Studies On The Synthesis Of Triarylimines Catalyzed By AlCl₃-Et₃N

Imines also known as schiff bases are a class of compounds contaningcarbon-nitrogen double bonds. Imines have good ability of coordination so that theycan react with metal ions to form metal complexes. Imines and their metal complexeshave many excellent properties such as antioxidation, antitumor, antibacterial, hightemperature resistance so they are widely used in medicine, agronomy, and functionalmaterial.At present, the methods for triarylimines have rarely been reported both at homeand abroad. Methods reported already are usually can’t afford imines by directcondensation of ketones and amines. What’s worse, most of the reported methods areof short comings more or less, such as long reaction time, high reaction temprature,expensive catalysts, low yields and tedious post-treatment procedures. In this articalwe reported an efficient synthetic method for triaryl schiff bases, which werecondensed directly from aromatic amines and diarylmethanones promoted by anLewis acid and base pair (AlCl3-Et3N).At first, possible mechanisms were studied with theoretical approach. Then, thereaction conditions were optimized through a large number of experiments. It wasfound that this Lewis acid-base pair is of high catalytic activity and good suitability ofsubstrates. What’s more, the yields obtained by this method are higher than thosesreported. The relationship between the structure of substrates and the yields was alsoanalyzed, it shows that the electronic effect of substrates and the steric hindrance playsignificant roles. The reactions carried out smoothly when substrates areelectron-sufficient arylamines and electron-deficient ketones. It is obvious that thesteric hindrance is unfavorable to this reaction.A series of high steric triarylamines have been successfully synthesized with thismethod and several typical products have been characterized by1HNMR and HRMS.