Dimethylamination of nitro-substituted aromatic halides in deep eutectic solvents
Objective To investigate the effects of reaction conditions on the amination of nitro-substituted aromatic halogenated hydrocarbons using the nucleophilic substitution reaction of halogenated aromatic hydrocarbons to introduce dimethylamine into the aromatic ring.Methods The optimal reaction conditions were explored using 2-bromo-1-fluoro-4-nitrobenzene as a model,and the range of reaction substrates was explored with nitrobenzene substituted at different positions and different halogen atoms.Results The optimal reaction conditions were as follows:1.00 mL of N,N-dimethylformamide(DMF)was used as aminating agent,1.5 equivalents of KOH was used to provide alkaline environment,5.00 mL of deep eutectic solvents(DESs)(choline chloride:glycerol=1:2)was used as solvent,and the reaction was carried out at 80℃for 24 h.A series of 4-dimethylamino nitrobenzene compounds and their derivatives were effectively obtained in the expansion of the substrates,and their structures were confirmed by 1H-NMR and 13C-NMR.Conclusion DMF can effectively act as a dimethyl amination reagent in DESs,which selectively improves the reactivity of nucleophilic substitution of halogen atoms at the para position of the nitro group while not activating the halogen atoms at the ortho position.Under optimized conditions,the highest yield can reach 84%.This unique regioselectivity is an advantage not found in other solvents.At the same time,this method is environmentally friendly,simple and convenient,and has a moderate yield.
deep eutectic solventsnucleophilic substitution reactionregioselectivityN,N-dimethyl-4-nitroanilineN,N-dimethylformamide
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