Synthesis of unsymmetrical diorganyl chalcogenides by using arylboronic acids or C (sp2)-H bond functionalization of arenes under greener conditions: Síntese de calcogenetos de diorganoíla via ácidos borônicos e funcionalização de ligação C(sp2)-H de arenos sob condições ambientalmente mais adequadas

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, 2016.No presente trabalho desenvolveram-se procedimentos robustos, econômicos e sustentável para a síntese de dicalcogentos de organoíla não simétricos usando uma variedade de ácidos borônicos arílicos substituídos e arenos [O- ou N-] subtituídos. Na primeira parte, desenvolvemos um sistema catalítico oxidativo que combina iodo/DMSO para a síntese de uma grande variedade de dicalcogenetos de diorganoíla não simétricos (S, Se, Te), utilizando vários ácidos borônicos arílicos sob irradiação de micro-ondas. As reações foram realizadas pela mistura de ácidos boronicos com os dicalgenetos desejados, na presença de 10 mol% de iodo, um equiv. ácidos borônicos arílicos II, 0,5 equiv. de vários dicalcogenetos de diorganoíla I e 2 equiv. de DMSO (como oxidante). Os produtos calcogenados desejados III foram obtidos em rendimentos de bons a excelentes. Todas as reações foram realizadas sem a exclusão de ar e umidade a 100 °C durante 10 minutos sob irradiação de microondas. Vários substituintes com diferentes efeitos eletrônicos e estéricos foram tolerados nas condições ótimas de reação. A metodologia desenvolvida demonstrou ser robusta e pode ser facilmente efetuada na escala de 10 mmol, sem qualquer perda significativa de rendimento. A química aqui descrita representa um protocolo livre de solvente e de metal de transição para a preparação de calcogenetos de diorganoíla não simétricos. O escopo da presente metodologia de acoplamento foi estendido usando trifluoroboratos de potássio vinilícos IV como uma alternativa para os ácidos borônicos, utilizando os parâmetros da condição otimizada. A reação de ditelureto e disseleneto de dirganoíla I ocorreu sem problemas e proporcionou a formação dos produtos acoplados correspondentes em rendimentos isolados de 87% e 89%. Considerando a importância dos compostos organocalcogênio, na segunda etapa deste trabalho, desenvolveu-se um método regiosseletivo, rápido e ambientalmente seguro, catalisado por iodo para a síntese de calcogentos de organoíla. Essa metodologia ocorre pela formação de ligações C-Se / C-S via clivagem oxidativa de ligação C (sp2) -H utilizando arenos [O- ou N-] substituídos. Esse processo é realizado pela calcogenação direta de dicalcogenetos de organoíla I com vários arenos VI, catalisados por 20 mol% de iodo na presença de 3 equivalentes de DMSO (como oxidante). Essa metodologia regiosseletiva, sob irradiação de micro-ondas, permitiu obter os produtos desejados funcionalizados com um substituinte organocalcogenoíla, em 10 min, em bons rendimentos. Outras vantagens desse método são: condições livres de solvente e metal de transição; procedimento experimental sem a exclusão de ar e umidade. A reação também foi efetuada em escala de 10 mmol sem perda significativa de rendimento. Além disso, por este protocolo, foi possível funcionalizar heteroarenos biologicamente importantes contendo S/Se, tais como: pirimidinas, piridinas e tiazóis. A versatilidade da metodologia desenvolvida permitiu ainda a utilização de tiofenol VIII e hidrazidas de sulfonila VIII como agentes sulfenilação e N,N-dimetilanilina IX alternativos, levando-se o produto tiolado X desejados em bom rendimentos, em um tempo de reação curto usando irradiação de micro-ondas.Abstract : In the present work we developed robust, economical and greener procedures for the synthesis of unsymmetrical diorganyl chalcogenides by using various substituted arylboronic acids and [O or N]- containing arenes. In the first part, we developed Iodine/DMSO catalyzed oxidative system for the synthesis of a variety of unsymmetrical diorganyl chalcogenides (S, Se, Te) using various arylboronic acids under microwave irradiations. The desired chalcogenated products III were obtained in good to excellent yields in the presence of 10 mol% of iodine, one equiv. of arylboronic acids II, half equiv. of various diorganyl dichalcogenides I and 2 equiv. of DMSO (as an oxidant). All the reactions were performed without the exclusion of air and moisture at 100 0C for 10 min under microwave irradiation. Various substituents with different electronic and steric effects tolerated in the optimized reaction conditions. The developed methodology was shown to be robust and could easily be scaled-up without any significant loss of yield. The chemistry described herein represents a transition metal and solvent free method for the preparation of unsymmetrical diorganyl chalcogenides. We were also successful in scaling up the reaction in up to 10 mmol. The scope of this coupling methodology was extended by using potassium vinyltrifluoroborate IV as an alternative to boronic acid in these tellurylation and selenylation reactions by applying the optimal reaction parameters. The reaction of ditelluride and diselenide I proceeded smoothly and afforded the corresponding coupled products V in 87% and 89% isolated yield. Considering the importance of diorganyl chalcogenides, we developed a regioselective, rapid and greener iodine-catalyzed method for the synthesis of diorganyl chalcogenides through oxidative C Se/C S formation via direct C(sp2)-H bond cleavage using [O or N]-containing arenes. In this work, we reported the synthesis of unsymmetrical diorganyl chalcogenides VII via direct chalcogenation reactions between dichalcogenides I and various arenes VI catalyzed by 20 mol% of iodine in the presence of 3 equiv. of DMSO (as an oxidant). This regioselective methodology allowed us to obtain desired chalcogenated product in good to excellent yields under transition metal and solvent-free conditions, without the exclusion of air and moisture, applying microwave irradiations for 10 min. The reaction was also scaled-up to 10 mmol. Additionally, by this protocol, we were able to access biologically important Se/S containing heteroarenes, such as, pyrimidines, pyridines, thiazole. The versatility of the developed methodology was observed by using thiophenol VIII and sulfonyl hydrazides VIII as another sulfenylating agents and N,N-dimethylaniline IX, affording the desired sulfonated product X in very good yield, in a short reaction time using MW irradiation

A Subjective Study on the Effects of Dynamic Virtual Chemistry Laboratory in a Secondary School Education

Virtual chemistry laboratories (VCLs) are the alternative solutions of the physical laboratories, where students can virtually conduct their experiments with a lower cost, and in an efficient and safer way. Considering the importance of technology-enhanced learning and that of the experimental study, several VCLs have been proposed. However, the existing VCLs are static and only provide the simulation of pre-defined experiments, procedures, or safety procedures and cannot be adapted according to the students’ level or new experimental tasks. In this paper, we proposed a dynamic virtual chemistry lab (DVCL) where instructors or experts are allowed to add a new chemical experiment by adding its apparatus, chemicals, glassware, and mechanism or add something new to its properties. We conducted a subjective study with field experts to investigate the effect of proposed DVCL in secondary school chemistry education. During evaluation, twenty-seven field experts were participated and evaluated the proposed DVCL with system usability scale (SUS)-questionnaire and by a simple questionnaire. The results showed that the proposed DVCL is very helpful for students’ performance and mental modeling and also for effortlessly uplifting their knowledge for hands-on experiments

(2-Amino­phen­yl)[(5S)-5-hydr­oxy-3,5-dimethyl-4,5-dihydro-1H-pyrazol-1-yl]methanone

In the mol­ecule of the title compound, C12H15N3O2, the pyrazole ring is oriented at a dihedral angle of 49.64 (6)° with respect to the benzene ring. Intra­molecular O—H⋯O, N—H⋯O and C—H⋯O inter­actions result in the formation of a trifurcated hydrogen bond. In the crystal structure, inter­molecular N—H⋯O and O—H⋯N hydrogen bonds link the mol­ecules, forming a network structure

Spectral characterization and crystal structure of 2-amino-N '-[(1Z)-1-(4-chlorophenyl)ethylidene]-benzohydrazide

The crystal structure of 2-amino-N'-[(1Z)-1-(4-chlorophenyl)ethylideneJbenzohydrazide (I) is determined by X-ray diffraction at room temperature. The structure of I also was characterized by elemental analysis, mass, FT-IR and NMR spectroscopic techniques. The compound crystallizes in triclinic system, and space group is P (1) over bar. Unit-cell dimensions are the following: a = 7.05380(10) angstrom, b = 7.65490(10) angstrom, c = 13.7094(4) angstrom, V = 694.01(2) angstrom(3), Z = 2. The title compound is nearly planar and has intermolecular N H center dot center dot center dot O hydrogen bonding. According to the spectral data, I exhibits an amide-iminol tautomerism. (C) 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved

De Quervain's Tenosynovitis and Thumb Pain in Physiotherapists Practicing Manual Therapy: Prevalence and Associated Factors

Background and Objective: Manual therapy is a treatment approach by physical therapists where different techniques are applied to patients with hands for rehabilitation purposes. The objective of the study was to find the frequency of De&rsquo;Quervain tenosynovitis and thumb and wrist pain in physical therapists working in different rehabilitation centers in relation to age, body mass index (BMI), and working hours. Methods: A cross-sectional study was conducted on 135 physical therapists working in different settings in Lahore, Pakistan. Physiotherapists were enrolled by convenience sampling. Data were recorded on a questionnaire form. Finkelstein test was performed to check De Quervain&rsquo;s tenosynovitis. A numeric pain rating scale was sued to measure pain. The data were tested for significance using statistical tests. Results: On the dominant hand, 99 (73.3%) physical therapists had no wrist pain, 104 (77%) had no thumb pain, 28 (20.7%) had mild wrist pain and 20 (14.8%) had mild thumb pain. Only 21 (15.6%) physiotherapists were tested positive for Finkelstein (De Quervain&rsquo;s tenosynovitis). Finkelstein test reported 100% negative result on the non-dominant side. There is a negative correlation between thumb pain with the age (r = -0.005), BMI (r = -0.110) and working hours (r = -0.033) of the physical therapists. Conclusion: The study concluded that the prevalence of De Quervain&rsquo;s tenosynovitis, thumb, and wrist pain was more on the dominant hand than on the non-dominant side. The majority of the physical therapists reported mild to no pain in the wrist and thumb. There is a negative correlation of thumb pain with age, BMI and working hours. &nbsp;</p

Layered Copper Hydroxide Salts as Catalyst for the “Click” Reaction and Their Application in Methyl Orange Photocatalytic Discoloration

The 1,2,3-triazoles are an important class of organic compounds that are found in a variety of biologically active compounds. The most usual and efficient methodology to synthetize these compounds is the Copper-catalyzed Azide–Alkyne Cycloaddition (CuAAC), preferably by use of click chemistry principles. Therefore, the development of simple, robust, easily accessible and efficient materials as catalysts for this kind of reaction is highly desirable. In this sense, layered hydroxide salts (LHS) emerge as an interesting alternative for the click reaction. Thus, we describe herein the preparation and characterization of copper (II) layered hydroxide salts and their application as catalysts for the CuAAC reaction under solvent-free conditions. This synthetic methodology of CuAAC reaction is attractive as it follows several concepts of green chemistry, such as being easy to perform, allowing purification without chromatographic column, the process forming no sub-products, affording the desired 1,2,3-traizoles in the specific 1,4-disubstituted position in high yield, and having a short reaction time. Moreover, the photocatalysis for the degradation of methyl orange was also highly efficient using the same catalyst