Synthesis of Allyl Cyanamides and N-Cyanoindoles via the Palladium-Catalyzed Three-Component Coupling Reaction

The palladium-catalyzed three-component coupling reaction (TCCR) of aryl isocyanides, allyl methyl carbonate, and trimethylsilyl azide was conducted in the presence of Pd2(dba)3·CHCl3 (2.5 mol %) and dppe (1,2-bis(diphenylphosphino)ethane) (10 mol %). Allyl aryl cyanamides with a wide variety of functional groups were obtained in excellent yields. This palladium-catalyzed TCCR was further utilized for the synthesis of N-cyanoindoles. The reaction of 2-alkynylisocyanobenzenes, allyl methyl carbonate, and trimethylsilyl azide in the presence of Pd2(dba)3·CHCl3 (2.5 mol %) and tri(2-furyl)phosphine (10 mol %) at higher temperatures afforded N-cyanoindoles in good to allowable yields. (η3-Allyl)(η3-cyanamido)palladium complex, an analogue of the bis-π-allylpalladium complex, is a key intermediate in the TCCR, and a π-allylpalladium mimic of the Curtius rearrangement is involved to generate the (η3-allyl)(η3-cyanamido)palladium intermediate.