171,175 research outputs found
A new protocol for the direct C-2 arylationj of azoles, including free (NH)-imidazole, -benzimidazole and -indole
No full textRecently, in the course of our investigations on the synthesis of vicinal diaryl-substituted 1H-imidazoles by transition metal-catalyzed direct arylation procedures via C–H bond activation,1,2 we reported a new, reliable and convenient method for the regioselective Pd- and Cu-mediated direct C-2 arylation of azoles, including free (NH)–imidazole, –benzimidazole and –indole, under base-free and ligandless conditions.3 The preliminary results obtained in this context encouraged us to perform a more in-depth study in order to determine the most suitable reaction conditions for performing efficiently the Pd- and Cu-mediated direct C-2 arylation of various kinds of azoles. Thus, we found that 1-aryl-1H-imidazoles, 1-methyl-1H-imidazole, 1H-imidazole, thiazole, 1H-benzimidazole, 1-benzyl-1H-imidazole and benzothiazole can undergo regioselective C-2 arylation by reaction with 2 equiv of an aryl iodide in DMF at 140°C for 48 h in the presence of 5 mol % Pd(OAc)2 and 2 equiv of CuI, under base-free and ligandless conditions, to provide the required 2-arylazoles in satisfactory to excellent yields. DMA and DMPU could also be used as solvents, but the arylation in toluene or dioxane didn’t proceed at all. The arylation reaction could also be performed using 5 mol % Pd/C and 2 equiv of CuI in DMF at 140 °C, and under these conditions the required azoles were prepared in yields similar to those obtained via reactions performed under homogeneous conditions, although the reaction times were longer (ca. 72 h). We also found that the best results for the C-2 arylation of indole could be obtained when the reaction was performed by treatment of the azole with 2 equiv of an aryl iodide in the presence of 5 mol % Pd(OAc)2 and 2 equiv of CuI in DMA at 160 °C instead of in DMF at 140 °C. However, also using these modified experimental conditions the required 2-aryl-1H-indoles were obtained in modest yields. Modified reaction conditions were also used to prepare in a good yield 2-(4-methoxyphenyl)oxazole which we previously obtained in a low yield.3 In fact, when 3 equiv of oxazole were reacted with 1 equiv of iodoanisole in DMF at 140°C for 74 h in the presence of 5 mol % Pd(OAc)2 and 2 equiv of CuI, the required 2-arylazole was obtained in 74 % yield. Interestingly, aryl bromides could also be used as electrophiles in the Pd- and Cu-mediated C-2 arylation of the above mentioned heterocycles, provided that 4 equiv of NaI were added to the reagents. 1,2-Diphenyl-1H-imidazole was so prepared in 47 % yield from 1-phenyl-1H-imidazole and 2 equiv of bromobenzene. Our new C-2 arylation method was then applied for preparing some bioactive heterocycle derivatives such as 4-methyl-2-(4-chlorophenyl)-1-(4-methylsulfonylphenyl)-1H-imidazole, which is a selective COX-2 inhibitor,4 and 2-(4-nitrophenyl)-1H-benzimidazole, which is a key intermediate for the synthesis of heparanase inhibitors,5 in 78 and 89 % yield, respectively. At present, we are performing studies on the synthesis of 2,4(5)-diaryl-1H-imidazoles via reaction sequences involving the Pd- and Cu-mediated C-2 arylation of 4(5)-aryl-1H-imidazoles or 5-aryl-1-benzyl-1H-imidazoles under base-free and ligandless conditions
Efficient and highly regioselective direct C-2 arylation of azoles, including free (NH)-imidazole, -benzimidazole and -indole, with aryl halides
No full textThe Pd- and Cu-mediated reaction of a large variety of p-electron sufficient heteroarenes, which include free (NH)-imidazoles, -benzimidazole and -indole, with aryl iodides under ligandless and base-free conditions provides regioselectively the required 2-arylhetero- cycle derivatives in high yields. 2-Aryl-1-phenyl-1H-imidazoles can also be prepared by a one-pot domino HALEX and Pd- and Cu-mediated arylation reactions of 1-phenyl-1H-imidazole with activated and unactivated aryl bromides under base-free and ligandless conditions. The protocol for the synthesis of 2-arylazoles involving the use of aryl iodides has been found to be suitable for the efficient preparation of three bioactive compounds and a key intermediate in the synthesis of a heparanase inhibitor
Development of an immobilized enzyme reactor based on epoxide hydrolase from Aspergillus niger for on-line synthesis of para-substitutes styrene oxides
No full textSelective, efficient and functional group-tolerant CuOAc-mediated N-arylation of 1H-indoles and 9H-carbazole with aryl iodides under base-free and ligandless conditions
No full textThe CuOAc-mediated N-arylation of 1H-indole derivatives and 1H-carbazole with aryl iodides under base-free and ligandless conditions provides with complete N-selectivity the required N-arylazoles in moderate to good yields. The experimental conditions of this new version of the Ullmann reaction allow an unprecedent tolerance of functional groups and facilitate the work-up of the reaction mixtures and isolation of the required chemically pure reaction products
Técnicas de procesado de imágenes aplicadas a microfotos de harina de quinoa
No full textFil: Rulloni, V. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.Fil: Maldonado, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.Fil: Maldonado, C. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Estudios de Matemática; Argentina.Fil: Bergesse, A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Ciencia y Tecnología de los Alimentos; Argentina.Fil: Bergesse, A. Universidad Nacional de Córdoba. Escuela de Nutrición; Argentina.Fil: Cervilla, N. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Ciencia y Tecnología de los Alimentos; Argentina.Fil: Cervilla, N. Universidad Nacional de Córdoba. Escuela de Nutrición; Argentina.Fil: Calandri, E. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Ciencia y Tecnología de los Alimentos; Argentina.Fil: Calandri, E. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencia y Tecnología de los Alimentos; Argentina.El presente trabajo pretendió realizar un aporte desde el punto de vista del procesamiento de
imágenes a la caracterización de harinas de quinoa.
Se analizaron microfotos de harinas provienentes de semillas lavadas 30 minutos en solución
hidroalcohólica. Las imágenes fueron clasificadas según el tamiz utilizado CIEGO (<74 µm); 200
ASTM (74 µm - 149 µm); 100 ASTM (>149 µm) y se tuvo como objetivo realizar mediciones
objetivas de ciertas características de las partículas correspondientes a los distintos tamices.
Se analizaron 6 imágenes del tamiz ciego, 3 del tamiz 100 y 4 del tamiz 200.
En cada una de ellas se consideraron dos etapas. Una de pre-procesado de la imagen y otra
de análisis de partículas.http://www.inv.icta.efn.uncor.edu/archivos/Libro_resumenes_Jornada_ICTA.pdfFil: Rulloni, V. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.Fil: Maldonado, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Matemática; Argentina.Fil: Maldonado, C. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Estudios de Matemática; Argentina.Fil: Bergesse, A. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Ciencia y Tecnología de los Alimentos; Argentina.Fil: Bergesse, A. Universidad Nacional de Córdoba. Escuela de Nutrición; Argentina.Fil: Cervilla, N. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Ciencia y Tecnología de los Alimentos; Argentina.Fil: Cervilla, N. Universidad Nacional de Córdoba. Escuela de Nutrición; Argentina.Fil: Calandri, E. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Ciencia y Tecnología de los Alimentos; Argentina.Fil: Calandri, E. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencia y Tecnología de los Alimentos; Argentina.Matemática Aplicad
A new, selective and functional group tolerant method for the synthesis of 1-aryl-1H-indoles and 9-aryl-9H-carbazoles
No full textSeveral methods have been described for the N-arylation of 1H-indoles and 9H-carbazoles, but some problems limit their synthetic utility. In fact, the Ullmann-type reactions suffer from a limited substrate scope, moderate yields, have been preferentially conducted with aryl halides activated by electron-withdrawing groups and involve the use of expensive phosphine ligands.
On the other hand, even the Cu-catalyzed N-arylation of 1H-indoles is not entirely satisfactory since the use in this methods of a ligand entails an increase of the cost of the reaction and problems in the isolation of the required chemically pure products. Furthermore, the experimental conditions of the Ullmann-type coupling and the Pd- or Cu-catalyzed N-arylations, that involve the use of a base, cause an intolerance of base sensitive groups such as the phenolic hydroxy group.
Recently, in the course of our studies on the development of new and efficient protocols for the highly regioselective arylation of azoles we found that the CuOAc-mediated N-arylation of 1H-indole derivatives and 9H-carbazole with aryl iodides in DMA at 160 °C under base-free and ligandless conditions provides with complete N-selectivity the required N-arylazoles in moderate to good yields (eqs. 1 and 2).This inexpensive new version of the classical Ullmann reaction allows an unprecedented tolerance of functional groups both in the 1H-indoles and aryl iodides and works well with electron-rich and electron-poor aryl iodides. Moreover, the experimental conditions of this protocol facilitate the work-up of the reaction mixtures and the isolation of the required chemically pure N-aryl derivatives
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
N-Arilazione altamente selettiva, mediata da sali di rame(I), di 1H-indoli in assenza di basi e di legandi
No full textLa presente invenzione riguarda un processo per l’ottenimento di composti caratterizzati da un gruppo arilico (Ar) legato ad un atomo di azoto (N).
In particolare, l’invenzione si riferisce ad un processo di sintesi di N-arilindoli a partire da 1H-indoli e da alogenuri arilici (Ar–X)
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Development and applications of new protocols for the direct and regioselective arylation of azoles
No full textAzoles are ubiquitous features of natural products, pharmaceuticals and fluorescent dyes as well as many other synthetics, and this, undoubtedly, plays a key role in the continued search for the development of new, efficient and cost-effective methods for the synthesis of these heterocycles. In particular, great attention has been paid in the last years to the selective functionalization of C–H and N–H bonds of five-membered heterocycles via direct transition metal-mediated C- and/or N-arylation with aryl halides.
In this context, we recently found that a variety of 1,5-diaryl-1H-imidazoles 1 can be regioselectively prepared in moderate yields by a Pd-catalyzed direct coupling of 1-aryl-1H-imidazoles 2 with aryl halides 3 in the presence of CsF. Subsequently, we prepared 5-aryl-1-methyl-1H-imidazoles 3 and 5-aryl-1-benzyl-1H-imidazoles 4 by a protocol similar to that used for compounds 1. We also found that 1,2-diaryl-1H-imidazoles 5 can be regioselectively prepared from compounds 2 and halides 3 in the presence of CsF and CuI and a catalytic amount of Pd(OAc)2. More recently, we have developed a new and convenient protocol for the regioselective Pd- and Cu-mediated C-2 arylation of a variety of azoles, including free (NH)-imidazole, -benzimidazole and -indole, under base-free and ligandless conditions, and we have employed this procedure for the preparation of 2,4(5)-diaryl-1H-imidazoles 6 via reaction sequences involving the C-2 arylation of the corresponding 4(5)-aryl-1H-imidazoles 7 or compounds 4. Interestingly, 4,5-diaryl-1H-imidazoles 8 and 4,5-diaryl-1-methyl-1H-imidazoles 9 have also been obtained from 4 and 3, respectively, via a two-steps sequence involving a regioselective C-4 halogenation and a Suzuki-type reaction. Finally, in the course of our studies on the direct C- and N-arylation of azoles we have observed a complete switch from C-2 to N-1 arylation performing the reaction of indole with aryl iodides under ligandless and base-free conditions in the presence of CuOAc instead of CuI and omitting Pd. Mechanistic proposals for our arylation protocols and some their applications to the synthesis of biologically interesting heterocyclic derivatives will be also reported and discussed
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