Catalytic, Enantioselective ß-Protonation through a Cooperative Activation Strategy.
J Org Chem
; 82(9): 4689-4702, 2017 05 05.
Article
em En
| MEDLINE
| ID: mdl-28441019
ABSTRACT
The NHC-catalyzed transformation of unsaturated aldehydes into saturated esters through an organocatalytic homoenolate process has been thoroughly studied. Leveraging a unique "Umpolung"-mediated ß-protonation, this process has evolved from a test bed for homoenolate reactivity to a broader platform for asymmetric catalysis. Inspired by our success in using the ß-protonation process to generate enals from ynals with good E/Z selectivity, our early studies found that an asymmetric variation of this reaction was not only feasible, but also adaptable to a kinetic resolution of secondary alcohols through NHC-catalyzed acylation. In-depth analysis of this process determined that careful catalyst and solvent pairing is critical for optimal yield and selectivity; proper choice of nonpolar solvent provided improved yield through suppression of an oxidative side reaction, while employment of a cooperative catalytic approach through inclusion of a hydrogen bond donor cocatalyst significantly improved enantioselectivity.
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1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Aldeídos
Idioma:
En
Revista:
J Org Chem
Ano de publicação:
2017
Tipo de documento:
Article
País de afiliação:
Estados Unidos