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Lucinda V. Reis - One of the best experts on this subject based on the ideXlab platform.
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Quinoline‑ and Benzoselenazole-Derived Unsymmetrical Squaraine Cyanine Dyes: Design, Synthesis, Photophysicochemical Features and Light-Triggerable Antiproliferative Effects against Breast Cancer Cell Lines.
Materials (Basel Switzerland), 2020Co-Authors: Eurico Lima, Paulo Almeida, Renato E.f. Boto, Diana Ferreira, José R. Fernandes, Luis F. Vieira Ferreira, Eliana B. Souto, Amélia M. Silva, Lucinda V. ReisAbstract:Photodynamic therapy is an innovative treatment approach broadly directed towards oncological diseases. Its applicability and efficiency are closely related to the interaction of three main components, namely a photosensitizer, light and molecular triplet oxygen, which should drive cell death. Recently, several studies have demonstrated that squaraine cyanine dyes have a set of photophysical and photochemical properties that have made of these compounds' potential photosensitizers for this therapeutic modality. In the present research work, we describe the synthesis and characterization of four quinoline‑ and Benzoselenazole‑derived unsymmetrical squaraine cyanine dyes. Except for the precursor of aminosquaraine dyes, i.e., O‑methylated derivative, all dyes were evaluated for their behavior and absorption capacity in different organic and aqueous solvents, their ability to form singlet oxygen, their light‑stability, and in vitro phototherapeutic effects against two human breast cancer cell cultures (BT‑474 and MCF‑7). Regardless of the nature of the used solvents, the synthesized dyes showed intense absorption in the red and near‑infrared spectral regions, despite the formation of aggregates in aqueous media. Dyes showed high light‑stability against light exposure. Despite the low ability to produce singlet oxygen, aminosquaraine dyes demonstrated worthy in vitro phototherapeutic activity.
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Synthesis, characterization and protein-association of dicyanomethylene squaraine dyes
Dyes and Pigments, 2017Co-Authors: Tiago Martins, Paulo Almeida, Renato E.f. Boto, Marlene L. Pacheco, José Paulo S. Farinha, Lucinda V. ReisAbstract:Abstract We prepared several new dicyanomethylene squaraine dyes derived from indolenine, benzothiazole and Benzoselenazole, with different substituent groups. All the obtained dyes display intense and narrow absorption bands and bright fluorescence emission in the Vis/NIR region (665–716 nm) when dissolved in organic solvents, especially for the unsymmetrical dyes containing sulphur and selenium atoms. The use of synthesized squaraine dyes as fluorescent probes for detection of bovine serum albumin (BSA) and human serum albumin (HSA) was explored in Tris-HCl buffer solutions. We observed that all the dyes are non-emissive in buffer solution but become fluorescent in the presence of BSA or HSA proteins, with the emission intensity increasing proportionally to the protein concentration (0.00–1.22 μM). The most pronounced effect was observed for the symmetrical squaraine having two moieties of indolenine.
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Crystal structures of a Benzoselenazole-derived squarylium cyanine dye and three derivatives substituted at the central squaric ring
CrystEngComm, 2011Co-Authors: Paulo F. Santos, Lucinda V. Reis, Paulo Almeida, Daniel E. LynchAbstract:The crystal structures of 4-[(3-hexylbenzoselenazol-3-ium-2-yl)methylidene]-2-[(3-hexyl-3H-benzoselenazol-2-ylidene)methyl]-3-oxocyclobut-1-en-1-olate and its analogues substituted at the squaric ring with O-methyl, NH-methyl and N,N-diethylamino groups have been determined using single crystal X-ray crystallography techniques. The unsubstituted squaraine dye is symmetrical and packs as a stepped ribbon array (via a C–H⋯O close interaction), which is in contrast to the slip-stacked arrangements observed in similar squaraine analogues. Each of the substituted analogues is asymmetric and pack in slightly differing slip-stacked charge-transfer columns. The NH-methyl analogue packs with a single water molecule per squaraine unit.
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the synthesis and characterization of novel aza substituted squarylium cyanine dyes
Dyes and Pigments, 2009Co-Authors: Lucinda V. Reis, Paulo Almeida, J P Serrano, P F SantosAbstract:Abstract Several squarylium cyanine dyes derived from benzothiazole, Benzoselenazole and quinoline were synthesised and the central four member ring functionalized by substitution of one of the oxygen atoms by benzylamine, aniline, 3-iodoaniline, N , N -dimethylhydrazine and 2-aminosulfonic acid groups. All of the ensuing, novel aza-substituted dyes displayed strong absorption within the range 651–709 nm.
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Delocalized cationic azo dyes derived from 2-aminoselenazole-5-carbaldehyde
Arkivoc, 2009Co-Authors: Maria A. Salvador, Lucinda V. Reis, Paulo Almeida, Paulo F. SantosAbstract:Several delocalized cationic azo dyes incorporating a selenazole ring have been prepared by Knoevenagel condensation of an intermediate azo compound bearing a 5-formylselenazole group with methylene bases derived from indolenine, benzothiazole, Benzoselenazole, and quinoline. All dyes display a strong absorption at around 700 nm, bathochromically shifted relative to their thiazole analogues, and show a negative solvatochromic behavior.
Paulo Almeida - One of the best experts on this subject based on the ideXlab platform.
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Quinoline‑ and Benzoselenazole-Derived Unsymmetrical Squaraine Cyanine Dyes: Design, Synthesis, Photophysicochemical Features and Light-Triggerable Antiproliferative Effects against Breast Cancer Cell Lines.
Materials (Basel Switzerland), 2020Co-Authors: Eurico Lima, Paulo Almeida, Renato E.f. Boto, Diana Ferreira, José R. Fernandes, Luis F. Vieira Ferreira, Eliana B. Souto, Amélia M. Silva, Lucinda V. ReisAbstract:Photodynamic therapy is an innovative treatment approach broadly directed towards oncological diseases. Its applicability and efficiency are closely related to the interaction of three main components, namely a photosensitizer, light and molecular triplet oxygen, which should drive cell death. Recently, several studies have demonstrated that squaraine cyanine dyes have a set of photophysical and photochemical properties that have made of these compounds' potential photosensitizers for this therapeutic modality. In the present research work, we describe the synthesis and characterization of four quinoline‑ and Benzoselenazole‑derived unsymmetrical squaraine cyanine dyes. Except for the precursor of aminosquaraine dyes, i.e., O‑methylated derivative, all dyes were evaluated for their behavior and absorption capacity in different organic and aqueous solvents, their ability to form singlet oxygen, their light‑stability, and in vitro phototherapeutic effects against two human breast cancer cell cultures (BT‑474 and MCF‑7). Regardless of the nature of the used solvents, the synthesized dyes showed intense absorption in the red and near‑infrared spectral regions, despite the formation of aggregates in aqueous media. Dyes showed high light‑stability against light exposure. Despite the low ability to produce singlet oxygen, aminosquaraine dyes demonstrated worthy in vitro phototherapeutic activity.
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Synthesis, characterization and protein-association of dicyanomethylene squaraine dyes
Dyes and Pigments, 2017Co-Authors: Tiago Martins, Paulo Almeida, Renato E.f. Boto, Marlene L. Pacheco, José Paulo S. Farinha, Lucinda V. ReisAbstract:Abstract We prepared several new dicyanomethylene squaraine dyes derived from indolenine, benzothiazole and Benzoselenazole, with different substituent groups. All the obtained dyes display intense and narrow absorption bands and bright fluorescence emission in the Vis/NIR region (665–716 nm) when dissolved in organic solvents, especially for the unsymmetrical dyes containing sulphur and selenium atoms. The use of synthesized squaraine dyes as fluorescent probes for detection of bovine serum albumin (BSA) and human serum albumin (HSA) was explored in Tris-HCl buffer solutions. We observed that all the dyes are non-emissive in buffer solution but become fluorescent in the presence of BSA or HSA proteins, with the emission intensity increasing proportionally to the protein concentration (0.00–1.22 μM). The most pronounced effect was observed for the symmetrical squaraine having two moieties of indolenine.
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Crystal structures of a Benzoselenazole-derived squarylium cyanine dye and three derivatives substituted at the central squaric ring
CrystEngComm, 2011Co-Authors: Paulo F. Santos, Lucinda V. Reis, Paulo Almeida, Daniel E. LynchAbstract:The crystal structures of 4-[(3-hexylbenzoselenazol-3-ium-2-yl)methylidene]-2-[(3-hexyl-3H-benzoselenazol-2-ylidene)methyl]-3-oxocyclobut-1-en-1-olate and its analogues substituted at the squaric ring with O-methyl, NH-methyl and N,N-diethylamino groups have been determined using single crystal X-ray crystallography techniques. The unsubstituted squaraine dye is symmetrical and packs as a stepped ribbon array (via a C–H⋯O close interaction), which is in contrast to the slip-stacked arrangements observed in similar squaraine analogues. Each of the substituted analogues is asymmetric and pack in slightly differing slip-stacked charge-transfer columns. The NH-methyl analogue packs with a single water molecule per squaraine unit.
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the synthesis and characterization of novel aza substituted squarylium cyanine dyes
Dyes and Pigments, 2009Co-Authors: Lucinda V. Reis, Paulo Almeida, J P Serrano, P F SantosAbstract:Abstract Several squarylium cyanine dyes derived from benzothiazole, Benzoselenazole and quinoline were synthesised and the central four member ring functionalized by substitution of one of the oxygen atoms by benzylamine, aniline, 3-iodoaniline, N , N -dimethylhydrazine and 2-aminosulfonic acid groups. All of the ensuing, novel aza-substituted dyes displayed strong absorption within the range 651–709 nm.
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Delocalized cationic azo dyes derived from 2-aminoselenazole-5-carbaldehyde
Arkivoc, 2009Co-Authors: Maria A. Salvador, Lucinda V. Reis, Paulo Almeida, Paulo F. SantosAbstract:Several delocalized cationic azo dyes incorporating a selenazole ring have been prepared by Knoevenagel condensation of an intermediate azo compound bearing a 5-formylselenazole group with methylene bases derived from indolenine, benzothiazole, Benzoselenazole, and quinoline. All dyes display a strong absorption at around 700 nm, bathochromically shifted relative to their thiazole analogues, and show a negative solvatochromic behavior.
Paulo F. Santos - One of the best experts on this subject based on the ideXlab platform.
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Synthesis, photochemical and in vitro cytotoxic evaluation of Benzoselenazole-based aminosquaraines.
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2019Co-Authors: Álvaro F. Magalhães, L.f. Vieira Ferreira, Vânia C. Graça, Ricardo C. Calhelha, I. Ferreira Machado, Isabel C.f.r. Ferreira, Paulo F. SantosAbstract:Squaraine dyes have recently attracted interest as potential second generation photosensitizers for photodynamic therapy. Several cationic aminosquaraine dyes bearing Benzoselenazole terminal nuclei were synthezised and their cytotoxic activity was tested against four different human tumor cell lines – breast (MCF-7), non-small cell lung (NCI-H460), cervical (HeLa) and hepatocellular (HepG2) carcinomas – and against a non-tumor porcine liver primary cell line (PLP2), both in the absence of light and under irradiation. All dyes, which displayed strong absorption within the phototherapeutic window, were found to exhibit photodynamic activity and were shown to be, in most cases, more cytotoxic, both in the dark and upon irradiation, than their benzothiazole analogues.
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Photochemical studies of new benzothiazole- and Benzoselenazole-derived aminosquarylium dyes
Tetrahedron, 2015Co-Authors: D.s. Conceição, Paulo F. Santos, Vânia C. Graça, Diana Ferreira, Cristina Mensato Rebello Da Silva, L.f. Vieira FerreiraAbstract:Abstract In this work, new modified squarylium dyes, namely two new groups of benzothiazole- and Benzoselenazole-derived squarylium dyes, were studied. An extensive photochemical characterization of all dyes was performed and the following parameters were studied: quantum yields of singlet oxygen formation, fluorescence quantum yields and fluorescence lifetimes. Depending on the nature of the substituent located in the squaric ring, significant results were obtained. The laser flash photolysis technique was used to determine triplet–triplet absorption spectra, in ethanol. In chloroform, photoproducts resulting from a reaction of the excited squarylium dye in the singlet state with CHCl3 were observed. A solute–solvent complex was detected, the primary product formed after excitation, being the complex [SQ+ ⋯ CHCl2 ⋯ Cl−]. The effect of two different counterions (CF3SO3− and I−) was also addressed by these techniques providing new insights about the external heavy atom effect mechanism.
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Photochemical properties of squarylium cyanine dyes
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2013Co-Authors: Diana Ferreira, Paulo F. Santos, Vânia C. Graça, D.s. Conceição, V. R. A. Ferreira, L.f. Vieira FerreiraAbstract:This study presents several new squarylium dyes derived from benzothiazole and Benzoselenazole with several structural variations, namely the nature of the heteroaromatic ring and the length of the N,N′-dialkyl groups. Before being investigated in connection with their effect on living cells and/or tissues, these novel compounds were characterized, namely with respect to the determination of their main photophysical parameters. Therefore, a study of the ground state absorption, fluorescence emission (quantum yields and lifetimes) and singlet oxygen generation quantum yields was performed for all the compounds synthesized in order to evaluate their efficiency as photosensitizers. An increase of the alkyl chain length from ethyl to hexyl did not produce a clear change in the fluorescence quantum yields, showing no influence on the photoisomerization process. Heavy atom inclusion (Se instead of S) enhanced the singlet oxygen generation efficiency and decreased the intensity of the fluorescence emission. The external heavy atom effect (I− as a counterion instead of CF3SO3−) produced a significant increase in the singlet oxygen formation quantum yield (about 20%). Transient absorption studies in aerated and oxygen free samples revealed that the photoisomerization process, which could compete with the triplet state formation for all dyes in solution, is a negligible pathway for the excited state deactivation, in accordance with the rigidity introduced by the squaric ring into the polymethine chain of the dye, both in chloroform and ethanol. However, in the case of the chloroform solution a new transient was detected in air equilibrated solutions, resulting from a reaction of the excited squarylium dye in the singlet state with CHCl3˙, and assigned to the radical cation (SQ+˙) of the dye.
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Crystal structures of a Benzoselenazole-derived squarylium cyanine dye and three derivatives substituted at the central squaric ring
CrystEngComm, 2011Co-Authors: Paulo F. Santos, Lucinda V. Reis, Paulo Almeida, Daniel E. LynchAbstract:The crystal structures of 4-[(3-hexylbenzoselenazol-3-ium-2-yl)methylidene]-2-[(3-hexyl-3H-benzoselenazol-2-ylidene)methyl]-3-oxocyclobut-1-en-1-olate and its analogues substituted at the squaric ring with O-methyl, NH-methyl and N,N-diethylamino groups have been determined using single crystal X-ray crystallography techniques. The unsubstituted squaraine dye is symmetrical and packs as a stepped ribbon array (via a C–H⋯O close interaction), which is in contrast to the slip-stacked arrangements observed in similar squaraine analogues. Each of the substituted analogues is asymmetric and pack in slightly differing slip-stacked charge-transfer columns. The NH-methyl analogue packs with a single water molecule per squaraine unit.
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Delocalized cationic azo dyes derived from 2-aminoselenazole-5-carbaldehyde
Arkivoc, 2009Co-Authors: Maria A. Salvador, Lucinda V. Reis, Paulo Almeida, Paulo F. SantosAbstract:Several delocalized cationic azo dyes incorporating a selenazole ring have been prepared by Knoevenagel condensation of an intermediate azo compound bearing a 5-formylselenazole group with methylene bases derived from indolenine, benzothiazole, Benzoselenazole, and quinoline. All dyes display a strong absorption at around 700 nm, bathochromically shifted relative to their thiazole analogues, and show a negative solvatochromic behavior.
Paulo H. Schneider - One of the best experts on this subject based on the ideXlab platform.
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Ground and excited-state properties of 1,3-Benzoselenazole derivatives: A combined theoretical and experimental photophysical investigation
Journal of Molecular Structure, 2020Co-Authors: Catia Schwartz Radatz, Felipe Lange Coelho, Eduarda Sangiogo Gil, Fabiano Da Silveira Santos, Juliana Maria Forain Miolo Schneider, Paulo F. B. Gonçalves, Fabiano Severo Rodembusch, Paulo H. SchneiderAbstract:Abstract A series of 1,3-Benzoselenazole derivatives were prepared with different substituents by complementary methodologies starting from aldehydes or carboxylic acids, using sodium metabisulfite and tributylphosphine, respectively, according to the substituent pattern. The photophysical behaviour in solution of the Benzoselenazoles was studied using UV–Vis absorption and steady-state fluorescence emission spectroscopies. These compounds present absorption maxima located in the UV region due to spin and symmetry, which allowed electronic transitions 1ππ*. The absorption maxima location, as well as the evidence of intramolecular charge transfer (ICT), was shown to be tailored by the position and electronic character of the substituents. Quantum chemical calculations using DFT and TDDFT were performed in order to investigate the electronic and photophysical features of the molecules. The calculations confirmed the presence of ICT in the molecules which contained nitro group in their structure and in all compounds where the allowed electronic transitions 1ππ* were taking place. In addition, the compounds showed significantly different fluorescence emissions depending on the solvent and their chemical structures, where structured and non-structured spectra in the range of 300–600 nm, with ICT character, were obtained.
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Synthesis of Benzoselenazoles and Benzoselenazolines by Cyclization of 2-Amino-benzeneselenol with β-Dicarbonyl Compounds.
ChemInform, 2015Co-Authors: Renata A. Balaguez, Catia S Radatz, Paulo H. Schneider, Daniel S. Rampon, Eder J. Lenardão, Roberta Krueger, Diego AlvesAbstract:2-Amino-benzeneselenol, generated in situ by treatment of substrate (I) with phosphoric acid, reacts with 1,3-diketones or β-keto esters to afford Benzoselenazoles and benzoselenazolines, respectively.
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Synthesis of 2-Substituted 1,3-Benzoselenazoles from Carboxylic Acids Promoted by Tributylphosphine.
ChemInform, 2015Co-Authors: Catia S Radatz, Diego Alves, Daniel S. Rampon, Renata A. Balaguez, Paulo H. SchneiderAbstract:The practical and simple method delivers not only 2-aryl-1,3-Benzoselenazoles (III), but for the first time also 2-alkyl-1,3-Benzoselenazoles (V).
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Synthesis of Benzoselenazoles and benzoselenazolines by cyclization of 2-amino-benzeneselenol with β-dicarbonyl compounds
Tetrahedron Letters, 2015Co-Authors: Renata A. Balaguez, Catia S Radatz, Paulo H. Schneider, Daniel S. Rampon, Roberta Krüger, Eder J. Lenardão, Diego AlvesAbstract:We describe here our results on the addition of 2-amino-benzeneselenol, generated in situ by reaction of bis(2-aminophenyl)-diselenide with H3PO2, to β-dicarbonyl compounds using glycerol as solvent. Depending on the nature of β-dicarbonyl compounds used in reactions, Benzoselenazoles or benzoselenazolines were obtained in good yields under mild conditions. When the reactions of in situ generated 2-amino-benzeneselenol were performed with 1,3-diketones, Benzoselenazoles were formed in good yields, whereas reactions carried out with β-keto-esters provided benzoselenazolines in high yields.
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Synthesis of 2‐Substituted 1,3‐Benzoselenazoles from Carboxylic Acids Promoted by Tributylphosphine
European Journal of Organic Chemistry, 2014Co-Authors: Catia S Radatz, Diego Alves, Daniel S. Rampon, Renata A. Balaguez, Paulo H. SchneiderAbstract:We report a general, practical, and simple metal-free method for the synthesis of 2-substituted 1,3-Benzoselenazoles by the reaction of bis(2-aminophenyl)diselenide with a wide range of carboxylic acids, promoted by tributylphosphine. This efficient reaction furnishes 2-aryl-1,3-Benzoselenazoles in good yields and tolerates a variety of substituents at the aryl moiety of carboxylic acids. For the first time, 2-alkyl-1,3-Benzoselenazoles could be obtained from aliphatic carboxylic acids and thiazolidine-4-carboxylic acid in high chemical yields. The use of focused microwave irradiation considerably decreased the reaction time from 48 to 2 h. The experimental data provide insights into the mechanism of the reaction.
Diego Alves - One of the best experts on this subject based on the ideXlab platform.
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α‐Keto Acids as Acylating Agents in the Synthesis of 2‐Substituted Benzothiazoles and Benzoselenazoles
European Journal of Organic Chemistry, 2017Co-Authors: David B. Lima, Diego Alves, Filipe Penteado, Marcelo M. Vieira, Gelson Perin, Claudio Santi, Eder J. LenardãoAbstract:Herein is reported the first decarboxylative oxidation of α-keto acids promoted by sodium metabisulfite (Na2S2O5) to obtain 2-substituted benzothiazoles and Benzoselenazoles. Diaryl disulfides and diselenides were used as chalcogen sources and the desired products were obtained in moderate to excellent yields. This protocol does not require inert atmosphere, transition metals or drastic reaction conditions and CO2 is released as an environmental benign co-product. The presence of Na2S2O5 was essential to guarantee the reaction completion and maximum yield of products.
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Synthesis of Benzoselenazoles and Benzoselenazolines by Cyclization of 2-Amino-benzeneselenol with β-Dicarbonyl Compounds.
ChemInform, 2015Co-Authors: Renata A. Balaguez, Catia S Radatz, Paulo H. Schneider, Daniel S. Rampon, Eder J. Lenardão, Roberta Krueger, Diego AlvesAbstract:2-Amino-benzeneselenol, generated in situ by treatment of substrate (I) with phosphoric acid, reacts with 1,3-diketones or β-keto esters to afford Benzoselenazoles and benzoselenazolines, respectively.
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Synthesis of 2-Substituted 1,3-Benzoselenazoles from Carboxylic Acids Promoted by Tributylphosphine.
ChemInform, 2015Co-Authors: Catia S Radatz, Diego Alves, Daniel S. Rampon, Renata A. Balaguez, Paulo H. SchneiderAbstract:The practical and simple method delivers not only 2-aryl-1,3-Benzoselenazoles (III), but for the first time also 2-alkyl-1,3-Benzoselenazoles (V).
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Synthesis of Benzoselenazoles and benzoselenazolines by cyclization of 2-amino-benzeneselenol with β-dicarbonyl compounds
Tetrahedron Letters, 2015Co-Authors: Renata A. Balaguez, Catia S Radatz, Paulo H. Schneider, Daniel S. Rampon, Roberta Krüger, Eder J. Lenardão, Diego AlvesAbstract:We describe here our results on the addition of 2-amino-benzeneselenol, generated in situ by reaction of bis(2-aminophenyl)-diselenide with H3PO2, to β-dicarbonyl compounds using glycerol as solvent. Depending on the nature of β-dicarbonyl compounds used in reactions, Benzoselenazoles or benzoselenazolines were obtained in good yields under mild conditions. When the reactions of in situ generated 2-amino-benzeneselenol were performed with 1,3-diketones, Benzoselenazoles were formed in good yields, whereas reactions carried out with β-keto-esters provided benzoselenazolines in high yields.
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Synthesis of 2‐Substituted 1,3‐Benzoselenazoles from Carboxylic Acids Promoted by Tributylphosphine
European Journal of Organic Chemistry, 2014Co-Authors: Catia S Radatz, Diego Alves, Daniel S. Rampon, Renata A. Balaguez, Paulo H. SchneiderAbstract:We report a general, practical, and simple metal-free method for the synthesis of 2-substituted 1,3-Benzoselenazoles by the reaction of bis(2-aminophenyl)diselenide with a wide range of carboxylic acids, promoted by tributylphosphine. This efficient reaction furnishes 2-aryl-1,3-Benzoselenazoles in good yields and tolerates a variety of substituents at the aryl moiety of carboxylic acids. For the first time, 2-alkyl-1,3-Benzoselenazoles could be obtained from aliphatic carboxylic acids and thiazolidine-4-carboxylic acid in high chemical yields. The use of focused microwave irradiation considerably decreased the reaction time from 48 to 2 h. The experimental data provide insights into the mechanism of the reaction.