Iron-Catalysed Carbene Transfer to Isocyanides as a Platform for Heterocycle Synthesis.

An iron-catalysed carbene transfer reaction of diazo compounds to isocyanides has been developed. The resulting ketenimines are trapped in situ with various bisnucleophiles to access a range of densely functionalized heterocycles (pyrimidinones, dihydropyrazolones, 1H-tetrazoles) in a one-pot process. The electron-rich Hieber anion ([Fe(CO) NO] ) facilitates efficient catalytic carbene transfer from acceptor-type α-diazo carbonyl compounds to isocyanides, providing a cost-efficient and benign alternative to similar noble metal-catalysed processes.