A protecting-group-free Mizoroki-Heck arylation of olefins with N-unprotected bromobisindole ethanamines and, more generally, N-unprotected heterocyclic electrophiles is described. Efficient palladium-catalyzed coupling is achieved through appropriate base selection: CsF is optimal for substrates bearing intrinsic basic sites, whereas 1-decylamine is required. The method tolerates a wide range of styrenes, heteroaryl olefins, acrylates, and N-containing substrates, including unprotected tryptamines, anilines, and haloindole derivatives. Its practicality is also demonstrated by the synthesis of the natural product trans-resveratrol.
Buono et al. (Wed,) studied this question.