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Search for "organocatalysts" in Full Text gives 176 result(s) in Beilstein Journal of Organic Chemistry.
Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides
Beilstein J. Org. Chem. 2017, 13, 1518–1523, doi:10.3762/bjoc.13.151
- Ryota Miyaji Yuuki Wada Akira Matsumoto Keisuke Asano Seijiro Matsubara Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo, Kyoto 615-8510, Japan 10.3762/bjoc.13.151 Abstract Bifunctional organocatalysts bearing amino and urea
- functional groups in a chiral molecular skeleton were applied to the enantioselective synthesis of axially chiral benzamides via aromatic electrophilic bromination. The results demonstrate the versatility of bifunctional organocatalysts for the enantioselective construction of axially chiral compounds
- . Moderate to good enantioselectivities were afforded with a range of benzamide substrates. Mechanistic investigations were also carried out. Keywords: axial chirality; benzamide; bifunctional organocatalyst; molecular conformation; multipoint recognition; Introduction Bifunctional organocatalysts have
Construction of highly enantioenriched spirocyclopentaneoxindoles containing four consecutive stereocenters via thiourea-catalyzed asymmetric Michael–Henry cascade reactions
Beilstein J. Org. Chem. 2017, 13, 1342–1349, doi:10.3762/bjoc.13.131
- strategies with chiral transition metals [27][28][29][30][31][32][33], organocatalysts such as secondary amines [34][35][36], nucleophilic phosphines [26][37][38][39][40][41][42][43][44], tertiary amines [45], N-heterocyclic carbenes (NHCs) [46][47][48], and cinchona alkaloid derivatives [25][28][49][50
- variety of organocatalysts (a–f) were investigated in CH2Cl2 at −20 °C for 12 h to evaluate their ability to promote the transformation (Table 1, entries 1–6). When cinchona alkaloid-derived catalyst a and quinine-derived amine catalyst b were tested, however, poor yields or ee values were obtained
Cyclodextrins tethered with oligolactides – green synthesis and structural assessment
Beilstein J. Org. Chem. 2017, 13, 779–792, doi:10.3762/bjoc.13.77
- modified with trimethylsilazane [13]. The L- or DL-lactide were polymerized in the presence of organocatalysts like 4-dimethylaminopyridine [12] using β-CD and modified CD (β-CD-(OBn)19(OH)2) as initiators. Normand et al. [14] applied a similar approach as Zinck and co-workers [12] in order to prepare CD
Sulfamide chemistry applied to the functionalization of self-assembled monolayers on gold surfaces
Beilstein J. Org. Chem. 2017, 13, 648–658, doi:10.3762/bjoc.13.64
- applications in medicinal chemistry, sulfamide groups have been incorporated in self-assembling molecules [22][23][24][25][26][27], peptides [28], polymers [29], ligands [30], chiral auxiliaries [31][32][33] and in organocatalysts [34][35][36][37]. In light of the importance of the sulfamide functionality, our
Synthesis of new pyrrolidine-based organocatalysts and study of their use in the asymmetric Michael addition of aldehydes to nitroolefins
Beilstein J. Org. Chem. 2017, 13, 612–619, doi:10.3762/bjoc.13.59
- organocatalysts with a bulky substituent at C2 were synthesized from chiral imines derived from (R)-glyceraldehyde acetonide by diastereoselective allylation followed by a sequential hydrozirconation/iodination reaction. The new compounds were found to be effective organocatalysts for the Michael addition of
- privileged motif [5] with a powerful capacity in aminocatalysis [6][7][8][9][10]. In this context diarylprolinol silyl ethers have proven to be extremely efficient organocatalysts for a wide variety of chemical transformations [11]. In the course of our research we have been involved in the synthesis of new
- evaluated as chiral organocatalysts in the enantioselective α-chlorination of β-ketoesters, with excellent results obtained after optimisation of the organocatalyst structure [12]. In an effort to identify new, easily accessible and tuneable organocatalysts with the privileged pyrrolidine motif from the
New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation
Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283
- evidence for two hydrogen bonds formed between the halide or bromide anion and C–H2/C–Hc bonds of another cation L13. Mixed N–H/C–H hydrogen bond donors as organocatalysts The involvement of the ortho C–H bond in the binding event with Lewis-basic sites was proposed by Etter in the late 1980s and later
- demonstrated by Schreiner in a detailed study of hydrogen-bonding thiourea organocatalysts containing a 3,5-bis(trifluoromethyl)phenyl group as the privileged motif [56][57][58]. A recent example of utilizing such interactions in catalysis was demonstrated by Bibal and co-workers [58]. In this study, Bibal and
- co-workers explored the use of α-halogenated acetanilides L14 and L15 as hydrogen-bonding organocatalysts that activate the carbonyl functionality of lactide and thus enhance their reactivity toward ROP (Scheme 11). In addition to their ability to form more conventional N–H hydrogen bonds, L14 and
From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer
Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264
- ], versatile organocatalysts [8][9][10], and starting materials for heterocycle syntheses [11][12][13]. Consequently books [14][15][16] and reviews cover the range from NHC structures in the light of their early history [17], syntheses [6][18], coordination chemistry [19][20], and catalysis [21][22], to
Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates
Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181
- Maurizio Selva Alvise Perosa Sandro Guidi Lisa Cattelan Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Via Torino, 155 – Venezia Mestre, Italy 10.3762/bjoc.12.181 Abstract The use of ionic liquids (ILs) as organocatalysts is reviewed for transesterification
- /nucleophilic) activation of reactants. Keywords: ionic liquids; transesterification; organocatalysts; organic carbonates; Review Introduction Transesterification catalysts The transesterification is one of the classical organic reactions that has found numerous applications in laboratory practice as well as
- ., glycerol) to produce the expected transesterification products with total conversion and selectivity. Ionic liquid-based organocatalysts Conventional acid or base liquid catalysts for transesterification processes often entail several synthetic and environmental concerns including equipment corrosion
Rearrangements of organic peroxides and related processes
Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162
- organocatalysts [262][263]. There are also Green chemistry approaches for Baeyer−Villiger oxidations based on enzyme-mediated processes, which are used for the preparation of chiral lactones. This type of biocatalysis is useful in synthetic chemistry and either isolated enzymes or living whole cells are applied
- % and 9% yields, respectively (Scheme 30) [273]. However, in order to perform the asymmetric oxidation of 3-substituted cyclobutanones 96a–f to the corresponding lactones 97a–f (Table 7) [274], it is necessary to employ chiral Brønsted acids [274][275][276][277], organocatalysts [278][279] or enzymes
Enantioselective addition of diphenyl phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified organocatalysts
Beilstein J. Org. Chem. 2016, 12, 1551–1556, doi:10.3762/bjoc.12.149
- of organocatalysts [38][39][40][41][42][43][44][45], we have reported the catalytic asymmetric decarboxylative aldol addition reaction of isatins with benzoylacetic acids catalyzed by chiral binaphthyl-based squaramide [46]. Here we wish to report the enantioselective addition reaction of diphenyl
- phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified bifunctional organocatalysts (Figure 1). Results and Discussion To determine suitable reaction conditions for the organocatalytic enantioselective addition reaction of diphenyl phosphonate to ketimines derived from isatins, we
- initially investigated a reaction system with ketimine 1a derived from N-allylisatin and diphenyl phosphonate (2) with organocatalyst in the presence of 4 Å molecular sieves. We first surveyed the effect of the structure of bifunctional organocatalysts I–VI (Figure 1) on enantioselectivity in ethyl acetate
Development of chiral metal amides as highly reactive catalysts for asymmetric [3 + 2] cycloadditions
Beilstein J. Org. Chem. 2016, 12, 1447–1452, doi:10.3762/bjoc.12.140
- have been reported; for example, Co [13], Cu [14][15][16][17][18][19][20][21][22][23], Ag [24][25][26][27][28][29][30][31][32], Zn [33][34], Ni [35][36], and Ca [37][38][39] catalyst systems, and organocatalysts [40][41][42][43][44][45] have been successfully employed. In most cases, however
Conjugate addition–enantioselective protonation reactions
Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116
- are further classified according to whether catalysis is achieved with chiral Lewis acids, organocatalysts, or transition metals. Keywords: asymmetric catalysis; conjugate addition; enantioselective protonation; enolate; Introduction Due to their ubiquity in natural products and drugs, many
- –enantioselective protonation reactions that have been reported in the literature. These reports have been grouped by class of Michael acceptor and further subdivided by the type of catalyst system used (Lewis acids, organocatalysts and transition metals). While numerous efficient methods have been developed for
- ) reacted in low yield and poor enantioselectivity. Sterically bulky 2-substituents (ortho-substituted phenyl, tert-butyl) showed attenuated reactivity but retained high enantioselectivity. Organocatalysts In a pioneering work from 1977 on conjugate addition–enantioselective protonation, Pracejus and co
Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update
Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98
- excellent ee values (up to 97% ee) from DMTr (Di(p-methoxyphenyl)phenylmethyl)-N-protected isatins in one-pot under modified conditions. Organocatalyzed synthesis of 3-substituted 3-hydroxyoxindoles Organocatalysis has witnessed significant progress in the last decades, a large number of new organocatalysts
- progress in this field, the asymmetric catalytic synthesis of 3-hydroxyoxindoles are summarized based on the organocatalysts used. Amino acid-derived organocatalysts Amino acids (AAs) have been widely used to develop novel AAs-based organocatalysts for asymmetric synthesis [30]. Representative examples are
- certain influence on the reactivity. Interestingly, the final compounds bear the 3-hydroxyoxindole and butenolide moieties and could be used for biological screening or serve as intermediates for further transformations. After screening different chicona alkanoid-derived organocatalysts, Chimni et al
1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis
Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90
- devoted to the development of new efficient chiral catalysts, both metal catalysts and organocatalysts, together with the search for appropriate (pro)nucleophiles and/or electrophiles. In this context, the enantioselective construction of tetrasubstituted stereocenters is another challenge [5][6][7][8][9
Stereoselective amine-thiourea-catalysed sulfa-Michael/nitroaldol cascade approach to 3,4,5-substituted tetrahydrothiophenes bearing a quaternary stereocenter
Beilstein J. Org. Chem. 2016, 12, 643–647, doi:10.3762/bjoc.12.63
- [22] with 1,4-dithiane-2,5-diol. Based on all above considerations and prompted by our interest in asymmetric synthesis of functionalized tetrahydrothiophenes [14], we wondered whether we could use bifunctional organocatalysts to develop a diastereo- and enantioselective cascade sulfa-Michael
- -dithiane-2,5-diol as precursor of mercaptoacetaldehyde, using 10 mol % loading of different bifunctional organocatalysts (Scheme 1, Table 1). In the case of trans-β-nitrostyrene (1), a mixture of diastereoisomers 5 and 6 were rapidly formed, irrespective of the catalyst used, with a poor level of diastereo
- the bifunctional organocatalyst structure and reaction conditions will be required for further improvements of the challenging cascade process. Organocatalysts screened in the cascade reaction. Synthesis of catalyst VIII. Asymmetric sulfa-Michael/nitroaldol reaction of nitroalkenes 1–3 with 1,4
Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions
Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61
- the thiourea derived from (L)-valine and 1,6-hexanediamine. The catalysts can be used in only 2 mol % loading, and reused for at least four cycles in neat conditions. The ball milling promoted additions also worked very well. Keywords: bifunctional organocatalysts; organocatalysis; stereoselective
- [12]. Cinchona-derived thioureas have been also prepared by co-polymerization of polyfunctionalized thiols with olefins [23]. Our interest in the search for novel bifunctional thioureas as organocatalysts [24][25][26][27] lead us to consider the preparation of different polymeric materials decorated
- organocatalysts in the stereoselective aza-Henry reaction [31]. Now we describe the results obtained in different stereoselective nitro-Michael additions promoted by these materials. Results and Discussion The ability of the supported catalysts (II–V) to promote the stereoselective nitro-Michael reaction was
The aminoindanol core as a key scaffold in bifunctional organocatalysts
Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50
- The 1,2-aminoindanol scaffold has been found to be very efficient, enhancing the enantioselectivity when present in organocatalysts. This may be explained by its ability to induce a bifunctional activation of the substrates involved in the reaction. Thus, it is easy to find hydrogen-bonding
- organocatalysts ((thio)ureas, squaramides, quinolinium thioamide, etc.) in the literature containing this favored structural core. They have been successfully employed in reactions such as Friedel–Crafts alkylation, Michael addition, Diels–Alder and aza-Henry reactions. However, the 1,2-aminoindanol core
- incorporated into proline derivatives has been scarcely explored. Herein, the most representative and illustrative examples are compiled and this review will be mainly focused on the cases where the aminoindanol moiety confers bifunctionality to the organocatalysts. Keywords: aminocatalysis; 1,2-aminoindanol
(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers
Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48
- will be summarized. Initially, the use of primary amine-thioureas as organocatalysts for the above transformation is being discussed, followed by the examples employing secondary amine-thioureas. Finally, the use of tertiary amine-thioureas and miscellaneous examples are presented. Keywords: multiple
- of intermediates have been proposed to be the reactive intermediates in many reactions such as aldol, Michael, Mannich, and α-functionalization (α-chlorination, α-amination, α-fluorination) reactions. Proline-type organocatalysts are considered priviliged, because their corresponding enamines exist
- depicted in the left, in Scheme 2, seems to be operative, when the R group of the organocatalyst possesses a moiety, that is able to form hydrogen bonds, being the hydrogen bond donor. Employing this logic, many organocatalysts have been developed, possessing various groups, that are able to form hydrogen
Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions
Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47
- Interdisciplinary Science and Technology,Trivandrum 695 019, India.; Fax: +91 471 2491712; Tel: +91 471 2490406 10.3762/bjoc.12.47 Abstract N-Heterocyclic carbenes (NHCs) have emerged as a powerful class of organocatalysts that mediate a variety of organic transformations. The Benzoin reaction constitutes one of
Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts
Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46
- asymmetric organocatalysis. This fascinating class of bifunctional catalyst offers a genuine alternative to the more commonly used thiourea systems and because of the different spacing between the functional groups, can control enantioselectivity where other organocatalysts have failed. In the main, this
- review covers the highlights from the last five years and attempts to show the diversity of reactions that these systems can control. It is hoped that chemists developing asymmetric methodologies will see the value in adding these easily accessible, but underused organocatalysts to their screens
Organocatalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones with bifunctional amine-thiourea catalysts bearing multiple hydrogen-bond donors
Beilstein J. Org. Chem. 2016, 12, 295–300, doi:10.3762/bjoc.12.31
- successfully used as chiral organocatalysts for the asymmetric Michael addition and Mannich reactions [12][13][14]. Meanwhile, the Henry reaction is one of the most important carbon–carbon bond-forming reactions that provides straightforward access to β-nitroalcohols, which can be further transformed into
- -carboxylate (1a) and nitromethane (2a) in the presence of various chiral bifunctional organocatalysts 3a–e in dichloromethane (Table 1). As expected, the reaction proceeded and gave the desired product 4a in 18% yield and 28% ee with cinchonidine and L-valine-based catalyst 3a (Table 1, entry 1). The
Asymmetric α-amination of β-keto esters using a guanidine–bisurea bifunctional organocatalyst
Beilstein J. Org. Chem. 2016, 12, 198–203, doi:10.3762/bjoc.12.22
- particular, catalytic asymmetric α-amination of β-keto esters has been widely explored, using both metal catalysts and organocatalysts [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. We have developed a series of guanidine–bis(thio)urea bifunctional organocatalysts, and have used them in a variety of
- procedures, copies of NMR spectra and HPLC chromatograms. Acknowledgements This work was supported in part by a Grant-in-Aid for Scientific Research on Innovative Areas “Advanced Molecular Transformations by Organocatalysts” (no. 23105013) from The Ministry of Education, Culture, Sports, Science and
Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen
Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16
- conditions. Oxidations of this kind using Oxone® [10][11], NaOCl [12] or especially peroxides [13][14][15][16][17][18][19] as the terminal oxidant are quite numerous. However, transformations using molecular oxygen are rare. Ishii showed that organocatalysts such as N-hydroxyphthalimide (NHPI) in combination
- , they can also be used to synthesize the 1st and 2nd generation antihistamines Carbinoxamine, Bepotastine and Triprolidine through an alternative synthetic route. In addition to these synthetic examples it has been shown by Kamijo that 4-benzoylpyridines can act as efficient organocatalysts in the
Diastereoselective Ugi reaction of chiral 1,3-aminoalcohols derived from an organocatalytic Mannich reaction
Beilstein J. Org. Chem. 2016, 12, 139–143, doi:10.3762/bjoc.12.15
- -selective organocatalysts. We prepared two known carbamoyl sulfones 1 [30][31] and transformed them without isolation of intermediates into a series of five Boc-protected β-aminoalcohols 4a–e (Scheme 2). Using caesium carbonate, carbamoyl sulfones were converted into the corresponding N-Boc-protected imines
Catalytic asymmetric formal synthesis of beraprost
Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285
- : Experimental procedures and characterization data. Acknowledgements We gratefully acknowledged a Grant-in-Aid for Scientific Research (YT) on Innovative Areas ‘Advanced Molecular Transformations by Organocatalysts’ from MEXT, Japan. We thank Dr. Taryn March (Kyoto University) for editing and proofreading of
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