Stereoselective Synthesis of Highly Functionalized Nitrocyclopropanes through the Organocatalyic Michael‐Addition‐Initiated Cyclization of Bromonitromethane and β,γ‐Unsaturated α‐Ketoesters
A highly diastereo‐ and enantioselective cyclopropanation of β,γ‐unsaturated α‐ketoesters with bromonitromethane has been successfully developed through a domino Michael‐addition/intramolecular‐alkylation strategy. Acceptable yields (up to 89 %) and enantioselectivities (up to 96 % ee) have been obtained.
A catalytic asymmetric carbonyl-ene reaction of [small beta],[gamma]-unsaturated [small alpha]-ketoesters with 5-methyleneoxazolines was accomplished. The process was based on the utilization of a chiral N,N'-dioxide/MgII catalyst, providing the desired products with excellent...
Organocatalytic asymmetric conjugate addition of cyclic 1,3-dicarbonyl compounds to β,γ-unsaturated α-ketoesters
作者:Jin-jia Wang、Jin-hua Lao、Zhi-peng Hu、Rui-Jiong Lu、Shao-zhen Nie、Quan-sheng Du、Ming Yan
DOI:10.3998/ark.5550190.0011.922
日期:——
The conjugateaddition of cyclic1,3-dicarbonylcompounds to β,γ-unsaturated α-keto-esters was studied using a series of chiral bifunctional organocatalysts. Takemoto’s catalyst was found to be most efficient for this transformation. Excellent yields and good enantioselectivities were achieved for a variety of β,γ-unsaturated α-keto-esters and cyclic1,3-dicarbonylcompounds. A bifunctional catalytic
The asymmetric construction of quaternarycarboncentersviacross-aldolreactions of ketones with β,γ-unsaturated keto esters catalyzed by 4-(tert-butyldiphenylsilyloxy)-pyrrolidine-2-carboxylic acid in water is described. The adducts bearing two adjacent chiral centers were obtained in high yields, mostly up to 99% ee, and with high diastereoselectivities. The corresponding polyfunctional products
Oxabenzomorphane: Synthese von 4-Phenyl-tetrahydropyran-2-carbonsäuren
作者:Fritz Eiden、Walter Winkler
DOI:10.1002/ardp.19863190806
日期:——
Durch [4+2]‐Cycloaddition der Enamine 6a–6f mit den Benzylidenbrenztraubensäureestern 7a–7g entstehen die 6‐Amino‐4‐phenyl‐dihydropyran‐2‐carbonsäureester 8a–8p. Aus 8d wird durch Hydrolyse, Wasserabspaltung und katalytische Hydrierung die 4‐Phenyl‐tetrahydropyran‐2‐carbonsäure 12a gewonnen.