Rositca D Nikolova | Sofia University "St. Kliment Ohridski" (original) (raw)
Papers by Rositca D Nikolova
The Cambridge Structural Database, 2023
The synthesis, IR, NMR and X-ray structure of 2-[(2,3-dihydro-2-oxo-3-benzoxazolyl)methyl]benzoic... more The synthesis, IR, NMR and X-ray structure of 2-[(2,3-dihydro-2-oxo-3-benzoxazolyl)methyl]benzoic acid-a potential new drug scaffold are reported. The compound crystallizes in the triclinic P-1 space group with unit cell parameters:
Synthetic Communications, May 17, 2023
ChemInform, Mar 1, 2005
Benzopyran derivatives R 0350 A New and Efficient Method for Conjugate Addition of Trialkylphosph... more Benzopyran derivatives R 0350 A New and Efficient Method for Conjugate Addition of Trialkylphosphites to 3-Acylsubstituted Coumarins.-Treatment of 3-acylsubstituted coumarins with trialkylphosphites results in unprecedented and preferred formation of 1,4-addition products. The enolphosphates, which result from 1,2-addition, can be converted into 4-phosphono-2-oxochromans after hydrolysis.
ChemInform, Jun 16, 2009
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Molecules
In the present study, the reaction conditions for homodimerization process of 3-acetylcoumarin we... more In the present study, the reaction conditions for homodimerization process of 3-acetylcoumarin were achieved under sonication using combination of zinc and metallic salt (ZnCl2 or Zn(OAc)2). Appropriate frequency and sound amplitude have been identified as significant variables for the initiation of the reaction. On the base of first principal calculations and experimental results, the mechanism of the reaction was investigated. The relative stability of the possible intermediates has been compared, including evaluation on the ionic and radical reaction pathways for the dimerization process. Theoretical results suggested that the radical mechanism is more favorable. The C-C bond formation between the calculated radical intermediates occurs spontaneously (∆G = −214 kJ/mol for ZnCl2, −163 kJ/mol in the case of Zn(OAc)2), which proves the possibility for the homodimerization of 3-acetylcoumarin via formation of radical species. Both experimental and theoretical data clarified the activ...
Phosphorus Sulfur and Silicon and the Related Elements, 2011
ABSTRACT (2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, i... more ABSTRACT (2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, isolated, and spectroscopically as well as structurally characterized by means of single crystal X-ray diffraction; conventional and linear-polarized IR spectroscopy; electronic (UV-VIS-NIR) spectroscopy; H, C, and P NMR. Quantum chemical DFT calculations have been performed in order to obtain information on the electronic structure and vibrational properties of 1, thus supporting the experimental data. The correlation between the structure and spectroscopic characteristics is discussed.GRAPHICAL ABSTRACT
Phosphorus, Sulfur, and Silicon and the Related Elements, 2011
(2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, isolated, ... more (2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, isolated, and spectroscopically as well as structurally characterized by means of single crystal X-ray diffraction; conventional and linear-polarized IR spectroscopy; electronic (UV-VIS-NIR) spectroscopy; 1H, 13C, and 31P NMR. Quantum chemical DFT calculations have been performed in order to obtain information on the electronic structure and vibrational properties of 1, thus supporting the experimental data. The correlation between the structure and spectroscopic characteristics is discussed. GRAPHICAL ABSTRACT
Molecules
Quantum-chemical calculations on the spectral properties of some aryl substituted 3-phosphonocoum... more Quantum-chemical calculations on the spectral properties of some aryl substituted 3-phosphonocoumarins were performed, and the effect of the substituents in the aryl moiety was evaluated. The structures possessing promising fluorescent properties were successfully synthesized via Suzuki and Sonogashira cross-coupling. The synthetic protocol was also applied for the phosphorous chemoisomer of 3-phosphonocoumarin, 1,2-benzoxaphosphorin, and their carboxylate analogues. The optical properties of the arylated and alkynylated products were experimentally determined. The obtained quantum-chemical and experimental results give the possibility for a fine tuning of the optical properties of phosphorous-containing coumarin systems by altering the substituent at its C-6 position.
Th conference is organised with the fiancial support of European Social Fund within the Project B... more Th conference is organised with the fiancial support of European Social Fund within the Project BG051PO001-3.1.07-0046 “Updating and approbation of the curricula of the Faculty of Pharmacy, Medical University of Varna according to the needs of the pharmaceutical business and the requirements of the labor market”
Phosphorus Sulfur and Silicon and The Related Elements, Mar 7, 2022
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Journal of Molecular Structure-Theochem, 2006
The paper reports a computational study at MP2 and B3LYP levels of a tandem reduction/acylation r... more The paper reports a computational study at MP2 and B3LYP levels of a tandem reduction/acylation reaction of the diethyl ester of coumarin-3-phosphonic acid with NaBH 4 and acetic anhydride, which experimentally results in formation of the C-acylated isomer only. The computational results and comparison with experimental observations suggest that an important role for a successful acylation plays dimethylaminopyridine, which associates the Lewis acid BH 3 generated in the first step of the reaction. In the absence of this base, BH 3 could bind to the nucleophilic centers of the anionic intermediate adduct and thus suppress its further acylation, as found experimentally. The observed regioselectivity for C-acylation could be explained by the higher stability of C-acylated as compared to O-acylated product both in pyridine and THF, by 54-56 kJ/mol. In addition to preferential stabilization of the C-acylated product, the solvent was found to be important with its influence on the relative stability of different complexes with BH 3. The analysis of the charge distribution and contributions in the molecular orbitals of the intermediate also suggests a preference to acylation at the carbon instead of oxygen nucleophilic centre. In all studied species, the C atom bound directly to a phosphonate substituent carries large negative charge, above K0.50 e according to NBO analysis, which implies high nucleophilicity.
Synthetic Communications, 2006
Phosphorus, Sulfur, and Silicon and the Related Elements, 2011
From the Michael addition reaction of CH3NO2 to the diethyl ester of coumarin-3-phosphonic acid 1... more From the Michael addition reaction of CH3NO2 to the diethyl ester of coumarin-3-phosphonic acid 1 in the presence of a base—KF or a nucleophilic agent (HNu = EtOH, piperidine, PrNH2)—the esters and amides 2, 4, and 5 were isolated. In order to avoid ring opening and to isolate only the product of the Michael addition reaction 3, the reaction was performed in the absence of a nucleophilic agent. In this case only, the product 3—a 2-oxochromane—was isolated. When the reaction was carried out in the presence of amines (Et3N, piperidine), a new product—1-hydroxy-4-(2′-hydroxyphenyl)-2,5-dioxopyrrolidin-3-yl-phosphonate 6—was formed by a new rearrangement reaction.[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: .cif files.]
International Journal of Quantum Chemistry, 2007
When an alkaline boron hydride is used as reduction reagent two byproducts are released, BH3 and ... more When an alkaline boron hydride is used as reduction reagent two byproducts are released, BH3 and alkaline cation, and both of them could influence the following reaction steps if a multi-step reaction is performed in tandem one-pot fashion. We report a theoretical study on the stability of possible complexes of the Lewis acids, BH3 and alkaline cations, with reaction intermediate,
Molecules, 2012
A newly found reaction for the synthesis of 3,4-disubstituted 1-hydroxypyrrolidine-2,5-diones fro... more A newly found reaction for the synthesis of 3,4-disubstituted 1-hydroxypyrrolidine-2,5-diones from 3-substituted coumarins and nitromethane has been elaborated. The reaction involved a simple and convenient experimental procedure. The applicability of the rearrangement reaction is determined.
The Cambridge Structural Database, 2023
The synthesis, IR, NMR and X-ray structure of 2-[(2,3-dihydro-2-oxo-3-benzoxazolyl)methyl]benzoic... more The synthesis, IR, NMR and X-ray structure of 2-[(2,3-dihydro-2-oxo-3-benzoxazolyl)methyl]benzoic acid-a potential new drug scaffold are reported. The compound crystallizes in the triclinic P-1 space group with unit cell parameters:
Synthetic Communications, May 17, 2023
ChemInform, Mar 1, 2005
Benzopyran derivatives R 0350 A New and Efficient Method for Conjugate Addition of Trialkylphosph... more Benzopyran derivatives R 0350 A New and Efficient Method for Conjugate Addition of Trialkylphosphites to 3-Acylsubstituted Coumarins.-Treatment of 3-acylsubstituted coumarins with trialkylphosphites results in unprecedented and preferred formation of 1,4-addition products. The enolphosphates, which result from 1,2-addition, can be converted into 4-phosphono-2-oxochromans after hydrolysis.
ChemInform, Jun 16, 2009
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Molecules
In the present study, the reaction conditions for homodimerization process of 3-acetylcoumarin we... more In the present study, the reaction conditions for homodimerization process of 3-acetylcoumarin were achieved under sonication using combination of zinc and metallic salt (ZnCl2 or Zn(OAc)2). Appropriate frequency and sound amplitude have been identified as significant variables for the initiation of the reaction. On the base of first principal calculations and experimental results, the mechanism of the reaction was investigated. The relative stability of the possible intermediates has been compared, including evaluation on the ionic and radical reaction pathways for the dimerization process. Theoretical results suggested that the radical mechanism is more favorable. The C-C bond formation between the calculated radical intermediates occurs spontaneously (∆G = −214 kJ/mol for ZnCl2, −163 kJ/mol in the case of Zn(OAc)2), which proves the possibility for the homodimerization of 3-acetylcoumarin via formation of radical species. Both experimental and theoretical data clarified the activ...
Phosphorus Sulfur and Silicon and the Related Elements, 2011
ABSTRACT (2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, i... more ABSTRACT (2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, isolated, and spectroscopically as well as structurally characterized by means of single crystal X-ray diffraction; conventional and linear-polarized IR spectroscopy; electronic (UV-VIS-NIR) spectroscopy; H, C, and P NMR. Quantum chemical DFT calculations have been performed in order to obtain information on the electronic structure and vibrational properties of 1, thus supporting the experimental data. The correlation between the structure and spectroscopic characteristics is discussed.GRAPHICAL ABSTRACT
Phosphorus, Sulfur, and Silicon and the Related Elements, 2011
(2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, isolated, ... more (2-Oxo-2H-chromen-3-yl)phosphonic acid monoethyl ester trihydrate (1) was synthesized, isolated, and spectroscopically as well as structurally characterized by means of single crystal X-ray diffraction; conventional and linear-polarized IR spectroscopy; electronic (UV-VIS-NIR) spectroscopy; 1H, 13C, and 31P NMR. Quantum chemical DFT calculations have been performed in order to obtain information on the electronic structure and vibrational properties of 1, thus supporting the experimental data. The correlation between the structure and spectroscopic characteristics is discussed. GRAPHICAL ABSTRACT
Molecules
Quantum-chemical calculations on the spectral properties of some aryl substituted 3-phosphonocoum... more Quantum-chemical calculations on the spectral properties of some aryl substituted 3-phosphonocoumarins were performed, and the effect of the substituents in the aryl moiety was evaluated. The structures possessing promising fluorescent properties were successfully synthesized via Suzuki and Sonogashira cross-coupling. The synthetic protocol was also applied for the phosphorous chemoisomer of 3-phosphonocoumarin, 1,2-benzoxaphosphorin, and their carboxylate analogues. The optical properties of the arylated and alkynylated products were experimentally determined. The obtained quantum-chemical and experimental results give the possibility for a fine tuning of the optical properties of phosphorous-containing coumarin systems by altering the substituent at its C-6 position.
Th conference is organised with the fiancial support of European Social Fund within the Project B... more Th conference is organised with the fiancial support of European Social Fund within the Project BG051PO001-3.1.07-0046 “Updating and approbation of the curricula of the Faculty of Pharmacy, Medical University of Varna according to the needs of the pharmaceutical business and the requirements of the labor market”
Phosphorus Sulfur and Silicon and The Related Elements, Mar 7, 2022
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Journal of Molecular Structure-Theochem, 2006
The paper reports a computational study at MP2 and B3LYP levels of a tandem reduction/acylation r... more The paper reports a computational study at MP2 and B3LYP levels of a tandem reduction/acylation reaction of the diethyl ester of coumarin-3-phosphonic acid with NaBH 4 and acetic anhydride, which experimentally results in formation of the C-acylated isomer only. The computational results and comparison with experimental observations suggest that an important role for a successful acylation plays dimethylaminopyridine, which associates the Lewis acid BH 3 generated in the first step of the reaction. In the absence of this base, BH 3 could bind to the nucleophilic centers of the anionic intermediate adduct and thus suppress its further acylation, as found experimentally. The observed regioselectivity for C-acylation could be explained by the higher stability of C-acylated as compared to O-acylated product both in pyridine and THF, by 54-56 kJ/mol. In addition to preferential stabilization of the C-acylated product, the solvent was found to be important with its influence on the relative stability of different complexes with BH 3. The analysis of the charge distribution and contributions in the molecular orbitals of the intermediate also suggests a preference to acylation at the carbon instead of oxygen nucleophilic centre. In all studied species, the C atom bound directly to a phosphonate substituent carries large negative charge, above K0.50 e according to NBO analysis, which implies high nucleophilicity.
Synthetic Communications, 2006
Phosphorus, Sulfur, and Silicon and the Related Elements, 2011
From the Michael addition reaction of CH3NO2 to the diethyl ester of coumarin-3-phosphonic acid 1... more From the Michael addition reaction of CH3NO2 to the diethyl ester of coumarin-3-phosphonic acid 1 in the presence of a base—KF or a nucleophilic agent (HNu = EtOH, piperidine, PrNH2)—the esters and amides 2, 4, and 5 were isolated. In order to avoid ring opening and to isolate only the product of the Michael addition reaction 3, the reaction was performed in the absence of a nucleophilic agent. In this case only, the product 3—a 2-oxochromane—was isolated. When the reaction was carried out in the presence of amines (Et3N, piperidine), a new product—1-hydroxy-4-(2′-hydroxyphenyl)-2,5-dioxopyrrolidin-3-yl-phosphonate 6—was formed by a new rearrangement reaction.[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: .cif files.]
International Journal of Quantum Chemistry, 2007
When an alkaline boron hydride is used as reduction reagent two byproducts are released, BH3 and ... more When an alkaline boron hydride is used as reduction reagent two byproducts are released, BH3 and alkaline cation, and both of them could influence the following reaction steps if a multi-step reaction is performed in tandem one-pot fashion. We report a theoretical study on the stability of possible complexes of the Lewis acids, BH3 and alkaline cations, with reaction intermediate,
Molecules, 2012
A newly found reaction for the synthesis of 3,4-disubstituted 1-hydroxypyrrolidine-2,5-diones fro... more A newly found reaction for the synthesis of 3,4-disubstituted 1-hydroxypyrrolidine-2,5-diones from 3-substituted coumarins and nitromethane has been elaborated. The reaction involved a simple and convenient experimental procedure. The applicability of the rearrangement reaction is determined.