Synthesis of 4,5,6,7-tetrahydro-1H-indole derivatives through successive sonogashira coupling/Pd-mediated 5-endo-dig cyclization

Article abstract of DOI:10.1002/ejoc.201201417

A one-pot Sonogashira cross-coupling/5-endo-dig cyclization procedure leading to 2-aryl-4,5,6,7-tetrahydroindoles was developed. This short (only two steps from commercially available compounds) sequence avoids harsh conditions and expensive catalysts. Our procedure is highly tolerant to a range of functional groups (amino, nitro, carboxy, cyano, hydroxy, and bromo). A family of 21 tetrahydroindoles was synthesized on a gram scale in a good to excellent yields, which is indicative of the general character and scalability of this reaction. This methodology allows access to indoles bearing miscellaneous substituents at the C2 position (by variation of ArI) and at the nitrogen atom (by variation of RNH₂, including chiral moieties). A one-pot sequence based on Sonogashira cross-coupling/Pd-mediated 5-endo-dig cyclization was developed and applied to the gram-scale synthesis of 2-aryl-4,5,6,7- tetrahydroindoles (21 examples). Copyright