Catalytic asymmetric [3+2] cycloaddition of aromatic aldehydes with oxiranes by C–C bond cleavage of epoxides: highly efficient synthesis of chiral 1,3-dioxolanes
A novel and efficient N,N'-dioxide-Gd(III) complex was developed for the highly diastereo- and enantioselective [3+2] cycloaddition of aryl oxiranyl diketones and aldehydes via C-C bondcleavage of oxiranes. The corresponding chiral 1,3-dioxolanes were obtained in excellent yields (up to 99%) with high diastereoselectivities (>95 : 5 dr) and enantioselectivities (up to 91% ee). Moreover, a possible
Asymmetric epoxidation of 2-arylidene-1,3-diketones: facile access to synthetically useful epoxides
作者:Alessio Russo、Alessandra Lattanzi
DOI:10.1039/c002587a
日期:——
enantioselective epoxidation reaction of acyclic and cyclic 2-arylidene-1,3-diketones is reported. Easily accessible or commercially available α,α-diaryl prolinols as the organocatalysts in the presence of tert-butyl hydroperoxide (TBHP) provide the corresponding epoxides in high to excellent yield (up to 99%) and up to 85% ee (ee >90% after crystallisation). These epoxides are pharmaceutically important
The catalytic asymmetricepoxidation of 2‐arylidene‐1,3‐diketones using aqueous 30% H2O2 as oxidant has been successfully realized by a N,N′‐dioxide–scandium(III) triflate [Sc(OTf)3] complex, giving the corresponding products in moderate to good yields (up to 85%) with excellent enantioselectivities (up to 99% ee) under mild reaction conditions without extra additives.
N,N'-二氧化物-三氟甲磺酸scan [Sc(OTf)3 ]配合物已成功实现了使用30%H 2 O 2水溶液作为氧化剂催化2-亚芳基-1,3-二酮的催化不对称环氧化。,在温和的反应条件下,无需额外的添加剂,即可以中等至良好的收率(高达85%)提供具有良好对映选择性(高达99%ee)的相应产品。
Lewis Acid Catalyzed Carbon−Carbon Bond Cleavage of Aryl Oxiranyl Diketones: Synthesis of <i>cis</i>-2,5-Disubstituted 1,3-Dioxolanes
作者:Zuliang Chen、Lai Wei、Junliang Zhang
DOI:10.1021/ol2000292
日期:2011.3.4
Carbonylylide is one of the most important intermediates which can undergo a series of 1,3-dipolar cycloaddition reactions. The C−C heterolysis of oxirane is believed to be the most atom-economic and straightforward way to generate carbonylylide. However, this chemistry was only achieved under photochemical and thermal conditions in past years. In this work, the one-step diastereoselective synthesis
Nickel-Catalyzed Annulation of Donor-Acceptor Oxiranes with Imines: Diastereoselective Access to Highly Substituted 2,4-<i>trans</i>-Oxazolidines
作者:Junqing Zhang、Yuanjing Xiao、Junliang Zhang
DOI:10.1002/adsc.201300449
日期:2013.10.11
AbstractAn efficient approach for the synthesis of highly substituted 2,4‐trans‐oxazolidines has been achieved by means of nickel(II) chlorate hexahydrate [Ni(ClO4)2⋅6 H2O]‐catalyzed [3+2] dipolar cycloaddition reactions of donor–acceptor oxiranes with imines via CC bond cleavage in good yields with moderate to high diastereoselectivity. The appropriate orientation of two activating ketones or esters is crucial for this chemoselective CC bond cleavage of the oxirane ring.magnified image