0000000000025195
AUTHOR
M. José Aurell
showing 25 related works from this author
A DFT study of the mechanism of NHC catalysed annulation reactions involving α,β-unsaturated acyl azoliums and β-naphthol.
2016
The mechanism of NHC catalysed annulation reactions involving an α,β-unsaturated acyl azolium and β-naphthol has been studied using DFT methods at the MPWB1K/6-311G(d,p) level in toluene. For the C-C bond formation step, which corresponds to the rate- and stereo-determining step of this NHC catalysed reaction, the two competitive addition modes, i.e. the 1,2- and the 1,4-additions, have been studied. In toluene, acyl azolium forms an ion pair (IP) with the counterion chloride anion. Interestingly, β-naphthol forms a hydrogen bond with the chloride anion of IP, increasing the nucleophilic character of β-naphthol and the electrophilic character of the acyl azolium moiety. For the first time, …
A DFT study of the role of Lewis acid catalysts in the mechanism of the 1,3-dipolar cycloaddition of nitrile imines towards electron-deficient acrylo…
2012
Abstract The role of the Mg complex formation in the reaction rate and regioselectivity of the 1,3-dipolar cycloaddition (13DC) reactions of nitrile imines (NIs) towards electron-deficient methacryloylpyrazolidinones has been theoretically studied using DFT methods at the B3LYP/6-31G * level. These 13DC reactions have an asynchronous concerted mechanism with a low polar character, displaying a high C regioselectivity induced by a steric repulsion between the phenyl substituent present at the C3 carbon of the NIs and the pyrazolidinone appendage present in the methacryloyl derivative, which increases with the formation of the bulky Mg–methacryloylpyrazolidinone complex. Solvent effect has be…
A DFT study of the domino reactions between imidazole NHC, ketenimines and DMAD or MP acetylene derivatives yielding spiro-pyrroles
2014
Abstract The domino reactions of imidazole carbene 9, ketenimine 10 and DMAD 5 or MP 7 to yield the formal [3+2] cycloadducts 12 or 14 have been investigated using DFT methods at the B3LYP/6-31G* level. These domino reactions are initialized by the nucleophilic attack of imidazole 9 on ketenimine 10 to yield the zwitterionic intermediate 11. The second reaction is a formal [3+2] cycloaddition (32CA) reaction between the zwitterionic intermediate 11 and acetylene carboxylates DMAD 5 or MP 7 yielding spiro-pyrroles 12 and 14. These formal 32CA reactions are initialized by the nucleophilic attack of the N3 nitrogen of intermediate 11 on the most electrophilic centres of these acetylene derivat…
Synthesis, Optical Properties, and DNA Interaction of New Diquats Based on Triazolopyridines and Triazoloquinolines
2017
New diquat derivatives based on [1,2,3]triazolo[1,5-a]pyridine and [1,2,3]triazolo[1,5-a]quinoline have been synthesized in excellent yields. To evaluate the effect of the alkyl bridge length, ethane and propane dibromo alkane substrates were used for their synthesis. Theoretical calculations predicted a very small energetic barrier between the two possible enantiomers P (Ra ) and M (Sa ), which makes them very difficult to resolve. Thermal denaturation studies, UV/Visible spectroscopy, and fluorescence titrations with ct-DNA evidenced the intercalation of the quinoline derivatives in DNA.
Crown ethers derived from cyclohexane. Influence of their stereochemistry in complexation and transport
2002
Abstract Crown ethers derived from cyclohexane have been prepared. The trans stereochemistry of the substituents on the carbocyclic ring makes that only one conformation can complex cations. The influence of the stereochemistry in complexation has been studied.
Toward an understanding of the 1,3-dipolar cycloaddition between diphenylnitrone and a maleimide:bisamide complex. A DFT analysis of the reactivity o…
2007
Abstract The 1,3-dipolar cycloaddition between diphenylnitrone and a maleimide:bisamide complex has been studied using density functional theory (DFT) methods at the B3LYP/6-31G∗ level. The molecular recognition of the bisamide receptor to maleimide favors the formation of the complex through three hydrogen bonds. However, they are not able to produce an efficient acceleration of the cycloaddition because the symmetric substitution of the dipolarophile sites. This poor capability is discussed in base of the transition state structures and the analysis of the reactivity indexes of the reagents.
A theoretical study on the regioselectivity of 1,3-dipolar cycloadditions using dft-based reactivity indexes
2004
The regioselectivity for a series of four 1,3-dipolar cycloaddition reactions has been studied using global and local reactivity indexes. The results of the theoretical analysis suggest that for asynchronous cycloadditions associated to polar processes, the regioselectivity is consistently explained by the most favorable two-center interactions between the highest nucleophilic and electrophilic sites of the reagents.
Mechanistic details of the domino reaction of nitronaphthalenes with the electron-rich dienes. A DFT study
2008
Abstract The reaction of 1-nitronaphthalene ( 1 ) with the Danishefsky diene ( 2 ) to give the dihydrophenanthrene derivative 11 has been theoretically studied using DFT methods. This reaction is a domino process that is initialized by a polar Diels–Alder reaction between 1 and 2 to give the formally [2 + 4] cycloadduct 3 . The subsequent concerted elimination of nitrous acid ( 4 ) from 3 yields 11 . Analysis of the global reactivity indices as well as the thermodynamic data for this domino process indicate that while the large electrophilic character of 1 together with the large nucleophilic character of 2 are responsible for the participation of these reagents in a polar Diels–Alder react…
Acceptorless dehydrogenative condensation: synthesis of indoles and quinolines from diols and anilines.
2021
The use of diols and anilines as reagents for the preparation of indoles represents a challenge in organic synthesis. By means of acceptorless dehydrogenative condensation, heterocycles, such as indoles, can be obtained. Herein we present an experimental and theoretical study for this purpose employing heterogeneous catalysts Pt/Al2O3 and ZnO in combination with an acid catalyst (p-TSA) and NMP as solvent. Under our optimized conditions, the diol excess has been reduced down to 2 equivalents. This represents a major advance, and allows the use of other diols. 2,3-Butanediol or 1,2-cyclohexanediol has been employed affording 2,3-dimethyl indoles and tetrahydrocarbazoles. In addition, 1,3-pro…
Toward an understanding of the acceleration of Diels-Alder reactions by a pseudo-intramolecular process achieved by molecular recognition. A DFT stud…
2007
The pseudo-intramolecular Diels−Alder (DA) reaction between a 2-substituted furan (1) and a N-maleimide derivative (2) has been analyzed using DFT methods. Formation of two hydrogen bonds between the appendages on furan and maleimide derivatives favors thermodynamically the formation of a molecular complex (MC1) through an efficient molecular recognition process. The large enthalpy stabilization associated with the molecular recognition overcomes the unfavorable activation entropy associated with the bimolecular process. As a consequence, the subsequent DA reaction is clearly accelerated through a pseudo-intramolecular process.
Biphenyl macrolactams in anion complexation. Selective naked-eye fluoride recognition
2004
Two colorimetric anion sensors 1 and 2 allow for the selective differentiation of fluoride in the presence of other anions. Two different types of species have been observed in the complexation process, one of them is a co-ordination complex and the other is a salt generated by ligand deprotonation. The deprotonation reaction induces a conformational change, giving rise to a symmetrical species. This species is responsible for colour development. Ligand 3 has a similar structure and does not give rise to any colour modification due to presence of the dimethylamino groups in the biphenyl moiety. The X-ray structure of ligand 2 is also reported and compared with that of ligand 1, that had bee…
4,4′-Substituted biphenyl coronands. Preparation of a new selective fluorescent sensor for mercury salts
2006
Six new 4,4′-substituted biphenyl coronands have been prepared. The ligands containing dimethylamino groups in the biphenyl moiety have been used in transition metal cations’ complexation and one of them (3) has demonstrated to be a selective fluorescent sensor for mercury. Stoichiometries of the formed complexes and complexation constants have been determined by titration experiments. In addition, the extractant ability of some ligands has also been studied. Finally, the electrochemical properties of some of these ligands are also described.
Quantitative characterization of the global electrophilicity power of common diene/dienophile pairs in Diels–Alder reactions
2002
Abstract The global electrophilicity power, ω, of a series of dienes and dienophiles commonly used in Diels–Alder reactions may be conveniently classified within a unique relative scale. Useful information about the polarity of transition state structures expected for a given reaction may be obtained from the difference in the global electrophilicity power, Δω, of the diene/dienophile interacting pair. Thus the polarity of the process can be related with non-polar (Δω small, pericyclic processes) and polar (Δω big, ionic processes) mechanisms.
A DFT study of the role of the Mg complex formation on the mechanism of the 1,3-dipolar cycloadditions of benzonitrile oxides with acryloylpyrazolidi…
2010
Abstract The role of the Mg complex formation on the mechanism, the reaction rate and regioselectivity of the 1,3-dipolar cycloaddition (13DC) reactions of benzonitrile oxides (BNOs) towards electron-deficient acryloylpyrazolidinones has been theoretically studied using DFT methods at the 6-31G* level. These 13DC reactions have asynchronous concerted mechanism with a non-polar character. These cycloadditions present a slight 5-regioselectivity induced by a steric repulsion between the phenyl substituent of the BNOs and the pyrazolidinone appendage present on the acryloyl derivative, which increases with the formation of the bulky Mg–acryloylpyrazolidinone complex. The present DFT study poin…
Theoretical study on the mechanism of the domino reactions of tertiary α-cyano-enamines and dimethyl acetylenedicarboxylate
2001
Abstract The mechanisms of the domino reaction between dimethyl acetylenedicarboxylate, 1 , and 2-( N , N -dimethylamino)acrylonitrile, 2 , and these in presence of acrylonitrile have been theoretically studied using ab initio methods. These domino reactions comprise several pericyclic-type reactions. The geometrical and electronic analysis of the HF/6-31G ∗ transition structures and intermediates allows characterizing the processes that take place along these domino reactions. B3LYP/6-31G ∗ energetic results are in agreement with the experimental outcomes.
Quantitative Characterization of the Local Electrophilicity of Organic Molecules. Understanding the Regioselectivity on Diels−Alder Reactions
2002
Regional electrophilicity at the active sites of the reagents involved in polar Diels−Alder processes may be described on a quantitative basis using an extension of the global electrophilicity inde...
Quantitative characterization of the global electrophilicity pattern of some reagents involved in 1,3-dipolar cycloaddition reactions
2003
Abstract The global electrophilicity power, ω, of a series of dipoles and dipolarophiles commonly used in 1,3-dipolar cycloadditions may be conveniently classified within a unique relative scale. The effects of chemical substitution on the electrophilicity of molecules have been evaluated using a representative set of electron-withdrawing and electron-releasing groups for a series of dipoles including nitrone, nitrile oxide and azide derivatives. The absolute scale of electrophilicity is used to rationalize the chemical reactivity of these species as compared to the static reactivity pattern of the reagents involved in the Diels–Alder reactions.
Cation and anion fluorescent and electrochemical sensors derived from 4,4′-substituted biphenyl
2005
Five new fluorescent macrocyclic ligands derived from biphenyl are described. These new compounds can be used in cation and anion recognition and sensing. Their fluorescent and electrochemical properties are studied and the influence of the biphenyl conformation on these properties is considered. The X-ray single crystal structure of one of the described ligands has been determined.
The role of the trifluoromethyl group in reactivity and selectivity in polar cycloaddition reactions. A DFT study
2012
Abstract The role of the trifluoromethyl group in reactivity, regio-, and stereoselectivity in cycloaddition reactions has been analyzed by studying the 1,3-dipolar cycloaddition (13DC) reactions of nitrone 4 with 3,3,3-trifluoro-1-nitropropene 7b and 3,3,3-trifluoro-2-nitropropene 14 using density functional theory (DFT) methods at the B3LYP/6-311G(d) level. The recent M06-2X functional has also been evaluated but, although the thermodynamic performance is improved, the kinetic data are not necessarily better than those obtained by the popular B3LYP functional for cycloaddition reactions. Four reactive channels associated with the meta and ortho regio- and endo and exo stereoselective appr…
Experimental and theoretical push-pull Chemo- and regioselectivity in 1,3-Dipolar cycloaddition reactions: the case of benzotriazepin-5-one with mesi…
2007
A novel heterocyclic compound 3-mesityl-5-methyl-4,5,11,11a-tetrahydro-6H-[1,2,4]oxadiazolo [5,4-b][1,3,4]benzotriazepin-6-one 4 has been synthesised by a 1,3 dipolar cycloaddition (13DC) reaction of 1,3,4-benzotriazepin-5-one 1 with mesitylnitrile oxide 3. The reaction, beside its synthetic interest, has shown to be completely chemo- and regioselective. The structure of the compound was determined by X-ray crystallography and analysed by spectral methods (NMR and mass spectrometry). The molecular mechanism for the reaction has been studied using quantum mechanical calculations at the B3LYP/6-31G* theory level. Two mechanisms are possible for the formation of the cycloadduct 4. The first on…
Theoretical study of the regio- and stereoselectivity of the intramolecular Povarov reactions yielding 5H-chromeno[2,3-c] acridine derivatives
2016
The intramolecular Povarov (IMP) reactions involved in the synthesis of 5H-chromeno[2,3-c] acridine derivatives [Tetrahedron Lett., 2010, 51, 3071–3074] have been studied using density functional theory (DFT) methods. The studied IMP reaction is a domino process that comprises two consecutive reactions: (i) a BF3 Lewis acid catalysed intramolecular aza-Diels–Alder (IMADA) reaction of an alkene tethered chromene imine (ATCI) giving a formal [4 + 2] cycloadduct, and (ii) a 1,3-hydrogen shift yielding the final chromeno product. The possible regio-(fused/bridged) and stereo-(cis/trans) isomeric channels associated with the IMADA reaction were thoroughly investigated and analysed. The activatio…
Understanding the Bond Formation in Hetero Diels-Alder Reactions. An ELF Analysis of the Reaction of Nitroethylene with Dimethylvinylamine
2012
[EN] The bonding evolution in hetero-Diels-Alder (HDA) reactions has been studied by an ELF analysis of the electron reorganization along the HDA reaction between nitroethylene 6 and dimethylvinylamine (DMVA) 9 at the B3LYP/6-31G* level. This cycloaddition takes place along a two-stages one-step mechanism. In the first stage of the reaction, the C1-C6 bond is formed by coupling of two pseudoradical centers positioned at the most electrophilic carbon of nitroethylene 6 and the most nucleophilic center of DMVA 9. In the second stage, the formation of the second O4-C7 bond takes place between a pseudoradical center positioned at the C7 carbon of DMVA and some electron-density provided by the l…
Density Functional Theory Study of the Cycloaddition Reaction of Furan Derivatives with Masked o-Benzoquinones. Does the Furan Act as a Dienophile in…
2002
The molecular mechanism for the cycloaddition reaction between 2-methylfuran and a masked o-benzoquinone has been characterized using quantum mechanical calculations at the B3LYP/6-31G theory level. An analysis of the results on the reaction pathway shows that the reaction takes place along a polar stepwise mechanism. The first and rate-determining step corresponds to the nucleophilic attack of the furan ring on the doubly conjugated position of the 2,4-dienone system present at the masked o-benzoquinone to give a zwitterionic intermediate. Closure of this intermediate affords the formally [2 + 4] cycloadduct. For the second step two reactive channels have been characterized corresponding t…
A DFT Characterization of the Mechanism for the Cycloaddition Reaction between 2-Methylfuran and Acetylenedicarboxylic Acid
1999
The molecular mechanism for the cycloaddition reaction between 2-methylfuran and acetylenedicarboxylic acid (ADA) has been characterized using density functional theory methods at the B3LYP/6-31+G* theory level. An analysis of the results on the reaction pathway shows that the reaction takes place along a stepwise mechanism. The initial step corresponds to the nucleophilic attack of the C5 position of the furan ring to one carbon atom of the conjugated acetylenic system of ADA to give a zwitterionic intermediate. Closure of this intermediate along the nucleophilic attack of the other acetylenic carbon to the substituted C2 position of the furan ring affords the Diels−Alder cycloadduct. Alth…
Understanding the mechanism of the N-heterocyclic carbene-catalyzed ring-expansion of 4-formyl-β-lactams to succinimide derivatives
2009
The mechanism of the N-heterocyclic carbene (NHC)-catalyzed ring-expansion of 4-formyl-β-lactams to succinimides has been studied using DFT methods at the B3LYP/6-31G∗∗ level. The first step is the nucleophilic attack of NHC to the aldehyde to yield the zwitterionic intermediate, which by a proton-transfer process affords the Breslow intermediate. The lactam N–C breaking bond in this intermediate yields an enol-amidate, which by a keto–enol type equilibrium becomes the ketone form. The subsequent ring-closure achieved by the nucleophilic attack of the amidate to carbonyl carbon allows the formation of the five-membered ring. Finally, elimination of NHC affords the succinimide. Analysis of t…