Palladium-catalyzed sequential indole synthesis using sterically hindered amines

Transition‐Metal‐Catalyzed Hydroamination Reactions

“…Ackermann published a series of papers exploring Pd and Ni complexes for the tandem reaction to prepare a variety of variously substituted indoles via an N-arylation-hydroamination sequence. By using a Pd-carbene complex [342,343], bulky substituents could be incorporated as the N-substituent, while Ni did not allow for this same flexibility for the incorporation of sterically demanding substituents (Scheme 15.108) [344]. By exploiting the known formation of indole from σ-ethynylaniline, Okuma was able to realize this Lewis-acid-mediated transformation with simple Zn 2+ salts (Scheme 15.109).…”

Cascade Palladium‐ and Copper‐Catalysed Aromatic Heterocycle Synthesis: The Emergence of General Precursors

“…[12] Hydrazine-based nucleophiles, [13] as well as hydrazine itself, [14] can also be incorporated to produce N-aminoindoles. In particular, the nature of the N-coupling partner has been extensively investigated.…”

Palladium-Catalyzed Heterofunctionalization of C-H, C=C and C≡ C Bonds

“…More recently, new Pd catalytic systems were also reported for the synthesis of N-heterocycles by intramolecular hydroamination of aminoalkynes, in the syntheses of pyrrolocoumarin [36] and indoles (Scheme 15) [37].…”