Aqueous copper-catalyzed N-arylation of indoles: the surfactant strategy

Surfactants have long been underestimated in synthetic organic chemistry despite their great potential in promoting solubility, reactivity and selectivity in metal-mediated cross-couplings. In this study the strategy of surfactant promotion was exemplified in copper-catalyzed N-arylation of indoles in water. The different effects of surfactants during the coupling reaction were first explored. The superior promoting effect of the natural zwitterionic surfactant, betaine, was found and attributed to the capability of the formed complex to stabilize the copper intermediate in the catalytic transformation and facilitate transportation of the reactants. The concept of surfactant promotion through complexation is valuable in metal-mediated cross-couplings. This method also exhibited good recycling ability. This study will greatly facilitate exploration of surfactant promotion in metal-mediated cross-couplings.