Study On The 1,2-difunctionalization Of Acetylene Enabled By Visible Light

Acetylene,also termed the ’mother of organic chemistry’,is a fundamental chemical raw material with numerous applications and a significant impact on the advancement of contemporary synthetic chemistry.Before the 1960 s,the majority of research on the conversion and use of acetylene in the industry was focused on the synthesis of bulk chemicals such as vinyl chloride,vinyl acetate,acrylates,and butynyl glycol.Additionally,substantial advances have been achieved in academia in the high value-added conversion of acetylene,giving a useful route for the quick synthesis of functional molecules with rich structural diversity.Currently,the existing techniques are focused on hydrogenation functionalization,cross-coupling,and dimerization/trimerization of acetylene.To achieve high value-added conversions of acetylene,researchers are currently relying on the synthesis of polar,utilizing superbasic,transition metal-catalyzed,or high-temperature thermal reactions,or even costly and complicated high-pressure reactors.Despite these elegant achievements,there is still much to be explored in this domain.For instance,developing mild and efficient methods for converting acetylene into high-value-added 1,2-functionalized molecules,such as macrocycles and S-containing vinyl frameworks.Recent advances in visible light-mediated synthesis techniques have made it viable to reexamine radical approaches,in particular certain synthetic transformations that were difficult or even impossible to achieve with polar reactions.By activation with visible light,a photocatalyst can function as a single-electron redox mediator or facilitate energy transfer to activate a diverse range of organic molecules.Based on the aforementioned context,this paper focuses on the following study on the bifunctionalization of acetylene that is visible light-enabled,which is mainly divided into the following three chapters:The first chapter presents an overview of the current state of acetylene development in synthetic chemistry.The second chapter investigates a photocatalyzed thiol-yne click reaction to forge diverse sulfur-containing macrocycles(up to a 35-membered ring)and linear C2-linked1,2-(S-S/S-P/S-N)functionalized molecules,starting from the simplest alkyne,acetylene.The scope examination shows good substrate generality and functional group tolerance.Preliminary mechanistic experiments support a visible light-mediated radical-polar crossover dihydrothiolation process,which is different than the previous thiol-acetylene chain addition reaction.This operationally straightforward reaction is also amenable to the synthesis of organometallic complexes,bis-sulfoxide compounds,and a pleuromutilin antibiotic drug Tiamulin,which provides a practical route to synthesize highly valued compounds from the feedstock acetylene gas.The third chapter investigates the 1,2-difunctionalization of acetylene using a photocatalyzed insertion process.This method,inserts acetylene directly into readily available bifunctional reagents,selectively forming two different C-X bonds.This 1,2-difunctionalization method,done under mild conditions,uses acetylene to access a variety of C2-linked functional structures,with a previously unattainable scope and functional-group tolerance.Applications for the functionalization of natural products and drug molecules are also demonstrated.The resulting S-containing vinyl frameworks are important and versatile scaffolds in synthetic chemistry.The scaffolds can be easily transformed into diverse functionalized molecules and chiral sulfoxidecontaining bidentate ligand libraries.Mechanistic studies and DFT calculations provide detailed insight into the reaction mechanism.We hope that this approach will address a long-standing unsolved problem posed by acetylene chemistry and inspire organic chemists to develop more general modes of synthesis for the value-added functionalization of the feedstock acetylene.