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Search for "enantioselective" in Full Text gives 479 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Oxidative radical ring-opening/cyclization of cyclopropane derivatives
Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23
- aerobic oxidation of easily available cyclopropanols 91 via intermediate formation of peroxyketone intermediates 145, followed by enantioselective epoxide formation in the presence of a poly-L-leucine catalyst and DBU (Scheme 40) [120]. In 2014, a practical method for the conversion of 1,2-disubstituted
Synthesis of nonracemic hydroxyglutamic acids
Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22
- (2S,3R,4S)-4 and (2R,3R,4S)-4. To secure the (3R,4R) and (3S,4S) configurations in 3,4-hydroxyglutamic acids enantioselective reduction of the carbonyl group of the cyclic imide (3R*,4S*)-110 prepared from meso-tartaric acid [108] needs to be elaborated (Scheme 27) [109]. Low temperature reduction of
- pyrrolidine-2-one (3S,4S,5R)-123 [111]. Oxidation of the hydroxymethyl group and acid hydrolysis gave (2S,3S,4S)-4 [112]. By enantioselective conjugate addition and asymmetric dihydroxylation An orthogonally protected 3,4-dihydroxy-L-glutamic acid was envisioned as an intermediate in the projected synthesis
- ; j) 6 M HCl, 80 °C. Synthesis of (2S,3S,4R)-127 by enantioselective conjugate addition and asymmetric dihydroxylation. Reagents and conditions: a) ethyl 1-phenylselenylacrylate, chiral PTC, 50% KOH, CH2Cl2; b) 1 M HCl, THF; c) 9-bromo-9-phenylfluorene, K2PO4, PbNO2, MeCN; d) NaIO4, NaHCO3, MeOH/H2O
Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands
Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292
- to 19b, resulting in 90% conversion within 3 hours [17]. No relevant differences in the catalyst reactivity were observed for the CM of 13 and 14 (Scheme 4). As a novel application of N-aryl, N’-aryl unsymmetrical ruthenium complexes in enantioselective catalysis, Grela and Schmidt very recently
Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine
Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214
- entails a direct, atropselective aryl–aryl bond formation step under asymmetric induction provided by internal or external factors. Also, the optical activation in the synthesis of biaryls may involve the separation of diastereomeric derivatives, or more elegantly, may be done by enantioselective
Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles
Beilstein J. Org. Chem. 2018, 14, 2375–2383, doi:10.3762/bjoc.14.213
- ][6]. Notably, organofluorine compounds bearing a tetrafluoroethylene (–CF2CF2–) unit have attracted significant interest as a promising framework for various functional molecules. In the medicinal field, for example, Linclau and co-workers reported the first enantioselective synthesis and the
A novel and practical asymmetric synthesis of eptazocine hydrobromide
Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209
- in the presence of catalyst PTC (3). The designed synthesis is shown in Scheme 3. Two key reactions are included in this novel strategy: 1. the enantioselective alkylation of 1-methyl-7-methoxy-2-tetralone (2) with chloroacetonitrile generate 4 through the use of a phase-transfer catalyst; and 2. the
- acetic acid gave compound 8 in 83% yield. Eventually, target compound 1 was obtained from 8 via demethylation with 48% aqueous HBr solution. Conclusion In summary, we developed a new and efficient synthesis of eptazocine hydrobromide involving enantioselective phase-transfer catalyzed alkylation of 1
Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I
Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206
- the first enantioselective total synthesis of the two diacetylenic diol natural products strongylodiol H and strongylodiol I and of an enantiomer of strongylodiol H. Our synthesis assisted us to revise the structure of both natural products strongylodiol H and I. The synthetic procedure involved the
D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation
Beilstein J. Org. Chem. 2018, 14, 2082–2089, doi:10.3762/bjoc.14.182
- enantioselectivity [1][2]. Probably the most effective approach in stereoselective synthesis is enantioselective catalysis, because cheap prochiral starting materials can be converted into chiral enantiopure products and no undesirable side products are formed [3][4]. Therefore, the development of new ligands is
- efficient catalysts in various asymmetric reactions, for instance allylic substitution and enantioselective hydrogenation [9]. They were also applied in the stereoselective synthesis of complex natural products [10][11][12]. PHOX ligands are nonsymmetrical ligands which can coordinate to a metal center
- starting from D-fructose. Two of these ligands were applied in enantioselective catalysis. Results and Discussion Starting from D-fructose, 1,2-isopropylidene-protected pyranosides with different protective groups (PG) at C-3, C-4 and C-5 can be prepared in two to four steps (Scheme 1). First, D-fructose
Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry
Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179
- exact definition of a reaction employed in LSF, Jiang and co-workers have described a procedure that allows the enantioselective aerobic olefination of α-amino sp3 C–H bonds, using cooperative asymmetric and organocatalysed photoredox catalysis (Scheme 29) [73]. This may not allow for direct
Chiral bisoxazoline ligands designed to stabilize bimetallic complexes
Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175
- -epoxides [16]. Trost et al. disclosed the synthesis of dinuclear zinc complexes 3 and their application to enantioselective Aldol reactions [17][18] and a host of other asymmetric transformations [18]. Other notable contributions in this area were provided by the groups of Martell [19][20], Maruoka [21][22
- the development of new catalytic enantioselective transformations. Examples of chiral bimetallic complexes utilized in asymmetric catalysis. Previously reported bisoxazoline ligands capable of stabilizing bimetallic complexes. Thermal ellipsoid plot (50% probability) of the molecular structure of 16
Asymmetric Michael addition reactions catalyzed by calix[4]thiourea cyclohexanediamine derivatives
Beilstein J. Org. Chem. 2018, 14, 1901–1907, doi:10.3762/bjoc.14.164
- Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China 10.3762/bjoc.14.164 Abstract A number of upper rim-functionalized calix[4]thiourea cyclohexanediamine derivatives have been designed, synthesized and used as catalysts for enantioselective Michael addition reactions between
- acetylacetone on the nitrostyrene creates a new C–C bond forming binary complex C from which the enantioselective product is released. Conclusion In summary, we have synthesized a series of upper rim-functionalized calix[4]arene-based chiral cyclohexanediamine thiourea catalysts 1–3 and tested as
- organocatalysts for the enantioselective Michael reactions of nitroolefins to 1,3-dicarbonyl compounds. Under the optimal conditions, catalyst 2 smoothly catalyzed the reactions in mixed solvent of toluene and water (v/v = 2:1) at room temperature to afford the products in high yields (90–99%) and with moderate
Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes
Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154
- reaction of hydroxylated substrate 8 afforded the dihydrofuran-fused isochromanone 9 with up to 91% ee (Scheme 4, top) [48]. The enantioselective control mode is the same as that described in stoichiometric reactions [49]. Recently, Masson and co-workers described an enantioselective iodoarene-catalyzed
- products. Recently, Jacobsen and co-workers reported a highly enantioselective gem-difluorination of various cinnamic acid derivatives through the same oxidative rearrangement (Scheme 16) [68]. During the catalysts screening, they found that the benzylic unit in the catalysts was essential for a high
- enantioselectivity (52 vs 53). Moreover, the more electron-deficient 3,4,5-trifluorophenyl analog 54 was found to be less enantioselective. The authors proposed that the benzylic groups can stabilize the cationic intermediates and/or transition states through cation–π interactions, which play an important role in
Synthesis of spirocyclic scaffolds using hypervalent iodine reagents
Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152
- precatalyst in iodine(III)-catalyzed enantioselective synthesis of spiroketals with high selectivities. In this report, substrates 128 were reacted with 10 mol % of chiral iodoarene 129a and 129b in the presence of mCPBA oxidant in chloroform at 0 °C. The desired ortho-spirocyclic ketals 130 were obtained in
- chiral auxiliaries 129a or 129b under similar reaction conditions mentioned in Scheme 48. Furthermore, the synthesized spiroketal 159 (R2 = iPr; R4 = SiMe3) was used as synthetic intermediate for enantioselective synthesis of natural product (−)-biscarvacrol [8] (Scheme 59). Additionally, Parra and
- ) reagents in enantioselective spirocyclizations with suitable detail. Conclusion In this review article, we have summarized different approaches for the synthesis of spirocyclic scaffolds using hypervalent iodine reagents in stoichiometric or catalytic amounts. Various iodine(III) reagents such as
β-Hydroxy sulfides and their syntheses
Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143
- notable; this was the first enantioselective thiolysis of a meso-epoxide in pure water as a solvent. Since this report, several epoxide thiolysis reactions in water have been reported and are part of several reviews [45][46]. Schneider and co-workers reported the same scandium–bipyridine complex as
- by the same group and its utility in the enantioselective ring-opening of cis-stilbene oxide with aniline and thiophenol was demonstrated. The reaction provided the corresponding β-hydroxy derivatives in good yields and excellent enantioselectivities (Scheme 15) [49]. Bipyridine as a scaffold in
- have thus for quite a while been an active area of research. Two popular routes to access β-hydroxy sulfides are the thiolysis of epoxides as well as the thiofunctionalization of alkenes, and these have found application in target oriented synthesis. Enantioselective variations of these approaches are
Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis
Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128
- , the same group has demonstrated the ability to perform the reaction with TIPS-EBX 37 in an enantioselective manner using the cyclopropylbisoxazoline ligand 38 (Scheme 12) [47]. Starting from various acceptor diazo compounds, the gem-addition of the carboxylate and the alkyne proceeds with ees of up to
Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine
Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119
- 10.3762/bjoc.14.119 Abstract In order to prepare asymmetrically (R)-(+)-1-(5-bromopentyl)-1-methyl-7-methoxy-2-tetralone (3a), a key intermediate of dezocine, 17 cinchona alkaloid-derived catalysts were prepared and screened for the enantioselective alkylation of 1-methyl-7-methoxy-2-tetralone with 1,5
- ] that the alkylation of 2 in the catalysis of N-(p-trifluoromethylbenzyl)cinchonidinium bromide in a two-phase system gave the enantioselective product 3a, although the ee value of the product was 60%, determined by 1H NMR. And so far, no further report on the stereoselective alkylation of 2a was found
- enantiocontrol (Table 1, entries 5 and 6). Fortunately, the p-CF3 derivative (C7) promoted the reaction to give a enantiomeric ratio of 83:17 (Table 1, entry 7). These findings suggested that the presence of electron-withdrawing groups on the benzyl group was favourable for the enantioselective reaction except
Recent applications of chiral calixarenes in asymmetric catalysis
Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117
- % ee), which displayed the importance of the calix[4]arene skeleton. We also employed calixarene-based chiral primary amine thioureas 47a and 47b in the enantioselective Michael addition of α,α-disubstituted aldehydes 51 to maleimides 52 (Scheme 14) [50]. The reactions proceeded under mild conditions
- (Scheme 17). Asymmetric Michael addition of 57 to 49 catalyzed by 64 at room temperature afforded the Michael adducts in high yields and moderate to excellent enantioselectivities (Scheme 18). To establish the role of the calixarene backbone on the enantioselective Michael addition, chiral monomeric
- hydrophilic region via hydrogen bonds between 75 and interfacial water molecules. The catalytic activity of compound 83 as an organocatalyst was evaluated in the enantioselective aldol reaction of 21 and 70 in different amounts of water. In the presence of 10 mol % catalyst, the aldol adduct was obtained in
Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines
Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114
- Helene Pellissier Aix-Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France 10.3762/bjoc.14.114 Abstract This review collects the recent developments in the synthesis of chiral 3-substituted 3-amino-2-oxindoles based on enantioselective catalytic nucleophilic additions to isatin
- organocatalyzed methodologies [10][13]. The simplest method to prepare chiral quaternary 3-amino-2-oxindoles is based on enantioselective catalytic nucleophilic additions to isatin imines. This is not only because of the easy access to isatin imines, but also by the possibility of using a wide range of
- chiral 3-substituted 3-amino-2-oxindoles based on enantioselective nucleophilic additions to isatin imines reported since 2015, since this field was recently reviewed by Chimni et al. [16]. It is divided into six parts, dealing successively with enantioselective Mannich reactions, aza-Morita–Baylis
Atom-economical group-transfer reactions with hypervalent iodine compounds
Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108
- –Hagihara reaction was developed by Dauban and co-workers (Scheme 16) [47]. The first step of this sequence includes an iodine(III)-mediated rhodium-catalysed enantioselective amination of an unactivated C(sp3)–H bond with a chiral sulfonimidamide 31. Afterwards, the iodoarene byproduct of the first step is
- of elemental nitrogen is lost over the course of the reaction. The overall AE is only diminished by the necessity to use two equivalents of the diazo compound (AE = 74% for 43b). Furthermore, an enantioselective version of this oxyalkynylation (for R1 = H) was developed [57]. Employing a chiral
- . Oxyalkynylation of diazo compounds 42. Enantioselective oxyalkynylation of diazo compounds 42’. Iron-catalysed oxyazidation of enamides 45. Acknowledgements A.B. is thankful for a scholarship from the Fonds der Chemischen Industrie. P.F. is thankful for a postdoctoral scholarship from the German Academic
A survey of chiral hypervalent iodine reagents in asymmetric synthesis
Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107
- application due to their reduced toxicity, ready availability and lower costs as replacement for transition metals leading to several “metal-free” like chemical transformations. The ongoing demand of modern synthetic chemistry for the development of catalytic enantioselective C–C bond formation reactions
- enantioselective oxidative dearomatization of phenolic derivatives 25 (spirolactonization) which is known as Kita oxidation to yield spirocyclic compounds 26 with good enantioselectivity [32]. The indication of an associative mechanism was also confirmed due to an increased enantioselectivity observed in polar
- -symmetric reagent 9a to obtain a C2-symmetric chiral iodoarene reagent 9b having an ester end group instead of an amide (as in case of Ishihara’s work). The enantioselective oxylactonization was achieved efficiently using stoichiometric amounts of chiral reagent 9b (Scheme 9). This lactate-derived I(III
Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones
Beilstein J. Org. Chem. 2018, 14, 992–997, doi:10.3762/bjoc.14.84
- enantioselective coupling of in situ formed aldehyde enamines with excess (2 equiv) trialkylsilyl enol ethers (Scheme 1c) [27]. This reaction was proposed to proceed through a mechanism involving the attack of an enamine radical on the trialkylsilyl enol ether. The last two examples concern the even more
Enantioselective dioxytosylation of styrenes using lactate-based chiral hypervalent iodine(III)
Beilstein J. Org. Chem. 2018, 14, 659–663, doi:10.3762/bjoc.14.53
- )-isomer. Keywords: 1,2-difunctionalization of alkenes; enantioselective synthesis; hypervalent iodine; oxidation; Findings Hypervalent aryl-λ3-iodanes have been widely used for metal-free oxidation with high selectivity in organic synthesis [1][2][3]. The reactivity of an aryl-λ3-iodane is controlled by
- for highly stereocontrolled oxidative transformations [4][5][6][7][8][9][10][11][12][13][14]. The enantioselective vicinal difunctionalization of alkenes constitutes one type of attractive transformation achieved by chiral hypervalent iodine compounds. As a seminal example in this field, Wirth et al
- iodine reagents using a lactate motif has been employed for several types of oxidation reaction since we first reported this procedure [18]. Enantioselective oxidative transformations include the dearomatization of phenols [19][20][21][22][23][24], α-functionalization of carbonyl compounds [25][26][27
Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue
Beilstein J. Org. Chem. 2018, 14, 593–602, doi:10.3762/bjoc.14.46
- reactions implying the use of a chiral auxiliary resulted effectively in various optically pure compounds [10][18][19][20]. Second, enantioselective syntheses of these bicylic lactams were performed by using chiral transition metal- or organocatalysts which control the configuration of the trisubstituted
Copper-catalyzed asymmetric methylation of fluoroalkylated pyruvates with dimethylzinc
Beilstein J. Org. Chem. 2018, 14, 576–582, doi:10.3762/bjoc.14.44
- methylation to give the desired alcohol 4a in 87% yield and 24% ee. Conclusion In summary, we have succeeded in the catalytic enantioselective methylation of fluoroalkylated pyruvates in the presence of chiral diphosphine–copper complexes, providing the corresponding tertiary alcohols with an RF group such as
Investigations towards the stereoselective organocatalyzed Michael addition of dimethyl malonate to a racemic nitroalkene: possible route to the 4-methylpregabalin core structure
Beilstein J. Org. Chem. 2018, 14, 553–559, doi:10.3762/bjoc.14.42
- . Stereoselective Michael addition, one of the most important organocatalytic reactions [8] usually serves as a key stereoinduction transformation. Earlier studies, performed by Hayashi and Wang employed iminium activation to perform the enantioselective addition of nitromethane to enals for syntheses of baclofen
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