AlCl₃ Participated In Nucleophilic Substitution Reactions Of Aryl Methaol Derivatives

In this thesis, a mild synthetic method has been developed to synthesize the 2-(diaryl) amino benzoxazoles (Scheme 2)from benzyl alcohol derivatives via Lewis acid AICI3 catalyzed nucleophilic substitution of ammonium thiocyanate and cyclization with o-aminophenol (Scheme 1). This method should be valuable for the construction of these kinds of benzoxazoles with biological and medicinal activities to treat HIV, neurodegenerative and inflammatory diseases.Firstly, the thiocyanates (A) and isothiocyanates (B) were synthesized via Lewis acid AICI3 catalyzed nucleophilic substitution of ammonium thiocyanate with benzyl alcohol derivatives. It was found that by using 1.eq. aluminum chloride as catalyst, acetonitrile as solvent under air atmosphere at -20℃, good to excellent yieids (67-99%) were obtained when the electron-rich benzoic alcohols derivatives were employed. However, when electron withdrawing substrates were used, lower yields were obtained (25-52%). And further application of isothiocyanates (B) to synthesize the 2-(diaryl) amino benzoxazoles were also obtained by using THF as solvent, Na2CO3 as base and oxidant as additive (37-80%) [1].