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Home / Seminar & Event /Past Seminars / (328) Catalytic asymmetric protonation of vinyl heterocycles
(328) Catalytic asymmetric protonation of vinyl heterocycles
Seminar: (328) Catalytic asymmetric protonation of vinyl heterocycles
Speaker: Dr. Chao Xu, University of St Andrews, Scotland
Time: 2018-10-12 13:00 to 2018-10-12 14:00
Venue: Meeting room (406), Building 24
Organizer:

Health Science Platform


Abstract:  The direct enantioselective synthesis of chiral azaheteroarylethylamines from various vinyl aza-heterocycles and anilines is reported. A chiral phosphoric acid (CPA) catalyst promotes dearomatizing aza-Michael addition giving a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization to deliver vicinal aminoheterocycles. The reaction accommodates a broad range of azaheterocycle, nucleophile, and substituent on the prochiral centre(C, F, P, Si, X...), generating the products in high enantioselectivity. Mechanistic study through DFT calculation and NMR analysis support a facile nucleophilic addition based on catalyst-induced LUMO lowering, with site-selective, rate-limiting, intramolecular asymmetric proton transfer from the ion-paired prochiral intermediate.

(328) Catalytic asymmetric protonation of vinyl heterocycles
Seminar: (328) Catalytic asymmetric protonation of vinyl heterocycles
Speaker: Dr. Chao Xu, University of St Andrews, Scotland
Time: 2018-10-12 13:00 to 2018-10-12 14:00
Venue: Meeting room (406), Building 24
Organizer:

Health Science Platform


Abstract:  The direct enantioselective synthesis of chiral azaheteroarylethylamines from various vinyl aza-heterocycles and anilines is reported. A chiral phosphoric acid (CPA) catalyst promotes dearomatizing aza-Michael addition giving a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization to deliver vicinal aminoheterocycles. The reaction accommodates a broad range of azaheterocycle, nucleophile, and substituent on the prochiral centre(C, F, P, Si, X...), generating the products in high enantioselectivity. Mechanistic study through DFT calculation and NMR analysis support a facile nucleophilic addition based on catalyst-induced LUMO lowering, with site-selective, rate-limiting, intramolecular asymmetric proton transfer from the ion-paired prochiral intermediate.