Domino Process in Silver-Catalyzed Reactions of N-Arylformimidates and Active Methylene Compounds Involving Cycloisomerization and 1,3-Alkenyl Shift

摘要

Substituted indoles form the core skeletons of a wide range of Pharmaceuticals and naturally occurring alkaloids. To date, numerous elegant approaches have been developed to generate this unique ring system via transition-metal catalysis. Recently, indole derivatives have been synthesized by employing inter- or intramolucular cyclization of alkynes and imines/In this communication, we report an atom-economical and highly efficient approach for the construction of 2,3-substituted indoles via silver-catalyzed condensation of N-arylformimidates and active methylene compounds followed by cycloisomerization and a novel and unprecedented 1,3-alkenyl shift to the Ag-activated site. Previously, Li and co-workers introduced an effective methodology for gold- and silver-catalyzed addition of active methylenes to alkenes. Later, Arcadi et al. reported gold-catalyzed coupling of active methylenes at the C3 position of indole. We considered the possibility of gold- and silver-catalyzed condensation of N-arylformimdate la and dimethyl malonate followed by in situ cycloisomerization with the triple bond, leading to the N-alkenylindole derivative.