Asymmetric Michael addition reactions catalyzed by a novel upper-rim functionalized calix[4]squaramide organocatalyst
作者:Ke Yang、Zhiyan Ma、Hong-Xiao Tong、Xiao-Qiang Sun、Xiao-Yu Hu、Zheng-Yi Li
DOI:10.1016/j.cclet.2020.02.057
日期:2020.12
Abstract A novel upper-rim functionalizedcalix[4]squaramide organocatalyst bearing bis-squaramide and cyclohexanediamine scaffolds was designed and prepared to catalyse a serial of asymmetric Michael addition of 1,3-dicarbonyl compounds to α,β-unsaturated carbonyl compounds in high yields (up to 99 %) and good to excellent enantiomeric excesses (up to 99% ee). The comparative experiments indicated
An efficient, organocatalyticenantioselectiveaddition of cyclic diketones with β,γ-unsaturated α-keto esters has been developed that affords products in high yields (up to 95 %) and excellent enantioselectivity (up to >99 % ee) under mild conditions with a low catalyst loading (2.5 mol-%). The unsaturated α-keto esters are effectively coordinated and activated through hydrogen bonds with the squaramides
Copper‐catalyzedconjugateaddition: A highlyenantioselectiveconjugateaddition of cyclicdiketones to β,γ‐unsaturated α‐ketoesters was achieved by using a two‐carbon‐linked N,N′‐dioxide‐Cu(OTf)2complex. Excellent yields (up to 99 %) and enantioselectivities (up to 99 % ee) were obtained with 2 mol % catalyst loading (see scheme). By using this method, adducts could be easily transformed into hexahydroquinolines
The dinuclear zinc–ProPhenol complex is applied as efficient catalyst in the highly stereoselective tandem Michael addition/acetalization reactions of cyclic 1,3-diketones and β,γ-unsaturatedα-ketoesters. A variety of substrates are well-tolerated, and a broad range of synthetically and pharmaceutically useful chiral chromene derivatives are directly produced in good yields of up to 96% and good