Non-Bonding Electron Pair versus pi-Electrons in Solution Phase Halogen Bond Catalysis: Povarov Reaction of 2-Vinylindoles and Imines

摘要

The non-bonding electron pair (n-pair) of heteroatoms and pi-electrons are both efficient halogen bond (XB) acceptors. In solid and gas phase studies, n-pairs generally prevail over pi-bonding orbitals as XB acceptors, whereas few studies have been conducted regarding the preference in solution phase. Herein, the Povarov reaction via the C-I...N XB interaction and [4+2] cycloaddition via the C-I...pi XB interaction were evaluated, revealing that the n-pair was more dominant in the XB catalysis system in solution. The XB donor-catalyzed Povarov reaction gave diverse indolyl-tetrahydroquinoline derivatives in good yields. Synthesis of indolyl-quinolines was also developed.