Showing 1-30 of 89 results for "organocatalysis"
Zhichao Jin et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 21(26), 9360-9363 (2015-05-28)
Direct β-carbon activation of propionic acid (C2H5CO2H) by carbene organocatalysis has been developed. This activation affords the smallest azolium homoenolate intermediate (without any substituent) as a 3-carbon nucleophile for enantioselective reactions. Propionic acid is an excellent raw material because it...
Marcus Frings et al.
Beilstein journal of organic chemistry, 8, 1443-1451 (2012-09-29)
For the first time, chiral sulfoximine derivatives have been applied as asymmetric organocatalysts. In combination with a thiourea-type backbone the sulfonimidoyl moiety leads to organocatalysts showing good reactivity in the catalytic desymmetrization of a cyclic meso-anhydride and moderate enantioselectivity in...
Dominika Krištofíková et al.
ChemSusChem, 13(11), 2828-2858 (2020-03-07)
Asymmetric organocatalysis is becoming one of the main tools for the synthesis of chiral compounds that are needed as medicines, crop protection agents, and other bioactive molecules. It can be effectively combined with various green chemistry methodologies. Intensification techniques, such...
Aitor Arlegui et al.
Molecules (Basel, Switzerland), 25(15) (2020-08-01)
Two chiral proline-derived amphiphilic 5-substituted-10,15,20-tris(4-sulfonatophenyl)porphyrins were prepared, and their pH-dependent supramolecular behavior was studied. In neutral aqueous solutions, the free-base form of the hybrids is highly soluble, allowing enamine-based organocatalysis to take place, whereas under acidic conditions, the porphyrinic protonated...
Romain Lambert et al.
Macromolecular rapid communications, 37(14), 1143-1149 (2016-03-19)
Statistical copoly(ionic liquid)s (coPILs), namely, poly(styrene)-co-poly(4-vinylbenzylethylimidazolium acetate) are synthesized by free-radical copolymerization in methanolic solution. These coPILs serve to in situ generate polymer-supported N-heterocyclic carbenes (NHCs), referred to as polyNHCs, due to the noninnocent role of the weakly basic acetate...
Christopher P Lakeland et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 26(1), 155-159 (2019-10-28)
Sydnone-based cycloaddition reactions are a versatile platform for pyrazole synthesis, however they operate under harsh conditions (high temperature and long reaction times). Herein we report a strategy that addresses this limitation utilizing the synergistic combination of organocatalysis and visible-light photocatalysis....
Kohei Fuchibe et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 23(12), 2831-2838 (2016-12-03)
Silyl dienol ethers, prepared from α,β-unsaturated ketones, underwent proton sponge-catalyzed difluorocyclopropanation with trimethylsilyl 2,2-difluoro-2-fluorosulfonylacetate in a regioselective manner, leading to 1,1-difluoro-2-siloxy-2-vinylcyclopropanes in good yields. The cyclopropanes thus obtained were in turn subjected to fluoride-ion-catalyzed ring opening to afford 1-fluorovinyl vinyl...
Henri A van Kalkeren et al.
ChemSusChem, 6(9), 1615-1624 (2013-09-17)
The conversion of oxygen-containing compounds is often achieved by the use of phosphorus reagents. The newly formed phosphine oxide bond delivers the enthalpic gain that drives reactions, such as the Wittig, Mitsunobu, and Appel reaction, to completion. However, phosphine oxides...
Michael Wilking et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 22(51), 18601-18607 (2016-10-12)
The cinchona alkaloid dimer (DHQD)2 PHAL has been shown to be a broadly applicable catalyst for asymmetric halogenations. However, this catalyst does not have to be dimeric and a class of monomeric quinidine and quinine-derived catalysts was prepared, often showing...
Ya Du et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 23(46), 10962-10968 (2017-06-28)
Photoredox catalysis is a versatile approach for the construction of challenging covalent bonds under mild reaction conditions, commonly using photoredox catalysts (PCs) derived from precious metals. As such, there is need to develop organic analogues as sustainable replacements. Although several...
Rafael Alonso et al.
Angewandte Chemie (International ed. in English), 53(17), 4368-4371 (2014-03-22)
Thioxanthone 1, which was synthesized in a concise fashion from methyl thiosalicylate, exhibits a significant absorption in the visible light region. It allows for an efficient enantioselective catalysis of intramolecular [2+2] photocycloaddition reactions presumably by triplet energy transfer.
Riccardo Porta et al.
ChemSusChem, 7(12), 3534-3540 (2014-10-23)
The use of immobilized metal-free catalysts offers the unique possibility to develop sustainable processes in flow mode. The challenging intermolecular organocatalyzed enantioselective alkylation of aldehydes was performed for the first time under continuous flow conditions. By using a packed-bed reactor...
Trevor V Nykaza et al.
Angewandte Chemie (International ed. in English), 59(11), 4505-4510 (2019-12-24)
An organocatalytic method for the modular synthesis of diverse N-aryl and N-alkyl azaheterocycles (indoles, oxindoles, benzimidazoles, and quinoxalinediones) is reported. The method employs a small-ring organophosphorus-based catalyst (1,2,2,3,4,4-hexamethylphosphetane P-oxide) and a hydrosilane reductant to drive the conversion of ortho-functionalized nitroarenes...
Haijian Yu et al.
Chemistry, an Asian journal, 8(11), 2859-2863 (2013-08-13)
A highly diastereo- and enantioselective cyclopropanation of β,γ-unsaturated α-ketoesters with bromonitromethane has been successfully developed through a domino Michael-addition/intramolecular-alkylation strategy. Acceptable yields (up to 89%) and enantioselectivities (up to 96% ee) have been obtained.
Antonio Puglisi et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 24(27), 6941-6945 (2018-03-25)
The organocatalyzed addition of several malonates to 1,4-benzoquinones affords benzofuranones bearing a quaternary stereocenter with good enantioselectivity. This reaction is an intramolecular desymmetrization since it proceeds through the formation of an arylated achiral malonate that cyclizes to give the reaction...
Mehdi Omri et al.
Journal of colloid and interface science, 536, 526-535 (2018-11-06)
A new series of supported organocatalysts, prepared by a simple method, were used for selective sugar oxidation. This approach is based on the immobilization of a nitroxide derivative through a carboxylic function on nanometric metal oxides (TiO2, Al2O3 and CeO2)...
Tyler J Auvil et al.
Angewandte Chemie (International ed. in English), 52(43), 11317-11320 (2013-09-17)
It takes two: A unique organocatalyzed cascade for the unsymmetric double arylation of α-nitrodiazoesters is described. This organocascade features the strategic use of carbene-activating anilines in conjunction with a urea catalyst, thus allowing for the synthesis of pharmaceutically attractive α-diarylesters...
Yong-Jun Lin et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 21(33), 11773-11778 (2015-07-17)
Enantioselective formal hetero-Diels-Alder reactions of trifluoromethylated enones and 2-amino-1,3-butadienes generated in situ from aliphatic acyclic enones and chiral primary amines are reported. The corresponding tetrahydropyran-4-ones are formed in up to 94 % yield and with up to 94 % ee. The reaction was...
Sankaranarayanapillai Shylesh et al.
ChemSusChem, 8(3), 466-472 (2014-10-15)
The catalytic activity of secondary amines supported on mesoporous silica for the self-condensation of n-butanal to 2-ethylhexenal can be altered significantly by controlling the Brønsted acidity of M--OH species present on the surface of the support. In this study, M--OH...
Xiaoqian Yu et al.
Polymers, 12(10) (2020-10-07)
Micellar catalysts with a switchable core are attractive materials in organic synthesis. However, little is known about the role of the shell forming block on the performance of the catalyst. Thermoresponsive block copolymers based on poly(N-isopropylacrylamide-co-vinyl-4,4-dimethylazlactone) attached to different permanently...
James R Frost et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 21(38), 13261-13277 (2015-08-01)
Since their isolation almost 20 years ago, the callipeltosides have been of long standing interest to the synthetic community owing to their unique structural features and inherent biological activity. Herein we present our full research effort that has led to the...
Ryozo Shibuya et al.
Angewandte Chemie (International ed. in English), 53(17), 4377-4381 (2014-03-08)
A dual platinum- and pyrrolidine-catalyzed direct allylic alkylation of allylic alcohols with various active methylene compounds to produce products with high monoallylation selectivity was developed. The use of pyrrolidine and acetic acid was essential, not only for preventing undesirable side...
Chang Min et al.
Angewandte Chemie (International ed. in English), 54(22), 6608-6612 (2015-04-14)
A readily available chiral Brønsted acid was identified as an efficient catalyst for intramolecular Povarov reactions. Polycyclic amines containing three contiguous stereogenic centers were obtained with excellent stereocontrol in a single step from secondary anilines and aldehydes possessing a pendent...
Tim Förster et al.
Chembiochem : a European journal of chemical biology, 18(12), 1098-1108 (2017-04-20)
Natural products provide evolutionary validated core structures to inspire the synthesis of new compound collections endowed with neurite growth-promoting activity. Rhynchophylline is the major component of Uncaria species, and has been used to treat neurological diseases in Chinese traditional medicine....
Thiophosphoramide-based cooperative catalysts for Brønsted acid promoted ionic Diels-Alder reactions.
Alina Borovika et al.
Angewandte Chemie (International ed. in English), 52(50), 13424-13428 (2013-10-19)
Peter H Huy et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 24(29), 7410-7416 (2018-03-07)
A general formamide-catalyzed protocol for the efficient transformation of alcohols into alkyl chlorides, which is promoted by substoichiometric amounts (down to 34 mol %) of inexpensive trichlorotriazine (TCT), is introduced. This is the first example of a TCT-mediated dihydroxychlorination of an OH-containing...
Water-compatible hydrogen-bond activation: a scalable and organocatalytic model for the stereoselective multicomponent aza-Henry reaction.
Fabio Cruz-Acosta et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 19(49), 16550-16554 (2013-11-28)
Lucia Caruso et al.
Molecules (Basel, Switzerland), 24(24) (2019-12-19)
Carbohydrates are abundant renewable resources and are a feedstock for green chemistry and sustainable synthesis of the future. Among the hexoses and the pentoses present in biomass, mannitol was selected in the present project as a valuable platform, directly available...
Nicolò Santi et al.
Molecules (Basel, Switzerland), 25(10) (2020-05-30)
In this report, the streptavidin-biotin technology was applied to enable organocatalytic aldol addition. By attaching pyrrolidine to the valeric motif of biotin and introducing it to streptavidin (Sav), a protein-based organocatalytic system was created, and the aldol addition of acetone...
Magda Monari et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 21(31), 11038-11049 (2015-06-03)
A new Michael-Michael cascade reaction between 2-(2-oxoindolin-3-ylidene)acetic esters 1 and nitroenoates 2, catalyzed by bifunctional thioureas, is investigated. The combination of the two Michael reactions results in a novel and facile [4+2] or [3+2] spiroannulation process, which is characterized by...

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