organic synthesis.In this thesis,we will explore the application of the variable-valence metal/peroxide catalytic system in the art of organic synthesis.Benzimidazole/thiazole and quinazolinone heterocyclic compounds have broad applications in the fields of chemistry,biology and materials science.However,the methods that have been reported for the efficient synthesis of benzimidazole/thiazole and quinazolinone were still limited.Therefore,it is of great significance to find new and efficient synthetic methods for benzimidazole/thiazole and quinazolinone.In this master’s thesis,the research work in the first and second chapters is to design an efficient clock catalytic system,and successfully integrate the catalytic system into the synthesis of benzimidazoles/thiazoles and quinazolinones,and study the clcok catalytic system’s catalytic mechanism;The third chapter of the research work is to construct a practical method for the efficient synthesis of benzimidazoles/thiazoles under solvent-free conditions with an acetylacetone variable metal/peroxide catalyst system.The specific research content is as follows:1.The first chapter of this thesis is to design N-phenyl-o-phenylenediamine and benzaldehyde as model reaction,using the reaction intermediate benzimidazoline as a reducing agent to initiate the clock reaction of phosphomolybdic acid(PMA)/peroxide to change the valence metal Mo,accordingly catalyzing the oxidative dehydrogenation of benzimidazoline to benzimidazole,and successfully integrate the clock reaction with the synthesis of benzimidazole;After a series of analysing conditions,it is finally determined that the PMA/TBHP clock catalytic system can efficiently synthesize benzimidazole in DMSO solvent,with low catalyst dosage,fast reaction time,high separation yield,and wide substrate application range.The reaction mechanism of benzimidazole was expanded,and different substituted benzothiazole and quinazolinone compounds were synthesized.2.The second chapter of this thesis is to study the catalytic mechanism of PMA/TBHP clock catalytic system.Through the 1H-nuclear magnetic resonance,31P-nuclear magnetic resonance,X-ray photoelectron spectroscopy,infrared spectroscopy,ultraviolet spectroscopy and the large polar solvation effect,PMA/phosphomolybdenum blue,which plays a catalytic role in the clock reaction,has been deeply explored.Finally,it is proved that the catalytic mechanism of the system is that Mo undergoes a redox cycle between the oxidation state Mo(VI)and the reduced state Mo(V).3.In the third chapter of this thesis,the research content is based on PMA/TBHP clock catalytic system to construct the acetylacetone metal compound MoO2(acac)2/TBHP clock catalytic system,but the result is not ideal.However,after a various of analysis of reaction conditions and document survey,we found that under solvent-free conditions,the Co(acac)3/H2O2 system can efficiently catalyze the synthesis of benzimidazole/thiazole.And through this method we synthesized 38 differently substituted benzimidazole compounds and 18 differently substituted benzothiazole compounds.This is a green method to synthesize benzimidazole/thiazole.