An efficient, asymmetric organocatalyst-mediated conjugate addition of nitroalkanes to unsaturated cyclic and acyclic ketones
作者:Claire E. T. Mitchell、Stacey E. Brenner、Jorge García-Fortanet、Steven V. Ley
DOI:10.1039/b601877g
日期:——
5-Pyrrolidin-2-yltetrazole is a versatile organocatalyst for the asymmetric conjugateaddition of nitroalkanes to enones. Using this catalyst, this transformation requires short reaction times, tolerates a broad substrate scope, and possibly proceeds via generation of an iminium species.
Highly Enantioselective Michael Addition of Nitroalkanes to Enones and Its Application in Syntheses of (R)-Baclofen and (R)-Phenibut
作者:Feng Sha、Xin-Yan Wu、Xing-Tao Guo、Jie Shen
DOI:10.1055/s-0034-1380203
日期:——
enantioselectivities. A highly enantioselective Michael addition of nitroalkanes to α,β-unsaturated ketones was developed. In the presence of a chiral primary amine–thiourea catalyst based on dehydroabietic amine, γ-nitro ketones were obtained with excellent enantioselectivities (up to 99% ee) and in up to 96% yield. This protocol was successfully applied in asymmetric syntheses of (R)-baclofen and (R)-phenibut
The asymmetricconjugateaddition of nitroalkanes to α,β-unsaturated ketones in the presence of a catalytic amount of a novel sulfonamide–thiourea organocatalyst resulted in the corresponding γ-nitro carbonyl products in high yields with excellent enantioselectivities (up to 97% ee).
The Michael addition of nitroalkanes to alpha,beta-unsaturated enones catalyzed by a novel chiral imidazolidine-2-yltetrazole organocatalyst has been investigated. The new more soluble organocatalyst decreases reaction times and improves enantioselectivities compared to other catalysts. The Michael addition adducts were obtained with up to 92% ee. [reaction: see text]