A novel and recyclable catalyst, a C3-symmetrical cinchonine-squaramide, has been developed for the asymmetric Michaeladdition of 1,3-dicarbonylcompounds to nitroalkenes. When using only 1 mol% of catalyst 1a for the reaction, high reaction yields with excellent enantioselectivities and diastereoselectivities (up to 96% yield,>99% ee,>99:1 dr) were achieved, in which the results for cyclic keto esters
Novelbifunctionalchiralsquaramide–amine organocatalysts have been developed by rational combination of pyrrolidine and a cinchona alkaloid. The catalysts promoted the enantioselective Michael addition of both mono- and diketones to a broad range of nitroalkenes providing the corresponding products in moderate to high yields with excellent enantioselectivities and diastereoselectivities (up to 96%
Ferrocene Analogues of Hydrogen-Bond-Donor Catalysts: An Investigative Study on Asymmetric Michael Addition of 1,3-Dicarbonyl Compounds to Nitroalkenes
作者:Rajiv Trivedi、Kadiyala Rao、M. Kantam
DOI:10.1055/s-0034-1379491
日期:——
moieties. A stepwise sequential route was used to assemble the various components of these ferrocene derivatives. The resulting bifunctional catalysts were used successfully in asymmetric Michael additions of 1,3-dicarbonylcompounds to β-nitrostyrenes. The corresponding products were obtained in high yields and in good to excellent enantioselectivities and diastereoselectivities under mild conditions by
Chiral Squaramide-Functionalized Imidazolium-Based Organic–Inorganic Hybrid Silica Promotes Asymmetric Michael Addition of 1,3-Dicarbonyls to Nitroalkenes in Brine
作者:Xiangming Xu、Tanyu Cheng、Xiaochen Liu、Jianyou Xu、Ronghua Jin、Guohua Liu
DOI:10.1021/cs5002459
日期:2014.7.3
cinchona-based squaramide active center is incorporated onto the organic–inorganic hybrid silica. As a bifunctional heterogeneous catalyst, it displays excellent catalytic activity and high enantioselectivity in asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroalkenes in brine. As presented in this study, the synergistic effect of confined site-isolated squaramide species and a salient imidazolium
Chiral squaramide as multiple H-bond donor organocatalysts for the asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroolefins
作者:Ze Dong、Guofu Qiu、Hai-Bing Zhou、Chune Dong
DOI:10.1016/j.tetasy.2012.10.016
日期:2012.12
A series of chiral bifunctional squaramide multiple H-bond donor organocatalysts have been designed and synthesized by the rational assembly of chiral privileged scaffolds of indanol and cinchona alkaloids. In the presence of 1 mol % 1a, the asymmetric Michael addition reaction of 1,3-dicarbonyl compounds to nitroolefins proceeded to provide the product in high yields (up to 92%) and with good to high