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α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping
- Source :
- Beilstein Journal of Organic Chemistry, Vol 19, Iss 1, Pp 1443-1451 (2023)
- Publication Year :
- 2023
- Publisher :
- Beilstein-Institut, 2023.
-
Abstract
- We demonstrate that α-(aminomethyl)acrylates are suitable acceptors for 1,4-additions of dialkylzincs in aerobic conditions. The air-promoted radical–polar crossover process involves the 1,4-addition of an alkyl radical followed by homolytic substitution at the zinc atom of dialkylzinc. Coordination of the nitrogen atom to zinc enables this SH2 process which represents a rare example of alkylzinc-group transfer to a tertiary α-carbonyl radical. The zinc enolate thus formed readily undergoes β-fragmentation unless it is trapped by electrophiles in situ. Enolates of substrates having free N–H bonds undergo protodemetalation to provide ultimately the 1,4-addition adduct. In the presence of carbonyl acceptors, aldol condensation occurs providing overall a tandem 1,4-addition–aldol process. When a tert-butanesulfinyl moiety is present on the nitrogen atom, these electrophilic substitution reactions occur with good levels of chiral induction, paving the way to enantioenriched β2-amino acids and β2,2-amino acids.
Details
- Language :
- English
- ISSN :
- 18605397
- Volume :
- 19
- Issue :
- 1
- Database :
- Directory of Open Access Journals
- Journal :
- Beilstein Journal of Organic Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.8be299227c5484aa98b9cb39ba0fbfe
- Document Type :
- article
- Full Text :
- https://doi.org/10.3762/bjoc.19.103