The First Anionic Thia-Fries Rearrangement at the Cobaltocenium Cation

While the chemistry of ferrocene is rich and widely explored, this is not the case for the isoelectronic cobaltocenium cation. Here we report the first syntheses of triflate substituted cobaltocenium cations based on respective (cyclopentadienone)(cylopentadienyl)cobalt(I) complexes, which have first been reported by Vollhardt et al. ca. forty years ago. Reaction with triflic anhydride affords the triflate substituted cobaltocenium cations, which upon treatment with lithium diisopropylamide undergo the first anionic thia-Fries rearrangements of cobaltocenium complexes. To our knowledge, this is, in addition, the first case of a deprotonation of a cobaltocenium complex by a lithium base. Alternatively, desilylation of silyl derivatives with cesium fluoride caused anion formation leading to the rearrangement products in higher yields. The 2-(trifluoromethylsulfonyl)(cyclopentadienone) complexes obtained were fully characterized including a crystal structure analysis. As with ferrocene, respective mesylates or tosylates do not undergo the rearrangement

Fluorosulfonylferrocene, (Trifluoromethylsulfonyl)ferrocene and New Ferrocenyl Sulfonates: Directed ortho Lithiation and New Anionic Thia-Fries Rearrangements at Ferrocene

Ferrocenyl triflates are known to undergo anionic thia-Fries rearrangements at low temperature in high yields. In order to expand the scope of this reaction, ferrocenyl sulfonates and sulfonylferrocenes were prepared and their reactivity investigated. Treatment of ferrocenyl fluorosulfonate with lithium 2,2,6,6-tetramethylpiperidide gave rise to a new anionic thia-Fries rearrangement at ferrocene. The formation of a rare oxathiine was observed with ferrocenyl (pentafluorophenyl)sulfonate as a result of an ortho lithiation and a subsequent intramolecular nucleophilic aromatic substitution. In contrast to fluorinated ferrocenyl sulfonates, fluorosulfonylferrocene as well as (trifluoromethylsulfonyl)ferrocene underwent ortho lithiation under comparable reaction conditions

Validation of the NEMO-ERSEM operational ecosystem model for the North West European Continental Shelf

This paper details updates to the Met Office's operational coupled hydrodynamic-ecosystem model from the 7 km Medium-Resolution Continental Shelf – POLCOMS-ERSEM (MRCS-PE) system (Siddorn et al., 2007) to the 7 km Atlantic Margin Model NEMO-ERSEM (AMM7-NE) system. We also provide a validation of the ecosystem component of the new operational system. Comparisons have been made between the model variables and available in situ, satellite and climatological data. The AMM7-NE system has also been benchmarked against the MRCS-PE system. The transition to the new AMM7-NE system was successful and it has been running operationally since March 2012 and has been providing products through MyOcean (<a href="http://www.myocean.eu.org" target="_blank">http://www.myocean.eu.org</a>) since that time. The results presented herein show the AMM7-NE system performs better than the MRCS-PE system with the most improvement in the model nutrient fields. The problem of nutrient accumulation in the MRCS-PE system appears to be solved in the new AMM7-NE system with nutrient fields improved throughout the domain as discussed in Sect. 4. Improvements in model chlorophyll are also seen but are more modest

Anionic Thia-Fries Rearrangement at Ferrocene: A Computational and Experimental Study

Ferrocenyl triflate (1) and 1,1′-ferrocenediyl ditriflate (5) undergo single and double anionic thia-Fries rearrangements at low temperatures in high yields with the latter forming exclusively the respective meso product. The detailed mechanisms of the anionic thia-Fries rearrangement of 1, as well as that of the double anionic thia-Fries rearrangement of 5, are examined with the aid of DFT calculations. Functionals, basis set and pseudopotentials applied were selected in accordance with a benchmark using the crystal structure analysis of the prime product 3 of the reaction of 1 before hydrolysis for comparison, which has so far not been reported. The unprecedented meso diastereoselectivity of the double anionic thia-Fries rearrangement of 5 is shown to be a result of a distinctive degree of chelation arising from two diastereomeric transition states

Efficient synthesis of novel bis(dihydropyrano[2,3c]pyrazoles), bis(4H-chromenes) and bis(dihydropyrano[3,2-c]chromenes) with amide functionality

A synthesis of novel bis(1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles), bis(4H-chromene-3-carbonitriles) and bis(dihydropyrano[3,2-c]chromenes), which are linked to aliphatic spacers via amide linkages was achieved via multicomponent reactions (MCR) of the appropriate bis-aldehyde with two equivalents of both of malononitrile and 3-methylpyrazol-5-one, dimedone or 4-hydroxycoumarin in a basic solution

New Azacycles by One-Pot Three-Component Hantzsch-Like Synthesis of Tetra(hexa)azacyclopenta[a]anthracenes, Tetraazaindeno[5,4-b]fluorenes, and Oxatetraazacyclopenta[m]tetraphenes

Multicomponent reactions (MCRs) are envisaged as an entry point for the synthesis of heterocyclic compounds with interesting biological activities. An efficient approach to annelated tetra(hexa)azacyclopenta[a]anthracenes, tetraazaindeno[5,4-b]fluorenes, and oxatetraazacyclopenta[m]tetraphene was accomplished using a three-component reaction involving 7-amino-2-methyl-3-phenylpyrazolo[1,5-a]pyrimidin-5-one with aromatic aldehydes and the corresponding active 1,3-dicarbonyl compounds (namely, dimedone, 1,3-dimethylbarbituric acid, 1,3-indanedione, and 4-hydroxycoumarine). The reactions were conducted in glacial acetic acid at reflux for 5 h to give the desired products in good yields (62–83 %). The chemical constitutions of all new products were confirmed spectroscopically

Two-loop electroweak fermionic corrections to sin^2 theta_{eff}^{b anti-b}

We present the first calculation of the two-loop electroweak fermionic correction to the flavour-dependent effective weak-mixing angle for bottom quarks, sin^2 theta_{eff}^{b anti-b}. For the evaluation of the missing two-loop vertex diagrams, two methods are employed, one based on a semi-numerical Bernstein-Tkachov algorithm and the second on asymptotic expansions in the large top-quark mass. A third method based on dispersion relations is used for checking the basic loop integrals. We find that for small Higgs-boson mass values, M_H ~ 100 GeV, the correction is sizable, of order O(10^{-4}).Comment: 17 pages, 2 figures, references added, accepted for publication in Nucl. Phys.

Versatile Coordination of Cyclopentadienyl-Arene Ligands and Its Role in Titanium-Catalyzed Ethylene Trimerization

Cationic titanium(IV) complexes with ansa-(η5-cyclopentadienyl,η6-arene) ligands were synthesized and characterized by X-ray crystallography. The strength of the metal-arene interaction in these systems was studied by variable-temperature NMR spectroscopy. Complexes with a C1 bridge between the cyclopentadienyl and arene moieties feature hemilabile coordination behavior of the ligand and consequently are active ethylene trimerization catalysts. Reaction of the titanium(IV) dimethyl cations with CO results in conversion to the analogous cationic titanium(II) dicarbonyl species. Metal-to-ligand backdonation in these formally low-valent complexes gives rise to a strongly bonded, partially reduced arene moiety. In contrast to the η6-arene coordination mode observed for titanium, the more electron-rich vanadium(V) cations [cyclopentadienyl-arene]V(NiPr2)(NC6H4-4-Me)+ feature η1-arene binding, as determined by a crystallographic study. The three different metal-arene coordination modes that we experimentally observed model intermediates in the cycle for titanium-catalyzed ethylene trimerization. The nature of the metal-arene interaction in these systems was studied by DFT calculations.

Surgical versus conservative treatment for odontoid fractures in older people:an international prospective comparative study

Background: The optimal treatment for odontoid fractures in older people remains debated. Odontoid fractures are increasingly relevant to clinical practice due to ageing of the population.Methods: An international prospective comparative study was conducted in fifteen European centres, involving patients aged ≥55 years with type II/III odontoid fractures. The surgeon and patient jointly decided on the applied treatment. Surgical and conservative treatments were compared. Primary outcomes were Neck Disability Index (NDI) improvement, fracture union and stability at 52 weeks. Secondary outcomes were Visual Analogue Scale neck pain, Likert patient-perceived recovery and EuroQol-5D-3L at 52 weeks. Subgroup analyses considered age, type II and displaced fractures. Multivariable regression analyses adjusted for age, gender and fracture characteristics. Results: The study included 276 patients, of which 144 (52%) were treated surgically and 132 (48%) conservatively (mean (SD) age 77.3 (9.1) vs. 76.6 (9.7), P = 0.56). NDI improvement was largely similar between surgical and conservative treatments (mean (SE) −11 (2.4) vs. −14 (1.8), P = 0.08), as were union (86% vs. 78%, aOR 2.3, 95% CI 0.97–5.7) and stability (99% vs. 98%, aOR NA). NDI improvement did not differ between patients with union and persistent non-union (mean (SE) −13 (2.0) vs. −12 (2.8), P = 0.78). There was no difference for any of the secondary outcomes or subgroups. Conclusions: Clinical outcome and fracture healing at 52 weeks were similar between treatments. Clinical outcome and fracture union were not associated. Treatments should prioritize favourable clinical over radiological outcomes.</p

The representation of alkalinity and the carbonate pump from CMIP5 to CMIP6 Earth system models and implications for the carbon cycle

Ocean alkalinity is critical to the uptake of atmospheric carbon in surface waters and provides buffering capacity towards the associated acidification. However, unlike dissolved inorganic carbon (DIC), alkalinity is not directly impacted by anthropogenic carbon emissions. Within the context of projections of future ocean carbon uptake and potential ecosystem impacts, especially through Coupled Model Intercomparison Projects (CMIPs), the representation of alkalinity and the main driver of its distribution in the ocean interior, the calcium carbonate cycle, have often been overlooked. Here we track the changes from CMIP5 to CMIP6 with respect to the Earth system model (ESM) representation of alkalinity and the carbonate pump which depletes the surface ocean in alkalinity through biological production of calcium carbonate and releases it at depth through export and dissolution. We report an improvement in the representation of alkalinity in CMIP6 ESMs relative to those in CMIP5, with CMIP6 ESMs simulating lower surface alkalinity concentrations, an increased meridional surface gradient and an enhanced global vertical gradient. This improvement can be explained in part by an increase in calcium carbonate (CaCO3) production for some ESMs, which redistributes alkalinity at the surface and strengthens its vertical gradient in the water column. We were able to constrain a particulate inorganic carbon (PIC) export estimate of 44–55 Tmol yr−1 at 100 m for the ESMs to match the observed vertical gradient of alkalinity. Reviewing the representation of the CaCO3 cycle across CMIP5/6, we find a substantial range of parameterizations. While all biogeochemical models currently represent pelagic calcification, they do so implicitly, and they do not represent benthic calcification. In addition, most models simulate marine calcite but not aragonite. In CMIP6, certain model groups have increased the complexity of simulated CaCO3 production, sinking, dissolution and sedimentation. However, this is insufficient to explain the overall improvement in the alkalinity representation, which is therefore likely a result of marine biogeochemistry model tuning or ad hoc parameterizations. Although modellers aim to balance the global alkalinity budget in ESMs in order to limit drift in ocean carbon uptake under pre-industrial conditions, varying assumptions related to the closure of the budget and/or the alkalinity initialization procedure have the potential to influence projections of future carbon uptake. For instance, in many models, carbonate production, dissolution and burial are independent of the seawater saturation state, and when considered, the range of sensitivities is substantial. As such, the future impact of ocean acidification on the carbonate pump, and in turn ocean carbon uptake, is potentially underestimated in current ESMs and is insufficiently constrained.</p