A Study On The Direct Alkylation Of Phenolic Compounds In Coal Tar

Phenol and its derivatives are widely used as raw materials for synthetic industry.The content of phenolic compounds in low temperature coal tar can reach 25 percent.Transition metal has great progress in the direction of alkylation of phenol and derivatives.In the study,the two aspects of separation of phenolic compounds in coal tar and transition-metal catalyzed reaction were combined to achieve transition-metal catalyzed direct alkylation of phenols.Due to variety of phenolic compounds in coal tar,phenol is selected as a model compound in this paper.Phenolic hydroxyl group had connection with a series of functional groups to investigate the effects of electronic and steric effects of different positioning groups/protection on location of the benzene ring of phenolic compounds and product yield of alkylation reaction.The following conclusions were obtained through a series of optimization of reaction conditions.1.In the condition of [Cp*Rh Cl2]2 as catalyst,diazo propionic acid diethyl as alkylation reagents,the substrate was 2-phenoxypyridine or 2-phenoxypyrimidine could be alkylated at C2 of benzene ring.In addition,the isolated yield of 2-phenoxypyridine for substrate was higher,reaching 54.3 %.2.In the corresponding condition,oxidant amount to 2 equiv of Cu(OAc)2,the isolated yield was 40.7%.3.In the alkylation of 2-phenoxypyridine and diazo propionic acid diethyl.The optimum reaction conditions were obtained: the reaction temperature was 70 ℃,recation time was 2 h,2.5 mol % [Cp*Rh Cl2]2 as catalyst based on substrate,10 mol % Ag NTf2 as oxidant,ethanol as solvent,no additive,no ligand.The isolated yield of the 2-(2-(2-pyridinyloxy)phenyl)diethyl malonate is up to 71.1 %,the conversion was 82.5 %.