A study for palladium-catalyzed chemoselective vinylation at C-3 position of 4-bromo-1-tosylindole

Palladium-catalyzed direct activation of carbon-hydrogen bond at C-3 position of 4-bromo-1-tosylindole (1) was investigated. The reaction of 1 with ethyl acrylate (4) in the presence of 0.1 eq. of Pd(OAc)(2) and MnO2-Cu(OAc)(2)-O-2 system afforded C-3 vinylated product (5) in 52% yield, and by-products (6 and 7) that were formed by the Michael addition of AcOH or H2O to 5, were obtained in 17% and 7% yields respectively.