Synthesis And Tandem Bicyclicization Of O-Enoyl Aryl Isocyanides

Nitrogen-containing fused heterocyclic compounds are a large number of organic compounds,which are structurally diverse and widely exist in nature,such as certain amino acids,alkaloids,pigments and perfumes.Among them,phenanthridine ring as an important nitrogen-containing fused heterocyclic ring is a key structural unit constituting certain natural products,pharmacological agents and functionalized molecules.Given its importance,numerous organic synthesis workers have done a lot of work in developing new methods for synthesizing such tricyclic structural heterocycles.In the developed method,the construction of phenanthridine by domino reaction is an important synthetic strategy starting from a simple and readily available functionalized isocyanide.However,most of this synthesis strategy relies on the structure of the ortho-aryl isonitrile precursor through the central ring(pyridine ring)to achieve the fused phenanthrylene ring,and the formation of 6-substituted phenanthridine derivatives However,a method for synthesizing phenanthridine by simultaneously constructing two rings(benzene ring and pyridine ring)by other aryl isocyanonitrile has few been reported.Recently,ortho-functionalized aryl isocyanide as an important nitrogen source block has shown significant advantages in the synthesis of various nitrogen-containing fused heterocycles,triggering an increasing number of organic chemists,attention.In this thesis,various o-enoyl aryl isonitriles prepared from simple,inexpensive,and readily available reactants,have good reactivity,and can be found to undergo a tandem double annulation with dimethyl glutaconate to provide straightforward access to potentially biologically active phenanthridine-8-carboxylate derivative and dihydrophenanthridine-8-carboxylate derivative under mild conditions.In this domino transformation,two rings(benzene ring and pyridine ring)and three bonds have been successively created,a mechanism involving tandem [3+3]-cyclization/intramolecular cyclization/desmethoxycarbonylation/oxygen oxidation dehydrogenation aromatization.This reaction provides a novel and efficient method for the synthesis of phenanthridine derivatives,and at the same time achieves the reactivity development of o-enoyl aryl isonitriles in organic synthesis.