New Chemistry of Imidazolinium ylides

Previous work in this group has shown 4,5-dihydroimidazolium ylides, formed by N- alkylation of 4,5-dihydroimidazoles, to undergo 1,3-dipolar cycloadditions with a range of dipolarophiles in a highly regio- and stereoselective fashion. We have investigated two further aspects of this chemistry: (1) the synthesis of 4,5-dihydroimidazoles substituted with a heteroatom at C-2 and the subsequent N-alkylation of those templates followed by deprotonation to potentially access novel azomethine ylides; and (2) an intramolecular variant of the 1,3-dipolar cycloaddition, synthesising for this purpose a series of bromomethyl(co-l)-oxoalkenoates as dipolarophiles and subsequently reacting these with some 4,5-dihydroimidazole templates. The synthesis of 4,5-dihydroimidazoles substituted with a heteroatom at C-2 was developed from 1-enzyltetrahydroimidazol-2-thione 131. Methylation of this with either iodomethane or methyl trifluoromethanesulfonate provided a key methylthioimidazolium iodide intermediate 135 from which 2-alkanethio- (136), 2-alkoxy (137) and 2-dialkylamino- (138) 4,5-dihydroimidazoles could be prepared by deprotonation, reaction with an alkoxide or reaction with a dialkylamine, respectively. N-Alkylation of the heterocycles was found to be unsuccessful. An alternative strategy, involving the synthesis of l-benzyl-3-methoxycarbonylmethyltetrahydroimidazol-2-one 143a and -2-thione 143b, was developed. The oxygen-containing compound 143a was transformed into its corresponding 0-substituted salts by treatment with triethyloxonium tetrafluoroborate, trimethylsilyl trifluoromethanesulfonate or trifluoromethanesulfonic anhydride. The sulfur analogue 143b was S-methylated using methyl trifluoromethanesulfonate. However, neither of the salts was found to undergo a 1,3-dipolar cycloaddition reaction upon treatment with DBU followed by methyl acrylate. Intramolecular 1,3-dipolar cycloaddition reactions of a variety of ɑ-bromoketones with 1- benzyl4,5-dihydroimidazoles proved successful. Thus, reaction of 1-benzyl-4,5- dihydroimidazole 29 with methyl E-8-bromo-7-oxooct-2-enoate 196a followed by treatment with DBU afforded the tricyclic pyrroloquinoxaline adducts methyl 1-benzyl-2,3,7,8,9,9a-hexahydro-1H-pyrrolo[1,2,3-de]quinoxaline-6-carboxylate 217. This arises from the primary cycloadduct undergoing a cascade involving an eliminative ring-opening, recyclisation, loss of water and prototropic shift cascade. Seven other examples of this reaction, involving 2- and 4-phenyl-4,5-dihydroimidazoles, and ethyl and tertbutyl E-8-bromo-7-oxooct-2-enoate, as well as with 2- and 3-methyl substituted octenoates (i.e trisubstituted double bonds). In these cases no cycloaddition reaction involving the double bond occurs. In one instance, the reaction of (R)-4-phenyl-4,5-dihydroimidazole 112 with tert-butyl E-8-bromo-7-oxooct-2-enoate 278, we were able to isolate the primary cycloadduct, tert-butyl (3R,4aR,8aS,9S,9aR)-1-benzyl-5-oxo-3-phenyldecahydro-1H-imidazo[1,2-ɑ] indole-9-carboxylate 283. It would appear that the combination of sterically demanding phenyl and tert-butyl groups precludes eliminative ring-opening

Synthesis of some new 2-heterosubstituted 4,5-dihydroimidazoles

Several new 4,5-dihydroimidazoles (and the corresponding imidazolium salts) carrying heteroatom substituents at C-2 have been prepared from the corresponding tetrahydroimidazol-2-ones and/or -thiones

Impact of temperature and mode polarization on the acoustic phonon range in complex crystalline phases: A case study on intermetallic clathrates

The low and weakly temperature-varying lattice thermal conductivity, κL (T), in crystals with a complex unit cell such as type-I clathrates is assumed to originate from a reduced momentum and energy space available for propagative lattice vibrations, which is caused by the occurrence of low-energy optical phonon modes. In the context of ab initio self-consistent phonon (SCP) theory, it has been shown that the cubic and quartic anharmonic interactions result in a temperature-induced energy renormalization of these low-lying optical branches which contributes to the anomalous behavior of κL (T) in structurally ordered type-I clathrates [T. Tadano and S. Tsuneyuki, Phys. Rev. Lett. 120, 105901 (2018)]. By means of inelastic neutron scattering, we provide evidence for this energy renormalization in temperature, which has been resolved for transversely and longitudinally polarized phonons in the single crystal type-I clathrate Ba7.81Ge40.67Au5.33. By mapping the neutron intensity in the momentum space, we demonstrate the coherent character of the low-lying optical phonons. The overall phonon spectrum and dynamical structure factors are satisfactorily reproduced by ab initio harmonic calculations using density functional theory with the meta-GGA SCAN functional and a fully ordered structure. However, a polarization-dependent cutoff energy with opposing temperature shifts for longitudinal and transverse acoustic dispersions is experimentally observed which is not reproduced by the simulations. Anharmonicity affects the energies of the low-lying optical phonons in the transverse polarization, which compares quantitatively well with available results from SCP theory, whereas differences are observed for the longitudinal polarizatio

Maternal deaths in Pakistan : intersection of gender, class and social exclusion.

Background: A key aim of countries with high maternal mortality rates is to increase availability of competent maternal health care during pregnancy and childbirth. Yet, despite significant investment, countries with the highest burdens have not reduced their rates to the expected levels. We argue, taking Pakistan as a case study, that improving physical availability of services is necessary but not sufficient for reducing maternal mortality because gender inequities interact with caste and poverty to socially exclude certain groups of women from health services that are otherwise physically available. Methods: Using a critical ethnographic approach, two case studies of women who died during childbirth were pieced together from information gathered during the first six months of fieldwork in a village in Northern Punjab, Pakistan. Findings: Shida did not receive the necessary medical care because her heavily indebted family could not afford it. Zainab, a victim of domestic violence, did not receive any medical care because her martial family could not afford it, nor did they think she deserved it. Both women belonged to lower caste households, which are materially poor households and socially constructed as inferior. Conclusions: The stories of Shida and Zainab illustrate how a rigidly structured caste hierarchy, the gendered devaluing of females, and the reinforced lack of control that many impoverished women experience conspire to keep women from lifesaving health services that are physically available and should be at their disposal

Ancient mitochondrial DNA provides high-resolution time scale of the peopling of the Americas

The exact timing, route, and process of the initial peopling of the Americas remains uncertain despite much research. Archaeological evidence indicates the presence of humans as far as southern Chile by 14.6 thousand years ago (ka), shortly after the Pleistocene ice sheets blocking access from eastern Beringia began to retreat. Genetic estimates of the timing and route of entry have been constrained by the lack of suitable calibration points and low genetic diversity of Native Americans. We sequenced 92 whole mitochondrial genomes from pre-Columbian South American skeletons dating from 8.6 to 0.5 ka, allowing a detailed, temporally calibrated reconstruction of the peopling of the Americas in a Bayesian coalescent analysis. The data suggest that a small population entered the Americas via a coastal route around 16.0 ka, following previous isolation in eastern Beringia for ~2.4 to 9 thousand years after separation from eastern Siberian populations. Following a rapid movement throughout the Americas, limited gene flow in South America resulted in a marked phylogeographic structure of populations, which persisted through time. All of the ancient mitochondrial lineages detected in this study were absent from modern data sets, suggesting a high extinction rate. To investigate this further, we applied a novel principal components multiple logistic regression test to Bayesian serial coalescent simulations. The analysis supported a scenario in which European colonization caused a substantial loss of pre-Columbian lineages.Bastien Llamas, Lars Fehren-Schmitz, Guido Valverde, Julien Soubrier, Swapan Mallick, Nadin Rohland, Susanne Nordenfelt, Cristina Valdiosera, Stephen M. Richards, Adam Rohrlach, Maria Inés Barreto Romero, Isabel Flores Espinoza, Elsa Tomasto Cagigao, Lucía Watson Jiménez, Krzysztof Makowski, Ilán Santiago Leboreiro Reyna, Josefina Mansilla Lory, Julio Alejandro Ballivián Torrez, Mario A. Rivera, Richard L. Burger, Maria Constanza Ceruti, Johan Reinhard, R. Spencer Wells, Gustavo Politis, Calogero M. Santoro, Vivien G. Standen, Colin Smith, David Reich, Simon Y. W. Ho, Alan Cooper and Wolfgang Haa

Corn nitrogen rate recommendation tools’ performance across eight US midwest corn belt states

Determining which corn (Zea mays L.) N fertilizer rate recommendation tools best predict crop N need would be valuable for maximizing profits and minimizing environmental consequences. Simultaneous comparisons of multiple tools across various environmental conditions have been limited. The objectives of this research were to evaluate the performance of publicly‐available N fertilizer recommendation tools across diverse soil and weather conditions for: (i) prescribing N rates for planting and split‐fertilizer applications, and (ii) economic and environmental effects. Corn N‐response trials using standardized methods were conducted at 49 sites, spanning eight US Midwest states and three growing seasons. Nitrogen applications included eight rates in 45 kg N ha−1 increments all at‐planting and matching rates with 45 kg N ha−1 at‐planting plus at the V9 development stage. Tool performances were compared to the economically optimal N rate (EONR). Over this large geographic region, only 10 of 31 recommendation tools (mainly soil nitrate tests) produced N rate recommendations that weakly correlated to EONR (P ≤ .10; r2 ≤ .20). With other metrics of performance, the Maximum Return to N (MRTN) soil nitrate tests, and canopy reflectance sensing came close to matching EONR. Economically, all tools but the Maize‐N crop growth model had similar returns compared to EONR. Environmentally, yield goal based tools resulted in the highest environmental costs. Results show that no tool was universally reliable over this study\u27s diverse growing environments, suggesting that additional tool development is needed to better represent N inputs and crop utilization at a larger regional level

Rebuild the Academy: Supporting academic mothers during COVID-19 and beyond

The issues facing academic mothers have been discussed for decades. Coronavirus Disease 2019 (COVID-19) is further exposing these inequalities as womxn scientists who are parenting while also engaging in a combination of academic related duties are falling behind. These inequities can be solved by investing strategically in solutions. Here we describe strategies that would ensure a more equitable academy for working mothers now and in the future. While the data are clear that mothers are being disproportionately impacted by COVID-19, many groups could benefit from these strategies. Rather than rebuilding what we once knew, let us be the architects of a new world

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente