Yin Y.
Dai Y.
Jia H.
Li J.
Bu L.
Qiao B.
Zhao X.
Jiang Z.
* Henan University and Henan University of Technology, P. R. of China
Conjugate Addition–Enantioselective Protonation of
N-Aryl Glycines to α-Branched 2-Vinylazaarenes via Cooperative Photoredox and Asymmetric Catalysis.
J. Am. Chem. Soc. 2018;
140: 6083-6087
Key words
enantioselective protonation - conjugate addition - cooperative catalysis - azaarenes
Significance
Jiang and co-workers report the enantioselective radical conjugate addition–protonation of N-aryl glycines to α-branched vinylazaarenes using a metal-free dual catalytic system (a photosensitizer and a chiral phosphoric acid). The corresponding products are obtained in high yields with good to excellent enantioselectivities, and the methodology is applied to the synthesis of the medicinal compound pheniramine.
Comment
Because α-amino acids are abundant, their use as starting materials for organic synthesis is desirable. In this report, N-aryl α-glycines undergo photooxidative decarboxylation and react further with highly activated olefins in a radical pathway followed by enantioselective protonation. While many examples are shown, the presented substrate scope is still limited to pyridine- and quinoline-containing substances.
