An efficient synthesis of N-substituted indoles from indoline/indoline carboxylic acid via aromatization followed by C–N cross-coupling reaction by using nano copper oxide as a recyclable catalyst

A new and elegant protocol for the synthesis of 1-substituted indoles was developed via aromatization of indoline/indoline carboxylic acid followed by C–N cross-coupling with various aryl halides in the presence of nano CuO as a recyclable catalyst, Cs2CO3 as a base in DMSO at 80 °C. 1-Substituted indoles were obtained in good to excellent yields and the catalytic system can be recycled up to four cycles without loss of catalytic activity.