(+)-Cinchonine-Decorated Dendrimers as Recoverable Organocatalysts
作者:Jordi Rull、Martí Casals、Rosa M. Sebastián、Adelina Vallribera、Jean-Pierre Majoral、Anne-Marie Caminade
DOI:10.1002/cctc.201500580
日期:2015.9.1
First‐ and fourth‐generation phosphorus dendrimers decorated on their surface with (+)‐cinchonine moieties for the use as organocatalysts have been prepared. The first‐generation dendrite showed the highest activity and enantioselectivity in the α‐amination of several β‐dicarbonyl compounds. A positive dendritic effect was observed. Its recovery and reuse over 10 cycles was demonstrated without loss
Using visible light as a driving force and molecular oxygen as a green oxidant, we developed bis(oxazoline)–Ni(acac)2 catalyzed asymmetric α-hydroxylation of β-keto esters under low photosensitizer loading, and the protocol enabled an efficient transformation to provide the desired chiral α-hydroxy-β-keto esters in high yields (up to 99%) and enantioselectivities (up to 99% ee) at room temperature
Bifunctional Guanidine via an Amino Amide Skeleton for Asymmetric Michael Reactions of β-Ketoesters with Nitroolefins: A Concise Synthesis of Bicyclic β-Amino Acids
Two activations are better than one: The chiralbifunctional guanidine 1, which features an amino amide backbone, catalyzes the asymmetric Michael addition of a range of substrates and gives products with excellent stereoselectivities. The method also allows the efficient synthesis of optically pure β‐amino acidesters. Both the guanidine group and the NH proton of the amide were important for the
Iron(iii)–salan complexes catalysed highly enantioselective fluorination and hydroxylation of β-keto esters and N-Boc oxindoles
作者:Xin Gu、Yan Zhang、Zhen-Jiang Xu、Chi-Ming Che
DOI:10.1039/c4cc01631a
日期:——
Chiral iron(III)âsalan complexes catalysed highly enantioselective α-fluorination and α-hydroxylation of β-keto esters and N-Boc oxindoles to give the corresponding products in high yields and good-to-excellent ee values under mild reaction conditions.
Although NHOs have been emerging as a new type of organocatalyst and ligand for metal complexes in organic synthesis, chiral NHO-mediated highly enantioselective organic transformations were still elusive. Herein, we developed a new type of chiral amine-derived C2-symmetric NHOs and employed them as efficient chiralbifunctionalorganocatalysts for asymmetric α-functionalization of β-ketoesters. With as