Transition Metal Catalyzed Selective Alkylation Of Phenols And Mechanistic Studies

Phenolic compounds are important raw materials in the area of organic synthesis.The combination of transition metal catalysts and phenolic compounds can undergo various types of chemical reactions.In this thesis,we focus on the catalysis of the same family of transition metals Rh and Co,The substrate scope for the ortho-selective alkylation of phenolic compounds has been extensively evaluated under the optimal reaction conditions and a possible mechanism was proposed accordingly.The specific experimental results and conclusions are as follows:1.At the beginning of the research,20 kinds of phenoxypyridine derivatives and 6 kinds of diazo compounds were synthesized as reaction substrates and alkylating reagents for the alkylation reaction.2.In this thesis,phenoxypyridine and its derivatives were introduced as substrates,[Cp*Rh Cl₂]₂ was the choice of the transition metal catalyst,and diethyldiazomalonate and its analogues were used as alkylating reagents,all these elements resluted in highly selective alkylation at the C2 position of the aromatic ring.In this catalytic reaction system,the reaction was conducted at the temperature of 70 ^oC for 2 h in Et OH as reaction medium,the amount of catalyst[Cp*Rh Cl₂]₂ was 2.5%of the amount of the substrate,Ag NTf₂ was added as the oxidant with four times,loading of the catalyst.A series of C2 alkylation products were isolated in moderate to high yields up to 97%.Preliminary mechanistic studies were carried out and a transition states was proposed.3.On the basis of the aforementioned results,in this thesis we examined the same alkylation reaction under inexpensive and easily available Co catalysis,In this transformation,we used[Cp*Co?CO?I₂]as a catalyst.Phenoxypyridine derivatives and?-carbonyl diazo compounds were selected as the reaction substrates and alkylation reagents respectively.The alkylation reaction was exactly carried out at the C2 position of the aromatic ring with high selectivity and get 82%of the alkylation products.The optimal reaction condition of the catalytic reaction system was shown as follows:the reaction was conducted at 120 ^oC under inert N₂atmosphere and it would take 14 h for total consumption of starting material.In this catalysis catalyst loading of[Cp*Co?CO?I₂]was 5 mol%in which Ag Sb F₆ and KOAc were served as oxidant additive,respectively.TFE represented as the best solvent to realize the desired transformation.