Catalyticasymmetric1,4-addition of β-ketoesters to nitroalkenes is described. 2.5 mol % of a homobimetallic Lewis acid/Brønsted base bifunctional Co2-Schiff basecomplex smoothly promoted the reaction in excellent yield (up to 99%), diastereoselectivity, and enantioselectivity (up to >30:1 dr and 98% ee). Catalyst loading was successfully reduced to 0.1 mol %. Mechanistic studies suggested that
描述了 β-酮酯与硝基烯烃的催化不对称 1,4-加成反应。2.5 mol% 的均双金属路易斯酸/Brønsted 碱双功能 Co2-Schiff 碱配合物以优异的产率(高达 99%)、非对映选择性和对映选择性(高达 >30:1 dr 和 98% ee)顺利促进反应。催化剂负载成功地降低到 0.1 mol%。机理研究表明,两个 Co 金属中心的分子内协同功能对于高催化活性和立体选择性很重要。
2-Azanorbornane-Based Amino Alcohol Organocatalysts for Asymmetric Michael Reaction of β-Keto Esters with Nitroolefins
A highly enantioselective Michael addition of β‐keto esters to nitroolefins was carried out using newly designed optically active 2‐azanorbornane‐based aminoalcohol organocatalysts to produce the corresponding chiral Michael adducts in good chemical yields (up to 99 %) and stereoselectivities (up to dr = 91:9, up to 91 % ee).
Hexafluorobenzene: a powerful solvent for a noncovalent stereoselective organocatalytic Michael addition reaction
作者:Alessandra Lattanzi、Claudia De Fusco、Alessio Russo、Albert Poater、Luigi Cavallo
DOI:10.1039/c2cc17488j
日期:——
A dramatic enhancement of the diastereo- and enantioselectivity in the nitro-Michaeladdition reaction organocatalysed by a commercially available alpha,alpha-L-diaryl prolinol was disclosed when performing the reaction in unconventional hexafluorobenzene as a medium. DFT calculations were performed to clarify the origin of stereoselectivity and the role of C(6)F(6).
The combined use of rhodium and cinchona-based squaramide has first been introduced for asymmetric relay catalysis, enabling a highly enantioselective semipinacol rearrangement/Michael addition cascade.