Enantioselective direct vinylogous Michael addition reaction catalyzed by organic molecules

Chiral 2-azanorbornyl-3-methanol is used as an organocatalyst for the highly enantioselective direct vinylogous Michael addition reaction of vinyl malononitriles to α,β-unsaturated aldehydes. In many cases, the products can be obtained in almost optically pure form (>95% ee) after a single recrystallization.     

用固体碱催化Michael加成反应的研究

Different Michael addition reactions catalyzed by solid base K2O/γ-Al2O3 and KF/γ-Al2O3, MgO/γ-Al2O3 prepared by microwave irradiation method were reported in this paper. For the K2O/γ-Al2O3, not only good yield was attained but also made the reaction of Acetonitrile that usually is regarded as inactive carbonion and α, β-unsatumted compound to carry out. The yield of Michael reaction of Ethyl acetoacetate and Crotonaldehyde catalyzed by KF/γ-Al2O3, MgO/γ-Al2O3, MgO/NaY all could reach to 80% and the latter could reach to 90%. At the same time, the catalysts of different content(the ratio of load) of MgO were also applied in this reaction, and it was found that the best content of MgO was 20% ～ 25%。     

Recyclable cinchona alkaloid catalyzed asymmetric Michael addition reaction

A highly enantioselective and diastereoselective Michael addition reaction of α-fluoro-β-ketoesters with maleimides is catalyzed by fluorous cinchona alkaloid to afford two adjacent chiral centers. The catalyst attached with a perfluroalkyl tag can be recovered by fluorous solid-phase extraction (F-SPE).     

Iron catalyzed Michael addition: Chloroferrate ionic liquids as efficient catalysts under microwave conditions

The iron containing ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate ([C4mim]Cl/FeCl3; = 0.5) proved to be an efficient catalyst for the solvent-free metal catalyzed Michael addition of β-keto esters and enones. Due to the ionic structure of the catalyst, a significant acceleration of the reaction rate was observed under microwave conditions. Furthermore, recycling of the ionic liquid catalyst could be performed after simply distilling off the products.     

Phosphinoyl-aziridines as a new class of chiral catalysts for enantioselective Michael addition

A series of new optically pure phosphine oxides containing chiral aziridine subunit were synthesized in good yields and applied as organocatalysts in asymmetric Michael reaction of various aliphatic aldehydes with β-nitrostyrene. The corresponding organocatalysts were synthesized starting from optically pure aziridines in a few simple efficient steps. The appropriate Michael adducts were obtained in most cases in very high chemical yield (up to 97%), excellent enantioselectivity (up to 98% of ee) and diastereoselectivity (up to 95:5 of dr).     

High Diastereoselectivity in the Conjugate Addition of Functionalized Alcohols to a Chiral(E)-Nitroalkene

Nitr0alkenesareversatilesyntheticintermediatesaspowerfulelectron-deficientreactantsincycloadditionandconjugatadditionreacti0ntoproducealargevarietyfunctionalizedcarbocyclicrings'.Purthermore,thenitrogrouPcanbeconvertedintoawiderangeoffiinctionalities2-Al0ughDiels-Alderreaction3andcyclopropanationoffunctionalizedcarbonnucleophiles4toY-chiralnitr0alkenehavebeenreportedrecently.Sofarthedetailedresearch0ftheconjugateadditionsoffimctionalizedalcoholst0chira1nitf0keneshasn0tbeenreported.Herewewish…     

A Diels-Alder reaction / oxa-Michael addition / acyloin rearrangement cascade on tropolonic substrates

We describe a novel pericyclic/anionic cascade reaction on tropolonic substrates that combines a Diels-Alder reaction, an oxa-Michael addition, and an acyloin rearrangement to afford tricyclic α-hydroxy-β-methoxyketones. Spectroscopic, crystallographic, and mechanistic studies indicate that the process requires stabilization of reaction intermediates through intramolecular H-bonding to take place, and suggest that the conjugate addition step involves a catalytic cycle with initial formation of an ammonium enolate and sustained by an alkoxide ion pair. Given the rich functionality and structural complexity generated in a single step, the process could be exploited in the preparation of natural product-like compound libraries.     

Chiral bis(2-oxazolinyl)xanthene (xabox)/transition-metal complexes catalyzed 1,3-dipolar cycloaddition reactions and Diels-Alder reactions

A series of chiral 4,5-bis(2-oxazolinyl)-(2,7-di-tert-butyl-9,9-dimethyl)-9H-xanthenes (xabox) and their transition-metal complexes were synthesized. The X-ray analysis of xabox-RhCl₃ complex shows a unique facial type structure. Xabox-Bn-Mn(II) and xabox-Bn-Mg(II) complexes were found to be efficient catalysts in nitrone 1,3-dipolar cycloaddition (1,3-D.C.) reaction resulting in good to excellent enantioselectivities ranging from 96:4 to >99:1of endo/exo ratio and 91-96% ee for the endo adduct. The correlation between enantiomeric excess of the ligand and the product in the nitrone 1,3-D.C. reaction shows a clear linear relationship, which suggests xabox-metal catalyst worked as a single molecular catalyst. In addition, xabox-i-Pr-Mn(II) complex was also found to be an active catalyst for Diels-Alder (D-A) reaction of acryloyloxazolidinone and cyclopentadiene affording the corresponding cycloadduct in quantitative yield along with 82% ee and 98:2 endo/exo ratio.     

苯并单氮杂15-冠-5-与α, β-不饱和羰基化合物的 Michael加成

本文报道借Michael加成使苯并单氮杂15-冠-5与α,β-不饱和羰基化合物反应,合成了氮支套索冠醚(1,2)和酯型双冠醚(3,4)。并提供了合成酯型双冠醚的一种方法,该法条件温和,操作简便,收率高。产物均经IR,^1HNMR和MS鉴定。     

Novel guanidinyl pyrrolidine salt-based bifunctional organocatalysts: application in asymmetric conjugate addition of malonates to enones

Novel guanidinyl pyrrolidine salts are useful bifunctional organocatalysts for the asymmetric addition of malonates to enones. These organocatalysts are effective under a wide range of reaction conditions and afford products in high yield and enantioselectivity.     

Enantioselective Michael addition of anthrone to nitroalkenes catalyzed by bifunctional thiourea-tertiary amines

A highly bifunctional thiourea-tertiary amine-catalyzed enantioselective Michael addition reaction of anthrone to a wide variety of nitroalkenes has been developed, and the corresponding adducts were obtained smoothly in high yields (up to 97%) and good enantioselectivities (up to 94% ee).     

A highly efficient asymmetric Michael addition of anthrone to nitroalkenes with cinchona organocatalysts

A highly efficient asymmetric Michael addition of anthrone to nitroalkenes catalyzed by cinchona alkaloids was described. Up to 99% ee of the corresponding adduct was obtained.     

Enantioselective synthesis of nitrocyclopropanes via conjugate addition of bromomalonate to nitroalkenes catalyzed by Ni(II) complexes

A novel one-pot methodology for the catalytic enantioselective synthesis of highly functionalized nitrocyclopropanes promoted by chiral nickel complexes is developed. The treatment of bromomalonates with nitroalkenes under the mild reaction conditions afforded the corresponding Michael adducts which cyclizes to controlled reaction conditions with excellent diasteroselectivities (>99 de) and enantioselectivities (up to 99% ee).     

Chiral zinc amidate catalyzed additions of diethylzinc to aldehydes

A series of bifunctional spiro ligands bearing “carboxamide–phosphine oxide” groups and ethylzinc carboxamidates from these ligands as catalysts for Et₂Zn additions to aldehydes were reported. Excellent yields were obtained with moderate ee′s in Et₂Zn additions to benzaldehyde derivatives, implying effectiveness of our newly designed catalytic structures as well as mediocre stereocontrol by these chiral ligands. Possible transition states were suggested based on the crystal structures of two ligands.     

A development of a reusable copper supported imidazolium functionalized ionic liquid catalyzed asymmetric Michael addition reaction

An eco-friendly copper supported Imidazolium functionalized ionic liquid [[Gmim]Cl–Cu (II)] used as green catalyst in solvent free asymmetric Michael addition at 25^OC. This technique covers simplified product isolation, high conversion and catalyst recycling.     

Solvent-free Michael addition reaction of fluorene with chalcon

A series of novel Michael addition products of fluorene to chalcone were obtained in the presence of sodium hydroxide under solvent-free condition.The advantages of this procedure were mild reaction conditions,simple protocol,and high yields.The structures of the products were characterized by IR,~1H NMR,MS and X-ray diffraction.The crystal of the new compound 3 h is Triclinic,space group P-1 with a = 0.97352(6) nm,b = 1.08918(7) nm,c = 2.58418(16) nm,α= 80.1400(10)°,β= 79.5490(10)°,γ= 64.2440(10)°,V = 2...     

冬凌草甲素和冬凌草乙素与谷胱苷肽的迈克尔加成反应

采用紫外光谱动力学方法测定了抗肿瘤对映贝壳杉烯二萜冬凌草甲素和冬凌草乙素与谷胱苷肽迈克尔加成反应的级数、速率常数和平衡常数.结果表明,冬凌草甲素和冬凌草乙素与与谷胱苷肽迈克尔加成反应符合二级动力学方程,25℃下的速率常数分别为16.196 0L·(mol·s)-1和7.480 5L·(mol·s)-1,平衡常数分别为177.98L/mol和85.60L/mol.冬凌草甲素与谷胱苷肽迈克尔加成反应速率和反应程度均比冬凌草乙素的大得多,反应活性更好.对映贝壳杉烯二萜通过与机体发生迈克尔加成反应而产生抗肿瘤作用;因此,冬凌草甲素可能比冬凌草乙素具有更好的抗肿瘤活性.     

A practical, green, and selective approach toward the synthesis of pharmacologically important quinone-containing heterocyclic systems using alumina-catalyzed Michael addition reaction

A convenient method for double Michael additions to quinone systems catalyzed by Al₂O₃, is reported. The advantages of this method include the use of a cheap and environment-friendly catalyst, a straightforward isolation of the pure product by filtration, high yields, and excellent selectivity, thus providing rapid access to useful building blocks for the preparation of biologically active quinones.     

Chiral spiroborate esters catalyzed highly enantioselective direct aldol reaction

Asymmetric catalysis of chiral spiroborate esters with an O₃BN framework toward the direct aldol reaction of acetone and aromatic aldehydes was examined, and a new, efficient chiral catalyst was discovered. In the presence of the novel catalyst, acetone was allowed to react with aromatic aldehydes at 0 °C for 50 h to afford chiral β-hydroxyketone in up to >99% ee and 92% yield. The catalyst, which is readily synthesized, is highly stable to hydrolysis, thermolysis, oxidation, and racemization, can be conveniently recovered.