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Steven Fletcher - One of the best experts on this subject based on the ideXlab platform.
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one pot synthesis of 2 1 Benzisoxazoles anthranils by a stannous chloride mediated tandem reduction heterocyclization of 2 nitroacylbenzenes under neutral conditions
Tetrahedron Letters, 2012Co-Authors: Jay Chauhan, Steven FletcherAbstract:Abstract Classically, 2,1-Benzisoxazoles (anthranils) are prepared from 2-nitroacylbenzenes by a reductive heterocyclization reaction with Sn or SnCl 2 concentrated HCl. Acid sensitive functionalities are expected to be incompatible with these conditions; milder approaches to the synthesis of 2,1-Benzisoxazoles would be welcomed. We demonstrate that SnCl 2 ·2H 2 O in a 1:1 mixture of EtOAc/MeOH is capable of mediating the tandem reduction–heterocyclization of a variety of 2-nitroacylbenzenes to their corresponding 2,1-Benzisoxazoles in good to excellent yields under essentially neutral conditions. Importantly, several commonly used acid–labile protecting groups, including Boc carbamate, tert -butyl ether, and tert -butyl ester, proved orthogonal to these reaction conditions.
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One-pot synthesis of 2,1-Benzisoxazoles (anthranils) by a stannous chloride-mediated tandem reduction–heterocyclization of 2-nitroacylbenzenes under neutral conditions
Tetrahedron Letters, 2012Co-Authors: Jay Chauhan, Steven FletcherAbstract:Abstract Classically, 2,1-Benzisoxazoles (anthranils) are prepared from 2-nitroacylbenzenes by a reductive heterocyclization reaction with Sn or SnCl 2 concentrated HCl. Acid sensitive functionalities are expected to be incompatible with these conditions; milder approaches to the synthesis of 2,1-Benzisoxazoles would be welcomed. We demonstrate that SnCl 2 ·2H 2 O in a 1:1 mixture of EtOAc/MeOH is capable of mediating the tandem reduction–heterocyclization of a variety of 2-nitroacylbenzenes to their corresponding 2,1-Benzisoxazoles in good to excellent yields under essentially neutral conditions. Importantly, several commonly used acid–labile protecting groups, including Boc carbamate, tert -butyl ether, and tert -butyl ester, proved orthogonal to these reaction conditions.
Jay Chauhan - One of the best experts on this subject based on the ideXlab platform.
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one pot synthesis of 2 1 Benzisoxazoles anthranils by a stannous chloride mediated tandem reduction heterocyclization of 2 nitroacylbenzenes under neutral conditions
Tetrahedron Letters, 2012Co-Authors: Jay Chauhan, Steven FletcherAbstract:Abstract Classically, 2,1-Benzisoxazoles (anthranils) are prepared from 2-nitroacylbenzenes by a reductive heterocyclization reaction with Sn or SnCl 2 concentrated HCl. Acid sensitive functionalities are expected to be incompatible with these conditions; milder approaches to the synthesis of 2,1-Benzisoxazoles would be welcomed. We demonstrate that SnCl 2 ·2H 2 O in a 1:1 mixture of EtOAc/MeOH is capable of mediating the tandem reduction–heterocyclization of a variety of 2-nitroacylbenzenes to their corresponding 2,1-Benzisoxazoles in good to excellent yields under essentially neutral conditions. Importantly, several commonly used acid–labile protecting groups, including Boc carbamate, tert -butyl ether, and tert -butyl ester, proved orthogonal to these reaction conditions.
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One-pot synthesis of 2,1-Benzisoxazoles (anthranils) by a stannous chloride-mediated tandem reduction–heterocyclization of 2-nitroacylbenzenes under neutral conditions
Tetrahedron Letters, 2012Co-Authors: Jay Chauhan, Steven FletcherAbstract:Abstract Classically, 2,1-Benzisoxazoles (anthranils) are prepared from 2-nitroacylbenzenes by a reductive heterocyclization reaction with Sn or SnCl 2 concentrated HCl. Acid sensitive functionalities are expected to be incompatible with these conditions; milder approaches to the synthesis of 2,1-Benzisoxazoles would be welcomed. We demonstrate that SnCl 2 ·2H 2 O in a 1:1 mixture of EtOAc/MeOH is capable of mediating the tandem reduction–heterocyclization of a variety of 2-nitroacylbenzenes to their corresponding 2,1-Benzisoxazoles in good to excellent yields under essentially neutral conditions. Importantly, several commonly used acid–labile protecting groups, including Boc carbamate, tert -butyl ether, and tert -butyl ester, proved orthogonal to these reaction conditions.
Rui Fausto - One of the best experts on this subject based on the ideXlab platform.
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on the photochemistry of 1 2 Benzisoxazole capture of elusive spiro 2h azirine and ketenimine intermediates
European Journal of Organic Chemistry, 2016Co-Authors: Claudio M Nunes, Sandra Pinto, Igor Reva, Rui FaustoAbstract:The photochemistry of 1,2-Benzisoxazole (1) was studied using low-temperature matrix isolation coupled with infrared spectroscopy and quantum chemistry calculations. We identified, for the first time, spiro-2H-azirine 2 and ketenimine 3 as intermediates in the photoisomerization of 1 to 2-cyanophenol (4). These results constitute indirect evidence for the existence of vinylnitrene intermediates in the photochemistry of 1,2-Benzisoxazoles. The potential energy surface (PES) resulting from the N–O bond cleavage of 1 was compared with the respective PES of the parent isoxazole. Calculations at the CBS-QB3 level show that no stabilization is gained for the triplet vinylnitrene upon introduction of a benzene ring fused with isoxazole. However, the energies of 2 and 3 are higher by 13–15 kcal/mol comparing with the 2H-azirine and ketenimine analogs resulting from isoxazole, which explains why they had not been observed before. Our general mechanistic proposal also predicts well the photoisomerizations of 2 and 3 to 4.
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Photochemistry of 3-amino-1,2-Benzisoxazole: unexpected photoisomerization of an amino-spiro-2H-azirine to a 1H-diazirine
Tetrahedron Letters, 2016Co-Authors: Claudio M Nunes, Sandra Pinto, Igor Reva, Rui FaustoAbstract:Abstract UV irradiation of 3-amino-1,2-Benzisoxazole isolated in an argon matrix leads to the formation of an amino-spiro-2 H -azirine. The amino-spiro-2 H -azirine was found to photoisomerize back to 3-amino-1,2-Benzisoxazole and also to a 1 H -diazirine, which isomerizes to a carbodiimide. All the reported species were characterized experimentally by IR spectroscopy and confirmed by comparison with theoretical IR spectra. The discovery of the transformation of an amino-spiro-2 H -azirine into a 1 H -diazirine is unprecedented in the chemistry of reactive intermediates.
Claudio M Nunes - One of the best experts on this subject based on the ideXlab platform.
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on the photochemistry of 1 2 Benzisoxazole capture of elusive spiro 2h azirine and ketenimine intermediates
European Journal of Organic Chemistry, 2016Co-Authors: Claudio M Nunes, Sandra Pinto, Igor Reva, Rui FaustoAbstract:The photochemistry of 1,2-Benzisoxazole (1) was studied using low-temperature matrix isolation coupled with infrared spectroscopy and quantum chemistry calculations. We identified, for the first time, spiro-2H-azirine 2 and ketenimine 3 as intermediates in the photoisomerization of 1 to 2-cyanophenol (4). These results constitute indirect evidence for the existence of vinylnitrene intermediates in the photochemistry of 1,2-Benzisoxazoles. The potential energy surface (PES) resulting from the N–O bond cleavage of 1 was compared with the respective PES of the parent isoxazole. Calculations at the CBS-QB3 level show that no stabilization is gained for the triplet vinylnitrene upon introduction of a benzene ring fused with isoxazole. However, the energies of 2 and 3 are higher by 13–15 kcal/mol comparing with the 2H-azirine and ketenimine analogs resulting from isoxazole, which explains why they had not been observed before. Our general mechanistic proposal also predicts well the photoisomerizations of 2 and 3 to 4.
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Photochemistry of 3-amino-1,2-Benzisoxazole: unexpected photoisomerization of an amino-spiro-2H-azirine to a 1H-diazirine
Tetrahedron Letters, 2016Co-Authors: Claudio M Nunes, Sandra Pinto, Igor Reva, Rui FaustoAbstract:Abstract UV irradiation of 3-amino-1,2-Benzisoxazole isolated in an argon matrix leads to the formation of an amino-spiro-2 H -azirine. The amino-spiro-2 H -azirine was found to photoisomerize back to 3-amino-1,2-Benzisoxazole and also to a 1 H -diazirine, which isomerizes to a carbodiimide. All the reported species were characterized experimentally by IR spectroscopy and confirmed by comparison with theoretical IR spectra. The discovery of the transformation of an amino-spiro-2 H -azirine into a 1 H -diazirine is unprecedented in the chemistry of reactive intermediates.
Igor Reva - One of the best experts on this subject based on the ideXlab platform.
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on the photochemistry of 1 2 Benzisoxazole capture of elusive spiro 2h azirine and ketenimine intermediates
European Journal of Organic Chemistry, 2016Co-Authors: Claudio M Nunes, Sandra Pinto, Igor Reva, Rui FaustoAbstract:The photochemistry of 1,2-Benzisoxazole (1) was studied using low-temperature matrix isolation coupled with infrared spectroscopy and quantum chemistry calculations. We identified, for the first time, spiro-2H-azirine 2 and ketenimine 3 as intermediates in the photoisomerization of 1 to 2-cyanophenol (4). These results constitute indirect evidence for the existence of vinylnitrene intermediates in the photochemistry of 1,2-Benzisoxazoles. The potential energy surface (PES) resulting from the N–O bond cleavage of 1 was compared with the respective PES of the parent isoxazole. Calculations at the CBS-QB3 level show that no stabilization is gained for the triplet vinylnitrene upon introduction of a benzene ring fused with isoxazole. However, the energies of 2 and 3 are higher by 13–15 kcal/mol comparing with the 2H-azirine and ketenimine analogs resulting from isoxazole, which explains why they had not been observed before. Our general mechanistic proposal also predicts well the photoisomerizations of 2 and 3 to 4.
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Photochemistry of 3-amino-1,2-Benzisoxazole: unexpected photoisomerization of an amino-spiro-2H-azirine to a 1H-diazirine
Tetrahedron Letters, 2016Co-Authors: Claudio M Nunes, Sandra Pinto, Igor Reva, Rui FaustoAbstract:Abstract UV irradiation of 3-amino-1,2-Benzisoxazole isolated in an argon matrix leads to the formation of an amino-spiro-2 H -azirine. The amino-spiro-2 H -azirine was found to photoisomerize back to 3-amino-1,2-Benzisoxazole and also to a 1 H -diazirine, which isomerizes to a carbodiimide. All the reported species were characterized experimentally by IR spectroscopy and confirmed by comparison with theoretical IR spectra. The discovery of the transformation of an amino-spiro-2 H -azirine into a 1 H -diazirine is unprecedented in the chemistry of reactive intermediates.