Pd(II)-Catalyzed Intramolecular C(sp2)–H Arylation of Tryptamines Using the Nonsteric NH2 as a Directing Group

The free amine-directed C-H functionalization reactions are challenging and mainly restricted to bulky amines. In this work, we report the nonsteric NH2-directed Pd(II)-catalyzed intramolecular C(sp2)-H arylation of tryptamines, which enables the efficient, gram-scale, and regioselective synthesis of versatile 2-aryltryptamines (35 examples, up to 98% yield). This approach broadens the substrate scope of the free amine-directed C-H functionalization, not limited to bulky amine substrates. Late-stage elaborations of 2-aryltryptamines achieve the divergent construction of the complex core structures that are prevalent in highly valuable natural products such as aurantioclavine, chimonanthine, and phalarine.