Study On Efficient Construction Of γ-lactone Compound Based On The Strategy Of Alkene Difunctionalization Reaction

γ-Lactones are an important class of chemical structural units that are frequently found in the manufacture of natural products,drugs,pesticides,fragrance ingredients,packaging materials,and polymers.In addition,γ-lactone scaffolds are widely used in organic synthesis as versatile synthetic intermediates and in the synthesis of structures of more complex molecules.And some traditional methods,such as intramolecular cyclization ofγ-hydroxy carboxylic acid and S_N2 reaction ofγ-halogenated carboxylic acid,have been proved to be effective methods to construct such structural units.Therefore,many efforts have been made in the synthesis ofγ-lactone derivatives.The use of bifunctionalization of olefins to generate functionalized backbones has been developed as a more favorable tool in organic synthesis,which can increase the complexity of molecules by simple design.In recent years,research on the bifunctionalization of olefins has progressed rapidly,including methods such as transition metal catalysis and metal-free conditions.However,in addition to the use of relatively expensive and toxic metal catalysts and the large number of synthesis steps,the expansion of substrates is also very limited,which seriously hinders the application of such compounds.Visible photocatalysis has the advantages of high efficiency,safety and mild reaction conditions,and is considered as a powerful tool in organic synthesis.Based on the above basis,we focused on the study of the efficient construction ofγ-lactone compounds based on olefin bifunctionalization reaction strategy,which can be divided into the following three parts:1.Synthesis of sulfonyl chloride sulfonyl lactone by visible-light photoredox-catalyzed of alkenic acid and sulfonyl chloride sulfonyl lactoneWe investigated a visible-light photoredox-catalyzed sulfonyl lactonization of unsaturated carboxylic acids with sulfonyl chloride.The reaction conditions were first optimized starting with the reaction of 2-vinylbenzoic acid and P-toluenesulfonyl chloride at room temperature,and a variety of substrates were expanded after the optimal reaction conditions were derived.The practicality of this reaction method was demonstrated by the gram-scale synthesis performed later.A study of the reaction mechanism revealed the possible involvement of a free radical pathway containing sulfonyl radicals in the conversion.The reaction is characterized by a wide range of substrates,good tolerance of functional groups,mild conditions and high reaction efficiency,providing a simple and efficient method for obtaining a wide range of sulfonyl lactones.2.Esterification of aldehydes with aldehydes catalyzed by visible-light photoredoxWe have studied the visible-light photoredox-catalyzed acyl-lactonization of an enolic acid with heterocyclic aromatic or aliphatic aldehydes as acyl precursors.The reaction conditions were firstly screened,and the optimal reaction conditions were derived and then the substrates were expanded.The yields of the expanded various heteroaromatic and aliphatic aldehyde substrates were high,and a series of acyl lactones with good functional group tolerance were obtained.The reaction mechanism was probed,and preliminary mechanistic studies suggest that acyl radicals are involved in the reaction,speculating that a free radical pathway may be involved.The raw materials used in this reaction method are cheap and easy to obtain,the reaction stereoselectivity is good,the functional group tolerance is high,and the visible light catalysis is mild to the environment,safe and non-polluting.3.Visible-light photoredox-catalyzed of alkene and aryl chloride aryl lactone esterification to aryl lactoneA mild and effective way,visible-light photoredox-catalyzed was used to study an acyl-lactonization reaction of aromatic chlorides as acyl precursors with enolic acids.We started the optimization of reaction conditions with the reaction of 2-vinylbenzoic acid derivatives and benzoyl chloride,and expanded the range of substrates after screening the conditions including the types of bases and solvents to arrive at the optimal reaction conditions.Simultaneous gram-level synthesis was performed to demonstrate the practicality of this scheme.The reaction mechanism was probed and the conversion products were barely detected after the addition of the radical trap,and benzoyl radicals could be isolated,so it was speculated that a radical pathway might be involved.Based on the above study,it was concluded that the reaction has good tolerance of functional groups and high reaction efficiency.