M Schmidt

Practical Ni-Catalyzed Aryl–Alkyl Cross-Coupling of Secondary Redox-Active Esters

A new transformation is presented that enables chemists to couple simple alkyl carboxylic acids with aryl zinc reagents under Ni-catalysis. The success of this reaction hinges on the unique use of redox-active esters that allow one to employ such derivatives as alkyl halides surrogates. The chemistry exhibits broad substrate scope and features a high degree of practicality. The simple procedure and extremely inexpensive nature of both the substrates and pre-catalyst (NiCl2·6H2O, ca.

Modifying the product pattern of Clostridium acetobutylicum Physiological effects of disrupting the acetate and acetone formation pathways

9.5/mol) bode well for the immediate widespread adoption of this method.

Regional high-resolution spatiotemporal gravity modeling from GRACE data using spherical wavelets

Clostridial acetone–butanol–ethanol (ABE) fermentation is a natural source for microbial n-butanol production and regained much interest in academia and industry in the past years. Due to the difficult genetic accessibility of Clostridium acetobutylicum and other solventogenic clostridia, successful metabolic engineering approaches are still rare. In this study, a set of five knock-out mutants with defects in the central fermentative metabolism were generated using the ClosTron technology, including the construction of targeted double knock-out mutants of C. acetobtuylicum ATCC 824. While disruption of the acetate biosynthetic pathway had no significant impact on the metabolite distribution, mutants with defects in the acetone pathway, including both acetoacetate decarboxylase (Adc)-negative and acetoacetyl-CoA:acyl-CoA transferase (CtfAB)-negative mutants, exhibited high amounts of acetate in the fermentation broth. Distinct butyrate increase and decrease patterns during the course of fermentations provided experimental evidence that butyrate, but not acetate, is re-assimilated via an Adc/CtfAB-independent pathway in C. acetobutylicum. Interestingly, combining the adc and ctfA mutations with a knock-out of the phosphotransacetylase (Pta)-encoding gene, acetate production was drastically reduced, resulting in an increased flux towards butyrate. Except for the Pta-negative single mutant, all mutants exhibited a significantly reduced solvent production.

SO3-einschiebungsreaktionen bei metallorganischen verbindungen von silicium, germanium, zinn und blei

We determine a regional spatiotemporal gravity field over northern South America including the Amazon region using GRACE inter-satellite range-rate measurements by application of a wavelet-based multiresolution technique. A major advantage of this method is that we are able to represent the Amazon hydrological signals in form of time series of detail signals with level-dependent temporal resolution: the coarser structures generally require only ten days, whereas the medium and finer details are computable from one month of data. To this end, we employ the basic property of multiresolution representations, which is to split a signal into detail signals, each related to a specific resolution level and computable from data covering a specific part of the spectrum. Our results, which for the first time fully exploit the spatial and temporal resolutions of GRACE data in modeling Amazon hydrological fluxes, are in good agreement with hydrological models and GPS-derived height variations.

Mono-Oxidation of Bidentate Bis-phosphines in Catalyst Activation: Kinetic and Mechanistic Studies of a Pd/Xantphos-Catalyzed C–H Functionalization

Abstract Due to its strong electrophilic character sulfur trioxide can be inserted in bonds between carbon and the elements silicium, germanium, tin and lead. This reaction takes place under very mild conditions and in general yields organometallic derivatives of sulfonic acids, R 3 MOSO 2 R (M = Si, Ge, Sn and Pb; R = alkyl or aryl). Under suitable conditions organometal sulfates and sulfonic acid anhydrides, (R 3 MO) 2 SO 2 and RSO 2 OSO 2 R, can be detected as products of a side-reaction. The properties of the obtained products are described and the reaction mechanism is discussed.

Regional four-dimensional hydrological mass variations from GRACE, atmospheric flux convergence, and river gauge data

Kinetic, spectroscopic, crystallographic, and computational studies probing a Pd-catalyzed C-H arylation reaction reveal that mono-oxidation of the bis-phosphine ligand is critical for the formation of the active catalyst. The bis-phosphine mono-oxide is shown to be a hemilabile, bidentate ligand for palladium. Isolation of the oxidative addition adduct, with structural elucidation by X-ray analysis, showed that the mono-oxide was catalytically competent, giving the same reaction rate in the productive reaction as the Pd(II)/xantphos precursor. A dual role for the carboxylate base in both catalyst activation and reaction turnover was demonstrated, along with the inhibiting effect of excess phosphine ligand. The generality of the role of phosphine mono-oxide complexes in Pd-catalyzed coupling processes is discussed.

Reaction engineering studies of acetone-butanol-ethanol fermentation with Clostridium acetobutylicum.

[1] The spatiotemporal behavior of the Earth’s gravity field is traditionally modeled as a series expansion in terms of spherical harmonics with a number of time-dependent coefficients. In this contribution we study regional effects, namely, hydrological mass variations observed by the Gravity Recovery And Climate Experiment (GRACE) satellite mission since 2002. As compared to the global spherical harmonics, scaling and wavelet functions are quasi-compactly supported, i.e., highly localizing with respect to space and time. Consequently, they establish a system of base functions well suited for regional modeling. We determine a spatiotemporal regional gravity model from GRACE using the spherical wavelet technique for the spatial part and a one-dimensional B spline expansion for the temporal variations; that is, we end up with a four-dimensional multiresolution representation (MRR) of the geopotential over selected regional areas and time intervals. For an exemplary area consisting of three large river basins in South America we compute mass variations expressed in terms of equivalent water heights. We demonstrate that a B spline expansion for modeling the temporal behavior is more appropriate than the classical Fourier series approach. In order to corroborate the results, our storage estimates are balanced with the net effect of river discharge from gauges (outflow) and the difference of precipitation and evaporation (inflow) from the convergence of vertically integrated water vapor fluxes. Furthermore, our results are compared with monthly mass grids from GRACE spherical harmonic solution data products. We conclude that the MRR means a robust tool to maximize the observational accuracy for GRACE, it considers the spatiotemporal resolution of the observations due to resolution-dependent highest levels, and it is applicable elsewhere globally to model hydrological or other phenomena of mass change.

Combination of various observation techniques for regional modeling of the gravity field

Acetone‐butanol‐ethanol (ABE) fermentation by Clostridium acetobutylicum has been extensively studied in recent years because the organism is recognized as an excellent butanol producer. A parallel bioreactor system with 48 stirred‐tank bioreactors on a 12 mL scale was evaluated for batch cultivations of the strictly anaerobic, butanol‐producing C. acetobutylicum ATCC 824. Continuous gassing with nitrogen gas was applied to control anaerobic conditions. Process performances of ABE batch fermentations on a milliliter scale were identical to the liter‐scale stirred‐tank reactor if reaction conditions were identical on the different scales (e.g., initial medium, pH, temperature, specific evaporation rates, specific power input by the stirrers). The effects of varying initial ammonia concentrations (0.1–4.4 g L−1) were studied in parallel with respect to glucose consumption and butanol production of C. acetobutylicum ATCC 824 as a first application example. The highest butanol yield of 33% (mol mol−1) was observed at initial ammonia concentrations of 0.5 and 1.1 g L−1. This is the first report on the successful application of a 48 parallel stirred‐tank bioreactor system for reaction engineering studies of strictly anaerobic microorganisms at the milliliter scale.

Ray tracing technique for global 3‐D modeling of ionospheric electron density using GNSS measurements

Modeling a very broad spectrum of the Earths gravity field needs observations from various measurement techniques with different spectral sensitivities. Typically, high-resolution regional gravity data are combined with low-resolution global observations. To exploit the gravitational information as optimally as possible, we set up a regional modeling approach using radial spherical basis functions, emphasizing the strengths of various data sets by the flexible combination of high- and middle-resolution terrestrial, airborne, shipborne, and altimetry measurements. The basis functions are defined and located in the region of interest in such a manner, which the highest measure of information of the input data is captured. Any functional of the Earths gravity field can be derived, as, e.g., quasi-geoid heights or gravity anomalies. Here we present results of a study area in Northern Germany. A comprehensive cross validation to external observation data delivers standard deviations less than 5 cm. Differences to an existing regional quasi-geoid model count on average ±6 cm and proof the plausibility of our solution. The comparison with existing global models reaches higher standard deviations for the more sensitive gravity anomalies as for quasi-geoid heights, showing the additional value of our solution in the high frequency domain. Covering a broad frequency spectrum, our regional models can be used as basis for various applications, such as refinement of global models, national geoid determination, and detection of mass anomalies in the Earths interior.

Ni-Catalyzed C–H Functionalization in the Formation of a Complex Heterocycle: Synthesis of the Potent JAK2 Inhibitor BMS-911543

For space geodetic techniques, operating in microwave band, ionosphere is a dispersive medium; thus, signals traveling through this medium are in the first approximation, affected proportional to the inverse of the square of their frequencies. This effect allows gaining information about the parameters of the ionosphere in terms of total electron content (TEC) or the electron density (Ne). Making use of this phenomenon, space geodetic techniques have turned into a capable tool for studying the ionosphere in the last decades. Up to now, two-dimensional (2-D) models of Vertical TEC (VTEC) have been widely developed and used by different communities; however, due to the fact that these models provide information about the integral of the whole electron content along the vertical or slant raypath, these maps are not useful when information about the ionosphere at different altitude is required. This paper presents a recent study which aims at developing a global 3-D model of the electron density, using measurements from Global Navigation Satellite Systems and by applying the ray tracing technique to the upper atmosphere. The developed modeling approach represents the horizontal variations of the electron density, with two sets of spherical harmonic expansions of degree and order 15. The height dependency of the electron density is represented by a multilayered Chapman profile function for the bottomside and topside ionosphere, and an appropriate model for the plasmasphere. In addition to the geodetic applications of the developed models, within this study, the 3-D models of electron density can include geophysical parameters like maximum electron density and its corresponding height. High-resolution modeling of these parameters allows an improved geophysical interpretation, which is essential in all studies of the upper atmosphere, space weather, and for the solar-terrestrial environment.