Pd(II)-Catalyzed One-Step Construction of Cycloalkane-Fused Indoles and Its Application in Formal Synthesis of (±)-Aspidospermidine

A highly efficient, redox-free Pd(II)-catalyzed tandem cyclization reaction initiated by intramolecular amino-palladation of alkynes followed by nucleophilic addition to nitrites is developed. This method provides a versatile approach for the synthesis of six- to eight-membered ring-fused indoles in one step and has also shown advantages in the formal synthesis of (+/-)-aspidospermidine.