Enantioselective Synthesis and Stereoselective Ring Opening of N‐Acylaziridines

Abstract

Die kinetische Racematspaltung von N‐Acylaziridinen gelingt durch nucleophile Ringöffnung mit (R)‐BINOL als chiralem Modifikator unter Bor‐katalysierten Bedingungen (siehe Schema; Ar=3,5‐Dinitrophenyl). Das verbrauchte Enantiomer des Aziridins kann zu einem enantiomerenangereicherten 1,2‐Chloramid weiter umgesetzt werden, und (R)‐BINOL wird zurückgewonnen.

Catalytic Enantioselective Aza‐Benzoin Reactions of Aldehydes with 2H‐Azirines

“…Ther eaction of 3c with hydrogen chloride in THF gave the b-chloro-a-aminoketone 6 in good yield (Scheme 3b). [21] In contrast, the transformation of the tosylated aziridine intermediate 7,prepared from 3a,led to the b-amino-a-hydroxyketone 8 (Scheme 3c). [22,23] In summary,wehave successfully developed anew NHCcatalyzed aza-benzoin reaction of aldehydes with 2H-azirines, thus paving the way for synthetic chemists to build various chiral aziridines in high yields with excellent enantioselectiv-ities.This new protocol allows the rapid assembly of optically active aziridines from simple and readily available starting materials under mild reaction conditions.F urther investigations on 2H-azirines as starting materials in asymmetric synthesis,aswell as adetailed mechanistic study,are currently underway in our laboratory.…”

Recent Developments in Asymmetric Aziridination

“…[127] The best results were obtained with 3,5-dinitrobenzoylA C H T U N G T R E N N U N G (DBN)-protected aziridines which underwent kinetic resolution in the presence of triphenyl borate and (R)-BINOL, the latter functioning as a nucleophile. [127] The best results were obtained with 3,5-dinitrobenzoylA C H T U N G T R E N N U N G (DBN)-protected aziridines which underwent kinetic resolution in the presence of triphenyl borate and (R)-BINOL, the latter functioning as a nucleophile.…”

“…In 2012, Morgan et al. reported a boron‐catalyzed kinetic resolution of aziridines, dealing with the resolution of N‐ acylaziridines with a broad scope, using ( R )‐BINOL as the resolution agent (Scheme ) 127. The best results were obtained with 3,5‐dinitrobenzoyl(DBN)‐protected aziridines which underwent kinetic resolution in the presence of triphenyl borate and ( R )‐BINOL, the latter functioning as a nucleophile.…”

Iridium-Catalyzed Direct Synthesis of Tryptamine Derivatives from Indoles: Exploiting N-Protected β-Amino Alcohols as Alkylating Agents

“…Although methods accessing these bioactive molecules have been reported, there are few one-step transformations that provide access to tryptamines. Classical methods involve the C-3 Friedel–Crafts alkylation of indoles with either nitroalkenes or aziridines as the electrophilic partner, promoted by Lewis acids and/or organocatalysts. However, due to the toxicity and instability of these strongly electrophilic reactants as well as selectivity issues during the required extra reduction step of the nitro group and/or aziridine ring opening, a more sustainable and efficient method is highly desired .…”