Chiral Phosphoric Acid-Catalyzed Enantioselective Dearomative Electrophilic Hydrazination: Access to Chiral Aza-Quaternary Carbon Indolenines

Direct
enantioselective synthesis of chiral aza-quaternary carbon
indolenines through the dearomative electrophilic hydrazination of
2,3-disubstituted indoles has been achieved. This catalytic asymmetric
strategy leads to the efficient construction of a series of enantioenriched
aza-quaternary carbon indolenines in high yields and excellent stereoselectivities.
The synthetic practicality of this reaction has been demonstrated
by the enantioselective modification and derivatization of drug molecules.
In-situ infrared and density functional theory calculations suggest
that our catalytic system could overcome the background reaction to
achieve effective enantioselective dearomatization.