Late-Stage Molecular Editing Enabled by Ketone Chain-Walking Isomerization

Herein, a method for the isomerization of ketones in a manner akin to the chain-walking reaction of alkenes is described. Widely available and inexpensive pyrrolidine and elemental sulfur are deployed as catalysts to achieve this reversible transformation. Key to the utility of this approach was the elucidation of a stereochemical model to determine the thermodynamically favored product of the reaction and the kinetic selectivity observed. With the distinct selectivity profile of our ketone chain-walking process, the isomerization of various steroids was demonstrated to rapidly access novel steroids with "unnatural" oxidation patterns.ISSN:0002-7863ISSN:1520-512

Catalyst-Controlled Wacker-Type Oxidation: Facile Access to Functionalized Aldehydes

The aldehyde-selective oxidation of alkenes bearing diverse oxygen groups in the allylic and homoallylic position was accomplished with a nitrite-modified Wacker oxidation. Readily available oxygenated alkenes were oxidized in up to 88% aldehyde yield and as high as 97% aldehyde selectivity. The aldehyde-selective oxidation enabled the rapid, enantioselective synthesis of an important pharmaceutical agent, atomoxetine. Finally, the influence of proximal functional groups on this anti-Markovnikov reaction was explored, providing important preliminary mechanistic insight

Regioselective Wacker Oxidation of Internal Alkenes: Rapid Access to Functionalized Ketones Facilitated by Cross-Metathesis

Wacka wacka: The title reaction makes use of a wide range of directing groups (DG) to enable the highly regioselective oxidation of alkenes, and occurs predictably at the distal position. Both E and Z alkenes afford valuable functionalized ketones and cross-metathesis was shown to facilitate the preparation of the starting materials. BQ=benzoquinone

Aldehyde-Selective Wacker-Type Oxidation of Unbiased Alkenes Enabled by a Nitrite Co-Catalyst

Breaking the rules: Reversal of the high Markovnikov selectivity of Wacker-type oxidations was accomplished using a nitrite co-catalyst. Unbiased aliphatic alkenes can be oxidized with high yield and aldehyde selectivity, and several functional groups are tolerated. ^(18)O-labeling experiments indicate that the aldehydic O atom is derived from the nitrite salt

Practical and General Palladium-Catalyzed Synthesis of Ketones from Internal Olefins

Make it simple! A convenient and general palladium-catalyzed oxidation of internal olefins to ketones is reported. The transformation occurs at room temperature and shows wide substrate scope. Applications to the oxidation of seed-oil derivatives and a bioactive natural product (see scheme) are described, as well as intriguing mechanistic features

Shocking features in the merging galaxy cluster RXJ0334.2-0111

© 2016 The Authors. We present a 66 ks Chandra X-ray observation of the galaxy cluster RXJ0334.2-0111. This deep observation revealed a unique bow shock system associated with a wide angle tail (WAT) radio galaxy and several intriguing substructures. The temperature across the bow shock jumps by a factor of ~1.5 (from 4.1 to 6.2 keV), and is consistent with the Mach numberM= 1.6+ 0.5 -0.3. A second inner surface brightness edge is a cold front that marks the border between infalling subcluster cool core and the intracluster medium of the main cluster. The temperature across the cold front increases from 1.3 +0.3 -0.8 to 6.2 +0.6 -0.6 keV. We find an overpressurized region ~250 kpc east of the cold front that is named 'the eastern extension (EE)'. The EE may be a part of the third subcluster in the ongoing merger. We also find a tail shaped feature that originates near the bow shock and may extend up to a distance of ~1 Mpc. This feature is also likely overpressurized. The luminous FR-I radio galaxy, 3C89, appears to be the cD galaxy of the infalling subcluster. We estimated 3C89's jet power from jet bending and the possible interaction between the X-ray gas and the radio lobes. A comparison between the shock standoff distance and the Mach number for all known shock front/cold front combinations suggests that the core is continuously shrinking in size by stripping

A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N-O Reagent as the "Amino" Source and "Oxidant".

Herein, we study the mechanism of iron-catalyzed direct synthesis of unprotected aminoethers from olefins by a hydroxyl amine derived reagent using a wide range of analytical and spectroscopic techniques (Mössbauer, Electron Paramagnetic Resonance, Ultra-Violet Visible Spectroscopy, X-ray Absorption, Nuclear Resonance Vibrational Spectroscopy, and resonance Raman) along with high-level quantum chemical calculations. The hydroxyl amine derived triflic acid salt acts as the "oxidant" as well as "amino" group donor. It activates the high-spin Fe(II) (St = 2) catalyst [Fe(acac)2(H2O)2] (1) to generate a high-spin (St = 5/2) intermediate (Int I), which decays to a second intermediate (Int II) with St = 2. The analysis of spectroscopic and computational data leads to the formulation of Int I as [Fe(III)(acac)2-N-acyloxy] (an alkyl-peroxo-Fe(III) analogue). Furthermore, Int II is formed by N-O bond homolysis. However, it does not generate a high-valent Fe(IV)(NH) species (a Fe(IV)(O) analogue), but instead a high-spin Fe(III) center which is strongly antiferromagnetically coupled (J = -524 cm-1) to an iminyl radical, [Fe(III)(acac)2-NH·], giving St = 2. Though Fe(NH) complexes as isoelectronic surrogates to Fe(O) functionalities are known, detection of a high-spin Fe(III)-N-acyloxy intermediate (Int I), which undergoes N-O bond cleavage to generate the active iron-nitrogen intermediate (Int II), is unprecedented. Relative to Fe(IV)(O) centers, Int II features a weak elongated Fe-N bond which, together with the unpaired electron density along the Fe-N bond vector, helps to rationalize its propensity for N-transfer reactions onto styrenyl olefins, resulting in the overall formation of aminoethers. This study thus demonstrates the potential of utilizing the iron-coordinated nitrogen-centered radicals as powerful reactive intermediates in catalysis

L'éducation à la culture informationnelle

La publication des actes du colloque international L'éducation à la culture informationnelle (Lille, octobre 2008 - sous le patronage de l'Unesco) présente les regards de chercheurs, de praticiens ou de représentants d'institutions sur cette notion et ouvre de larges perspectives interdisciplinaires. Le nouveau concept de « culture informationnelle » est proposé par la communauté internationale pour mieux appréhender la complexification actuelle des relations entre l'enseignement, l'éducation et l'information, liée au développement exponentiel des technologies numériques. Quel rapport entretient l'éducation à l'information (information literacy) avec l'éducation aux médias (media literacy) et l'éducation numérique (digital literacy) ? Le périmètre de la « culture informationnelle » s'étend maintenant clairement au-delà du monde de la documentation et des bibliothèques. La notion même doit être précisée, revue, alors que les pratiques continuent d'évoluer. Une place importante est consacrée dans l'ouvrage à l'analyse comparée des approches théoriques et de plusieurs expériences menées dans différents pays