Palladium- Catalyzed One- Pot Three- or Four- Component Coupling of Aryl Iodides, Alkynes, and Amines through C ∼ N Bond Cleavage: Efficient Synthesis of Indole Derivatives

An efficient synthesis of N-substituted indole derivatives was realized by combining the Pd-catalyzed one-pot multicomponent coupling approach with cleavage of the C(sp(3))N bonds. Three or four components of aryl iodides, alkynes, and amines were involved in this coupling process. The cyclopentadiene-phosphine ligand showed high efficiency. A variety of aryl iodides, including cyclic and acyclic tertiary amino aryl iodides, and substituted 1-bromo-2-iodobenzene derivatives could be used. Both symmetric and unsymmetric alkynes substituted with alkyl, aryl, or trimethylsilyl groups could be applied. Cyclic secondary amines such as piperidine, morpholine, 4-methylpiperidine, 1-methylpiperazine, 2-methylpiperidine, and acyclic amines including secondary and primary amines all showed good reactivity. Further application of the resulting indole derivatives was demonstrated by the synthesis of benzosilolo[2,3-b]indole.