Dual Activation of Nucleophiles and Electrophiles by N-Heterocyclic Carbene Organocatalysis: Chemoselective N-Imination of Indoles with Isocyanides.

The first chemoselective N-imination of indoles with isocyanides by using an N-heterocyclic carbene (NHC) as an organocatalyst was achieved. A concurrent activation of nucleophile (indole) and electrophile (isocyanide) took place facilitated by the novel NHC organocatalysis via initial activation of isocyanide. The in situ generated indole anion and imine-azolium species performed a coupling reaction, producing several new indole-based formamidines in high yields under mild conditions, which was not feasible via previously reported strategies.