Palladium-catalyzed direct C-H alkylation of electron-deficient pyrrole derivatives.

The apparent and the real: What looks like a Friedel-Crafts alkylation reaction of electron-deficient pyrroles is actually a Pd(II)-catalyzed, norbornene-mediated C-H activation reaction, in which the alkylation of the pyrrole core occurs by reductive elimination. As well as ethyl-1H-pyrrole-2-carboxylate, several other 2,3-disubstituted pyrroles underwent the selective C5 alkylation in good yield.