Improved indole syntheses from anilines and vicinal diols by cooperative catalysis of ruthenium complex and acid

Abstract

By developing a new and efficient dinuclear catalyst [Ru(CO)₂(Xantphos)]₂ [Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethyl-9H-xanthene], an improved synthesis of indole from vicinal diols and anilines by cooperative catalysis of ruthenium complex and p-TSA (para-toluenesufonic acid) has been demonstrated. The presented synthetic protocol allows assembling a wide range of products in an efficient manner. Comparing to the existed protocols, our indole syntheses can be achieved at lower reaction temperature, in shorter reaction time, and with improved substrate tolerance.