Hydrocarbon Activation And Diverse Cyclization Studies Of Hydroxybenzoic Acid

Transition metal-catalyzed direct functionalization of C–H bonds has provided an efficient and environmental-friendly strategy for the construction of C–C and C–hetero bonds.Some functionalized oxygen-containing heterocycles and multisubstituted carboncyclic molecules have wide prospect of application in pharmaceutical chemistry and materials chemistry.For example,some benzofurans and their derivatives as well as carboncyclic molecules have biological activities like anticancer and anti-inflammatory,which makes it possible to become pharmaceutical molecule.Multisubstituted 2-naphthols is a common ligand in asymmetric organic synthesis.By adopting the strategy of C–H activation and starting from the well-sourced hydroxybenzoic acids,the thesis has developed efficient and green catalytic systems,and achieved diversified annulation reaction to synthesize of functionalized oxygen-containing heterocycles and multisubstituted carboncyclic molecules.This thesis is composed of three parts.The first section summarizes the previous research about C–H activation and other related fields,and expounds the research ideas of this thesis.The second section is about the synthesis of functionalized benzofurans from m-hydroxybenzoic acid and diaryl alkynes via C–H activation and[3+2]alkyne annulation catalyzed by Ru.The reaction is based on biomass-derived?-valerolactone as a green reaction medium and air as the single oxidant,contaning the advantages of green reaction conditions,high atom economy and step economy.Various substituted benzofuran-4-carboxylic acids can be efficiently synthesized using this strategy.The free carboxyl group in the products can be used for further transformations.For example,intramolecular Friedel-Crafts reaction can be used to construct the core skeleton of the natural product diptindonesin G.We also completed the synthesis of methyl protected diptindonesin G.In addition,the analogues of amurensin H can be synthesized by decarboxylative olefination.Finally,a possible catalytic cycles were proposed based on the results of mechanism reaction research.The third section is about Pd catalyzed[2+2+1]annulation/dearomatization of m-hydroxybenzoic acid and diphenylacetylene.Using this reaction procedure,the functionalized carbon spirocycles can be synthesized with air as oxidant in green reaction medium.The obtained multisubstituted spirocyclohexanedione contains a free carboxyl group,which can be used for various derivatization.Firstly,the C–C bond rearrangement can be realized by Friedel-Crafts reaction and the benzoanthrone fluorophore containing free phenolic hydroxyl groups can be synthesized.Secondly,carboxyl-directed non-aromatic C(sp~2)–H activation can also be achieved under Rh-catalyzed conditions,and a complex oxygen-containing heterocyclic molecules can be selectively obtained by reacting with acrylates.The application of this catalytic system to biomass-derived salicylic acid can also realize the dual C–H activation and[2+2+2]alkyne annulation to obtain multisubstituted 2-naphthols.