Jozsef Kupai

Jozsef Kupai
Budapest University of Technology and Economics · Department of Organic Chemistry and Technology

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46
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591
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Publications

Publications (46)
Article
Since the first application of natural quinine as an anti-malarial drug, cinchona alkaloids and their derivatives have been exhaustively studied for their biological activity. In our work, we tested 13 cinchona alkaloid organocatalysts, synthesised from quinine. These derivatives were screened against MES-SA and Dx5 uterine sarcoma cell lines for i...
Article
The synthesis of chiral proline-derived squaramide and thiosquaramide organocatalysts, which are capable of the dual activation in asymmetric reactions is reported. The (thio)squaramide moiety can form hydrogen bonds to activate the substrates and to stereocontrol the reaction, while the pyrrolidine unit can form enamines to activate carbonyl compo...
Article
Full-text available
This work presents the synthesis of six new phase-transfer organocatalysts in which the squaramide unit is directly linked to the nitrogen atom of an aza-crown ether. Four chiral skeletons, namely hydroquinine, quinine, cinchonine (cinchonas), and α-d-glucopyranoside were responsible for the asymmetric construction of an all-carbon quaternary stere...
Article
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In this work, anchoring of cinchona derivatives to trifunctional cores (hub approach) was demonstrated to obtain size-enlarged organocatalysts. By modifying the cinchona skeleton in different positions, we prepared four C3-symmetric size-enlarged cinchona derivatives (hub-cinchonas), which were tested as organocatalysts and their catalytic activiti...
Preprint
In this work, anchoring of cinchona derivatives to trifunctional cores (hub approach) was demonstrated to obtain size-enlarged organocatalysts. By modifying the cinchona skeleton in different positions, we prepared four C3-symmetric size-enlarged cinchona derivatives (hub-cinchonas), which were tested as organocatalysts and their catalytic activiti...
Article
Full-text available
As catalysis plays a significant role in the development of economical and sustainable chemical processes, increased attention is paid to the recovery and reuse of high-value catalysts. Although homogeneous catalysts are usually more active and selective than the heterogeneous ones, both catalyst recycling and product separation pose a challenge fo...
Article
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Our work presents the immobilization of cinchona squaramide organocatalyst on poly(glycidyl methacrylate) solid support. Preparation of the well‐defined monodisperse polymer microspheres was facilitated by comprehensive parameter optimization. Exploiting the reactive epoxy groups of the polymer support, three amino‐functionalized cinchona derivativ...
Article
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The catalytic transformation of bio‐derived compounds, specifically 5‐hydroxymethylfurfural (HMF), into value‐added chemicals may provide sustainable alternatives to crude oil and natural gas‐based products. HMF can be obtained from fructose and successfully converted to 2,5‐diformylfuran (DFF) by an environmentally friendly organic electrosynthesi...
Cover Page
The Front Cover shows the efficient TEMPO‐based electrocatalytic transformation of biomass‐based C6‐platform chemical HMF to DFF. Molecular design, and comparison of size‐enlarged homogeneous and solid supported TEMPOs for the oxidation in the ElectraSyn reactor with cost‐effective electrodes and green solvents are presented. Computation modelling...
Cover Page
Invited for this month′s cover is the group of Gyorgy Szekely at King Abdullah University of Science and Technology (KAUST). The image shows the efficient TEMPO‐based electrocatalytic transformation of biomass‐based C6‐platform chemical HMF to DFF using non‐precious‐metal‐based electrodes in green solvents with nanofiltration‐enabled catalyst recov...
Article
Full-text available
Numerous cinchona organocatalysts with different substituents at their quinuclidine unit have been described and tested, but the effect of those saturation has not been examined before. This work presents the synthesis of four widely used cinchona-based organocatalyst classes (hydroxy, amino, squaramide, and thiourea) with different saturation on t...
Article
Full-text available
This work presents the first successful applications of cinchona-thiosquaramides in asymmetric reactions. Binaphthyl-cinchona squaramides and thiosquaramides were synthesised, and then used as organocatalysts to promote the catalytic enantioselective Michael addition reaction of pentane-2,4-dione to trans-β-nitrostyrene with excellent yields (up to...
Article
Full-text available
This work presents a cyclodextrin-enhanced organocatalytic method from molecular to process design. Cinchona-thiourea and -squaramide catalysts were covalently anchored to inherently large, stable and well-defined permethyl-β-cyclodextrins. The asymmetric catalysis was successfully demonstrated on the Michael reaction of 1,3-diketones and trans-β-n...
Article
Full-text available
Two new pyridine-based asymmetric bifunctional organocatalysts containing one or two camphorsulfonamide units were synthesized. Asymmetric Michael addition of pentane-2,4-dione to β-nitrostyrene was catalyzed by these organocatalysts. During our experiments, influence of the solvent and temperature on the yield and enantioselectivity was studied. U...
Article
Thiosquaramides are the thio analogues of squaramides that are widely applicable in the fields of asymmetric catalysis, pharmaceutical research, and chemical biology. Having four-membered ring system derived from squaric acid, thiosquaramides are feasible hydrogen bond donors and acceptors. A high affinity for hydrogen bonding is driven through a c...
Article
Full-text available
In this work we introduce a sustainable membrane-based synthesis-separation platform for enantioselective organocatalysis. An azido derivatised cinchona squaramide bifunctional catalyst was synthesised, and subsequently grafted to the surface of a polybenzimidazole based nanofiltration membrane. The favourable effect of the covalent grafting — due...
Article
A Medium Throughput Screening (MTS) for iron porphyrin catalyst based biomimetic drug metabolite synthesis is developed. The microplate based method in combination with HPLC‐MS analysis was shown to be a useful tool for process development and parameter optimization in the production of targeted metabolites and/or oxidation products of forty‐three...
Article
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Three cinchona derivatives have shown remarkable activity to catalyze the aza-Markovnikov addition reaction of N-heterocycles to vinyl esters. The synthesis of the aza-Markovnikov adducts possessing valuable biological activity was thoroughly optimized. Studying the ratio of the starting materials, bases and solvents, we achieved a new and efficien...
Article
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In the last decades, the rapid advancement of solvent-resistant membranes and catalysis led to the development of more efficient and sustainable materials and processes. The present article critically assesses membrane-assisted catalysis in organic media, which is a multidisciplinary field combining materials science, reaction engineering, organic...
Article
The solvent usage in the pharmaceutical sector accounts for as much as 90% of the overall mass during manufacturing processes. Consequently, solvent consumption poses significant costs and environmental burden. Continuous processing, in particular continuous-flow reactors have a great potential in the sustainable production of pharmaceuticals but s...
Article
Full-text available
Three new glucose-based asymmetric bifunctional organocatalysts containing a 6-aminopyridyl or a 6-methylpyridyl or a cinchona unit were synthesized. Asymmetric Michael addition of pentane-2,4-dione to β-nitrostyrene was catalyzed successfully by these catalysts. In case of the cinchona based glucose-thiourea derivate the S enantiomer of the corres...
Article
This paper reports a new continuous-flow synthesis of chiral and achiral pyridino-18-crown-6 ethers. Macrocyclizations have been performed in a packed-bed flow reactor where deprotonation of a bifunctional primary or a secondary alcohol takes place with potassium hydroxide as a heterogeneous base avoiding the use of stronger and more dangerous one,...
Article
Molecularly imprinted materials are man-made mimics of biological receptors. Their polymer network has recognition sites complementary to a substrate in terms of size, shape and chemical functionality. They have diverse applications in various chemical, biomedical and engineering fields such as solid phase extraction, catalysis, drug delivery, phar...
Article
Molecularly imprinted materials are man-made mimics of biological receptors. Their polymer network has recognition sites complementary to a substrate in terms of size, shape and chemical functionality. They have diverse applications in various chemical, biomedical and engineering fields such as solid phase extraction, catalysis, drug delivery, phar...
Article
The metalation of chloro- and methoxy-substituted acetophenone ketals with butyllithium (BuLi) and with N,N,N′,N″,N″-pentamethyldiethylenetriamine-complexed butyllithium (BuLi/PMDTA) has been investigated. The lithio species thus generated were carboxylated to benzoic acids. Lithiations with BuLi occurred regioselectively ortho to the ketal substit...
Article
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This paper reports the preparation of eight new enantiopure amide type crown ethers and their optically active precursors. Chiral diamines were transformed to amide type pyridino-crown ethers reacting them with pyridine dicarbonyl dichlorides by high dilution technique. Two of the new pyridino-crown ethers were reduced to their piperidino analogues...
Article
A new synthetic route was elaborated at our laboratory providing a convenient access to 5,7-dihydro-6H-pyrrolo[2,3-d]pyrimidin-6-ones (diazaoxindoles), a compound family of biological relevance. Treatment of the easily available ethyl 2-(4-chloropyrimidin-5-yl)acetate derivatives with ammonia afforded the corresponding 2-(4-aminopyrimidin-5-yl)acet...
Article
This paper reports the enantioseparation ability of a pyridino-18-crown-6 ether-based chiral stationary phase [(S,S)-CSP-1]. The enantiomeric discrimination of chiral stationary phase (S,S)-CSP-1 was evaluated by HPLC using the mixtures of enantiomers of various protonated primary aralkylamines [1-phenylethylamine hydrogen perchlorate (PEA), 2,3-di...
Article
Enantioselective discrimination of chiral amines is of great importance as their biological properties often differ. Therefore, here we report the development of synthetic receptors for their enantioselective recognition and pH-sensitive drug release. This paper reports the preparation of three pyridine and two benzene derivatives containing an all...
Article
This paper reports a novel method for the preparation of chiral stationary phases (CSPs) using an acridino-18-crown-6 ether selector as a model compound. Chiral stationary phase (R,R)-CSP- 2A: was obtained by in situ continuously recirculating the solution of carboxyl-substituted acridino-18-crown-6 ether (R,R)- 4: , dicyclohexylcarbodiimide and 3-...
Article
The enantiomeric separation ability of the newly prepared chiral stationary phases containing acridino-18-crown-6 ether selectors was studied by high-performance liquid chromatography (HPLC). The chiral stationary phases separated the enantiomers of selected protonated primary aralkylamines efficiently. The best results were found for the separatio...
Article
A novel optically active 5,5-dioxophenothiazine-1,9 bis(thiourea) containing glucopyranosyl groups was synthesized and its enantiomeric recognition properties were examined towards the enantiomers of tetrabutylammonium salts of chiral α-hydroxy and N-protected α-amino acids using UV–vis spectroscopy.
Article
An enantiomerically pure dimethyl-substituted pyrid ino-18-crown-6 ether containing a hydroxy- methyl group at position 4 of the pyridine ring (( S,S )-1) has been prepared. This by Swern oxidation gave the formyl-substituted (( S,S )-2), then by further oxidation carboxy-substituted (( S,S )-3) pyridino-18-crown-6 ether derivatives. These enan tio...
Article
New enantiopure crown ethers containing either an ethyl diarylphosphinate moiety [(S,S)-4 to (S,S)-7] or a proton-ionizable diarylphosphinic acid unit [(S,S)-8 to (S,S)-11] have been synthesized. Electronic circular dichroism (ECD) studies on the complexation of these new enantiopure crown ethers with the enantiomers of alpha-(1-naphthyl)ethylammon...
Article
This paper reports the preparation and testing of three new pyridino-18-crown-6 ether-based chiral stationary phases (S,S)-CSP-12, (S,S)-CSP-17 and (S,S)-CSP-20. Secondary amine (S,S)-7 was first transformed to triethoxysilyl derivative (S,S)-11, which contains a urea unit by treating the former with 3-(triethoxysilyl)propyl isocyanate. Next, (S,S)...
Article
Full-text available
An enantiomerically pure dimethyl-substituted pyridino-18-crown-6 ether containing a hydroxymethyl group at position 4 of the pyridine ring [(S,S)-1] has been prepared. This by Swern oxidation gave the formyl-substituted [(S,S)-2], then by further oxidation carboxy-substituted [(S,S)-3] pyridino-18-crown-6 ether derivatives. These enantiopure dimet...
Article
Full-text available
New enantiomerically pure dimethyl- and diisobutyl-substituted pyridino-18-crown-6 ethers containing a halogen atom or a methoxy group at position 4 of the pyridine ring [(S,S)-1, (S,S)-2, (S,S)-3, (S,S)-4] have been synthesized. A new synthetic route and the solid state structure of the reported enantiopure dimethyl-substituted pyridino-18-crown-6...
Article
Full-text available
Direct capillary zone electrophoretic methods were developed for the separation of the enantiomers of 1-(α-aminoarylmethyl)-2-naphthol and 2-(α-aminoarylmethyl)-1-naphthol analogues. The effects of selector and buffer concentrations, electrolyte pH and applied voltage on the separation efficiency were studied. Variation of the electrophoretic condi...
Article
New enantiomerically pure dimethyl-substituted pyridino-18-crown-6 ether derivatives containing chloro, N-allylamino, N-allylacetamido, N-benzylamino and cyano functional groups at position 4 of the pyridine ring have been synthetized. This paper also reports the transformation of the known enantiopure parent dimethyl-substituted pyridino-18-crown-...

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