The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Pierluigi Caramella - One of the best experts on this subject based on the ideXlab platform.
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A Straightforward Synthesis of Isoxazoline‐Based Carbocyclic Nucleosides from 1,3‐Cyclohexadiene through Nitrosocarbonyl Chemistry
European Journal of Organic Chemistry, 2007Co-Authors: Paolo Quadrelli, Mariella Mella, Serena Carosso, Bruna Bovio, Pierluigi CaramellaAbstract:3-Benzoyl-2-oxa-3-azabicyclo[2.2.2]oct-5-ene undergoes cycloaddition with Benzonitrile Oxide to afford a mixture of syn and anti regioisomeric cycloadducts. The anti cycloadducts were easily elaborated to stereodefined isoxazoline-based carbocyclic aminols that serve as synthons for the linear construction of purine nucleosides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
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Cycloaddition of Benzonitrile Oxide to pyridazine, pyrimidine and pyrazine
Tetrahedron, 1996Co-Authors: Antonino Corsaro, G. Perrini, Venerando Pistarà, Paolo Quadrelli, Anna Gamba Invernizzi, Pierluigi CaramellaAbstract:Abstract Cycloaddition of Benzonitrile Oxide to pyridazine affords an isolable mono-cycloadduct. In cycloadditions to pyrimidine and pyrazine the primary mono-cycloadducts are labile intermediates which undergo further cycloaddition affording isolable bis- and tris-cycloadducts.
Gabriele Wagner - One of the best experts on this subject based on the ideXlab platform.
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quantum chemical study of the lewis acid influence on the cycloaddition of Benzonitrile Oxide to acetonitrile propyne and propene
Tetrahedron, 2007Co-Authors: Gabriele Wagner, Timothy N Danks, Vincenzo VulloAbstract:Abstract Quantum chemical methods (MP2 and B3LYP) together with a topological analysis of the charge density have been used to study the BH 3 - or BF 3 -mediated reaction of Benzonitrile Oxide with acetonitrile, propyne and propene. In the reaction with propene or propyne, addition of Lewis acids has only little influence on the outcome of the reactions. The cycloaddition of nitrile Oxides with nitriles, however, is generally promoted by strong Lewis acids. When the Lewis acid coordination takes place at the nitrile Oxide the reactant is activated and the product binds weakly to the Lewis acid so that the reaction is expected to be catalytic. In the case of coordination to the nitrile the reaction is Lewis acid mediated. Here the reactant is not much influenced by addition of Lewis acid, but the transition state and the product are stabilised and consequently such processes require a stoichiometric amount of Lewis acid and form a stable Lewis acid–product complex. It has also been demonstrated that the different activation routes for these reactions involve different reaction mechanisms. Whereas the reaction of a Lewis acid coordinated nitrile Oxide is of ‘inverse electron demand’, the Lewis acid coordinated nitrile reacts through a ‘normal electron demand’ cycloaddition.
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cycloaddition of Benzonitrile Oxide to acetonitrile propyne and propene a comparative theoretical study of the reaction mechanism and regioselectivity
European Journal of Organic Chemistry, 2004Co-Authors: Vincenzo Vullo, Timothy N Danks, Gabriele WagnerAbstract:Quantum chemical calculations (MP2/6-31G* and B3LYP/6-31G*) were used to compare the reactivity, regioselectivity and orbital involvement of the reaction of Benzonitrile Oxide with the dipolarophiles acetonitrile, propyne and propene. All reactions are thermodynamically favoured. The product stability decreases in an order propyne > acetonitrile > propene, and reflects the degree of aromatic stabilisation of the product. The activation barriers depend strongly on the computational method used and decrease in the expected order of increasing reactivity (acetonitrile > propyne > propene) in the MP2 calculations, but are similar to each other when B3LYP is applied. The regiochemistry is correctly predicted for all reactions and the experimentally observed regioisomer is both thermodynamically and kinetically favoured. The transition state geometries indicate that, in some of the reactions, the Benzonitrile Oxide does not interact through its frontier orbitals, as traditionally assumed. Instead, the FMO±2 are involved in the reaction, indicating that the classical FMO concept should be applied with care as it might lead to wrong conclusions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
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Cycloaddition of Benzonitrile Oxide to Acetonitrile, Propyne and Propene − A Comparative Theoretical Study of the Reaction Mechanism and Regioselectivity
European Journal of Organic Chemistry, 2004Co-Authors: Vincenzo Vullo, Timothy N Danks, Gabriele WagnerAbstract:Quantum chemical calculations (MP2/6-31G* and B3LYP/6-31G*) were used to compare the reactivity, regioselectivity and orbital involvement of the reaction of Benzonitrile Oxide with the dipolarophiles acetonitrile, propyne and propene. All reactions are thermodynamically favoured. The product stability decreases in an order propyne > acetonitrile > propene, and reflects the degree of aromatic stabilisation of the product. The activation barriers depend strongly on the computational method used and decrease in the expected order of increasing reactivity (acetonitrile > propyne > propene) in the MP2 calculations, but are similar to each other when B3LYP is applied. The regiochemistry is correctly predicted for all reactions and the experimentally observed regioisomer is both thermodynamically and kinetically favoured. The transition state geometries indicate that, in some of the reactions, the Benzonitrile Oxide does not interact through its frontier orbitals, as traditionally assumed. Instead, the FMO±2 are involved in the reaction, indicating that the classical FMO concept should be applied with care as it might lead to wrong conclusions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Paolo Quadrelli - One of the best experts on this subject based on the ideXlab platform.
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doi:10.1100/2012/643647 The cientificWorldJOURNAL Research Article The Chemoselective Reduction of Isoxazoline γ-Lactams Through Iminium Aza-Diels-Alder Reactions: A Short-Cut Synthesis of Aminols as Valuable Intermediates towards Nucleoside Derivati
2016Co-Authors: Mariella Mella, Paolo QuadrelliAbstract:License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Isoxazoline γ-lactams are prepared starting from the regioisomeric cycloadducts of Benzonitrile Oxide to the N-alkyl 2-azanorbornenes taking advantage of the efficient catalytic oxidation by RuO4. The reduction of the amide groups is easily conducted in the presence of LiAlH4 under mild conditions, which allowed for the chemoselective reduction of the amide moiety followed by ring opening to afford the desired conformationally locked isoxazoline-carbocyclic aminols, as valuable intermediates for nucleoside synthesis. 1
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The Chemoselective Reduction of Isoxazoline γ-Lactams Through Iminium Aza-Diels-Alder Reactions: A Short-Cut Synthesis of Aminols as Valuable Intermediates towards Nucleoside Derivatives
TheScientificWorldJournal, 2012Co-Authors: Misal Giuseppe Memeo, Mariella Mella, Paolo QuadrelliAbstract:Isoxazoline γ-lactams are prepared starting from the regioisomeric cycloadducts of Benzonitrile Oxide to the N-alkyl 2-azanorbornenes taking advantage of the efficient catalytic oxidation by RuO4. The reduction of the amide groups is easily conducted in the presence of LiAlH4 under mild conditions, which allowed for the chemoselective reduction of the amide moiety followed by ring opening to afford the desired conformationally locked isoxazoline-carbocyclic aminols, as valuable intermediates for nucleoside synthesis.
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From 1,3-cyclohexadiene through nitrosocarbonyl chemistry, the synthesis of pyrimidine isoxazoline-carbocyclic nucleosides
Tetrahedron, 2008Co-Authors: Paolo Quadrelli, Mariella Mella, Giulio Assanelli, Andrea PiccanelloAbstract:Abstract N -Benzoyl-2-oxa-3-azabicyclo[2.2.2]oct-5-ene undergoes cycloaddition with Benzonitrile Oxide affording a mixture of syn and anti regioisomeric cycloadducts. The anti cycloadducts were easily elaborated to stereodefined isoxazoline-carbocyclic aminols that served as synthons for the linear construction of pyrimidine nucleosides, while the syn cycloadducts do not enter the same synthetic route.
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A Straightforward Synthesis of Isoxazoline‐Based Carbocyclic Nucleosides from 1,3‐Cyclohexadiene through Nitrosocarbonyl Chemistry
European Journal of Organic Chemistry, 2007Co-Authors: Paolo Quadrelli, Mariella Mella, Serena Carosso, Bruna Bovio, Pierluigi CaramellaAbstract:3-Benzoyl-2-oxa-3-azabicyclo[2.2.2]oct-5-ene undergoes cycloaddition with Benzonitrile Oxide to afford a mixture of syn and anti regioisomeric cycloadducts. The anti cycloadducts were easily elaborated to stereodefined isoxazoline-based carbocyclic aminols that serve as synthons for the linear construction of purine nucleosides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
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Cycloaddition of Benzonitrile Oxide to pyridazine, pyrimidine and pyrazine
Tetrahedron, 1996Co-Authors: Antonino Corsaro, G. Perrini, Venerando Pistarà, Paolo Quadrelli, Anna Gamba Invernizzi, Pierluigi CaramellaAbstract:Abstract Cycloaddition of Benzonitrile Oxide to pyridazine affords an isolable mono-cycloadduct. In cycloadditions to pyrimidine and pyrazine the primary mono-cycloadducts are labile intermediates which undergo further cycloaddition affording isolable bis- and tris-cycloadducts.
Mohammad Izadyar - One of the best experts on this subject based on the ideXlab platform.
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The origin of regio- and stereoselectivity in the 1,3-dipolar cycloaddition of nitrile Oxides with C1-substituted 7-oxabenzonorbornadienes, a DFT study
RSC Advances, 2015Co-Authors: Javad Tajabadi, Mehdi Bakavoli, Mostafa Gholizadeh, Hossein Eshghi, Mohammad IzadyarAbstract:In this computational study, density functional theory (DFT) calculations were performed in order to achieve a deep understanding of the regio- and stereoselectivity of 1,3-dipolar cycloadditions (1,3-DC) of C1-substituted 7-oxabenzonorbornadienes (OBNDs) (2a–2d) with acetonitrile Oxide (1a) and Benzonitrile Oxide (1b). The potential energy surface analysis, Wiberg bond orders (BOs) and global electron density transfer (GEDT) at the transition states (TSs) show that these cycloadditions take place through a low asynchronous one-step mechanism with non-polar character. Mechanism studies show that these reactions are exo-stereoselective and anti-regioselective (3X) and classified as (pseudodiradical) pr-type 1,3-DC reactions. These results are in excellent agreement with the experimental observations. A distortion-interaction model has been used successfully for understanding regio- and stereoselectivity in these reactions.
Vincenzo Vullo - One of the best experts on this subject based on the ideXlab platform.
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quantum chemical study of the lewis acid influence on the cycloaddition of Benzonitrile Oxide to acetonitrile propyne and propene
Tetrahedron, 2007Co-Authors: Gabriele Wagner, Timothy N Danks, Vincenzo VulloAbstract:Abstract Quantum chemical methods (MP2 and B3LYP) together with a topological analysis of the charge density have been used to study the BH 3 - or BF 3 -mediated reaction of Benzonitrile Oxide with acetonitrile, propyne and propene. In the reaction with propene or propyne, addition of Lewis acids has only little influence on the outcome of the reactions. The cycloaddition of nitrile Oxides with nitriles, however, is generally promoted by strong Lewis acids. When the Lewis acid coordination takes place at the nitrile Oxide the reactant is activated and the product binds weakly to the Lewis acid so that the reaction is expected to be catalytic. In the case of coordination to the nitrile the reaction is Lewis acid mediated. Here the reactant is not much influenced by addition of Lewis acid, but the transition state and the product are stabilised and consequently such processes require a stoichiometric amount of Lewis acid and form a stable Lewis acid–product complex. It has also been demonstrated that the different activation routes for these reactions involve different reaction mechanisms. Whereas the reaction of a Lewis acid coordinated nitrile Oxide is of ‘inverse electron demand’, the Lewis acid coordinated nitrile reacts through a ‘normal electron demand’ cycloaddition.
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cycloaddition of Benzonitrile Oxide to acetonitrile propyne and propene a comparative theoretical study of the reaction mechanism and regioselectivity
European Journal of Organic Chemistry, 2004Co-Authors: Vincenzo Vullo, Timothy N Danks, Gabriele WagnerAbstract:Quantum chemical calculations (MP2/6-31G* and B3LYP/6-31G*) were used to compare the reactivity, regioselectivity and orbital involvement of the reaction of Benzonitrile Oxide with the dipolarophiles acetonitrile, propyne and propene. All reactions are thermodynamically favoured. The product stability decreases in an order propyne > acetonitrile > propene, and reflects the degree of aromatic stabilisation of the product. The activation barriers depend strongly on the computational method used and decrease in the expected order of increasing reactivity (acetonitrile > propyne > propene) in the MP2 calculations, but are similar to each other when B3LYP is applied. The regiochemistry is correctly predicted for all reactions and the experimentally observed regioisomer is both thermodynamically and kinetically favoured. The transition state geometries indicate that, in some of the reactions, the Benzonitrile Oxide does not interact through its frontier orbitals, as traditionally assumed. Instead, the FMO±2 are involved in the reaction, indicating that the classical FMO concept should be applied with care as it might lead to wrong conclusions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
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Cycloaddition of Benzonitrile Oxide to Acetonitrile, Propyne and Propene − A Comparative Theoretical Study of the Reaction Mechanism and Regioselectivity
European Journal of Organic Chemistry, 2004Co-Authors: Vincenzo Vullo, Timothy N Danks, Gabriele WagnerAbstract:Quantum chemical calculations (MP2/6-31G* and B3LYP/6-31G*) were used to compare the reactivity, regioselectivity and orbital involvement of the reaction of Benzonitrile Oxide with the dipolarophiles acetonitrile, propyne and propene. All reactions are thermodynamically favoured. The product stability decreases in an order propyne > acetonitrile > propene, and reflects the degree of aromatic stabilisation of the product. The activation barriers depend strongly on the computational method used and decrease in the expected order of increasing reactivity (acetonitrile > propyne > propene) in the MP2 calculations, but are similar to each other when B3LYP is applied. The regiochemistry is correctly predicted for all reactions and the experimentally observed regioisomer is both thermodynamically and kinetically favoured. The transition state geometries indicate that, in some of the reactions, the Benzonitrile Oxide does not interact through its frontier orbitals, as traditionally assumed. Instead, the FMO±2 are involved in the reaction, indicating that the classical FMO concept should be applied with care as it might lead to wrong conclusions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)