Regioselective preferential CH activation of sterically hindered 1,3-dienes over [4+2] cycloaddition

The study of Pd-catalyzed preferential CH activation of sterically hindered α, β-olefinic indoles onto alkenes beyond [4 + 2] cycloaddition has been described. The carbazole derivatives were readily synthesized via activation of vinylic CH bonds with excellent regioselectivity. Further, the one-pot strategy has been employed for the synthesis of tricyclic carbazoles. The double and triple CH activation followed by concomitant Michael addition provides an economical approach for the synthesis of N-protected carbazole. A wide range of alkenes at the α- and β-position are compatible with this reaction. The mechanistic and X-ray crystallographic studies supported the designed chemistry of CH activation.