Study On Ruthenium Complex Catalyzed Oxdative Coupling Of Amines And Oxdation Of Alcohols

The oxidation of amines to imines and alcohols to the corresponding aldehydes and ketones are very important reactions in organic and medical synthesis,and show high atom-economy.Using molecular oxygen or peroxides as oxidant to realize these processes is environmentally friendly and meets the requirements of green chemistry.In this paper,a ruthenium complex[Et₃NH]₂[Ru?dipic?Cl₃]?dipic=2,6-pyridinedicarboxylate,dipicolinate?was firstly synthesized from RuCl₃,triethylamine and dipicH.This ruthenium complex is applied to the self?condensation of primary amines to imines with air as oxidant under atmospheric pressure.The optimized conditions were obtained by investigating the types of solvent,catalyst loading and reaction temperature with benzylamine as a model substrate,which were:the catalyst loading of 1.0 mol%,the reaction temperature of 100?and running the reaction without presence of solvent.The catalytic system showed good performances on the homo-coupling of aromatic,aliphatic and heterocyclic primary amines,and cross-coupling of benzylamine with anilines and aliphatic amines to the corresponding imines under the optimized conditions.Two additional ruthenium complexes[PhCH₂N?CH₃?₂H]₂[Ru?dipic?Cl₃]and[C₁₁H₂₃N?CH₃?₂H]₂[Ru?dipic?Cl₃]were synthesized by replacing triethylamine with N,N-dimethylbenzyamine and N,N-dimethyldodecanamine,respectively.The ruthenium complexes were applied to the oxidation of alcohols to the corresponding aldehydes and ketones with various oxidants.The optimal reaction conditions were obtained with1-phenylethanol as a model substrate by investigating the effects of catalyst loading,oxidant loading and reaction temperature on the reaction.The optimized conditions were:using[PhCH₂N?CH₃?₂H]₂[Ru?dipic?Cl₃]as catalyst,the catalyst loading of 0.01 mol%,the oxidant?TBHP?loading of 2 equiv.,running the reaction at 40?without presence of solvent.This system was then applied to the oxidation of various alcohols and the results indicated that it not only showed good performances in the oxidation of secondary benzylic alcohols with either an electron-withdrawing or an electron-donating group,but also has certain catalytic activity in the oxidation of aliphatic alcohols.However,in the cases of primary benzylic alcohols as substrates,the main products were carboxylic acids due to the deep oxidation of alcohols.The protocol was also applied to the oxidation of methylene to ketones,and good to excellent results were received.