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Chemistry of Heterocyclic Compounds
Journal Prestige (SJR): 0.325  Citation Impact (citeScore): 1 Number of Followers: 5  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1573-8353 - ISSN (Online) 0009-3122 Published by Springer-Verlag  [2468 journals]
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- Prediction of the regioselectivity of the ruthenium-catalyzed [3+2]
cycloadditions of benzyl azide with internal alkynes using conceptual DFT
indices of reactivity-
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Abstract:
[3+2] Cycloadditions of benzyl azide with unsymmetrical internal alkynes, in the presence of pentamethylcyclopentadienyl ruthenium chloride [Cp*RuCl] complex as catalyst, leading to trisubstituted 1,2,3-triazole regioisomers are rationalized by means of DFT-based reactivity indices. The four activated azide/[Ru]/alkyne complexes have been modeled for all their possible conformers and were classified using the Maxwell–Boltzmann distribution. The local electrophilicity and nucleophilicity indices, based on Parr functions, have been calculated for the terminal sites of the benzyl azide and the carbon atoms of the internal alkynes. The calculations were performed at the B3LYP level of theory together with the LANL2DZ basis set for Ru and Cl and the standard 6-31G(d) basis set for the other atoms. The obtained results agree well with the experimental findings which stipulate that the formed cycloadducts depend strongly on the nature of substituents carried by the internal alkynes. The regioselectivity of six additional reactions of benzyl azide with other internal alkynes are also predicted.
PubDate: 2023-04-24
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- Exploring the factors controlling the mechanism and the high
stereoselectivity of the polar [3+2] cycloaddition reaction of the
N,N'-cyclic azomethine imine with 3-nitro-2-phenyl-2H-chromene. A
molecular electron density theory study-
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Abstract:
A molecular electron density theory study of the [3+2] cycloaddition reaction of 5-oxo-2-(phenylmethylidene)pyrazolidin-2-ium-1-ide, a simple azomethine imine, with 3-nitro-2-phenyl-2H-chromene was carried out at the B3LYP/6-311G(d,p) computational level in order to unravel the origin of the stereoselectivity experimentally observed. Electron localization function and natural population analysis showed that the azomethine imine is a zwitterionic three-atom component. Analysis of the conceptual density functional theory reactivity indices indicates that azomethine imine is a strong nucleophile, while 3-nitro-2-phenyl-2H-chromene is a good electrophile, which accounts for a polar process confirmed by the high global electron density transfer values. The Parr function indices explain well the experimentally obtained ortho regioselectivity. Analysis of the energy profiles of the possible reactive pathways in gas phase and in solution of i-PrOH points to high exo stereoselectivity and complete ortho regioselectivity of the reaction in excellent agreement with the experimental findings. Analysis of the transition state structures indicates a very asynchronous molecular mechanism for the favored orthoregioisomeric reaction channels. Analysis using noncovalent interactions, quantum theory of atoms in molecules, and independent gradient model based on Hirshfeld distribution indicates that the presence of several hydrogen bonds and van der Waals intermolecular noncovalent interactions are the factors favoring the ortho-exo selectivity. The bonding evolution theory study of the most favorable pathway reveals a two-stage one-step molecular mechanism.
PubDate: 2023-04-24
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- The [3+2] cycloaddition reaction as an attractive way for the preparation
of nicotine analogs (microreview)-
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Abstract:
In this microreview, the application of [3+2] cycloaddition reactions in the synthesis of nicotine analogs is critically reviewed and analyzed on the basis of available literature data. It was found that [3+2] cycloaddition with the participation of differently functionalized azomethine ylides is particularly well represented. This enables the synthesis of nicotine analogs not available by other routes. 
PubDate: 2023-04-22
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- Recent advances in intramolecular [2+2] photocycloaddition for the
synthesis of indoline-based scaffolds (microreview)-
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Abstract:
This microreview provides an overview of recent advances in [2+2] photocycloaddition for the synthesis of indoline-based frameworks (2020–2022). 
PubDate: 2023-04-22
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- A molecular electron density theory study of mechanism and selectivity of
the intramolecular [3+2] cycloaddition reaction of a
nitrone–vinylphosphonate adduct-
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Abstract:
The selectivity and the molecular mechanism of the intramolecular [3+2] cycloaddition reaction of a nitrone–vinylphosphonate adduct was computationally studied within the molecular electron density theory using density functional theory method at the B3LYP/6-31G(d,p) level of theory. Conceptual density functional theory indices show that the nitrone–vinylphosphonate adduct has dual strong electrophilic and nucleophilic character. Local Parr functions reactivity indices reveal that this reaction favors the formation of the fused regioisomers in accordance with the experimental data. Analysis of different energetic profiles indicates that the fused-endo competitive pathway is favored kinetically, whereby this intramolecular reaction is characterized by exothermic and exergonic character. The geometry of transition states structures shows that the mechanism of this cycloaddition reaction is synchronous. Electron localization function topological analysis of the changes in electron density during the most favored reaction pathway shows that the mechanism is synchronous non-concerted.
PubDate: 2023-04-22
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- Regio- and stereoselectivity of [3+2] cycloaddition reactions between
(Z)-1-(anthracen-9-yl)-N-methyl nitrone and analogs of
trans-β-nitrostyrene on the basis of MEDT computational study-
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Abstract:
The regio- and stereoselectivity of [3+2] cycloaddition reactions of (Z)-1-(anthracen-9-yl)-N-methyl nitrone with analogs of trans-β-nitrostyrene were studied within the molecular electron density theory at the B3LYP/6-31G(d) and MPWB95/6-311G(d,p) theory levels. Analysis of the reactivity indices for presented reactions suggests that nitrone participates as nucleophile, while studied nitroalkenes play a role of electrophiles. According to electron localization function and conceptual density functional theory, kinetic and thermodynamic aspects of processes as well as analysis of all critical structures, the most favored reaction path is the formation of (3RS,4RS,5SR)-3-(anthracen-9-yl)-5-aryl-2-methyl-4-nitroisoxazolidine, independently of simulated solvent.
PubDate: 2023-04-22
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- Thematic issue “Cycloaddition reactions: recent progress”
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PubDate: 2023-04-20
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- On the question of selective protocol for the preparation of juglone via
(4+2) cycloaddition involving 3-hydroxypyridazine: DFT mechanistic study-
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Abstract:
The possibility of preparation of juglone via Diels–Alder reaction of 3-hydroxypyridazine and 2-nitroquinone was analyzed on the basis of DFT computational study. It was found that key stage of the proposed transformation is head-to-head, polar cycloaddition process, which is realized without formation of zwitterionic intermediate. Further transformations of the intermediate exhibit nature of pseudocyclic reactions with nonconcerted reorganization of the electron density.
PubDate: 2023-04-20
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- A MEDT study of the mechanism and selectivity of the hetero-Diels–Alder
reaction between 3-benzoylpyrrolo[1,2-c][1,4]-benzoxazine-1,2,4-trione and
vinyl acetate-
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Abstract:
The chemo-, regio-, and stereoselectivity of the hetero-Diels–Alder reaction between 3-benzoylpyrrolo[1,2-c][1,4]benzoxazine-1,2,4-trione and vinyl acetate, has been investigated within molecular electron density theory at the B3LYP/6-311(d,p) level of theory. The conceptual density functional theory reactivity indices, as well as the activation and reaction energies have been analyzed, and five possible reaction paths for this cycloaddition reaction, resulting from the presence of three heterodiene frameworks in the molecule of the diene reactant have been studied. The conceptual density functional theory analysis indicates that vinyl acetate acts as a nucleophile and 3-benzoylpyrrolo[1,2-c][1,4]benzoxazine-1,2,4-trione acts as a strong electrophile. The computed activation and reaction energies reveal that that this reaction is chemo-, stereo-, and regioselective, which is consistent with the experimental findings. Topological electron localization function analysis was used to look into how the electron densities were reorganized along the preferred reaction path. According to this analysis, the reaction takes place through a two-stage one-step mechanism.
PubDate: 2023-04-20
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- Unveiling the exclusive stereo and site selectivity in [3+2] cycloaddition
reactions of a tricyclic strained alkene with nitrile oxides from the
molecular electron density theory perspective-
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Abstract:
The [3+2] cycloaddition reactions of formonitrile oxide and benzonitrile oxide with a tricyclic strained alkene bearing norbornene and cyclohexene double bonds have been studied from the molecular electron density theory perspective at the MPWB1K/6-311G(d,p) computational level. Electron localization function shows the absence of pseudoradical and carbenoid centers, classifying formonitrile and benzonitrile oxides as zwitterionic three-atom components, consistent with the high activation free energies of 26.0 and 28.5 kcal·mol–1, respectively, in their cycloaddition reaction with the strained alkene in CH2Cl2. These reactions follow a one-step mechanism under kinetic control and present total site selectivity, as the addition of formonitrile and benzonitrile oxides to the norbornene double bond is energetically preferred by 4.9 and 8.0 kcal·mol–1, respectively, over the cyclohexene double bond in agreement with the experiments, and complete exo-stereoselective control is predicted. The minimal global electron density transfer predicts nonpolar character, while the electron localization function topological analysis implies that the activation energy is related only to the formation of non-bonding electron density at N2 nitrogen and pseudoradical center at C3 atom of the nitrile oxides. The total electron densities less than 0.1 e and positive Laplacian of electron density at the forming C–C and C–O bond critical points of the early transition states indicate noncovalent interactions which were characterized by visualization of the AIM-RDG isosurfaces.
PubDate: 2023-04-20
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- [2+1] Cycloaddition reaction of α-atlantone with m-CPBA in the light of
experimental and MEDT quantum-chemical study-
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The two diastereoisomers of 6-(3,4-epoxy-4-methylcyclohexyl)-2-methylhepta-2,5-dien-4-one were synthesized in the [2+1] cycloaddition reaction of α-atlantone, isolated compound from Cedrus atlantica essential oil, with m-chloroperbenzoic acid in CH2Cl2. The chemoselectivity of this cycloaddition reaction has been both experimentally and theoretically studied within the molecular electron density theory. Parr functions and electron localization function analysis of the reagents correctly predicted the experimental chemoselectivity with the most favorable interaction at C3'=C4' bond. These reactions follow a two-stage one-step mechanism.
PubDate: 2023-04-20
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- Investigation of the solvent effect, regioselectivity, and the mechanism
of the cycloaddition reaction between 2-chlorobenzimidazole and
benzonitrile oxide-
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Abstract:
This theoretical study, performed using density functional theory at the B3LYP/6-311+G(d,p) level, shows that the most likely route to obtain 3-phenyl[1,2,4]oxadiazolo[4,5-a]benzimidazole from the reaction of 2-chlorobenzimidazole with benzonitrile oxide implies the presence of anionic species. A concerted [3+2] cycloaddition reaction on the imidoyl group of 2-chlorobenzimidazole is not possible. The presence of a polar protic solvent (MeOH) favors the reaction. The analysis of the Wiberg indices shows that the transition states are earlier in MeOH than in THF or gas phase. Finally, topological analysis of the electron localization function indicates that the formation of the N4–C3 and C5–O bonds and the breaking of the C5–Cl bond in the preparation of 3-phenyl[1,2,4]oxadiazolo[4,5-a]benzimidazole are marked for each by the presence of an asynaptic basin V(Asyn) and proceed through tetrahedral intermediates, indicating the nonconcerted nature of the mechanism. These results are in good agreement with the experimental results.
PubDate: 2023-04-20
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- An overview of the synthetic routes leading to the 1,3,4-oxadiazoles
(microreview)-
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1,3,4-Oxadiazoles are essential building blocks from the medicinal chemistry viewpoint. Herein, an overview of both classical and recently developed synthetic routes leading to these heterocycles are summarized. 
PubDate: 2023-04-11
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- Nitroquinolines in the Synthesis of Heterocyclic Compounds (microreview)
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This microreview presents data on the synthesis of polynuclear heterocyclic compounds based on quinoline nitro derivatives published over the past 10 years. 
PubDate: 2023-04-11
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- The synthesis of New 5-R-aminoazolo[1,5-a]pyrimidin-7-ones from an
N,S-acetal Derivative of Meldrum’s Acid-
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Abstract:
A one-step method for the synthesis of new 5-aminoazolo[1,5-a]pyrimidines was developed. The use of a synthetic equivalent of carbonyl dielectrophile based on Meldrum's acid made it possible to introduce a substituted amino group into position 5 of azolo[1,5-a]-pyrimidines without the use of severe conditions and palladium catalysts. The tolerance of the reaction to various substituents was also investigated. Based on the isolated intermediates, a reaction mechanism of the process was proposed. Moreover, the possibility of synthesizing analogs of biologically active molecules based on the obtained compounds was demonstrated.
PubDate: 2023-03-14
DOI: 10.1007/s10593-023-03164-4
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- Carbocation Catalysis in the Synthesis of Heterocyclic Compounds
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The data on the use of carbocationic catalysis in the synthesis of heterocyclic compounds presented in the literature over the last 5–10 years are summarized and analyzed. Particular attention is paid to the discussion of reaction mechanisms and the problem of selectivity.
PubDate: 2023-03-10
DOI: 10.1007/s10593-023-03157-3
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- A formal [4+1] cycloaddition of dimethoxycarbene to
3-perfluoroacyl-4H-chromenes: the synthesis of areno-condensed
7,7a-dihydro-4H-furo[3,4-b]pyrans-
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Abstract:
The [4+1] annulation of in situ generated dimethoxycarbene to 3-trifluoroacetyl-4H-chromenes led to cyclic ortho esters, trifluoromethylsubstituted dihydrofuro[3,4-b]chromenes. In the case of 2-perfluoroacyl-1H-benzo[f]chromenes, representatives of a new heterocyclic system 7a,8-dihydro-11H-benzo[f]furo[3,4-b]chromene, were formed.
PubDate: 2023-03-09
DOI: 10.1007/s10593-023-03167-1
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- The effect of electron-donating moiety structure on the electrochemical
and photophysical properties of dithiophene- and
naphtho[2,1-b:3,4-b']dithiophene-substituted 1,3,4-oxadiazoles and
1,3,4-thiadiazoles-
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Abstract:
3-Alkyl- and 3-aryl-substituted [2,2'-dithiophene]-5-carboxylate esters, as well as naphtho[2,1-b:3,4-b']dithiophene-2-carboxylates were used in the synthesis of 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives. The obtained compounds were characterized with regard to their electrochemical and photophysical properties. The replacement of alkyl side chains with aryl substituents led to a substantial decrease of luminescence quantum yield and narrowing the energy gap between HOMO and LUMO, as well as a bathochromic shift of the absorption and emission peaks in the absorption and luminescence spectra. Changing from 3-aryldithiophene- to naphtho[2,1-b:3,4-b']-dithiophene-substituted 1,3,4-oxadiazoles and 1,3,4-thiadiazoles led to a slight increase of quantum yields, while the positions of LUMO and HOMO changed insignificantly.
PubDate: 2023-03-08
DOI: 10.1007/s10593-023-03166-2
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- Formation of Five- and Six-membered Oxygen-containing Heterocycles on the
Basis of 1-halo-1-nitroalkenes-
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Abstract:
This minireview covers recent progress in the synthesis of five- and six-membered oxygen-containing heterocycles on the basis of 1-halo-1-nitroalkenes, reported since 2017.
PubDate: 2023-03-07
DOI: 10.1007/s10593-023-03155-5
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- Methyl 3-aryl(pyridyl)-5-oxopyrrolidine-2-carboxylates: synthesis and
structure-
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Abstract:
A convenient diastereoselective method for the preparation of methyl (2R*,3R*)-3-aryl(pyridyl)-5-oxopyrrolidine-2-carboxylates was developed on the basis of the neutralization reaction of diastereohomogeneous dimethyl (2R*,3R*)-3-aryl(pyridyl)glutamate hydrochlorides.
PubDate: 2023-03-07
DOI: 10.1007/s10593-023-03161-7
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