Brønsted Acid Catalyzed Asymmetric Hydroamination of Alkenes: Synthesis of Pyrrolidines Bearing a Tetrasubstituted Carbon Stereocenter

Abstract

The first highly enantioselective Brønsted acid catalyzed intramolecular hydroamination of alkenes enables the efficient construction of a series of chiral (spirocyclic) pyrrolidines with an α-tetrasubstituted carbon stereocenter with excellent functional group tolerance. A unique feature of this strategy is the use of a thiourea group acting as both the activating and the directing group through cooperative multiple hydrogen bonding with a Brønsted acid and the double bond. The utility of this method is highlighted by the facile construction of chiral synthetic intermediates and important structural motifs that are widely found in organic synthesis. The enantioselective Brønsted acid catalyzed intramolecular hydroamination of alkenes is enabled by the use of a thiourea group that acts as both the activating and directing group by cooperative multiple hydrogen bonding. This method can be employed for the efficient construction of a series of chiral (spirocyclic) pyrrolidines and tricyclic amines with α-tetrasubstituted carbon stereocenters.