Investigation On Alkylation And Acylation Of Aromatic Ring Under Promoter-Free Condition

The alkylation and acylation of aromatic rings play an important role in modern organic synthesis.Their products can be applied to many fields.Compounds such as styrene,ethylbenzene,ethers,and alkylamines synthesized through alkylation are important raw materials and intermediates in the fields of plastics,solvents,detergents,and pharmaceuticals.Some of these products are also drugs,fuels,and fragrances,Catalysts,surfactants and other functional products.The acylation of aromatic rings plays an important role in the synthesis of natural products,active drugs,agricultural chemicals,fine chemicals and spices.Chemists have paid much attention to this type of reaction and have developed the following strategies.One is the Friedel-Crafts reaction based on the formation of carbon cations.It usually requires a stoichiometric Lewis acid,Bronsted acid,or solid acid catalyst.Another strategy relies on the transition metal to catalyze the cleavage of the aromatic ring C-H bond.The reaction requires the use of a transition metal to catalyze the activation of the aromatic ring C-H bond,and the alkylation or acylation reaction takes place.In recent years,free radical oxidative coupling has emerged as an interesting way for the alkylation of aromatic hydrocarbons,and the reaction requires the alkylating reagent to be oxidized to an alkyl radical.Obviously,the above strategy relies on the presence of various accelerators or additives.In contrast,from the perspective of environmental protection and economy,the reaction without accelerators and additives is more attractive.In this paper,it is found that benzyl chloride and benzyl bromide can react directly with electron rich aromatics,benzoyl chloride can also react with electron rich aromatics without any catalyst or promoter.The main research contents and results are as follows:1.The direct alkylation of benzyl halides with aromatic hydrocarbons was studied.In this experiment,the reaction of benzyl chloride and mesitylene was used as a model reaction.The effects of reaction atmosphere,solvent and temperature on the reaction were investigated,and the reaction effects of different substrates were studied.The optimal reaction conditions were 0.5 mmol substrate,2 m L trimethylbenzene(reactant and solvent),140 °C and 20 h.This experiment does not require any catalysts and additives for alkylation.The reaction cost is low and the yield is high.A series of substrate reactions gave 32% to 93% yield.Using molecular simulation calculations,free radical suppression,kinetic analysis and other means to study the reaction mechanism,the results show that the reaction has undergone an autocatalytic process.The initial rate of the reaction is small,and HCl with catalytic effect is generated.With the increase of HCl,the reaction rate continues to accelerate,and benzyl halides are catalyzed to generate benzyl cations,and Friedel-Crafts type alkylation reactions occur.2.The direct acylation of benzoyl chloride and its derivatives with aromatic hydrocarbons was studied.Using the reaction of benzoyl chloride and anisole as a model reaction,the reaction time,temperature,reaction atmosphere,solvent and other conditions were optimized,and the reaction effects of different substrates were investigated.The optimal reaction conditions obtained were 0.5 mmol substrate,2 m L anisole(reactant and solvent),140 °C and 20 h.The reaction can be acylated without any catalyst and additives.The reaction effect is good and the yield is high.It is suitable for most acid chloride compounds.When the aromatic hydrocarbon is a high melting point compound,additional solvent needs to be added.The optimal reaction conditions are 0.5 mmol substrate,2 mmol aromatic hydrocarbon,1 m L cyclohexane,140 °C and 20 h.However,aromatic hydrocarbons containing electron-withdrawing substituents are difficult to react under such conditions.