Halogen bond catalysis of the [4+2] cycloaddition reaction of 2-alkenylindoles: catalytic modes and stereoselectivity

Abstract

I⋯π halogen bond catalysis on the [4+2] cycloaddition reaction was investigated. There are two modes either on the ethenyl or the five-membered ring of 2-alkenylindole. Moreover, the stereoselectivity of the endo and exo pathways was compared.

Halogen Bond Catalysis: A Physical Chemistry Perspective

“…There are two modes of C–I···π XB catalysis: on the ethenyl of 2-alkenylindole (mode A) or the 5-membered rings of 2-alkenylindole (mode B). Both models involve two steps of carbon–carbon bond formation and six-membered ring formation …”

“…98 The above studies mainly focus on π-electrons in the reaction catalyzed by XB donors in the gas phase and solid phase, while there were few studies on the solution phase in the experiment. Arai et al 103 Recent research advances further indicate that π catalysis should be considered when studying the catalytic properties of XB donors. XB catalysts involved in π catalysis can be used to selectively catalyze different functional groups on complex molecules.…”