Convenient synthesis of spiroindolenines from tryptamine-derived isocyanides and organic azides by cobalt catalysis in pure water

A Co-catalyzed coupling of 3-(2-isocyanoethyl)indoles with organic azides in pure water for accessing spiroindolenine derivatives was developed. This strategy features mild reaction conditions, high atom-economy, excellent yields, wide substrate scopes, and broad functional group tolerance. The products were obtained simply by sequential operation involving extraction, concentration, precipitation, and filtration, without tedious column chromatography. More importantly, the aqueous catalytic system could be recycled at least ten times without reducing the catalytic activity. The strategy provides a green and efficient method for the construction of spiroindolenine derivatives.