Environment-friendly synthesis of nitrogen-containing heterocyclic compounds

A novel environment-friendly vapour phase synthesis of different classes of nitrogen-containing heterocyclic compounds was developed using non-hazardo us, commercially available and low cost feeds. 2-Methyl-8-ethylquinoline (M EQUI) was obtained from 2-ethylaniline (2-ETAN) and ethylene glycol (EG); o r chloroethanol (CE), operating at high temperature in the presence of acid -treated K10 montmorillonite or ZnCl2/K10 montmorillonite. At lower tempera tures and using copper chromite catalysts, 7-ethylindole (7-ETI) or 5-ethyl indole (5-ETI) were obtained from 2-ETAN or 4-ethylaniline (4-ETAN), respec tively, and EG; excess of alkylaniline was required to avoid the formation of polyalkylated by-products. Mixing SiO2 with the best copper chromite, ma de it possible to operate with higher LHSV values, thus improving the yield in alkylindoles. Finally, N-(2-ethylphenyl)pyrrole (EPP) and N-(2-ethylphe nyl)pyrrolidine (EPD) were synthesised using a commercial copper chromite c atalyst and feeding 2-ETAN and 2,3-dihydrofuran (DHF), EPP being favoured b y high temperatures and absence of water in the feed. The possible reaction pathway for each synthesis is proposed, to evidence the key features of th e best catalysts identified. (C) 2000 Elsevier Science B.V. All rights rese rved.