Synthesis of 1-phenylindole

In this paper,n-phenylaniline and oxalyl chloride were used to prepare 1-phenylindole.The experimental conditions,such as material ratio,reaction time,the amount of catalyst and so on were investigated.The optimal conditions of the coupling reaction were found as:n(n-phenyl-aniline)∶ n(oxalyl chloride) =1∶3,reaction temperature 20—25 ℃,reaction time 2.5 h,under which the yield of 1-(diphenylamino)-2-chloro-ethanedione was up to 98.02% based on n-phenyl-aniline and the purity was 97.68% as determined by HPLC.The best reaction conditions for preparing 1-phenyl isatin were found as: n(1-(diphenylamino)-2-chloro-ethanedione)∶n(Anhydrous AlCl3)=1∶3,reaction temperature 10 ℃,reaction time 2 h,under which the yield of 1-phenylisatin was 86.76% based on 1-(diphenylamino)2-chloro-ethanedione and the purity was 98.45% as determined by HPLC.The reduction reaction conditions were optimized as:n(1-phenylisatin)∶n(sodium borohydride) = 1∶3,n(1-phenylisatin)∶ n(zinc chloride) = 1∶0.05,reaction temperature 110 ℃,reaction time 12 h,under which the yield of 1-phenylisatin was 72.41% based on 1-phenylisatin and the purity was 98.14% as determined by HPLC.The structures of the product were identified by1H NMR,MS and Micro melting point instrument.