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Silvestre Buscemi - One of the best experts on this subject based on the ideXlab platform.
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Rearrangements of 1,2,4-Oxadiazole: “One Ring to Rule Them All”
Chemistry of Heterocyclic Compounds, 2017Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre BuscemiAbstract:1,2,4-Oxadiazoles are heterocycles characterized by low aromaticity and the presence of a weak O–N bond and are widely studied due to their tendency to rearrange into more stable heterocyclic compounds. This review covers literature from the last fifteen years, highlighting the general features of 1,2,4-oxadiazoles and their applications. Regarding the reactivity, the development of classical reactions (thermal and photochemical Rearrangements) is presented in terms of synthetic utility and mechanistic insight. Among the relevant Rearrangement reactions, the Boulton–Katritzky Rearrangement (BKR), Migration – Nucleophilic Attack – Cyclization (MNAC), and Addition of the Nucleophile, Ring Opening, and Ring Closure (ANRORC) reactions are discussed, together with recent noteworthy syntheses and applications of the 1,2,4-oxadiazole ring.
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Synthesis of Isoxazoline Derivatives Through Boulton—Katritzky Rearrangement of 1,2,4-Oxadiazoles.
ChemInform, 2013Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Annalisa Guarcello, Silvestre BuscemiAbstract:This is the first report of the Rearrangement of 1,2,4-oxadiazole with saturated C—C—O side chains and an unusual example of an irreversible Rearrangement that allows the formation of nonaromatic heterocycles.
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Synthesis of Isoxazoline Derivatives through Boulton–Katritzky Rearrangement of 1,2,4-Oxadiazoles
European Journal of Organic Chemistry, 2013Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Annalisa Guarcello, Silvestre BuscemiAbstract:The base-induced Rearrangement of 1,2,4-oxadiazoles into isoxazoline derivatives is reported. This represents the first example of a three-atom side-chain Rearrangement that involves a saturated CCO side chain at C-3 of the oxadiazole. Nonaromatic 3-amino-isoxazoline derivatives are obtained in good yields. Interestingly, this reaction occurs through the Rearrangement of aromatic oxadiazoles to form less stable bonds than those that are broken.
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Synthesis of fluorinated 1,2,4-oxadiazin-6-ones through ANRORC Rearrangement of 1,2,4-oxadiazoles
Tetrahedron Letters, 2009Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre Buscemi, Nicolò Vivona, Gianluca GiorgiAbstract:Abstract The reaction of 3-ethoxycarbonyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydroxylamines has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of hydroxylamine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring-opening and ring-closure with enlargement, leads to high yield and in very mild experimental conditions to the formation of 5-hydroxyamino-3-perfluoroalkyl-6 H -1,2,4-oxadiazin-6-ones, one of these presenting water gelation ability. In turn, reactions with N -methylhydroxylamine lead the exclusive formation of 4-perfluoroacylamino-2-methyl-2 H -1,2,5-oxadiazol-3-ones through the well known Boulton–Katritzky Rearrangement.
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Synthesis of trifluoromethylated 2-benzoyl-and 2-aminoimidazoles from ring Rearrangement of 1,2,4-oxadiazole derivatives
Tetrahedron, 2008Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre Buscemi, Nicolò Vivona, M. PaniAbstract:Abstract Fluoroalkylated 2-ylamino-imidazoles have been synthesized by reaction of 3-amino-5-phenyl-1,2,4-oxadiazole with fluorinated β-dicarbonyl compounds and subsequent base-induced Boulton–Katritzky Rearrangement (BKR) of the isolated β-enaminocarbonyl intermediate. Alternatively, one-pot reactions performed in the presence of Montmorillonite K10 favoured the condensation at the 3-amino moiety of the oxadiazole and, in some cases, allowed the direct synthesis of 2-benzoylamino-imidazoles. Hydrolysis of 2-benzoylamino-imidazoles easily yielded fluorinated 2-amino-imidazoles targets.
Antonio Palumbo Piccionello - One of the best experts on this subject based on the ideXlab platform.
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Unexpected Substituent Effects in the Iso-Heterocyclic Boulton-Katritzky Rearrangement of 3-Aroylamino-5-Methyl-1,2,4-Oxadiazoles: a Mechanistic Study
The journal of physical chemistry. A, 2019Co-Authors: Vincenzo Frenna, Antonio Palumbo Piccionello, Paolo Lo Meo, Domenico SpinelliAbstract:The kinetics of the iso-heterocyclic mononuclear Rearrangement of some 3-aroylamino-5-methyl-1,2,4-ozadiazoles was carefully examined under largely variable acidic or alkaline conditions. This reaction may proceed via two different mechanistic pathways (an uncatalyzed and a base-catalyzed one), as accounted for also by the evaluation of the relevant activation parameters. Substituent effects, as quantified by means of the Hammett’s equation, appear relatively modest; however, they reveal some interesting anomalies, which enabled us to draw a very precise picture of the intimate reaction course.
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Rearrangements of 1,2,4-Oxadiazole: “One Ring to Rule Them All”
Chemistry of Heterocyclic Compounds, 2017Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre BuscemiAbstract:1,2,4-Oxadiazoles are heterocycles characterized by low aromaticity and the presence of a weak O–N bond and are widely studied due to their tendency to rearrange into more stable heterocyclic compounds. This review covers literature from the last fifteen years, highlighting the general features of 1,2,4-oxadiazoles and their applications. Regarding the reactivity, the development of classical reactions (thermal and photochemical Rearrangements) is presented in terms of synthetic utility and mechanistic insight. Among the relevant Rearrangement reactions, the Boulton–Katritzky Rearrangement (BKR), Migration – Nucleophilic Attack – Cyclization (MNAC), and Addition of the Nucleophile, Ring Opening, and Ring Closure (ANRORC) reactions are discussed, together with recent noteworthy syntheses and applications of the 1,2,4-oxadiazole ring.
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Synthesis of Isoxazoline Derivatives Through Boulton—Katritzky Rearrangement of 1,2,4-Oxadiazoles.
ChemInform, 2013Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Annalisa Guarcello, Silvestre BuscemiAbstract:This is the first report of the Rearrangement of 1,2,4-oxadiazole with saturated C—C—O side chains and an unusual example of an irreversible Rearrangement that allows the formation of nonaromatic heterocycles.
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Synthesis of Isoxazoline Derivatives through Boulton–Katritzky Rearrangement of 1,2,4-Oxadiazoles
European Journal of Organic Chemistry, 2013Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Annalisa Guarcello, Silvestre BuscemiAbstract:The base-induced Rearrangement of 1,2,4-oxadiazoles into isoxazoline derivatives is reported. This represents the first example of a three-atom side-chain Rearrangement that involves a saturated CCO side chain at C-3 of the oxadiazole. Nonaromatic 3-amino-isoxazoline derivatives are obtained in good yields. Interestingly, this reaction occurs through the Rearrangement of aromatic oxadiazoles to form less stable bonds than those that are broken.
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Synthesis of fluorinated 1,2,4-oxadiazin-6-ones through ANRORC Rearrangement of 1,2,4-oxadiazoles
Tetrahedron Letters, 2009Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre Buscemi, Nicolò Vivona, Gianluca GiorgiAbstract:Abstract The reaction of 3-ethoxycarbonyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydroxylamines has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of hydroxylamine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring-opening and ring-closure with enlargement, leads to high yield and in very mild experimental conditions to the formation of 5-hydroxyamino-3-perfluoroalkyl-6 H -1,2,4-oxadiazin-6-ones, one of these presenting water gelation ability. In turn, reactions with N -methylhydroxylamine lead the exclusive formation of 4-perfluoroacylamino-2-methyl-2 H -1,2,5-oxadiazol-3-ones through the well known Boulton–Katritzky Rearrangement.
Andrea Pace - One of the best experts on this subject based on the ideXlab platform.
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Rearrangements of 1,2,4-Oxadiazole: “One Ring to Rule Them All”
Chemistry of Heterocyclic Compounds, 2017Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre BuscemiAbstract:1,2,4-Oxadiazoles are heterocycles characterized by low aromaticity and the presence of a weak O–N bond and are widely studied due to their tendency to rearrange into more stable heterocyclic compounds. This review covers literature from the last fifteen years, highlighting the general features of 1,2,4-oxadiazoles and their applications. Regarding the reactivity, the development of classical reactions (thermal and photochemical Rearrangements) is presented in terms of synthetic utility and mechanistic insight. Among the relevant Rearrangement reactions, the Boulton–Katritzky Rearrangement (BKR), Migration – Nucleophilic Attack – Cyclization (MNAC), and Addition of the Nucleophile, Ring Opening, and Ring Closure (ANRORC) reactions are discussed, together with recent noteworthy syntheses and applications of the 1,2,4-oxadiazole ring.
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Synthesis of Isoxazoline Derivatives Through Boulton—Katritzky Rearrangement of 1,2,4-Oxadiazoles.
ChemInform, 2013Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Annalisa Guarcello, Silvestre BuscemiAbstract:This is the first report of the Rearrangement of 1,2,4-oxadiazole with saturated C—C—O side chains and an unusual example of an irreversible Rearrangement that allows the formation of nonaromatic heterocycles.
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Synthesis of Isoxazoline Derivatives through Boulton–Katritzky Rearrangement of 1,2,4-Oxadiazoles
European Journal of Organic Chemistry, 2013Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Annalisa Guarcello, Silvestre BuscemiAbstract:The base-induced Rearrangement of 1,2,4-oxadiazoles into isoxazoline derivatives is reported. This represents the first example of a three-atom side-chain Rearrangement that involves a saturated CCO side chain at C-3 of the oxadiazole. Nonaromatic 3-amino-isoxazoline derivatives are obtained in good yields. Interestingly, this reaction occurs through the Rearrangement of aromatic oxadiazoles to form less stable bonds than those that are broken.
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Synthesis of fluorinated 1,2,4-oxadiazin-6-ones through ANRORC Rearrangement of 1,2,4-oxadiazoles
Tetrahedron Letters, 2009Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre Buscemi, Nicolò Vivona, Gianluca GiorgiAbstract:Abstract The reaction of 3-ethoxycarbonyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydroxylamines has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of hydroxylamine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring-opening and ring-closure with enlargement, leads to high yield and in very mild experimental conditions to the formation of 5-hydroxyamino-3-perfluoroalkyl-6 H -1,2,4-oxadiazin-6-ones, one of these presenting water gelation ability. In turn, reactions with N -methylhydroxylamine lead the exclusive formation of 4-perfluoroacylamino-2-methyl-2 H -1,2,5-oxadiazol-3-ones through the well known Boulton–Katritzky Rearrangement.
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Synthesis of trifluoromethylated 2-benzoyl-and 2-aminoimidazoles from ring Rearrangement of 1,2,4-oxadiazole derivatives
Tetrahedron, 2008Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre Buscemi, Nicolò Vivona, M. PaniAbstract:Abstract Fluoroalkylated 2-ylamino-imidazoles have been synthesized by reaction of 3-amino-5-phenyl-1,2,4-oxadiazole with fluorinated β-dicarbonyl compounds and subsequent base-induced Boulton–Katritzky Rearrangement (BKR) of the isolated β-enaminocarbonyl intermediate. Alternatively, one-pot reactions performed in the presence of Montmorillonite K10 favoured the condensation at the 3-amino moiety of the oxadiazole and, in some cases, allowed the direct synthesis of 2-benzoylamino-imidazoles. Hydrolysis of 2-benzoylamino-imidazoles easily yielded fluorinated 2-amino-imidazoles targets.
Nicolò Vivona - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of fluorinated 1,2,4-oxadiazin-6-ones through ANRORC Rearrangement of 1,2,4-oxadiazoles
Tetrahedron Letters, 2009Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre Buscemi, Nicolò Vivona, Gianluca GiorgiAbstract:Abstract The reaction of 3-ethoxycarbonyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydroxylamines has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of hydroxylamine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring-opening and ring-closure with enlargement, leads to high yield and in very mild experimental conditions to the formation of 5-hydroxyamino-3-perfluoroalkyl-6 H -1,2,4-oxadiazin-6-ones, one of these presenting water gelation ability. In turn, reactions with N -methylhydroxylamine lead the exclusive formation of 4-perfluoroacylamino-2-methyl-2 H -1,2,5-oxadiazol-3-ones through the well known Boulton–Katritzky Rearrangement.
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Synthesis of trifluoromethylated 2-benzoyl-and 2-aminoimidazoles from ring Rearrangement of 1,2,4-oxadiazole derivatives
Tetrahedron, 2008Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre Buscemi, Nicolò Vivona, M. PaniAbstract:Abstract Fluoroalkylated 2-ylamino-imidazoles have been synthesized by reaction of 3-amino-5-phenyl-1,2,4-oxadiazole with fluorinated β-dicarbonyl compounds and subsequent base-induced Boulton–Katritzky Rearrangement (BKR) of the isolated β-enaminocarbonyl intermediate. Alternatively, one-pot reactions performed in the presence of Montmorillonite K10 favoured the condensation at the 3-amino moiety of the oxadiazole and, in some cases, allowed the direct synthesis of 2-benzoylamino-imidazoles. Hydrolysis of 2-benzoylamino-imidazoles easily yielded fluorinated 2-amino-imidazoles targets.
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Experimental and DFT studies on competitive heterocyclic Rearrangements. Part 2: a one-atom side-chain versus the classic three-atom side-chain (Boulton-Katritzky) ring Rearrangement of 3-acylamino-1,2,4-oxadiazoles.
The Journal of organic chemistry, 2007Co-Authors: Andrea Pace, Antonio Palumbo Piccionello, Silvestre Buscemi, Nicolò Vivona, Ivana Pibiri, Giampaolo BaroneAbstract:The experimental investigation of the base-catalyzed Rearrangements of 3-acylamino-1,2,4-oxadiazoles evidenced a new reaction pathway which competes with the well-known ring-degenerate Boulton-Katritzky Rearrangement (BKR). The new reaction consists of a one-atom side-chain Rearrangement that is base-activated, occurs at a higher temperature than the BKR, and irreversibly leads to the corresponding 2-acylamino-1,3,4-oxadiazoles. An extensive DFT study is reported to elucidate the proposed reaction mechanism and to compare the three possible inherent routes: (i) the reversible three-atom side-chain ring-degenerate BKR, (ii) the ring contraction-ring expansion route (RCRE), and (iii) the one-atom side-chain Rearrangement. The results of the computational investigation point out that the latter route is kinetically preferred over the RCRE and can be considered as the ground-state analogue of a previously proposed C(3)-N(2) migration-nucleophilic attack-cyclization (MNAC) photochemically activated pathway. The MNAC consists of the formation of a diazirine intermediate, involving the exocyclic nitrogen, that eventually evolves into a carbodiimide intermediate (migration); the latter undergoes a single intramolecular nucleophilic attack-cyclization step leading to the final 2-acylamino-1,3,4-oxadiazole.
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five to six membered ring Rearrangements in the reaction of 5 perfluoroalkyl 1 2 4 oxadiazoles with hydrazine and methylhydrazine
Journal of Organic Chemistry, 2006Co-Authors: Silvestre Buscemi, Antonio Palumbo Piccionello, Andrea Pace, Nicolò Vivona, Gianluca Giorgi, Ivana Pibiri, Andrea Mazzanti, Domenico SpinelliAbstract:The hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine or methylhydrazine as bidentate nucleophiles has been investigated. The reaction occurred through the addition of the bidentate nucleophile to the C(5)−N(4) double bond of the 1,2,4-oxadiazole followed by ring-opening and ring-closure (ANRORC) involving the second nucleophilic site of the reagent. This ring-closure step could involve either the original C(3) of the 1,2,4-oxadiazole (giving a five-to-five membered ring Rearrangement) or an additional electrophilic center linked to it (exploiting a five-to-six membered ring Rearrangement). An alternative initial nucleophilic attack may involve the additional electrophilic center linked at C(3), that is the carbonyl group, leading to the formation of the hydrazones which undergo the Boulton−Katritzky Rearrangement (BKR). The chosen reaction path is a function of the used nucleophile and of the nature of the substituent at C(3). At variance with previous hypotheses, when methylhy...
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Fluorinated heterocyclic compounds. An effective strategy for the synthesis of fluorinated Z-oximes of 3-perfluoroalkyl-6-phenyl-2h-1,2,4-triazin-5-ones via a ring-enlargement reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles and hydrazine.
The Journal of organic chemistry, 2005Co-Authors: Silvestre Buscemi, Antonio Palumbo Piccionello, Andrea Pace, Nicolò Vivona, Gabriella Macaluso, Domenico Spinelli, Gianluca GiorgiAbstract:The reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of the hydrazine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring opening and ring closure with enlargement, leads with high yield and in very mild experimental conditions to the formation of Z-oximes of 3-perfluoroalkyl-6-phenyl-2H-1,2,4-triazin-5-ones (11a−c) as major products of the reaction. In turn, the hydrazine can attack the electrophilic carbonyl carbon giving 4-perfluoroacylamino-5-phenyl-2H-1,2,3-triazoles (13a−c) through the well-known Boulton−Katritzky Rearrangement of the intermediate hydrazones.
Gianluca Giorgi - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of fluorinated 1,2,4-oxadiazin-6-ones through ANRORC Rearrangement of 1,2,4-oxadiazoles
Tetrahedron Letters, 2009Co-Authors: Antonio Palumbo Piccionello, Andrea Pace, Silvestre Buscemi, Nicolò Vivona, Gianluca GiorgiAbstract:Abstract The reaction of 3-ethoxycarbonyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydroxylamines has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of hydroxylamine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring-opening and ring-closure with enlargement, leads to high yield and in very mild experimental conditions to the formation of 5-hydroxyamino-3-perfluoroalkyl-6 H -1,2,4-oxadiazin-6-ones, one of these presenting water gelation ability. In turn, reactions with N -methylhydroxylamine lead the exclusive formation of 4-perfluoroacylamino-2-methyl-2 H -1,2,5-oxadiazol-3-ones through the well known Boulton–Katritzky Rearrangement.
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five to six membered ring Rearrangements in the reaction of 5 perfluoroalkyl 1 2 4 oxadiazoles with hydrazine and methylhydrazine
Journal of Organic Chemistry, 2006Co-Authors: Silvestre Buscemi, Antonio Palumbo Piccionello, Andrea Pace, Nicolò Vivona, Gianluca Giorgi, Ivana Pibiri, Andrea Mazzanti, Domenico SpinelliAbstract:The hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine or methylhydrazine as bidentate nucleophiles has been investigated. The reaction occurred through the addition of the bidentate nucleophile to the C(5)−N(4) double bond of the 1,2,4-oxadiazole followed by ring-opening and ring-closure (ANRORC) involving the second nucleophilic site of the reagent. This ring-closure step could involve either the original C(3) of the 1,2,4-oxadiazole (giving a five-to-five membered ring Rearrangement) or an additional electrophilic center linked to it (exploiting a five-to-six membered ring Rearrangement). An alternative initial nucleophilic attack may involve the additional electrophilic center linked at C(3), that is the carbonyl group, leading to the formation of the hydrazones which undergo the Boulton−Katritzky Rearrangement (BKR). The chosen reaction path is a function of the used nucleophile and of the nature of the substituent at C(3). At variance with previous hypotheses, when methylhy...
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Fluorinated heterocyclic compounds. An effective strategy for the synthesis of fluorinated Z-oximes of 3-perfluoroalkyl-6-phenyl-2h-1,2,4-triazin-5-ones via a ring-enlargement reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles and hydrazine.
The Journal of organic chemistry, 2005Co-Authors: Silvestre Buscemi, Antonio Palumbo Piccionello, Andrea Pace, Nicolò Vivona, Gabriella Macaluso, Domenico Spinelli, Gianluca GiorgiAbstract:The reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of the hydrazine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring opening and ring closure with enlargement, leads with high yield and in very mild experimental conditions to the formation of Z-oximes of 3-perfluoroalkyl-6-phenyl-2H-1,2,4-triazin-5-ones (11a−c) as major products of the reaction. In turn, the hydrazine can attack the electrophilic carbonyl carbon giving 4-perfluoroacylamino-5-phenyl-2H-1,2,3-triazoles (13a−c) through the well-known Boulton−Katritzky Rearrangement of the intermediate hydrazones.