Benign synthesis of indoles from anilines and epoxides: New application for ruthenium pincer catalysts

Abstract

For the first time, ruthenium pincer complexes such as Ru-MACHO-BH were successfully used as catalysts in the domino-synthesis of indoles from anilines and epoxides. Following previously optimised procedures, a variety of indoles were produced in an atom-efficient manner with water and hydrogen as the only stoichiometric side-products. The ß-amino alcohol, resulting from the ring-opening of the epoxide with the aniline derivative, undergoes dehydrogenation, followed by condensation with excess aniline and the final intramolecular cyclisation affords the desired indole. Ru-MACHO-BH showed similar catalytic activity than our previously reported in situ prepared catalyst (Ru3(CO)12/dppf) without further optimisation of the reaction conditions. © Schweizerische Chemische Gesellschaft.