- Asymmetric Epoxidation of Enones Promoted by Dinuclear Magnesium Catalyst
-
Asymmetric synthesis with cheaper and non-toxic alkaline earth metal catalysts is becoming an important and sustainable alternative to conventional catalytic methodologies mostly relying on precious metals. In spite of some sustainable methods for enantioselective epoxidation of enones, the development of a well-defined and efficient catalyst based on magnesium complexes for these reactions is still a challenging task. In this perspective, we present the application of chiral dinuclear magnesium complexes for asymmetric epoxidation of a broad range of electron-deficient enones. We demonstrate that the in situ generated magnesium-ProPhenol complex affords enantioenriched oxiranes in high yields and with excellent enantioselectivities (up to 99% ee). Our extensive study verifies the literature data in this area and provides a step forward to better understand the factors controlling the oxygenation process. Elaborated catalyst offers mild reaction conditions and a truly wide substrate scope. (Figure presented.).
- Jaszczewska-Adamczak, Joanna A.,Mlynarski, Jacek
-
supporting information
p. 4247 - 4255
(2021/07/17)
-
- Synthesis of methyl 4,6-di-o-ethyl-α-d-glucopyranoside-based azacrown ethers and their effects in asymmetric reactions
-
Carbohydrate-based crown ethers have been reported to be able to generate asymmetric induction in certain reactions. Previously, it was proved that the monosaccharide unit, the anomeric substituent, and the sidearm could influence the catalytic activity of the monoaza-15-crown-5 macrocycles derived from sugars. In order to gain information about the effect of the flexibility, 4,6-di-O-ethyl-glucoside-based crown compounds were synthesized, and their efficiency was compared to the 4,6-O-benzylidene analogues. It was found that the absence of the two-ring annulation has a negative effect on the enantioselectivity in liquid-liquid two-phase reactions: in the Darzens condensation of 2-chloroacetophenone and in the epoxidation of chalcone. The same trend was observed in the solid-liquid phase Michael addition of diethyl acetamidomalonate. Surprisingly, in the solid-liquid phase cyclopropanation of benzylidenemalononitrile, one of the new catalysts was highly enantioselective (99% ee).
- Bagi, Péter,Bakó, Péter,Heged?s, László,Orbán, István,Rapi, Zsolt,Varga, Bertalan
-
-
- Synthesis and a Catalytic Study of Diastereomeric Cationic Chiral-at-Cobalt Complexes Based on (R, R)-1,2-Diphenylethylenediamine
-
Here we report the first synthesis of two diastereomeric cationic octahedral Co(III) complexes based on commercially available (R,R)-1,2-diphenylethylenediamine and salicylaldehyde. Both diastereoisomers with opposite chiralities at the metal center (Λ and Δconfigurations) were prepared. The new Co(III) complexes possessed both acidic hydrogen-bond donating (HBD) NH moieties and nucleophilic counteranions and operate as bifunctional chiral catalysts for the challenging kinetic resolution of terminal and disubstituted epoxides by the reaction with CO2 under mild conditions. The highest selectivity factor (s) of 2.8 for the trans-chalcone epoxide was achieved at low catalyst loading (2 mol %) in chlorobenzene, which is the best achieved result currently for this type of substrate.
- Emelyanov, Mikhail A.,Stoletova, Nadezhda V.,Smol'Yakov, Alexander F.,Il'In, Mikhail M.,Maleev, Victor I.,Larionov, Vladimir A.
-
supporting information
p. 13960 - 13967
(2021/09/11)
-
- Asymmetric epoxidation of α,β-unsaturated ketones catalyzed by rare-earth metal amides RE[N(SiMe3)2]3with chiral TADDOL ligands
-
The catalytic asymmetric epoxidation of α,β-unsaturated ketones by tert-butylhydroperoxide (TBHP) has been well established using rare-earth metal amides RE[N(SiMe3)2]3 (RE = La(1), Nd(2), Sm(3), Y(4), Yb(5)) with chiral TADDOL ligands. It was found that
- Shan, Haiwen,Lu, Chengrong,Zhao, Bei,Yao, Yingming
-
p. 1043 - 1053
(2021/01/25)
-
- Asymmetric Epoxidation of Olefins Catalyzed by Substituted Aminobenzimidazole Manganese Complexes Derived from L-Proline
-
A family of manganese complexes [Mn(Rpeb)(OTf)2] (peb=1-(1-ethyl-1H-benzo[d]imidazol-2-yl)-N-((1-((1-ethyl-1H-benzo[d]imidazol-2-yl)methyl) pyrrolidin-2-yl)methyl)-N-methylmethanamine)) derived from L-proline has been synthesized and characterized, where R refers to the group at the diamine backbone. X-ray crystallographic analyses indicate that all the manganese complexes [Mn(Rpeb)(OTf)2] exhibit cis-α topology. These types of complexes are shown to catalyze the asymmetric epoxidation of olefins employing H2O2 as a terminal oxidant with up to 96% ee. Obviously, the R group of the diamine backbone can influence the catalytic activity and enantioselectivity in the asymmetric epoxidation of olefins. In particular, Mn(i-Prpeb)(OTf)2 bearing an isopropyl arm, cannot catalyze the epoxidation reaction with H2O2 as the oxidant. However, when PhI(OAc)2 is used as the oxidant instead, all the manganese complexes including Mn(i-Prpeb)(OTf)2 can promote the epoxidation reactions efficiently. Taken together, these results indicate that isopropyl substitution on the Rpeb ligand inhibits the formation of active Mn(V)-oxo species in the H2O2/carboxylic acid system via an acid-assisted pathway.
- Lin, Jin,Sun, Wei,Tian, Jing,Xia, Chungu,Zhang, Jisheng
-
supporting information
(2021/11/16)
-
- Asymmetric epoxidation of α,β-unsaturated ketones via an amine-thiourea dual activation catalysis
-
A simple asymmetric epoxidation method is developed to effectively synthesize chiral α-carbonyl epoxides through an amine-thiourea dual activation catalysis. In this method, TBHP, as an oxidant, determined the reaction rate, and the chiral amine-thiourea catalyst effectively controlled the stereoselectivity of the reaction, and KOH promoted deprotonation. 22 examples of α,β-unsaturated ketones with various substituent groups are smoothly converted into α-carbonyl epoxides with moderate to excellent enantiomeric excess.
- Zhang, Lu-Wen,Wang, Li,Ji, Nan,Dai, Si-Yang,He, Wei
-
supporting information
(2021/03/15)
-
- Efficient Aliphatic C-H Oxidation and C═C Epoxidation Catalyzed by Porous Organic Polymer-Supported Single-Site Manganese Catalysts
-
Bioinspired manganese complexes have emerged over recent decades as attractive catalysts for a number of selective oxidation reactions. However, these catalysts still suffer from oxidative degradation. In the present study, we prepared a series of porous Mn-N4 catalysts in which the catalytic units are embedded in the skeleton of porous organic polymers (POPs). These POP-based manganese catalysts demonstrated high reactivity in the oxidation of aliphatic C-H bonds and the asymmetric epoxidation of olefins. Furthermore, these catalysts could be readily recycled and reused due to their heterogeneous nature. Morphological characterization revealed that the Mn-N4 complex was individually distributed over a porous polymer network. Remarkably, the nature of the single-site catalyst prevented oxidative degradation during the reaction. The present work has thus developed a successful approach for bioinspired single-site manganese catalysts in which the oxidation reaction is confined to a specific channel in an enzyme-like mode.
- Wang, Bingyang,Lin, Jin,Sun, Qiangsheng,Xia, Chungu,Sun, Wei
-
p. 10964 - 10973
(2021/09/08)
-
- Peroxide- And transition metal-free electrochemical synthesis of α,β-epoxy ketones
-
A novel electrochemical method for the synthesis of α,β-epoxy ketones is reported. With KI as the redox mediator, methyl ketones reacted with aldehydes under peroxide- and transition metal-free electrolytic conditions and afforded α,β-epoxy ketones in one pot (36 examples, 52-90% yield). This safe and environmental-friendly method has a broad substrate scope and can readily provide a variety of α,β-epoxy ketones in gram-scales for evaluation of their anti-cancer activities.
- Zhang, Mengxun,Chen, Tie,Fang, Shisong,Wu, Weihua,Wang, Xin,Wu, Haiqiang,Xiong, Yongai,Song, Jun,Li, Chenyang,He, Zhendan,Lee, Chi-Sing
-
supporting information
p. 2481 - 2486
(2021/04/02)
-
- Organocatalytic Enantioselective γ-Elimination: Applications in the Preparation of Chiral Peroxides and Epoxides
-
An organocatalyzed enantioselective γ-elimination process has been achieved and applied in the kinetic resolution of peroxides to access chiral peroxides and epoxides. The reaction provided a pathway for the preparation of two useful synthetic and biologically important structural motifs through a single-step reaction. A range of substrates has been resolved with a selectivity factor up to 63. The obtained enantioenriched peroxides and epoxides allowed a series of transformations with retained optical purities.
- Chen, Zhili,Gong, Xiangnan,Hu, Fangli,Huang, Shengli,Jia, Shiqi,Qin, Wenling,Tan, Yu,Xu, Da,Yan, Hailong
-
p. 1934 - 1940
(2020/03/24)
-
- Ligand regulation for manganese-catalyzed enantioselective epoxidation of olefins without acid
-
A novel manganese catalyst bearing an l-proline-derived N4 ligand has been developed for enabling acid-free asymmetric epoxidation of olefins with tert-butyl hydroperoxide as the oxidant. A variety of olefins that are well-matched in size with the ligand
- Xu, Daqian,Sun, Qiangsheng,Lin, Jin,Sun, Wei
-
supporting information
p. 13101 - 13104
(2020/11/09)
-
- Synthesis of xylal- and arabinal-based crown ethers and their application as asymmetric phase transfer catalysts
-
New xylal- and arabinal-based monoaza-15-crown-5 ethers were synthesized starting from l- and d-xylose, and l- and d-arabinose, respectively. These monosaccharide-based chiral macrocycles were tested as phase transfer catalysts in a few asymmetric reactions. The xylal-based crown compounds proved to be efficient catalysts in a few liquid-liquid phase reactions. The epoxidation of trans-chalcone and the Darzens condensation of α-chloroacetophenone with benzaldehyde took place with complete diastereoselectivity and up to 77% ee and 58% ee, respectively. It was found that the substituents in the aromatic ring of the chalcone and the α-chloroacetophenone had an influence on the enantioselectivity. The highest ee values were obtained in the epoxidation of 4-chlorochalcone (81% ee) and in the reaction of a 2-naphthyl analogue (96% ee), while in the Darzens condensation of 4-phenyl-α-chloroacetophenone with benzaldehyde, a maximum ee of 91% was detected. The configuration of the monosaccharide unit in the crown ring influenced the absolute configuration of the epoxyketones synthesized.
- Nemcsok, Tamás,Rapi, Zsolt,Bagi, Péter,Keglevich, Gy?rgy,Bakó, Péter
-
p. 107 - 119
(2019/11/16)
-
- Highly Enantioselective Epoxidation of α,β-Unsaturated Ketones Using Amide-Based Cinchona Alkaloids as Hybrid Phase-Transfer Catalysts
-
A series of 20 one chiral epoxides were obtained with excellent yields (up to 99%) and enantioselectivities (up to >99% ee) using hybrid amide-based Cinchona alkaloids. Our method is characterized by low catalyst loading (0.5 mol %) and short reaction times. Moreover, the epoxidation process can be carried out in 10 cycles, without further catalyst addition to the reaction mixture. This methodology significantly enhance the scale of the process using very low catalyst loading.
- Jurczak, Janusz,Majdecki, Maciej,Tyszka-Gumkowska, Agata
-
supporting information
(2020/11/13)
-
- Synthesis and characterization of 1,3,5-triarylpyrazol-4-ols and 3,5-diarylisoxazol-4-ols from chalcones and theoretical studies of the stability of pyrazol-4-ol toward acid dehydration
-
The synthesis of diverse pyrazol-4-ol and isoxazole-4-ol heterocycles involving only 3 reaction steps is reported in this study. However, the synthesis of carboxamide pyrazol-4-ol has failed in the conditions used in the synthesis, acid methanol solution. The carboxamide pyrazol-4-ol decomposes via dehydration, forming the respective pyrazol. Theoretical calculations were used to elucidate the dehydration reaction. We have found a mechanism for acid-catalyzed dehydration that can explain the experimental observations. The calculated free energy profile for acid-catalyzed dehydration of the carboxamide pyrazol-4-ol and phenylpyrazole-4-ol point out that the latter is more stable in relation dehydration, with a dehydration rate 100 times smaller in acid methanol solution.
- Cipagauta Esquivel, Edna Carolina,Rufino, Virgínia Camila,Trindade Nogueira, Matheus Henrique,Carbonaro Souza, Ana Carolina,Pliego Júnior, Josefredo Rodriguez,Valle, Marcelo Siqueira
-
-
- Lanthanide complexes combined with chiral salen ligands: Application in the enantioselective epoxidation reaction of α,β-unsaturated ketones
-
Readily available lanthanide amides Ln[N(SiMe3)2]3 (Ln = Nd (1), Sm (2), Eu (3), Yb (4), La (5)), combined with chiral salen ligands H2La ((S,S)-N,N′-di-(3,5-disubstituted-salicylidene)-1,2-cyclohexan
- Xia, Xuexiu,Lu, Chengrong,Zhao, Bei,Yao, Yingming
-
p. 13749 - 13756
(2019/05/16)
-
- Synthesis of novel phase transfer catalysts derived from proline-mandelic acid/tartaric acid: their evaluation in enantioselective epoxidation and Darzen condensation
-
Abstract : Herein, we have described the synthesis of novel chiral cyclic phase transfer catalysts (PTCs). These catalysts are synthesized from proline, mandelic acid and tartaric acid by using simple synthetic methods with competitive yields. These chira
- Mahajan, Deepak P,Godbole, Himanshu M,Singh, Girij P,Shenoy, Gautham G
-
-
- High-Spin and Low-Spin Perferryl Intermediates in Fe(PDP)-Catalyzed Epoxidations
-
Two bioinspired hydroxo-bridged diferric complexes 6 and 7 with N4-donor ligands of the PDP type (PDP=N,N′-bis(pyridin-2-ylmethyl)-2,2′-bipyrrolidine), differing by substituents at the pyridine rings (4-NMe2 in 7 vs. 3,5-Me2-4-OMe in 6), efficiently catalyze the enantioselective alkene epoxidation with H2O2 and peracetic acid in the presence of a carboxylic acid additive (up to 99 catalyst turnover numbers, TON, toward epoxide, up to 94 % ee). Catalyst systems based on complex 7 display the high-spin perferryl intermediate 7 aAA (S=3/2, g1, g2=3.69, g3=1.96), whereas catalyst systems based on complex 6 exhibit the low-spin perferryl intermediate 6 aAA (S=1/2, g1=2.07, g2=2.01, g3=1.96). The S=3/2 and the S=1/2 intermediates directly react with cyclohexene and cyclohexane at low temperatures (?40 °C and ?85 °C, respectively). The catalyst systems, exhibiting less reactive intermediate 7 aAA, demonstrate higher enantioselectivity (% ee) in the epoxidation of chalcone. The origin of the unprecedented high-spin state of the perferryl intermediate is discussed.
- Zima, Alexandra M.,Lyakin, Oleg Y.,Bryliakov, Konstantin P.,Talsi, Evgenii P.
-
p. 5345 - 5352
(2019/08/12)
-
- An efficient Darzens reaction promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)
-
An efficient DBU promoted Darzens reaction utilising α-haloketones containing an enolizable α′-hydrogen is reported. This method diastereoselectively afforded the corresponding α,β-epoxy ketones good to excellent yields in an one-pot reaction without using any transition metals or additives. Furthermore, haloketones without an α′-hydrogen are also applicable in this reaction.
- Luo, Juan,Hu, Lanfang,Zhang, Minghao,Tang
-
supporting information
p. 1949 - 1951
(2019/07/03)
-
- Synthesis of alkyl α- and β-d-glucopyranoside-based chiral crown ethers and their application as enantioselective phase-transfer catalysts
-
Chiral monoaza-15-crown-5-type lariat ethers annelated to alkyl 4,6-O-benzylidene-α- and β-d-glucopyranosides have been synthesized. These macrocycles generated significant asymmetric induction as phase-transfer catalysts in a few two-phase reactions. The catalytic effect of the lariat ethers with methoxy, ethoxy, and i-propoxy substituents on C-1 of the sugar unit in both α and β positions was compared. In liquid–liquid two-phase reactions, the nature and position of the substituents did not have much effect. The α-anomers were somewhat more efficient in terms of enantioselectivity than the β forms. In asymmetric Darzens condensations, in the epoxidation of trans-chalcone, in the Michael addition of β-nitrostyrene and diethyl acetamidomalonate, and in the reaction of 2-benzylidene-1,3-indandione with diethyl bromomalonate, maximum enantioselectivities of 73, 94, 78, and 72%, respectively, were obtained in presence of glucopyranoside-based lariat ethers as catalysts.
- Pálv?lgyi, ádám,Rapi, Zsolt,Ozohanics, Olivér,Tóth, Gábor,Keglevich, Gy?rgy,Bakó, Péter
-
p. 1627 - 1645
(2017/11/16)
-
- Mechanistic Insights into the Enantioselective Epoxidation of Olefins by Bioinspired Manganese Complexes: Role of Carboxylic Acid and Nature of Active Oxidant
-
Bioinspired manganese and iron complexes bearing nonporphyrinic tetradentate N4 ligands are highly efficient catalysts in asymmetric oxidation reactions by hydrogen peroxide (H2O2), in which carboxylic acid is employed as an essentia
- Du, Junyi,Miao, Chengxia,Xia, Chungu,Lee, Yong-Min,Nam, Wonwoo,Sun, Wei
-
p. 4528 - 4538
(2018/05/22)
-
- Papain-catalysed mechanochemical synthesis of oligopeptides by milling and twin-screw extrusion: Application in the Juliá-Colonna enantioselective epoxidation
-
The oligomerisation of l-amino acids by papain was studied in a mixer ball mill and in a planetary ball mill. The biocatalyst proved stable under the ball milling conditions providing the corresponding oligopeptides in good to excellent yields and with a variable degree of polymerisation. Both parameters were found to be dependent on the reaction conditions and on the nature of the amino acid (specifically on its side-chain size and hydrophobicity). In addition, the chemoenzymatic oligomerisation was demonstrated by utilising twin-screw extrusion technology, which allowed for a scalable continuous process. Finally, the synthesised oligo(l-Leu) 2b proved to be active as a catalyst in the Juliá-Colonna enantioselective epoxidation of chalcone derivatives.
- Ardila-Fierro, Karen J.,Crawford, Deborah E.,K?rner, Andrea,James, Stuart L.,Bolm, Carsten,Hernández, José G.
-
supporting information
p. 1262 - 1269
(2018/03/26)
-
- Crown-ether-modified cyclic dipeptides as supramolecular chiral catalysts
-
With the objective to develop supramolecular catalysts for useful chemical transformations, we report here a rapid and efficient solid-phase synthesis of novel cyclic dipeptides (crown-CDPs) with a diversity of L-DOPA derived crown ether substituents and
- Bérubé, Christopher,Voyer, Normand
-
p. 184 - 195
(2017/10/26)
-
- Chiral calcium-catalyzed asymmetric epoxidation reactions using hydrogen peroxide as the terminal oxidant
-
Asymmetric epoxidation reactions of chalcone derivatives catalyzed by chiral calcium complexes using hydrogen peroxide were developed. The epoxidation reactions proceeded smoothly to afford the desired products in good yields with good enantioselectivitie
- Yamashita, Yasuhiro,Macor, Joseph Alexander,Fushimi, Seiya,Tsubogo, Tetsu,Kobayashi, Shū
-
p. 847 - 850
(2018/09/10)
-
- Syntheses, Structures, and Catalytic Activities of the Anionic Heterobimetallic Rare-Earth Metal Complexes Supported by Pyrrolyl-Substituted 1,2-Diimino Ligands
-
A series of the anionic heterobimetallic rare-earth metal complexes supported by trans- or chiral pyrrolyl-substituted 1,2-diimino ligands were synthesized in good yields via reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3
- Wang, Wei,Wang, Xiaojia,Zhou, Shuangliu,Xu, Xiaolong,Du, Jun,Zhang, Lijun,Mu, Xiaolong,Wei, Yun,Zhu, Xiancui,Wang, Shaowu
-
supporting information
p. 10390 - 10400
(2018/08/28)
-
- Synthesis of d-mannitol-based crown ethers and their application as catalyst in asymmetric phase transfer reactions
-
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 ?-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.
- Nemcsok, Tamás,Rapi, Zsolt,Keglevich, Gy?rgy,Grün, Alajos,Bakó, Péter
-
p. 407 - 419
(2018/01/01)
-
- Revisiting the Juliá-Colonna enantioselective epoxidation: Supramolecular catalysis in water
-
We describe an efficient epoxidation process leading to chiral epoxyketones using the reusable homo-oligopeptide poly-l-leucine (PLL) in pure water, without any organic co-solvent. A range of substituted epoxyketones can be accessed with good conversions and high enantioselectivities. Based on the experimental results and computational studies, we propose a mechanism that demonstrates the importance of both the α-helical structure and the presence of a hydrophobic groove of the homo-oligopeptide catalyst for reactivity and selectivity.
- Bérubé, Christopher,Barbeau, Xavier,Lagüe, Patrick,Voyer, Normand
-
supporting information
p. 5099 - 5102
(2017/07/12)
-
- Synthesis of enantiomerically pure 2-(N-aryl, N-alkyl-aminomethyl)aziridines: a new class of ligands for highly enantioselective asymmetric synthesis
-
A simple and effective synthesis of enantiomerically pure 2-(N-aryl-, N-alkyl-aminomethyl)aziridines from (2S)-N-tritylaziridine-2-carboxylic acid methyl ester has been developed. Treating of this key ester with several primary and secondary amines in the presence of AlMe3 provided the corresponding chiral N-trityl-2-carboxamides, and their reduction performed with different reagents resulted in the formation of the expected 2-(aminomethyl)aziridines. The choice of reaction conditions allows to either keep or leave the trityl substituent in the product. Such 2-(aminoalkyl)aziridines have shown very high catalytic efficiency in the asymmetric arylation of aldehydes and in other testing asymmetric reactions. On the other hand, homochiral N-trityl-2-carboxamides are interesting building blocks for the synthesis of various biologically active compounds.
- Jarzyński, Szymon,Le?niak, Stanis?aw,Rachwalski, Micha?
-
p. 1808 - 1816
(2017/11/17)
-
- Asymmetric Cascade Catalysis with Chiral Polyoxometalate-Based Frameworks: Sequential Direct Aldol and Epoxidation Reactions
-
Catalytic asymmetric cascade reactions in which the substrates are transferred through well-choreographed consecutive independent steps by a single catalyst have received increasing interest. By incorporating a chiral organocatalyst pyrrolidine, an oxidat
- Han, Qiuxia,Li, Wenwen,Wang, Shugai,He, Jiachen,Du, Wei,Li, Mingxue
-
p. 1801 - 1807
(2017/05/29)
-
- Asymmetric synthesis of new γ-butenolides: Via organocatalyzed epoxidation of chalcones
-
γ-Butenolides have been recognized as an important structural framework in a number of natural products and medicinally important agents. In this work we describe a new metal-free sequential strategy for the asymmetric synthesis of substituted γ-butenolides having epoxychalcones as the advanced intermediate. Using the optimized reaction conditions, we were able to carry out the three-step sequence, epoxidation, olefination and hydrolysis, with only one single chromatographic purification of the final product, furnishing new enantiomerically enriched γ-butenolides in moderate overall yield and good enantiomeric excess.
- Vieira, Lucas C. C.,Matsuo, Bianca T.,Martelli, Lorena S. R.,Gall, Mayara,Paix?o, Marcio W.,Corrêa, Arlene G.
-
p. 6098 - 6103
(2017/08/02)
-
- Highly enantioselective asymmetric reactions involving zinc ions promoted by chiral aziridine alcohols
-
Enantiomerically pure, chiral secondary and tertiary aziridine alcohols (including the aziridine analogue of ProPhenol—AziPhenol) have proven to be highly effective catalysts for enantioselective asymmetric reactions in the presence of zinc ions, including arylation of aromatic aldehydes, epoxidation of chalcone and addition of diethylzinc to aldehydes, leading to the desired chiral products in high chemical yields (up to 90%) and with ee's up to 90%. A higher catalytic activity of Prophenol-type bis(aziridine alcohol) in the aforementioned asymmetric transformations has been demonstrated.
- Jarzyński, Szymon,Utecht, Greta,Le?niak, Stanis?aw,Rachwalski, Micha?
-
p. 1774 - 1779
(2017/11/16)
-
- Enantioselective Epoxidation of Electron-Deficient Alkenes Catalyzed by Manganese Complexes with Chiral N4 Ligands Derived from Rigid Chiral Diamines
-
A series of tetradentate sp2N/sp3N hybrid chiral N4 ligands derived from rigid chiral diamines were synthesized, which enabled the first manganese-catalyzed enantioselective epoxidation of electron-deficient alkenes with hydrogen peroxide (H2O2) as an oxidant. The reaction furnishes enantiomerically pure epoxy amides, epoxy ketones as well as epoxy esters in good yields and excellent enantioselectivities (up to 99.9% ee) with lower catalyst loading. Preliminary studies on structure–activity relationship demonstrated that maintaining comparatively lower electron-donating ability of the sp3N and relatively higher electron-donating ability of sp2N of the N4 ligands is beneficial to getting higher activity and selectivity, thus providing us a new view to understand epoxidation with H2O2. (Figure presented.).
- Chen, Xiangning,Gao, Bao,Su, Yijin,Huang, Hanmin
-
supporting information
p. 2535 - 2541
(2017/08/16)
-
- Bioinspired Manganese Complexes and Graphene Oxide Synergistically Catalyzed Asymmetric Epoxidation of Olefins with Aqueous Hydrogen Peroxide
-
Bioinspired manganese complexes of N4ligands and graphene oxide (GO) synergistically catalyze the highly enantioselective epoxidation of olefins (up to 99% ee), which is a rare example with GO as a co-catalyst in asymmetric catalysis. GO as a new and key additive not only successfully functions in catalytic amounts, but also has a positive effect for improving the enantioselectivity of the asymmetric epoxidation compared with the traditional stoichiometric organic carboxylic acid method [e.g., chalcone, 95% ee (3.5 mg GO) vs. 84% ee (5 equiv., 75 mg acetic acid), ethyl cinnamate, 84% ee (3.5 mg GO) vs. 19% ee (5 equiv., 75 mg acetic acid)]. The X-ray photoelectron spectroscopy (XPS) spectra of GO before and after the reaction indicate that the intensities of C–O become stronger after the reaction, which may have a certain relationship with hydrogen peroxide (H2O2) and gives a reasonable rationale for the large consumption of H2O2. Also, part of the hydrogen peroxide was used for the oxidation of GO. (Figure presented.).
- Miao, Chengxia,Yan, Xingbin,Xu, Daqian,Xia, Chungu,Sun, Wei
-
p. 476 - 484
(2017/02/10)
-
- Asymmetric Epoxidation of Olefins with H2O2 Catalyzed by a Bioinspired Aminopyridine N4 Iron Complex
-
An iron complex with a chiral aminopyridine N4 ligand bearing strong electron-donating and bulky morpholine groups on the ligand is synthesized and characterized. The iron complex serves to efficiently catalyze the asymmetric epoxidation of various olefins by employing aqueous hydrogen peroxide as the green oxidant, providing the corresponding epoxides in good to excellent yields and enantioselectivities (up to 93 % yield and 99.9 % ee). Owing to the introduction of morpholine functional groups on the ligand, the Fe-catalyzed reaction can proceed with a catalytic amount of the carboxylic acid partner (3 mol %).
- Wang, Wenfang,Sun, Qiangsheng,Xu, Daqian,Xia, Chungu,Sun, Wei
-
p. 420 - 424
(2017/02/15)
-
- Interfacial supramolecular biomimetic epoxidation catalysed by cyclic dipeptides
-
We synthesised a library of cis- and trans-cyclic dipeptides and evaluated their efficacy as catalysts in the asymmetric Weitz-Scheffer epoxidation of trans-chalcone. A thorough investigation relying on structure-activity studies and computational studies provided insights into the mechanism of the process. Our results revealed some structural features required for efficient conversion and for introduction of chirality into the product. The cyclic dipeptide acts as a catalyst by templating a supramolecular arrangement at the aqueous-organic interface required for efficient transformations to occur. Among all cyclic dipeptides investigated, cyclo(Leu-Leu) was the most efficient supramolecular catalyst.
- Bérubé, Christopher,Barbeau, Xavier,Cardinal, Sébastien,Boudreault, Pierre-Luc,Bouchard, Corinne,Delcey, Nicolas,Lagüe, Patrick,Voyer, Normand
-
p. 330 - 349
(2017/03/15)
-
- Synthesis and Catalytic Asymmetric Applications of Quinazolinol Ligands
-
A range of chiral quinazolinol ligands were efficiently synthesized and subsequently investigated for catalytic chiral induction in both the asymmetric phenylation of aryl aldehydes and the asymmetric epoxidation of chalcones. Encouragingly, high enantioselectivities (up to 95%) and yields (up to 98%) were achieved under the optimized reaction conditions.
- Karakaya, Idris,Karabuga, Semistan,Mart, Mehmet,Altundas, Ramazan,Ulukanli, Sabri
-
p. 1719 - 1726
(2016/05/24)
-
- Synthesis, applications and mechanistic investigations of C2 symmetric guanidinium salts
-
A range of guanidinium catalysts was prepared in six or seven synthetic steps and applied to the phase transfer alkylation of a glycinate Schiff's base in 21-86% ee as well as the phase transfer epoxidation of some chalcones in 85-94% ee. Using a spectrophotometric method, pKa values in the range 13.2-13.9 in DMSO have been determined for some of the catalysts highlighting an increase in basicity relative to achiral tetramethylguanidine (pKa=13.0) and a mechanism involving the protonated guanidinium ion as a phase transfer catalyst is proposed. The use of two of the catalysts for the addition of nucleophiles in Michael addition reactions was investigated and both were found to be effective catalysts. A counterion effect was apparent in these reactions, but no enantioselectivity was observed.
- Allingham, Matthew T.,Bennett, Elliot L.,Davies, Deniol H.,Harper, Philip M.,Howard-Jones, Andrew,Mehdar, Yassin T.H.,Murphy, Patrick J.,Thomas, Dafydd A.,Caulkett, Peter W.R.,Potter, David,Lam, Casey M.,O'Donoghue, Annmarie C.
-
supporting information
p. 496 - 503
(2015/12/31)
-
- Asymmetric epoxidation of alkenes catalyzed by novel chiral porphyrin metal complexes
-
Novel chiral porphyrin ligands were synthesized from four different chiral aldehydes. In situ transition metal complexes of these novel chiral porphyrin ligands were found to catalyze asymmetric epoxidation reaction of styrene possessing various substituents. The chiral epoxides were formed in excellent yield and ee.
- Sakthipriya, Pachiannan,Ananthi, Nallamuthu
-
p. 730 - 737
(2016/08/30)
-
- Highly selective multifunctional nanohybrid catalysts for the one-pot synthesis of α,β-epoxy-chalcones
-
An efficient one-pot heterogeneous process for producing chiral α,β-epoxy-chalcones from the corresponding aldehydes and ketones has been described. The nanohybrid materials based on poly-l-leucine immobilised into rehydrated hydrotalcites did not require any pre-activation and were easily recovered and recycled for four consecutive runs without losing their catalytic efficiency in terms of conversion, total selectivity towards the corresponding epoxy-chalcones and excellent enantioselectivity.
- Crivoi, Dana-Georgiana,Segarra, Anna M.,Medina, Francesc
-
p. 120 - 128
(2016/01/09)
-
- Proton-Promoted and Anion-Enhanced Epoxidation of Olefins by Hydrogen Peroxide in the Presence of Nonheme Manganese Catalysts
-
We report a remarkable Br?nsted acid effect in the epoxidation of olefins by nonheme manganese catalysts and aqueous hydrogen peroxide. More specifically, a mononuclear nonheme manganese complex bearing a tetradentate N4 ligand, MnII(Dbp-MCP)(OTf)2 (Dbp-MCP = (1R,2R)-N,N′-dimethyl-N,N′-bis((R)-(3,5-di-tert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine; OTf- = CF3SO3-), is a highly efficient catalyst in the epoxidation of olefins by aqueous H2O2 in the presence of H2SO4 (1-3 mol %). The yields of epoxide products as well as the chemo- and enantioselectivities increase dramatically in the presence of H2SO4; no formation of epoxides is observed in the absence of H2SO4. In addition, the product yields and enantioselectivities are dependent significantly on the manganese catalysts and Br?nsted acids. The catalytic epoxidation of olefins by other oxidants, such as peracids, alkyl hydroperoxides, and iodosylbenzene, is also affected by the presence of H2SO4; product yields and enantioselectivities are high and similar irrespective of the oxidants in the presence of H2SO4, suggesting that a common epoxidizing intermediate is generated in the reactions of [MnII(Dbp-MCP)]2+ and the oxidants. Mechanistic studies, performed with 18O-labeled water (H218O) and cumyl hydroperoxide, reveal that a high-valent manganese-oxo species is formed as an epoxidizing intermediate via O-O bond heterolysis of Mn-OOH(R) species. The role of H2SO4 is proposed to facilitate the formation of a high-valent Mn-oxo species and to increase the oxidizing power and enantioselectivity of the Mn-oxo oxidant in olefin epoxidation reactions. Density functional theory (DFT) calculations support experimental results such as the formation of a Mn(V)-oxo species as an epoxidizing intermediate.
- Miao, Chengxia,Wang, Bin,Wang, Yong,Xia, Chungu,Lee, Yong-Min,Nam, Wonwoo,Sun, Wei
-
supporting information
p. 936 - 943
(2016/02/05)
-
- Rate Acceleration of Solid-Liquid Phase-Transfer Catalysis by Rotor-Stator Homogenizer
-
A rotor-stator homogenizer was found to be an effective mixing tool that accelerated solid-liquid phase-transfer reactions. In the asymmetric alkylation under phase-transfer conditions using the homogenizer, a considerably high turnover frequency was observed. (Figure presented.).
- Kano, Taichi,Aota, Yusuke,Maruoka, Keiji
-
supporting information
p. 2996 - 2999
(2016/09/16)
-
- Quest for Efficient Catalysts based on Zinc tert-Butyl Peroxides for Asymmetric Epoxidation of Enones: C2- vs C1-Symmetric Auxiliaries
-
Zinc tert-butyl peroxide-based catalysts for the asymmetric epoxidation of enones using tert-butyl hydroperoxide as an oxidant have been developed. A comparative study of chiral monoanioninc N,N′-bidentate ligands, C2-symmetric bisoxazolinates and C1-symmetric enaminooxazolinates, revealed excellent performance of C1-symmetric auxiliary ligands on catalytic asymmetric epoxidation of enones (up to 96% yield, 91% ee).
- Raheem Keeri, Abdul,Justyniak, Iwona,Jurczak, Janusz,Lewiński, Janusz
-
supporting information
p. 864 - 868
(2016/04/05)
-
- Biomimetic epoxidation in aqueous media catalyzed by cyclic dipeptides
-
We have developed a practical epoxidation of electron-deficient enones in aqueous media using cyclic dipeptides as bioinspired green catalyst. Optimizing the reaction conditions in a triphasic system led to efficient conditions providing epoxides with good enantioselectivities. Depending on the catalyst substituent chirality, both enantiomers are obtained. The cyclic rigidity impacts significantly the enantioselectivity.
- Bérubé, Christopher,Voyer, Normand
-
supporting information
p. 395 - 403
(2016/04/05)
-
- Kinetic resolution of 2,3-epoxy 3-aryl ketones via catalytic asymmetric ring-opening with pyrazole derivatives
-
A highly efficient catalytic kinetic resolution of 2,3-epoxy 3-aryl ketones via asymmetric ring-opening with pyrazole derivatives has been achieved by using a chiral N,N′-dioxide-Sc(III) complex as the catalyst. A wide variety of substrates were readily scoped, and the selectivity factors obtained were excellent (up to >300).
- Huang, Tianyu,Lin, Lili,Hu, Xiaolei,Zheng, Jianfeng,Liu, Xiaohua,Feng, Xiaoming
-
p. 11374 - 11377
(2015/08/18)
-
- Chiral octahedral complexes of Co(iii) as catalysts for asymmetric epoxidation of chalcones under phase transfer conditions
-
Stereochemically inert and positively charged chiral complexes of Co(iii) were shown to catalyze the asymmetric epoxidation of chalcones with H2O2 under phase transfer conditions. The reaction products had enantiomeric purities of up to 55%. It was also shown that complex 1a I- catalyzed the coupling reaction of a resulting epoxide with CO2 (conversion 72%).
- Larionov, Vladimir A.,Markelova, Elina P.,Smol'yakov, Alexander F.,Savel'yeva, Tat'yana F.,Maleev, Victor I.,Belokon, Yuri N.
-
p. 72764 - 72771
(2015/09/15)
-
- Side-arm effect of a methyl ?±-D-glucopyranoside based lariat ether catalysts in asymmetric syntheses
-
Methyl ?±-D-glucopyranoside based monoaza-15-crown-5 type lariat ethers with different heteroatom-containing side arm attached to the nitrogen of the macrocyclic ring have been synthesized. These compounds were used as chiral phase transfer catalysts in a few asymmetric reactions, such as Michael additions, Darzens condensation, and epoxidation of chalcone. The side arms of the macrocycles had a significant impact on the chemical yields and the enantioselectivity. The effect of the lariat ethers with side arms having heteroatom (O, N, and S) was compared with the effect of the analogues having substituents without a heteroatom. The terminal allyl group also generated a significant enantioselectivity (79% enantiomeric excess) in one of the Michael additions. The application of crown ethers with substituents (CH2)3OH or (CH2)3OCH3 leads to the best enantioselectivities 85% and 99%, respectively.
- Rapi, Zsolt,Bak?3, P??ter,Drahos, L??szl?3,Keglevich, Gy??rgy
-
-
- Highly Enantioselective Epoxidation of α,β-Unsaturated Ketones Catalyzed by Rare-Earth Amides [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with Phenoxy-Functionalized Chiral Prolinols
-
A simple and efficient catalytic enantioselective epoxidation of α,β-unsaturated ketones has been successfully developed, which was catalyzed by rare-earth metal amides [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Yb (1), La (2), Sm (3), Y (4), Lu (5)) in the presence of phenoxy-functionalized chiral prolinols at room temperature using tert-butylhydroperoxide (TBHP) as the oxidant. The combination of an Yb-based amide 1 and a chiral proligand (S)-2,4-di-tert-butyl-6-((2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)phenol) performed very well, and both the yields and the enantiomeric excess of the chiral epoxides reached up to 99% and 99% ee. (Figure Presented).
- Zeng, Chao,Yuan, Dan,Zhao, Bei,Yao, Yingming
-
p. 2242 - 2245
(2015/05/13)
-
- Mononuclear Nonheme Iron(III)-Iodosylarene and High-Valent Iron-Oxo Complexes in Olefin Epoxidation Reactions
-
High-spin iron(III)-iodosylarene complexes are highly reactive in the epoxidation of olefins, in which epoxides are formed as the major products with high stereospecificity and enantioselectivity. The reactivity of the iron(III)-iodosylarene intermediates is much greater than that of the corresponding iron(IV)-oxo complex in these reactions. The iron(III)-iodosylarene species - not high-valent iron(IV)-oxo and iron(V)-oxo species - are also shown to be the active oxidants in catalytic olefin epoxidation reactions. The present results are discussed in light of the long-standing controversy on the one oxidant versus multiple oxidants hypothesis in oxidation reactions. On active duty: High-spin iron(III)-iodosylarene complexes epoxidize olefins with high stereospecificity and enantioselectivity. The iron(III)-iodosylarene species, not high-valent iron(IV)- and iron(V)-oxo species, are the active oxidants in catalytic olefin epoxidation reactions. The present results resolve the long-standing controversy on the one oxidant versus multiple oxidants hypothesis in oxidation reactions.
- Wang, Bin,Lee, Yong-Min,Seo, Mi Sook,Nam, Wonwoo
-
supporting information
p. 11740 - 11744
(2015/10/05)
-
- N-Heterocyclic Carbene Catalyzed Oxidative Coupling of Alkenes/ α-Bromoacetophenones with Aldehydes: A Facile Entry to α,β-Epoxy Ketones
-
A novel, N-heterocyclic carbene (NHC) catalyzed direct oxidative coupling of styrenes with aldehydes has been described for the synthesis of α,β-epoxy ketones in good yields. This unprecedented regioselective oxidative coupling employs NBS/DBU/DMSO (DBU=1,8-diazabicyclo [5.4. 0] undec-7-ene, DMSO=dimethylsulfoxide, NBS=N-bromosuccinimide) as an oxidative system at ambient conditions. Additionally, first NHC-catalyzed Darzens reaction of α-bromoketones and aldehydes under mild reaction conditions has also been described. Interestingly, mechanistic studies have revealed the preferred reactivity of NHC with alkene/α-bromoketone rather than aldehydes, thus proceeding via the ketodeoxy Breslow intermediate.
- Reddi, Rambabu N.,Prasad, Pragati K.,Sudalai, Arumugam
-
supporting information
p. 14150 - 14153
(2016/01/25)
-
- Asymmetric epoxidation of unsaturated ketones catalyzed by heterobimetallic rare earth-lithium complexes bearing phenoxy-functionalized chiral diphenylprolinolate ligand
-
Four novel heterobimetallic complexes [REL2]{[(THF)3Li]2(μ-Cl)} stabilized by chiral phenoxy-functionalized prolinolate (RE = Yb (1), Y (2), Sm (3), Nd (4), H2L = (S)-2,4-di-tert-butyl-6-[[2-(hydroxydiphenylmethyl)pyrrolidin-1-yl]methyl]phenol have been synthesized and characterized. These readily available complexes are highly active in catalyzing the epoxidation of α,β-unsaturated ketones, while the enantioselectivity varies according to the ionic radii of the rare earth center. A series of chalcone derivatives were converted to chiral epoxides in 80 → 99% ee at 0 °C using TBHP as the oxidant in the presence of 10 mol % of 1.
- Qian, Qinqin,Tan, Yufang,Zhao, Bei,Feng, Tao,Shen, Qi,Yao, Yingming
-
p. 4516 - 4519
(2015/01/16)
-
- Highly enantioselective bioinspired epoxidation of electron-deficient olefins with H2O2 on aminopyridine mn catalysts
-
The asymmetric epoxidation of various electron-deficient olefins with H2O2 in the presence of a novel family of chiral bioinspired bipyrrolidine-derived aminopyridine manganese(II) complexes [LM II(OTf)2] is rep
- Ottenbacher, Roman V.,Samsonenko, Denis G.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
-
p. 1599 - 1606
(2014/05/20)
-
- Manganese complexes with non-porphyrin N4 ligands as recyclable catalyst for the asymmetric epoxidation of olefins
-
New chiral manganese complexes of N4 ligands derived from 2-acetylpyridine were prepared and used as catalysts in the enantioselective epoxidation of olefins, using H2O2 as an oxidant to give epoxides, with excellent conversions (up to 99%) and enantiomeric excess (up to 88%) within 1 h at 0°C. A detailed mechanistic study was undertaken based on the information obtained by single crystal X-ray, optical rotation, UV-Vis, CD spectra and kinetic studies, and revealed that the reaction is first order with respect to the concentration of catalyst and oxidant and independent of substrate concentration. The complex (0.1 mol%) was successfully subjected to recyclability experiments over 3 cycles in the epoxidation of styrene with H2O2 as an oxidant and acetic acid as an additive at 0°C with retention of performance.
- Maity, Nabin Ch.,Kumar Bera, Prasanta,Ghosh, Debashis,Abdi, Sayed H. R.,Kureshy, Rukhsana I.,Khan, Noor-Ul H.,Bajaj, Hari C.,Suresh
-
p. 208 - 217
(2014/01/06)
-