Highly enantioselective trapping of zwitterionic intermediates by imines

Imines, activated by chiral organocatalysts, have been employed to trap the zwitterionic intermediates to give polyfunctionalized indole and oxindole derivatives in a single step with excellent diastereoselectivity and enantioselectivities.

Abstract

Reactions with the unstable and highly reactive zwitterionic intermediates generated in processes catalysed by transition metals are providing new opportunities for molecular constructions. Insertion reactions involve the collapse of zwitterionic intermediates, but trapping them would allow structural elaborations that are not currently available. To synthesize complex molecules in this manner, reactive electrophiles can be used to trap the zwitterionic intermediates. Here, we describe the use of imines, activated by chiral organocatalysts, and a highly efficient integrated rhodium and chiral Brønsted acid co-catalysed process to trap zwitterionic intermediates that have been proposed previously to undergo a formal C-H insertion reaction, allowing us to obtain polyfunctionalized indole and oxindole derivatives in a single step with excellent diastereoselectivity and enantioselectivity.