Asymmetric [3 + 3] annulation of 3-hydroxyquinolin-2-ones <i>via</i> NHC organocatalysis

An efficient N-heterocyclic carbene (NHC)-catalyzed asymmetric C4-functionalization of quinolin-2-ones through a [3 + 3] annulation/ring-opening cascade reaction has been developed. This method employs 2-bromoenals and 3-hydroxyquinolin-2(1<i>H</i>)-ones to construct enantioenriched quinoline derivatives in moderate to good yields and with excellent enantioselectivity under mild conditions.