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.