Nano Au/Pd-catalysed 'on-water' synthesis of C3-C3′ diaryl-oxindole scaffolds via N2-selective dearomatization of indole

'On-water' synthesis of 2,2-bis(indoly-3-yl)indoline-3-ones via N-2-selective dearomatization of '(N-H) protection-free' indole derivatives is described. An oxidative homo trimerization of indole via nano Au/Pd catalysis with oxone as additive was successfully demonstrated for the first time. In situ generation of isatin at room temperature and with water as solvent are key features.