N-alkylation Of Imines Using Alcohols And Sulfuryl Fluoride

N-alkylation reaction is an important method in amine synthesis.N-Alkylamines play a central role in nature,being present in essential compounds for life,such as amino acids,nucleotides,and alkaloids.Among the direct amine N-alkylation methods,the use of halogenated hydrocarbons,carbonyl compounds,olefins,alcohols have prevailed for synthesis through substitution,reduction,addition or cross-coupling.Nevertheless,toxicity and other limitation persisted.Consequently,the development of efficient and environment-friendly N-alkylation methods continues to be of great interest for researchers.In this paper,we report the N-alkylation of 3H-indoles by using alcohol and sulfuryl fluoride,avoidind the toxic methyl halide or dimethyl sulfate in the traditional process.Further,the method was successfully applied in a one-pot synthesis of photochromic compounds.In the first part,sulfuryl fluoride gas was applied in N-methylation reactions,which simply involves bubbling SO2F2 through a mixture of 3H-indole,alcohol,and sodium hydroxide.The reaction is successful for a wide range of 3H-indole direvatives,to afford the methylated amines with isolated yield up to 87%.It's also applicable to other primary alcohols,affording ethylation,trifluoroethylation,benzylation amines in good yields,as well as isopropanylation with secondary isopropanol.The reaction also displays excellent functional group tolerance.On the basis of the first part,the N-alkylated product of 3H-indole 1,3,3-trimethyl-2-methylene indoline compounds were used to prepare the corresponding spiropyrene,which greatly saves the reaction time,improves the reaction efficiency,and saves a lot of separation processes.It provides a practical method for the synthesis of spiropyran photochromic materials.