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1.
Hayriye Nevin Genc 《Chirality》2019,31(9):711-718
Novel chiral secondary amines bearing a tetraoxacalix[2]arene[2]triazine scaffold were created and used for catalytic asymmetric Michael reaction of anthrone with nitroalkenes. The relevant adducts were obtained in good to excellent yields (82%‐98%) and enantioselectivities (75%‐98%). 相似文献
2.
《Chirality》2017,29(6):257-272
A few new l ‐threitol‐based lariat ethers incorporating a monoaza‐15‐crown‐5 unit were synthesized starting from diethyl l ‐tartrate. These macrocycles were used as phase transfer catalysts in asymmetric Michael addition reactions under mild conditions to afford the adducts in a few cases in good to excellent enantioselectivities. The addition of 2‐nitropropane to trans ‐chalcone, and the reaction of diethyl acetamidomalonate with β‐nitrostyrene resulted in the chiral Michael adducts in good enantioselectivities (90% and 95%, respectively). The substituents of chalcone had a significant impact on the yield and enantioselectivity in the reaction of diethyl acetoxymalonate. The highest enantiomeric excess (ee ) values (99% ee ) were measured in the case of 4‐chloro‐ and 4‐methoxychalcone. The phase transfer catalyzed cyclopropanation reaction of chalcone and benzylidene‐malononitriles using diethyl bromomalonate as the nucleophile (MIRC reaction) was also developed. The corresponding chiral cyclopropane diesters were obtained in moderate to good (up to 99%) enantioselectivities in the presence of the threitol‐based crown ethers. 相似文献
3.
A series of new highly efficient chiral aliphatic–aromatic diamine catalysts have been designed and successfully applied to the asymmetric Michael addition of cyclohexanone with nitroolefins under solvent‐free conditions without any acidic additives. The desired adducts were obtained in high yields with excellent enantio‐ and diastereoselectivities of syn products (up to >99% ee, >99:1 dr). Chirality 2010. © 2010 Wiley‐Liss, Inc 相似文献
4.
We have developed the first operationally simple and environmentally benign protocol for the aqueous asymmetric Michael addition
reaction of chiral nickel(II) glycinate with nitroalkenes. The reactions proceeded smoothly in the presence of TBAB (tetrabutyl
ammonium bromide) in neat water at room temperature and provided good yields of β-substituted α,γ-diaminobutyric acid derivatives
with excellent diastereoselectivities. 相似文献
5.
Merrifield resin‐supported pyrrolidine‐based chiral organocatalysts A ? D through A3‐coupling reaction linkage have been developed and found to be highly effective catalysts for the Michael addition reaction of ketones with nitrostyrenes. The reactions generated the corresponding products in good yields (up to 92%), excellent enantioselectivities (up to 98% ee), and high diastereoselectivities (up to 99:1 dr). In addition, the catalysts can be reused at least five times without a significant loss of catalytic activity and stereoselectivity. Chirality, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
6.
The Michael addition of cyclohexanone with trans‐β‐nitrostyrene catalyzed by a chiral ionic liquid (CIL) pyrrolidine‐imidazolium bromide, which represents a prototype of CIL‐promoted asymmetric syntheses, has been investigated by performing density functional theory calculations. We show the details of the mechanism and energetics, the influence of the acid additive on the reactivity, and the functional role of the CIL in the asymmetric addition. It is found that the reaction proceeds via two stages, i.e., the initial enamine formation, where the imine complex is first created and then isomerizes into the enamine intermediate, and the subsequent Michael addition involving a three‐step mechanism. The calculations show that the presence of the acid additive changes the imine formation mechanism and lowers the reaction barrier, as well as, more importantly, makes the reaction become highly thermodynamically favored. It is also suggested that both the anion and cation of the CIL synergically facilitate the reaction, which act as the proton acceptor in the imine‐enamine tautomerism and the stabilizer of the negative charge in the C? C bond formation process, respectively. The present theoretical study rationalizes the early experimental findings well and provides aid to some extent for the rational design of efficient CIL catalysts. Chirality 2010. © 2010 Wiley‐Liss, Inc. 相似文献
7.
Synthesis of d‐mannitol‐based crown ethers and their application as catalyst in asymmetric phase transfer reactions
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A few new d ‐mannitol‐based monoaza‐15‐crown‐5 type chiral lariat ethers and 18‐crown‐6 type macrocycles were synthesized. These crown compounds were used as phase transfer catalysts in asymmetric Michael addititons and in a Darzens condensation under mild conditions to afford the corresponding products in a few cases in good to excellent enantioselectivities. In the Michael addition of diethyl acetoxymalonate to trans‐chalcone, in the addition of diethyl acetamidomalonate to ß‐nitrostyrene, in the reaction of diethyl bromomalonate with benzylidene malononitriles, in the cyclopropanation reaction of diethyl bromomalonate and 2‐benzylidene‐1,3‐indandione, and in the Darzens condensation of α‐chloroacetophenone with benzaldehyde, maximum enantioselectivities of 39%, 65%, 99%, 56%, and 62%, respectively, were obtained in the presence of the d ‐mannitol‐based macrocycles as the catalysts. 相似文献
8.
G‐quadruplex DNA‐based asymmetric catalysis of michael addition: Effects of sonication,ligands, and co‐solvents
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There is an escalating interest of using double stranded DNA molecules as a chiral scaffold to construct metal‐biomacromolecule hybrid catalysts for asymmetric synthesis. Several recent studies also evaluated the use of G‐quadruplex DNA‐based catalysts for asymmetric Diels‐Alder and Friedel‐Crafts reactions. However, there is still a lack of understanding of how different oligonucleotides, salts (such as NaCl and KCl), metal ligands and co‐solvents affect the catalytic performance of quadruplex DNA‐based hybrid catalysts. In this study, we aim to systematically evaluate these key factors in asymmetric Michael addition reactions, and to examine the conformational and molecular changes of DNA by circular dichroism (CD) spectroscopy and gel electrophoresis. We achieved up to 95% yield and 50% enantiomeric excess (ee) when the reaction of 2‐acylimidazole 1a and dimethylmalonate was catalyzed by 5′‐G3(TTAG3)3?3′ (G4DNA1) in 20 mM MOPS (pH 6.5) containing 50 mM KCl and 40 µM [Cu(dmbipy)(NO3)2], and G4DNA1 was pre‐sonicated in ice bath for 10 min prior to the reaction. G‐quadruplex‐based hybrid catalysts provide a new tool for asymmetric catalysis, but future mechanistic studies should be sought to further improve the catalytic efficiency. The current work presents a systematic study of asymmetric Michael addition catalyzed by G‐quadruplex catalysts constructed via non‐covalent complexing, and an intriguing finding of the effect of pre‐sonication on catalytic efficiency. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:891–898, 2016 相似文献
9.
Blanca M. Santoyo Carlos Gonzlez‐Romero Daniel Zrate‐Zrate R. Israel Hernndez‐Benitez Vanessa Pelayo Edson Barrera Carlos H. Escalante Ayde Fuentes‐Benites Guadalupe Martínez‐Morales Julio Lpez Miguel A. Vzquez Francisco Delgado Hugo A. Jimnez‐Vzquez Joaquín Tamariz 《Chirality》2019,31(9):719-749
Enantiopure 3‐((R)‐ and 3‐((S)‐1‐phenylethyl)‐4‐oxazoline‐2‐ones were evaluated as chiral building blocks for the divergent construction of heterocycles with stereogenic quaternary centers. The N‐(R)‐ or N‐(S)‐1‐phenylethyl group of these compounds proved to be an efficient chiral auxiliary for the asymmetric induction of the 4‐ and 5‐positions of the 4‐oxazolin‐2‐one ring through thermal and MW‐promoted nucleophilic conjugated addition to Michael acceptors and alkyl halides. The resulting adducts were transformed via a cascade process into fused six‐membered carbo‐ and heterocycles. The structure of the reaction products depended on the electrophiles and reaction conditions used. Alternative isomeric 4‐methylene‐2‐oxazolidinones served as chiral precursors for a versatile and divergent approach to highly substituted cyclic carbamates. DFT quantum calculations showed that the formation of bicyclic pyranyl compounds was generated by a diastereoselective concerted hetero‐Diels‐Alder cycloaddition. 相似文献
10.
Highly Enantioselective Michael Addition Promoted by a New Diterpene‐Derived Bifunctional Thiourea Catalyst: A Doubly Stereocontrolled Approach to Chiral Succinimide Derivatives
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Zhong‐Tai Song Tao Zhang Hai‐Long Du Zhi‐Wei Ma Chang‐Hua Zhang Jing‐Chao Tao 《Chirality》2014,26(2):121-127
A doubly stereocontrolled organocatalytic asymmetric Michael addition to the synthesis of substituted succinimides is described. Starting from aldehydes and maleimides, both enantiomers of the succinimides could be obtained in high to excellent yields (up to 98%) and enantioselectivities (up to 99%) when one of the two special chiral diterpene‐derived bifunctional thioureas was individually used as a catalyst. Moreover, these catalysts can be efficiently used in large‐scale catalytic synthesis with the same level of yield and enantioselectivity. Chirality 00:000–000, 2014. © 2014 Wiley Periodicals, Inc. 相似文献
11.
Utilization of deep‐sea microbial esterase PHE21 to generate chiral sec‐butyl acetate through kinetic resolutions
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We previously identified and characterized 1 novel deep‐sea microbial esterase PHE21 and used PHE21 as a green biocatalyst to generate chiral ethyl (S)‐3‐hydroxybutyrate, 1 key chiral chemical, with high enantiomeric excess and yield through kinetic resolution. Herein, we further explored the potential of esterase PHE21 in the enantioselective preparation of secondary butanol, which was hard to be resolved by lipases/esterases. Despite the fact that chiral secondary butanols and their ester derivatives were hard to prepare, esterase PHE21 was used as a green biocatalyst in the generation of (S)‐sec‐butyl acetate through hydrolytic reactions and the enantiomeric excess, and the conversion of (S)‐sec‐butyl acetate reached 98% and 52%, respectively, after process optimization. Esterase PHE21 was also used to generate (R)‐sec‐butyl acetate through asymmetric transesterification reactions, and the enantiomeric excess and conversion of (R)‐sec‐butyl acetate reached 64% and 43%, respectively, after process optimization. Deep‐sea microbial esterase PHE21 was characterized to be a useful biocatalyst in the kinetic resolution of secondary butanol and other valuable chiral secondary alcohols. 相似文献
12.
Highly enantioselective Michael addition of pyrazolin‐5‐ones to nitroolefins catalyzed by cinchona alkaloid derived 4‐methylbenzoylthioureas
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Mengchen Yang Min Zhang Zhenyu Wang Li Tang Wenbin Chen Shurong Ban Qingshan Li 《Chirality》2018,30(9):1096-1104
Cinchona alkaloid‐derived 4‐methyl/nitro benzoylthioureas were synthesized, which smoothly catalyzed the asymmetric Michael addition of pyrazolin‐5‐ones to nitroolefins. The results showed that electronic effects of substituents in the benzene ring of benzoylthioureas have subtle influences on their catalytic abilities and electron donating methyl group is favored than electron withdrawing nitro group. Preliminary Hartree‐Fock calculations revealed that in the catalytic cycle, hydrogen bond energies of the complex formed with 4‐methylbenzoylthioureas are about 0.19 to 1.56 kcal/mol higher than with the corresponding 4‐nitrobenzoylthioureas. 4‐Methylbenzoylthioureas were identified as the most effective catalysts that promoted asymmetric Michael addition of pyrazolin‐5‐ones to nitroolefins to give the S‐ or R‐products with high enantioselectivities. 相似文献
13.
Four novel chiral amino alcohols were synthesized from D‐(+)‐camphor and utilized as ligands in a Cu(I)‐catalyzed asymmetric Henry reaction. The reactions were carried out under mild conditions with excellent enantioselectivities and moderate yields without the exclusion of air or moisture. The highest enantioselectivity was observed up to 94% enantiomeric excess (ee) with ligand L1 in toluene at room temperature. Chirality 27:761–765, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
14.
Fulvia Felluga Cristina Forzato Patrizia Nitti Giuliana Pitacco Fabio Prati Ennio Valentin Ennio Zangrando 《Chirality》2012,24(12):1005-1012
(R)‐(+) and (S)‐(?)‐1‐phenylethylamine have been shown to promote highly diastereoselective and complementary enantioselective formal [3 + 2]carbocyclization reactions between 2,3‐butanedione and conjugated nitroalkenes with formation of enantiomerically rich 2‐hydroxy‐3‐nitrocyclopentanone derivatives. The reactions were carried out both in solvent and under solvent‐free conditions. The absolute configurations of the products were assigned by X‐ray and circular dichroism spectra analyses. Chirality 24:1005–1012, 2012. © 2012 Wiley Periodicals, Inc. 相似文献
15.
Several pyrrolidine-camphor derived organocatalysts were designed and synthesized. These organocatalysts were used for direct Michael reaction of aldehydes with nitroalkenes to give the desired γ-nitrocarbonyl compounds in high yields (up to 99%), high diastereoselectivities (syn:anti up to 92:8), and good to excellent enantioselectivities (up to 94% ee). Possible transition-state model was also proposed for this asymmetric transformation, which may involve hydrogen-bond interactions between the nucleophilic enamine formed in situ and the nitroalkenes. 相似文献
16.
Highly enantioselective Michael addition of cyclohexanone to nitroolefins catalyzed by pyrrolidine‐based bifunctional benzoylthiourea in water
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Organocatalysis and aqueous reactions are identified as the focus of the greening of chemistry. Combining these two strategies effectively remains an interesting challenge in organic synthesis. Herein, we used pyrrolidine‐based benzoylthiourea 1c to catalyze the asymmetric Michael addition of cyclohexanone to various nitroolefins in water to afford the corresponding compounds in moderate to good yields, and with excellent diastereoselectivities (up to >99:1 dr) and enantioselectivities (up to 99% ee). 相似文献
17.
Xiao Sun Xueyang Wang Feipeng Liu Zidong Gao Qinghua Bian Min Wang Jiangchun Zhong 《Chirality》2019,31(9):682-687
A novel enantioselective synthesis of (R)‐cinacalcet with 99% enantiomeric excesses (ee) has been achieved. The main strategies of the approach include a gram‐scale cobalt‐catalysed asymmetric cross‐coupling of racemic ester with arylzinc reagent, Hoffman‐type rearrangement of acidamide, the amidation of chiral amine, and improving the ee of chiral amide from 87% to 99% via recrystallization. 相似文献
18.
The reduction of the axially chiral N‐(o‐aryl)‐5,5‐dimethyl‐2,4‐oxazolidinediones by NaBH4 yielded axially chiral N‐(o‐aryl)‐4‐hydroxy‐5,5‐dimethyl‐2‐oxazolidinone enantiomers having a chiral center at C‐4, with 100% diastereoselectivity as has been shown by their 1H and 13C NMR spectra and by enantioselective HPLC analysis. The resolved enantiomeric isomers were found to interconvert thermally through an aldehyde intermediate formed upon ring cleavage via a latent ring‐chain‐ring tautomerization. It was found that the rate of enantiomerization depended on the size and the electronic effect of the ortho substituent present on the aryl ring bonded to the nitrogen of the heterocycle. Chirality 2010. © 2009 Wiley‐Liss, Inc. 相似文献
19.
A novel type of oxacalix[2]arene[2]triazine‐based organocatalysts for asymmetric Michael reactions are reported for the first time. Chiral subunits were attached to the heteroatom‐bridged calixaromatic platform by a reaction of (R)‐ and (S)‐1‐aminotetraline with tetraoxacalix[2]arene[2]triazine in both enantiomeric forms. To evaluate the catalytic efficiency of the novel organocatalysts, isobutyraldehyde reacted with various substituted and unsubstituted aromatic trans‐β‐nitrostyrenes in tetrahydrofuran (THF), leading to Michael adducts in excellent yields and enantioselectivites (up to 97% yield and 99% ee). 相似文献
20.
Bushra Nisar Abdul Rauf Raza David Stc. Black Naresh Kumar Muhammad Nawaz Tahir 《Chirality》2013,25(12):865-870
Novel 3‐alkyl‐4,1‐benzoxazepine‐2,5‐diones were synthesized in good ee exploiting the chiral pool methodology, an economical way of asymmetric synthesis. Various anthranilic acids are coupled with different α‐haloacids to afford N‐acylated anthranilic acid intermediates which undergo cyclization to (3R)‐3‐alkyl‐4,1‐benzoxazepines‐2,5‐diones. Chirality 25:865–870, 2013. © 2013 Wiley Periodicals, Inc. 相似文献