Photo-induced Excited-Palladium-Cataly Zed Reactions Of The Biomass Platform Molecules

As the only renewable organic carbon resources,biomass shows the advantages of wide distribution,large reserves and environmentally friendly properties and it will absoultely become the main raw material of liquid fuel and organic chemicals in the post fossil economy era.Among them,alkyl carboxylic acids and alkyl alcohols are important biomass platform molecules and their transformation has attracted wide attention of scientists in recent years.In this paper,by sample dehydration and halogenated method,we transform the alkyl carboxylic acids and alkyl alcohols into alkyl electrophiles,such as alkyl carboxylates and alkyl halides.And then under the irradiation of the blue LEDs,these alkyl electrophiles can be activated by excite-state-palladium catalyst and coupled with the other nucleophiles to achieve the further transformation.In the first chapter of the thesis,we reviewed the development of biomass energy utilization and the status quo of our country and abroad.We proposed the way of photocatalysis to promote the transformation of biomass platform molecules.However,the photocatalytic reaction that has been reported has the disadvantages of complex preparation of photocatalyst,high price and rare reaction types.Therefore,we proposed to develop the new photoinitiator,such as excited transition metal,to improve the catalytic efficiency and enrich the type of reaction transformation.Heck reaction is a classic method for the construction of C-C bonds in synthetic chemistry,which plays an important role in the synthesis of drug molecules and intermediates.However,alkyl Heck reaction,especially for the unactivated tertiary alkyl halides that possess eliminable β-hydrogen atoms is still a big challenge.In the second chapter of the thesis,we rationalized this unprecedented transformation by utilizing the photoexcited-state reactivity of the palladium complex and overcomed this historic challenge.In addition,Through the UV-vis absorption experiments,we determined the existence of excited-state-palladium and found that the ligand played a vital role in the reaction system.Based on this discovery,we have further applied the system to the conversion of alkyl carboxylic acids,a wide,cheap and readily available biomass platform molecule.In the third chapter of the thesis,we further studied irradiation-induced palladium-catalyzed decarboxylative Heck reaction of aliphatic carboxylates.A broad scope of secondary,tertiary,and quaternary carboxylates,including a-amino acid derived esters,can be applied as amenable substrates,which provided a effective alternative way for alkyl Heck reaction.Heterocyclic structure is the backbone structure of most drug molecules and the modification can always effectively improve its physiological activity and metabolic stability.In order to further enhance the application value of the reaction system,we have studied the irradiation-induced palladium-catalyzed directed C-H alkylation reaction of heterocycles in the fourth chapter.The reaction has achieved the C-H alkylation of tertiary and secondary alkyl bromides under mild conditions,providing a novel and efficient method for the heterocyclic modification.In a word,we have efficiently converted the alkyl carboxylic acids and alkyl alcohols to a series of important organic intermediates by irradiation-induced palladium-catalyzed method.In addition,we also studied the excited-state catalytic properties of palladium catalyst for the first time,which break through the limitations of the traditional ground-state palladium catalysis.