Pd(II)-Catalyzed Transient Directing Group-Assisted Regioselective Diverse C4-H Functionalizations of Indoles.

The development of a rational strategy for achieving site-selective C4-H halogenation of indoles is an appealing yet challenging task. Herein, we disclose a Pd(II)-catalyzed transient directing group (TDG)-assisted methodology for realizing C4 chlorination/bromination of indoles employing glycine as the TDG and NFSI as a bystanding oxidant. The use of inexpensive and commercially available CuX 2 as the halide source is the key highlight of this protocol. Furthermore, the TDG methodology was also extended to accessing C4 acetoxylated indoles employing acetic acid as the acetate source and 1-fluoro-2,4,6-trimethylpyridinium triflate as the oxidant.