Directed Palladation: Fine Tuning Permits the Catalytic 2-Alkenylation of Indols

Significance

The synthesis of 2-vinyl indoles by a Pd-catalyzed C-H activation process induced by coordination from a N-picolinyl is described. By testing several different N-substituents e.g. oxazolino methyl, dimethylcarbamoyl, and allylmethylcarbamoyl, the picolinyl group is shown to be optimal for the C-H activation of the indole 2-position. In the three examples given (R = CO₂Me, SO₂Ph and CN), the reactions proceed in almost quantitative yields. Although not indicated, the starting substrate may be easily prepared
(T. Guengoer, P. Malabre, J. Teulon Synth. Commun. 1994, 24, 2247).