Synthesis Of Six-membered Benzonitrogen Heterocycles Via Transfer Hydrogenative Coupling Reactions Of Alcohols

Nitrogen-containing heterocyclic compounds play a very important role in medicine,pesticides and functional materials that are a class of indispensable substances related to the people's livelihood and development.Therefore,the research on the synthesis of nitrogen heterocyclic compounds has long been a hot topic for chemists.Traditionally,the syntheses of nitrogen-containing heterocycles usually require the preparation of raw materials and the participation of halogen-containing reagents,which are liable to cause environmental pollution and low atom-economic efficency.Hence,the development of efficient and green synthetic methods for the preparation of nitrogen-containing heterocyclic compounds is quite requisite.Meanwhile,alcohols are a class of cost-effective and renewable resources that widely distribute in nature,the effective transformation of such resources into useful nitrogen heterocyclic compounds for the human-being would be a subject with great significance.Therefore,the main research content of this thesis is on the synthesis of benzotriene nitrogen heterocyclic compounds via transfer hydrogenative coupling reactions of alcohols with other reagents under mild conditions.Firstly,we studied on the synthesis of 2-arylquinoxalines from 2-nitroanilines with an equimolar amount of monoalcohols via a base-catalyzed hydrogen-transfer coupling reaction.This synthetic protocol proceeds in a step-and atom-economic fashion together with the advantages of operational simplicity,broad substrate scope,water as the only byproduct,and no need for noble transition-metal catalysts,external reducing agents,or less environmentally benign halogenated reagents,offering a highly practical approach to access 2-arylquinoxalines.Mechanistic investigations suggest the reaction undergoes a MPV-O type hydrogen transfer-mediated alkylation process.Furthermore,a new one-pot synthetic protocol,enabling the facile access to 2-alkylaminoquinolines and 1,8-naphthyridines by successive ruthenium-catalyzed dehydrogenative annulation and N-alkylation processes,has been demonstrated.A series of 2-aminoarylmethanols were efficiently converted in combination with different types of nitriles and alcohols into various desired products in moderate to excellent yields after isolation.Advantageously,the synthesis proceeds with high atom-efficiency,broad substrate scope,operational simplicity,no need for external hydrogen sources and less environmentally benign halogenated reagents,thus offering a practical approach to access these two types of compounds that are currently difficult to prepare with the conventional methods.