Study On The Synthesis Of Nitrogen Heterocycles Via Supported Nano-cobalt Catalyzed Oxidative Coupling Reaction Of Polyols

Nitrogen-containing heterocyclic compounds are important structural units and synthetic intermediates in organic chemistry,possessing unique pharmacological and biological activities,and have very important roles in organic synthesis,materials chemistry,pharmaceutical chemistry and other fields.In recent years,the use of recyclable and inexpensive metals as a green and sustainable synthetic route to construct nitrogen heterocyclic compounds has been a hot topic of research in organic synthetic chemistry.In addition,most of the abundant biomass resources in nature are substances containing polyhydroxy groups,and it would be a relevant research topic to develop efficient recyclable catalytic systems to transform low-value,renewable resources into high-value,functionalized nitrogen heterocyclic chemicals.In this thesis,based on the oxidative coupling strategy,the prepared nano-cobalt catalysts were applied to the synthesis of nitrogen-containing heterocyclic compound from biomass-derived polyols.The details are as follows:(1)Firstly,a novel highly dispersed cobalt catalyst supported on OMS-2 nanorods was prepared by high temperature pyrolysis of cobalt(Ⅱ)hydroxide embedded in the framework of manganese oxide molecular sieve(OMS-2)by impregnation method.On this basis,the prepared catalyst was applied to the dehydrocyclization of o-diols and amidines for the first time to construct imidazolinone derivatives.Through the optimization and screening of various reaction conditions,Co/OMS-2-800 and KOH were finally selected as the most efficient catalytic system for the reaction,and the efficient synthesis of a series of imidazolinone products was achieved.The cycling experiments showed that the catalyst had good catalytic activity and stability even after five times of repeated use.In addition,the developed catalytic system features broad substrate universality,good functional group compatibility,the use of air as a green oxidant and the use of reusable and inexpensive metal catalysts,which provide an important platform for the conversion of abundant and sustainable biomass alcohol resources into functionalized nitrogen heterocycles compounds.(2)Secondly,we prepared a core-shell structured nitrogen-doped carbon-supported cobalt nanocatalyst(Co@N-C-800)using XC-72 R as the carbon support and phenanthroline and dicyandiamide as the nitrogen source,and applied it to the dehydrogenation coupling reaction of o-diols and amidine compounds for the synthesis of 1,3,5-triazine derivatives.The catalyst exhibited good catalytic performance in the oxidative cleavaged reaction of o-diols and showed no significant deactivation even after five cycles.In addition,the target product was also successfully obtained when glycerol,a biomass resource,was used as the reaction substrate,indicating that it can be used as a potential alternative to propylene glycol.The developed reaction strategy has the advantages of broad substrate range and functional group compatibility,high regioselectivity and oxidation selectivity,and recyclability of the catalyst.This synthetic approach provides an important pathway for the efficient conversion of biomass-derived o-diols to nitrogen-containing heterocyclic compounds.