Visible-light-promoted oxidative difunctionalization of alkenes with sulfonyl chlorides to access β-keto sulfones under aerobic conditions

A mild, practical and efficient strategy to prepare β-keto sulfones has been developed by visible light promoted reactions. This reaction involves Ir(ppy)₂(dtbbpy)PF₆ catalyzed direct funcationalization of alkenes with sulfonyl chlorides under mild conditions. Air was used as oxidant without any additives. The transformation affords the corresponding products in moderate to high yields.     

Visible light-promoted metal-free aerobic oxyphosphorylation of olefins: A facile approach to β-ketophosphine oxides

A metal-free direct aerobic oxyphosphorylation of alkenes with H-phosphine oxides has been developed utilizing visible light photoredox catalysis. A variety of β-ketophosphine oxides have been obtained in good yields from simple olefins under air with inexpensive rhodamine B as the non-metallic photocatalyst. This method provides a mild, green, and practical synthetic approach to valuable β-ketophosphine oxides.     

Facile synthesis of α, β-unsaturated esters through a one-pot copper-catalyzed aerobic oxidation-Wittig reaction

An efficient one-pot synthesis of α, β-unsaturated esters through the aerobic oxidation – Wittig tandem reaction of alcohols and phosphorous ylide is developed. This new method operates under mild reaction conditions, and uses CuI/TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) as co-catalyst and air (O₂) as the oxidant. It tolerates a wide range of functionalized benzylic alcohol and aliphatic alcohols.     

A direct approach to β-keto sulfones via AgNO3/K2S2O8 catalyzed aerobic oxysulfonylation of alkenes in aqueous medium

An efficient, AgNO₃/K₂S₂O₈ catalyzed one-pot radical route to β-keto sulfones from alkenes is reported. The protocol involves oxysulfonylation of alkenes with air (O₂) and inexpensive sodium arenesulfinate salts under mild conditions. It is highly practical and allows the use of easily available starting materials in an open flask and aqueous medium at ambient temperature.     

FeCl_3·6H_2O-catalyzed selective reduction of allylic halides to alkenes with concomitant oxidation of benzylic alcohols to aldehydes

Iron-catalyzed direct reduction of allylic halides with benzylic alcohol was achieved,providing a new,simple,and efficient method for conducting highly regioselective hydrodehalogenation.This method not only features a readily available reductant,an inexpensive catalyst,simple manipulation,and good tolerance of functional groups including nitriles,nitro,esters,and methoxyl groups,it also has mild reaction conditions and shows complete regioselectivity in that only halides sited at the allylic position are reduced.Alternatively,this method can be applied in the selective transformation of benzylic alcohols to aromatic aldehydes without overoxidation to carboxylic acids.     

Novel cobalt(Ⅱ) complexes of amino acids-Schiff bases catalyzed aerobic oxidation of various alcohols to ketones and aldehyde

<正>Two cobalt(Ⅱ) complexes 1 and 2 of Schiff bases derived from amino acids were synthesized and used for oxidation of benzyl alcohol with molecular oxygen at different conditions of pH,solvent,temperature and complex/alcohol molar ratio to optimize reaction conditions and to evaluate the catalytic efficiency of new cobalt Schiff base complexes.Under obtained optimum conditions,various alcohols were oxidized to corresponding aldehydes and ketones.     

One-electron oxidation of alkyl alkoxybenzenes by ω-fluorosulfonylperfluorodiacyl peroxide

The oxidation of p-methylanisole 3a, dialkoxybenzenes 3b, 3c and alkyl dialkoxybenzenes 3d-h by perfluorodi[1-(2-fluorosulfonyl) ethoxy]propionyl peroxide 1 afforded main products 4-ω-fluorosulfonylperfluoroalkyl-4-alkoxy-2,5-cyclohexa-dienones and minor ring ω-fluorosulfonylperfluoroalkylation products. The electron transfer mechanism of the reactions is also proved by ESR detection of the radical cations of the donor molecules.     

Metal-free one-pot α-benzoxylation of benzylic alcohols with acids or aldehydes

A metal-free strategy has been developed for α-benzoxylation of benzylic alcohols with acids or aldehydes. The reaction proceeds via sequential oxidation and α-benzoxylation in one pot. Importantly, the reactions are performed in metal-free condition and utilize cheap aqueous TBHP as an oxidant, affording α-benzoxy ketones in moderate to good yields.     

An access to α, β-unsaturated ketones via dual cooperative catalysis

A dual cooperative organocatalytic approach for the synthesis of α, β-unsaturated ketones is described. This one pot transformation is realized via a domino Knoevenagel-Michael-retro Michael reaction sequence. Various aliphatic ketones reacted smoothly with aromatic as well as aliphatic aldehydes in presence catalytic amount of Meldrum’s acid and bifunctional amine. The highlights of this protocol are the easy availability of catalysts, high selectivity, and functional group tolerance. The reaction proved to highly E-selective with no side products emanating from self-condensation, unlike the base-mediated reactions.     

Ab-initio structure determination of β-La2WO6

The structure of the low-temperature form of β-La₂WO₆ has been determined from laboratory X-ray, neutron time-of-flight and electron diffraction data. This tungstate crystallizes in the non-centrosymmetric orthorhombic space group (no. 19) P2₁2₁2₁, with Z=8, a=7.5196(1) Å, b=10.3476(1) Å, c=12.7944(2) Å, and a measured density 7.37(1) g cm⁻³. The structure consists of tungsten [WO₆] octahedra and tetrahedral [OLa₄]. Tungsten polyhedra are connected such that [W₂O₁₁]¹⁰⁻ units are formed.     

SiCl4-catalyzed/PR3-mediated β-C(sp3)−H functionalization of nitrones to α,β-unsaturated imines and aromatic heterocycles

A novel method of SiCl₄-catalyzed/PR₃-mediated β-C(sp³)?H functionalization of nitrones with aldehydes/ketones to α,β-unsaturated imines was developed. The synthesis of α,β-unsaturated imines mainly invovles deoxygenation and aldol condensation, each proceeding under a cooperation effect between Lewis acid and Lewis base. In addition, both the acidity and hydrolytic stability of the weak SiCl₄ were supposed to be enhanced by coordination with phosphine oxide (R?=?Et) or phosphoric triamide (R?=?NMe₂) that originated from deoxygenation of nitrones by PR₃. In the case of 6-membered nitrone, a [1,3]-hydride shift within the resulted α,β-unsaturated imines renders the aromatization leading to 3,5-dialkylpyridines.     

Critical β-values of all coil planet centrifuges

I-type, J-type and non-synchronous centrifuges are all coil planet centrifuges. Analysing the motion of I-type and J-type centrifuges has advanced the understanding of how to manufacture and use these centrifuges. This paper analyses the motion of non-synchronous centrifuges producing equations of motion that can be applied to all coil planet centrifuges. This has also produced simple equations to determine the critical β-values for any coil planet centrifuge. This paper also demonstrates that I-type centrifuges also have 2 critical β-values when it was thought that β-value did not influence the understanding of the processes within I-type centrifuges. For the I-type instrument both of these critical values are at bobbin radii approaching infinity. In practice this means all I-types function within one β-value range hence the unilateral distribution and type/effectiveness of the mixing is consistent. Finally the paper shows the influence that the tangential velocity has on the Archimedean screw effect and thus the unilateral distribution of the upper and lower phases in the columns of coil planet centrifuges. This explains why the maximum stationary phase retention in an I-type centrifuge is limited to 50%.     

Enantioselective α-chlorination of β-keto esters and amides catalyzed by chiral imidodiphosphoric acids

Chiral imidodiphosphoric acids were employed as catalysts for the enantioselective α-chlorination of β-keto esters and amides using NCS as the chlorine source, providing a series of optically active products with good to high enantioselectivities (74–95% ee) and excellent yields (92–99%). This represents the first report of the Brønsted acid catalyzed enantioselective α-chlorination of cyclic β-keto derivatives.     

Bimetallic Co–Pd alloy nanoparticles as magnetically recoverable catalysts for the aerobic oxidation of alcohols in water

Co–Pd bimetallic alloy nanoparticle catalysts were prepared from CoCl₂, Pd(OAc)₂ and several capping agents with Li(C₂H₅)₃BH. The nanoparticle catalysts were applied to the aerobic oxidation of a variety of alcohols in water to give the corresponding carbonyl products. The catalyst was magnetically recovered and reused for further oxidation. The nanoparticle catalysts were characterized with TEM, ICP, and XPS analyses.     

Charge states of Ca atoms in β-dicalcium silicate

In order to study the crystal structure of β‐Ca₂SiO₄, time-of-flight neutron powder diffraction experiments were carried out at temperatures between room temperature (RT) and 600 °C. Rietveld refinement at RT has shown that β‐Ca₂SiO₄ is monoclinic based on P2₁/n symmetry and two different types of Ca sites, Ca(1) and Ca(2). All interatomic distances within 3 Å were calculated, with the valences of Ca(1) with seven CaO bonds and Ca(2) with eight were estimated to be 1.87+ and 2+ by the Zachariasen-Brown-Altermatt formula (bond valence sum). Applying charge neutrality the two charge states of Ca in β‐Ca₂SiO₄ are [Ca(1)SiO₄]²⁻ and Ca(2)²⁺, respectively. Furthermore, the [Ca(1)SiO₄]²⁻ unit has the shortest Ca-O distance, and its length kept constant at 2.23 Å at all temperatures. In the short-range structure analysis at RT, the shortest Ca-O bond was also observed in a radial distribution function. These results imply that the [Ca(1)SiO₄]²⁻ unit has covalency on the shortest Ca-O in addition to Si-O.     

β-Olefination of 2-alkynoates leading to trisubstituted 1,3-dienes

A phosphine-mediated olefination of 2-alkynoates with aldehydes forming 1,3-dienes with high E-selectivity and up to 88% yield is described. Reaction conditions are optimized and reactions are demonstrated for various aryl, alkyl, and alkenyl aldehydes and for ethyl 2-alkynoates with different substituents in the δ-position. Proof of concept is shown for the generation of a β,γ-unsaturated lactone by intramolecular olefination, and furthermore the use of the generated 1,3-dienes in the Diels-Alder reaction has been demonstrated.     

Raman characterization of α- and β-LiFe5O8 prepared through a solid-state reaction pathway

Lithium ferrite, a mixed-inverse spinel of type A_xB_y[A_1−xB_1−y]O₄ was produced through solid state synthesis by calcining a Li₂CO₃/Fe₂O₃ mixture at 900 °C. The presence of both the ordered α-phase and disordered β-phase of LiFe₅O₈ was confirmed by XRD analysis, while formation of the latter was achieved by air quenching from high temperature. Laser Raman analysis was performed on both the α-LiFe₅O₈ and β-LiFe₅O₈ powders in order to achieve a reference set of Raman shifts for the spinel. The strongest, characteristic Raman peaks were determined to be 493, 382, 358, 300, and 263 cm⁻¹ for both phases while smaller peaks at 202 and 236 cm⁻¹ present in the α-phase were diminishing in intensity when the β-phase was present, thus providing unique identifiers for the presence of the disordered ferrite structure. SEM images taken of the synthesized LiFe₅O₈ powders showed particle sizes of less than 300 nm and an even particle size distribution.     

A new umpolung for direct γ-regioselective nucleophilic addition of alcohols to γ-enolizable α,β-unsaturated aldehydes

A direct γ-regioselective nucleophilic addition of alcohols toward γ-enolizable α,β-unsaturated aldehydes was developed using a catalytic amount of MeSO₃H (30 mol%) and a stoichiometric amount of chloranil (1.0 equiv) as the oxidant. The addition of hexafluoroisopropanol (HFIP) was found to accelerate this cross-dehydrogenative coupling, furnishing diverse alcoholic adducts with high γ-regio- and E-stereoselectivities.