Nickel Catalyzed Carbonylation/Carboxylation Sequence via Double CO2 Incorporation

A carbonylation-carboxylation synthetic sequence, via double CO2 fixation, is described. The productive merger of a Ni-catalyzed cross-electrophile coupling manifold, with the use of AlCl3, triggered a cascade reaction with the formation of three consecutive C-C bonds in a single operation. This strategy traces an unprecedented synthetic route to ketones under Lewis acid assisted carbon dioxide valorization. Computational insights revealed a unique double function of AlCl3, and labeling (13CO2) experiments validate the genuine incorporation of CO2 in both functional groups.

Manganese(I)-Catalyzed Asymmetric Hydrophosphination of α,β-Unsaturated Carbonyl Derivatives

Here we report catalytic asymmetric hydrophosphination of α,β-unsaturated carbonyl derivatives using a chiral Mn(I) complex as a catalyst. Through H-P bond activation, various phosphine-containing chiral products can be accessed via hydrophosphination of various ketone-, ester-, and carboxamide-based Michael acceptors.

Catalytic Access to Chiral δ-Lactams via Nucleophilic Dearomatization of Pyridine Derivatives

Nitrogen-bearing rings are common features in the molecular structures of modern drugs, with chiral δ-lactams being an important subclass due to their known pharmacological properties. Catalytic dearomatization of preactivated pyridinium ion derivatives emerged as a powerful method for the rapid construction of chiral N-heterocycles. However, direct catalytic dearomatization of simple pyridine derivatives are scarce and methodologies yielding chiral δ-lactams are yet to be developed. Herein, we describe an enantioselective C4-dearomatization of methoxypyridine derivatives for the preparation of functionalised enantioenriched δ-lactams using chiral copper catalysis. Experimental ¹³ C kinetic isotope effects and density functional theory calculations shed light on the reaction mechanism and the origin of enantioselectivity.

Enantio- and Z-selective synthesis of functionalized alkenes bearing tertiary allylic stereogenic center

Olefins are ubiquitous in biologically active molecules and frequently used as building blocks in chemical transformations. However, although many strategies exist for the synthesis of stereodefined E-olefines, their thermodynamically less stable Z counterparts are substantially more demanding, while access to those bearing an allylic stereocenter with an adjacent reactive functionality remains unsolved altogether. Even the classic Wittig reaction, arguably the most versatile and widely used approach to construct Z-alkenes, falls short for the synthesis of these particularly challenging yet highly useful structural motives. Here, we report a general methodology for Z-selective synthesis of functionalized chiral alkenes that establishes readily available alkene-derived phosphines as an alternative to alkylating reagents in Wittig olefination, thus offering previously unidentified retrosynthetic disconnections for the formation of functionalized disubstituted alkenes. We demonstrate the potential of this method by structural diversification of several bioactive molecules.

Direct Synthesis of α-Aryl-α-Trifluoromethyl Alcohols via Nickel Catalyzed Cross-Electrophile Coupling

A nickel-catalyzed reductive cross-electrophile coupling between the redox-active N-trifluoroethoxyphthalimide and iodoarenes is documented. The protocol reproduces a formal arylation of trifluoroacetaldehyde under mild conditions in high yields (up to 88 %) and with large functional group tolerance (30 examples). A combined computational and experimental investigation revealed a pivotal solvent assisted 1,2-Hydrogen Atom Transfer (HAT) process to generate a nucleophilic α-hydroxy-α-trifluoromethyl C-centered radical for the Csp² -Csp³ bond forming process.

Electrophilic Trapping of Semibenzenes

In this work, we demonstrate how allylative dearomatization of benzyl chlorides can provide direct access to a variety of semibenzenes. These scaffolds behave as highly reactive nucleophiles in the presence of carbocations. In addition, semibenzenes are susceptible to intramolecular rearrangements rendering a broad scope of functionalized arenes. An analysis of this new reactivity is reported, as well as the rationale behind the observed intramolecular reorganizations.

Violations to the Principle of Least Motion: the Shortest Path is not Always the Fastest

The reaction between two molecules is usually envisioned as following a least-motion path with both molecules travelling minimum distances to meet each other. However, the reaction path of lowest activation...

Manganese(I)-Catalyzed H-P Bond Activation via Metal-Ligand Cooperation

Here we report that chiral Mn(I) complexes are capable of H–P bond activation. This activation mode enables a general method for the hydrophosphination of internal and terminal α,β-unsaturated nitriles. Metal−ligand cooperation, a strategy previously not considered for catalytic H–P bond activation, is at the base of the mechanistic action of the Mn(I)-based catalyst. Our computational studies support a stepwise mechanism for the hydrophosphination and provide insight into the origin of the enantioselectivity.

Enantioselective Catalytic Dearomative Addition of Grignard Reagents to 4-Methoxypyridinium Ions

We describe a general catalytic methodology for the enantioselective dearomative alkylation of pyridine derivatives with Grignard reagents, allowing direct access to nearly enantiopure chiral dihydro-4-pyridones with yields up to 98%. The methodology involves dearomatization of in situ-formed N-acylpyridinium salts, employing alkyl organomagnesium reagents as nucleophiles and a chiral copper (I) complex as the catalyst. Computational and mechanistic studies provide insights into the origin of the reactivity and enantioselectivity of the catalytic process.

Lewis Acid Promoted Dearomatization of Naphthols

Two-step dearomative functionalization of naphthols promoted by Lewis acids and copper(I) catalysis was developed. Initially, Lewis acid complexation inverted the electronic properties of the ring and established an equilibrium with the dearomatized counterpart. Subsequent trapping of the dearomatized intermediate with organometallics as well as organophosphines was demonstrated and provided the corresponding dearomatized products.

Nucleophilic Dearomatization of N-Heteroaromatics Enabled by Lewis Acids and Copper Catalysis

Dearomative functionalization of heteroaromatics, a readily available chemical feedstock, is one of the most straightforward approaches for the synthesis of three-dimensional, chiral heterocyclic systems, important synthetic building blocks for both synthetic chemistry and drug discovery. Despite significant efforts, direct nucleophilic additions to heteroaromatics have remained challenging because of the low reactivity of aromatic substrates associated with the loss of aromaticity, as well the regio- and stereoselectivities of the reaction. Here we present a catalytic system that leads to unprecedented, high-yielding dearomative C-4 functionalization of quinolines with organometallics with nearly absolute regio- and stereoselectivities and with a catalyst turnover number (TON) as high as 1000. The synergistic action of the chiral copper catalyst, Lewis acid, and Grignard reagents allows us to overcome the energetic barrier of the dearomatization process and leads to chiral products with selectivities reaching 99% in most cases. Molecular modeling provides important insights into the speciation and the origin of the regio- and enantioselectivity of the catalytic process. The results reveal that the role of the Lewis acid is not only to activate the substrate toward a potential nucleophilic addition but also to subtly control the regiochemistry by preventing the C-2 addition from happening.

Synthesis and Functionalization of Allenes by Direct Pd-Catalyzed Organolithium Cross-Coupling

A palladium-catalyzed cross-coupling between in situ generated allenyl/propargyl-lithium species and aryl bromides to yield highly functionalized allenes is reported. The direct and selective formation of allenic products preventing the corresponding isomeric propargylic product is accomplished by the choice of SPhos or XPhos based Pd catalysts. The methodology avoids the prior transmetalation to other transition metals or reverse approaches that required prefunctionalization of substrates with leaving groups, resulting in a fast and efficient approach for the synthesis of tri- and tetrasubstituted allenes. Experimental and theoretical studies on the mechanism show catalyst control of selectivity in this allene formation.

Synthesis of Spirobicyclic Pyrazoles by Intramolecular Dipolar Cycloadditions/[1s, 5s] Sigmatropic Rearrangements

The formation of fused pyrazoles via intramolecular 1,3-dipolar cycloadditions of diazo intermediates with pendant alkynes is described. A subsequent thermal [1s, 5s] sigmatropic shift of these pyrazole systems resulted in a ring contraction, forming spirocyclic pyrazoles. The limitations of this rearrangement were explored by changing the substituents on the nonmigrating aromatic ring and by using substrates lacking an aromatic linkage to the propargyl group.

Pushing the limits of concertedness. A waltz of wandering carbocations

Coupling multiple 1,n-shifts in reactions of biosynthetically relevant carbocations defies previous limits on the concertedness of multiple chemical events.

Among the array of complex terpene-forming carbocation cyclization/rearrangement reactions, the so-called “triple shift” reactions are among the most unexpected. Such reactions involve the asynchronous combination of three 1,n-shifts into a concerted process, e.g., a 1,2-alkyl shift followed by a 1,3-hydride shift followed by a second 1,2-alkyl shift. This type of reaction so far has been proposed to occur during the biosynthesis of diterpenes and the sidechains of sterols. Here we describe efforts to push the limits of concertedness in this type of carbocation reaction by designing, and characterizing with quantum chemical computations, systems that could couple additional 1,n-shift events to a triple shift leading, in principle to quadruple, pentuple, etc. shifts. While our designs did not lead to clear-cut examples of quadruple, etc. shifts, they did lead to reactions with surprisingly flat energy surfaces where more than five chemical events connect reactants and plausible products. Ab initio molecular dynamics simulations demonstrate that the formal minima on these surfaces interchange on short timescales, both with each other and with additional unexpected structures, allowing us a glimpse into a very complex manifold that allows ready access to great structural diversity.

Mechanism of the Molybdenum-Mediated Cadogan Reaction

Oxygen atom transfer reactions are receiving increasing attention because they bring about paramount transformations in the current biomass processing industry. Significant efforts have therefore been made lately in the development of efficient and scalable methods to deoxygenate organic compounds. One recent alternative involves the modification of the Cadogan reaction in which a Mo(VI) core catalyzes the reduction of o-nitrostyrene derivatives to indoles in the presence of PPh₃. We have used density functional theory calculations to perform a comprehensive mechanistic study on this transformation, in which we find two clearly defined stages: an associative path from the nitro to the nitroso compound, characterized by the reduction of the catalyst in the first step, and a peculiar mechanism involving oxazaphosphiridine and nitrene intermediates leading to an indole product, where the metal catalyst does not participate.

Análise Elementar e da Molhabilidade de Filmes Finos de Hexametildisiloxano Depositados por Plasma em Materiais Restauradores Indiretos

Uma porcelana (VM9, VITA, Zahnfabrik) e dois compósitos, (Enamic Lava Ultimate <3M ESPE, Seefeld>), foram usados. Os filmes foram obtidos a partir de: PAr PO2 (polimerização a plasma com Argônio e Oxigênio, respectivamente) e PIDP (técnica hibrida de implantação iônica e polimerização a plasma). A morfologia foi estudada por microscopia eletrônica de varredura e a análise química por espectroscopia por energia dispersiva (EDS) e por espectroscopia de fotoelétrons excitados por raios-X (XPS). A molhabilidade e a rugosidade (Ra) foram determinadas através do método da gota séssil e perfilometria por contato, respectivamente. Os resultados foram analisados com ANOVA com o teste de Tukey (a<0,05). A análise morfológica demonstrou que os filmes finos revestiram os materiais uniformemente. Detectou-se a presença de estruturas granulares por toda a superfície, que variou em tamanho e quantidade para cada filme. EDS e XPS demonstraram a presença principal dos elementos químicos carbono, oxigênio  e silício. Foram obtidos filmes hidrofóbicos (PAr e PO2) e hidrofílicos (PIDP) (p<0,001). Para Ra, houve diferença pontualmente na rugosidade de alguns filmes (p<0,001) e os valores mantiveram-se abaixo de 2µm. Conclui-se que a morfologia e composição química foi filme-dependente, houve produção de superfícies hidrofílica (PIDP) e hidrofóbicas (PAr e PO2) e rugosidade permaneceu inferior a 2μm.Palavras-chave: Gases em Plasma. Propriedades de Superfície. Materiais Dentários.

Cotton genotypes selection through artificial neural networks

Breeding programs currently use statistical analysis to assist in the identification of superior genotypes at various stages of a cultivar's development. Differently from these analyses, the computational intelligence approach has been little explored in genetic improvement of cotton. Thus, this study was carried out with the objective of presenting the use of artificial neural networks as auxiliary tools in the improvement of the cotton to improve fiber quality. To demonstrate the applicability of this approach, this research was carried out using the evaluation data of 40 genotypes. In order to classify the genotypes for fiber quality, the artificial neural networks were trained with replicate data of 20 genotypes of cotton evaluated in the harvests of 2013/14 and 2014/15, regarding fiber length, uniformity of length, fiber strength, micronaire index, elongation, short fiber index, maturity index, reflectance degree, and fiber quality index. This quality index was estimated by means of a weighted average on the determined score (1 to 5) of each characteristic of the HVI evaluated, according to its industry standards. The artificial neural networks presented a high capacity of correct classification of the 20 selected genotypes based on the fiber quality index, so that when using fiber length associated with the short fiber index, fiber maturation, and micronaire index, the artificial neural networks presented better results than using only fiber length and previous associations. It was also observed that to submit data of means of new genotypes to the neural networks trained with data of repetition, provides better results of classification of the genotypes. When observing the results obtained in the present study, it was verified that the artificial neural networks present great potential to be used in the different stages of a genetic improvement program of the cotton, aiming at the improvement of the fiber quality of the future cultivars.

[MoO2]2+-Mediated Oxygen Atom Transfer via an Unusual Lewis Acid Mechanism

Density functional theory is applied to the study of the oxygen atom transfer reaction from sulfoxide (DMSO) to phosphine (PMe₃) catalyzed by the [MoO₂]²⁺ active core. In this work, two fundamentally different roles are explored for this dioxometal complex in the first step of the catalytic cycle: as an oxidizing agent and as a Lewis acid. The latter turns out to be the favored pathway for the oxygen atom transfer. This finding may have more general implications for similar reactions catalyzed by the same [MoO₂]²⁺ core.

Evaluation of genetic diversity among soybean (Glycine max) genotypes using univariate and multivariate analysis

The genetic diversity study has paramount importance in breeding programs; hence, it allows selection and choice of the parental genetic divergence, which have the agronomic traits desired by the breeder. This study aimed to characterize the genetic divergence between 24 soybean genotypes through their agronomic traits, using multivariate clustering methods to select the potential genitors for the promising hybrid combinations. Six agronomic traits evaluated were number of days to flowering and maturity, plant height at flowering and maturity, insertion height of the first pod, and yield. The genetic divergence evaluated by multivariate analysis that esteemed first the Mahalanobis' generalized distance (D2), then the clustering using Tocher's optimization methods, and then the unweighted pair group method with arithmetic average (UPGMA). Tocher's optimization method and the UPGMA agreed with the groups' constitution between each other, the formation of eight distinct groups according Tocher's method and seven distinct groups using UPGMA. The trait number of days for flowering (45.66%) was the most efficient to explain dissimilarity between genotypes, and must be one of the main traits considered by the breeder in the moment of genitors choice in soybean-breeding programs. The genetic variability allowed the identification of dissimilar genotypes and with superior performances. The hybridizations UFU 18 x UFUS CARAJÁS, UFU 15 x UFU 13, and UFU 13 x UFUS CARAJÁS are promising to obtain superior segregating populations, which enable the development of more productive genotypes.

Radioactivity from Fukushima nuclear accident detected in Lisbon, Portugal

The radioactivity released from the Fukushima Dai-ichi nuclear accident was transported around the globe by atmospheric processes. Several artificial radionuclides were detected and measured in aerosols and atmospheric surface depositions in the Lisbon area during late March and early April 2011. The highest concentrations measured in aerosols were those of particulate (131)I, 1.39 ± 0.08 mBq m(-3). Cesium-134, (137)Cs and (132)Te were also determined but at lower concentrations. The total atmospheric depositions on the ground were higher on the first week of April with values for (131)I, (134)Cs, and (137)Cs of 0.92 ± 0.11, 0.59 ± 0.06, and 0.62 ± 0.12 Bq m(-2), respectively. The four artificial radionuclides measurable, (131)I, (132)Te (134)Cs, and (137)Cs, caused little radiation exposure to the members of the public, that was five orders of magnitude lower than the ionizing radiation effective dose limits for members of the public for one year (1 mSv y(-1)).

Tracking of airborne radionuclides from the damaged Fukushima Dai-ichi nuclear reactors by European networks

Radioactive emissions into the atmosphere from the damaged reactors of the Fukushima Dai-ichi nuclear power plant (NPP) started on March 12th, 2011. Among the various radionuclides released, iodine-131 ((131)I) and cesium isotopes ((137)Cs and (134)Cs) were transported across the Pacific toward the North American continent and reached Europe despite dispersion and washout along the route of the contaminated air masses. In Europe, the first signs of the releases were detected 7 days later while the first peak of activity level was observed between March 28th and March 30th. Time variations over a 20-day period and spatial variations across more than 150 sampling locations in Europe made it possible to characterize the contaminated air masses. After the Chernobyl accident, only a few measurements of the gaseous (131)I fraction were conducted compared to the number of measurements for the particulate fraction. Several studies had already pointed out the importance of the gaseous (131)I and the large underestimation of the total (131)I airborne activity level, and subsequent calculations of inhalation dose, if neglected. The measurements made across Europe following the releases from the Fukushima NPP reactors have provided a significant amount of new data on the ratio of the gaseous (131)I fraction to total (131)I, both on a spatial scale and its temporal variation. It can be pointed out that during the Fukushima event, the (134)Cs to (137)Cs ratio proved to be different from that observed after the Chernobyl accident. The data set provided in this paper is the most comprehensive survey of the main relevant airborne radionuclides from the Fukushima reactors, measured across Europe. A rough estimate of the total (131)I inventory that has passed over Europe during this period was <1% of the released amount. According to the measurements, airborne activity levels remain of no concern for public health in Europe.

Patients with nephrolithiasis and blood hypertension have higher calciuria than those with isolated nephrolithiasis or hypertension?

AIM

The aim of this study was to determine urinary excretion of calcium, uric acid and sodium and to evaluate insulin resistance in patients with nephrolithiasis and blood hypertension, isolated and in association, and in healthy controls, in absence of obesity and diabetes.

METHODS

The study included 83 non-obese or diabetic patients: 17 with nephrolithiasis and hypertension (group D); 25 with nephrolithiasis (group C); 17 with hypertension (group B) and 24 healthy controls (group A). Urinary analysis was done in 24-hour urine collection and insulin resistance was evaluated through the HOMA-IR index.

RESULTS

Calciuria was higher in group D in relation to groups A (P<0.01), B (P<0.01) and C (P=0.01). There was no significant difference between groups A and B (P=0.32), A and C (P=0.10) and B and C (P=0.68). Correlation analysis between urinary calcium detected strong correlation with uric acid in group A, regular in groups B and C and, strong with sodium in groups B and C. No differences were detected in uric acid and sodium excretion or insulin resistance among groups.

CONCLUSIONS

Patients with blood hypertension and nephrolithiasis present higher calciuria than healthy people, with hypertension or with lithiasis and do not have the positive correlation observed in these latter groups with renal excretion of uric acid and sodium. These results suggest that impaired renal calcium reabsorption in non-obese or diabetic individuals is involved in the association between hypertension and urolithiasis.

Radioactivity in the environment around past radium and uranium mining sites of Portugal

Measurements of ambient radiation doses and determination of radionuclide concentrations in mining waste and soils were performed in 60 areas of former radium and uranium mining. In several places, mining waste and low-grade uranium ore left on the surface contain radioactivity above regional background. Most of the former mining sites present no enhanced radionuclide concentrations. However, in the mining facilities where the radioactive ore was chemically extracted, mill tailings contain materials with elevated levels of radioactivity, up to 200 times the levels in unaffected soils of the region. Mud from neutralization ponds used to treat acid mine waters contains also elevated radionuclide concentrations. Furthermore, depending on the type of waste, the radioelement composition varies. Environmental rehabilitation measures shall take these differences into account in order to prevent in the long term the radioactive contamination of agriculture soils and water resources, and to ensure adequate radiological protection to the public and to the environment.

226Ra, 228Ra and 228Th in scale and sludge samples from the Campos Basin oilfield E&P activities

More than 40 scale and sludge samples from the Campos Basin oilfield were analysed in terms of 226Ra, 228Ra and 228Th. Although the exact origin of the samples was not known, scale samples derived from production pipes and sludge samples from water-oil separation units. Reported values ranged from 0.13 to 331 kBq.kg(-1) for 226Ra, from 0.10 to 245 kBq.kg(-1) for 228Ra and <0.10 to 272 kBq.kg(-1) for 228Th in sludge samples. The concentrations in scales were much more regular than in sludges and ranged from 16.2 to 93.2 kBq.kg(-1) for 226Ra, from 4.0 to 36.9 kBq.kg(-1) for 228Ra and from 4.5 to 18.5 kBq.kg(-1) for 228Th. Based on the Basic Safety Standards recommendations and on the derived results, these activities cannot be regarded as exempted and specific procedures should be designed for their radiological control.

[Accidents with children in the region of Campinas, Brazil]

OBJECTIVE: Evaluate prospectively the frequency and cause of accidents in children seen at the Pediatric Emergency Service of a University Hospital. The main aim is to subsidize the development of education and preventive programs.METHODS: Data of all children, less than 14 years old, from March 1997 to February 1998 were collected with a standard questionnaire.RESULTS: Accidents in 3,214 children were studied, 11.4% of the total. Males predominated (62.1%). Accidents were more common in the 9 to 13 year age group (33.4%), 2 to 5 year age group (27.2%) and 5 to 9 year group (25,5%). Traumatism, mainly due to falls, was the cause in 74%. Head trauma was important in the younger than 1 year, and trauma involving the extremities in the 9 to 13 age group. Bites and stings predominated in the 5 to 13 year age group, intoxication and foreign bodies in the 2 to 5 years age group. Burns predominated in the younger than 5 years. Most accidents (89.7%) were of low complexity but 20 patients had to be admitted to an ICU and 4 died in the Emergency Room.CONCLUSIONS: The child older than 9 years, male, with trauma of the extremities due to a fall was the most frequent case of accident. Prevention programs must be targeted to specific age ranges. Accidents are responsible for a great part of the overload of Emergency Services as 89.7% were of low complexity. Primary care health facilities personnel must be trained to manage accidents that do not involve complex procedures.

[Inguinal hernia repair with the Shouldice technique]

The authors analyze the result of Shouldice inguinal hernia repair in 1000 patients. In a total of 1034 hernias, 966 of them were unilateral and 68 bilateral. The hernias were indirect (61.7%), direct (24.9%) and combined (3.5%). There were 102 recurrent hernias (9.9%) and the mean age of the patients was 50 years. In most cases the patients were male (96.9%) and peasants (47.6%). The post-operative follow-up was annual in 65.8% of the patients, for a period up to 10 years. The recurrence rate was 0.8% in the cases of primary hernias and 4.9% in the case of recurrent ones.

[Prevalence of schistosomiasis mansoni and parasitic intestinal diseases among students of the rural area of the Municipality of Jaboticatubas, MG, 1992-1993]

Students from a Rural Boarding house of UFMG School of Medicine performed a survey of prevalence of schistosomiasis mansoni and other intestinal parasites in 20 rural schools in Jaboticatubas, MG. An evaluation of house and sanitation conditions was made and stool parasitological examinations were realised in all school children. It was noticed that 15.43% of the children presented S. mansoni's ova in stool--that was the most prevalent parasite. From the examinations we verify 13.76% positive cases for G. lamblia; 12.89% for S. stercoralis; 11.13% for A. lumbricoides; 9.96% for hookworms; 9.57% for E. histolytica. The other parasites appeared with lower prevalence. All the children that presented parasite's ova in stool received treatment. The result that was found shows that schistosomiasis mansoni is a very serious problem of public health and basic sanitation actions are necessary to the endemic control.