Direct asymmetric functionalization of the inert α C−H bonds of N‐unprotected propargylic amines is a big challenge in organic chemistry, due to the low acidity (pKa≈42.6) of the α C−H bonds and interruption of the nucleophilic NH2 group. By using a chiral pyridoxal as carbonyl catalyst, we have successfully realized direct asymmetric α‐C−H addition of N‐unprotected propargylic amines to trifluoromethyl ketones, producing a broad range of chiral alkynyl β‐aminoalcohols in 54–84 % yields with excellent stereoselectivities (up to 20 : 1 dr and 99 % ee). The α C−H bonds of propargylic amines are greatly activated by the pyridoxal catalyst via the formation of an imine intermediate, resulting in the increase of acidity by up to 1022 times (from pKa 42.6 to pKa 20.1), which become acidic enough to be deprotonated under mild conditions for the asymmetric addition. This work presented an impressive example for asymmetric functionalization of inert C−H bonds enabled by an organocatalyst.

Biosynthesis utilizes kinetic strategies to regulate the chemoselectivity for the transformations of molecules containing multiple active reaction sites. But it is a grand challenge to realize the transformations without protecting group manipulations for chemosynthesis. α-Amino acid esters contain NH2 and α-C-H, two nucleophilic sites. Direct asymmetric α-C-alkylation of NH2-unprotected amino acid esters with alkyl halides represents one of the most straightforward strategies to access chiral quaternary α-amino acids, which are widely present in many pharmaceuticals. However, the transformation is challenging due to the high reactivity of intrinsic N-alkylation. Here, by using chiral pyridoxal 6 having a benzene-pyridine biaryl skeleton as a carbonyl catalyst, we successfully unlock the nucleophilic reactivity of the α-amino C–H bonds of α-amino acid esters toward alkyl halides without protection of the NH2 group, forming a wide range of chiral quaternary α-amino acid esters in up to 99% yield and 99% ee. Like transformations in biological systems, this protocol is featured with no protecting group manipulations and high atom and step efficiencies enabled by a biomimetic organocatalyst.

Direct asymmetric functionalization of the inert α C−H bonds of N‐unprotected propargylic amines is a big challenge in organic chemistry, due to the low acidity (pKa≈42.6) of the α C−H bonds and interruption of the nucleophilic NH2 group. By using a chiral pyridoxal as carbonyl catalyst, we have successfully realized direct asymmetric α‐C−H addition of N‐unprotected propargylic amines to trifluoromethyl ketones, producing a broad range of chiral alkynyl β‐aminoalcohols in 54–84 % yields with excellent stereoselectivities (up to 20 : 1 dr and 99 % ee). The α C−H bonds of propargylic amines are greatly activated by the pyridoxal catalyst via the formation of an imine intermediate, resulting in the increase of acidity by up to 1022 times (from pKa 42.6 to pKa 20.1), which become acidic enough to be deprotonated under mild conditions for the asymmetric addition. This work presented an impressive example for asymmetric functionalization of inert C−H bonds enabled by an organocatalyst.