Study On The Synthesis Of Indole

Indole, which is an important chemical material, has widely been applied inmanufacture of medicine, pesticide, dyestuff and other fine chemicals. Thus,systematic investigation onto the synthetic processes of indole and its derivatives isvery important.Firstly, 1-phenylamino-2-propanol was obtained in 80.2% yield from aniline andoxirane; while the reaction proceeded in presence of BiCl₃ at room temperature, theyield was up to 90%. A series of Cu based catalysts were prepared and employed inthe cyclization of 1-phenylamino-2-propanol to 3-methylindole in the presence ofhydrogen, however, aniline was detected to be the main hydrogenolysis product.A series of catalysts, including Cu-Zn-Mn/ SiO₂, Cu-Fe-Mn/ SiO₂ andAg-Cd-Mg-Ca/ SiO₂ , were prepared and examined with the reaction of aniline andethylene glycol to indole in a fixed-bed reactor. The reaction mixtures wereanalysized by GC and GC-Mass. Both of the newly prepared and used catalystsamples were characterized by XRD, XPS, BET, ICP and ESEM. It was found thatthe addition of Mn to this kind of catalysts could dramatically improve the dispersityof Cu, Zn on SiO2 and the stability of catalysts. Furthermore, obtained experimentalresults indicated that the catalysts obtained by impregnation exhibited better activityand stability than the catalysts prepared by co-precipitation due to smaller metalparticles and better dispersion on carrier than the later.The reaction parameters were optimized. Thus, indole was obtained from anilineand ethylene glycol in 76.0%,73.5% and 81.9% yields respectively with Cu-Fe-Mn/SiO₂, Cu-Fe-Mn/ SiO₂ and Ag-Cd-Mg-Ca/ SiO₂ as catalysts.The reaction mechanism for the synthesis of indole from aniline and ethyleneglycol was discussed and proposed in the present paper.