Efficient palladium-catalysed carbonylative and Suzuki-Miyaura cross-coupling reactions with bis(di-tert-butylphosphino)-o-xylene

The use of the ligand bis(di-tert-butylphosphino)-o-xylene (dtbpx) in palladium-catalysed carbonylative and Suzuki-Miyaura cross-coupling reactions is described. Aryl and vinyl halides readily entered into the carbonylative catalytic cycle affording carboxylic acids, amides as well as primary, secondary and tertiary esters, respectively, in good yields. Aryl iodides, bromides and chlorides gave high yields of biphenyl products upon reaction with both activated and unactivated boronic acids.     

The effect of harvest periods on the chemical compositions of essential oils of sage (Salvia aucheri L.) leaves

The essential oils of sage leaves (Salvia aucheri Bentham var. canescens Boiss. & Heldr.), growing wild in South Anatolia, were extracted by hydrodistillation and analysed by GC and GC-MS. The percentage yields of the essential oils from sage leaves harvested at different years were 1.0%, 1.3%, 1.3%, 1.0%, 1.4%, 1.5% and 1.2%, respectively. In this study, 1,8-cineole, camphre, camphene α-pinene and β-pinene were identified as the major components of sage leaves collected at different periods. The main constituents of sage oil collected over the years were 1,8-cineole (35.01-48.06%), camphre (13.58-23.92%), camphene (6.77-8.82%), α-pinene (5.79-8.54%) and β-pinene (4.32-6.28%).     

Catalytic conversion of benzene to phenol

Phenol is very useful intermediate in the manufacture of petrochemicals, drugs, agrochemicals, and plastics. Commercially, phenol is produced by a three-step, high-energy consumption process known as the cumene process. The conversion of a chemical to a value-added product is always economically desirable. More than 90% of phenol consumption in the world is manufactured by the multistep cumene process, in which acetone is coproduced in 1: 1 molar ratio with respect to phenol. However, the drawbacks of the three-step cumene process have spurred the development of more economical routes to decrease energy consumption, avoid the formation of explosive cumene hydroperoxide, and increase the yield. The objective of this article is to highlight benzene-to-phenol conversion technologies with emphasis on direct conversion methods. Gas phase and liquid phase reactions are the two main routes for direct oxidation of benzene to phenol. Indirect methods, such as the cumene process, and direct methods of benzene-to-phenol conversion are discussed in detail. Also discussed is the single-step reaction of benzene to phenol using oxidants such as O₂, N₂O, and H₂O₂. Catalytic conversion of benzene to value-added phenol using a chemically converted graphene-based catalyst, a cost-effective carbon material, is discussed.     

Sodium congener of the classical lithium methylchromate dimer: synthetic, X-ray crystallographic, and magnetic studies of Me8Cr2[Na(OEt2)]4

One of the milestone structures in the development of transition-metal complexes with metal-metal bonds of multiple bond order was the lithium methylchromate dimer Me(8)Cr(2)[Li(donor)](4) (donor = THF or Et(2)O). Using a simple salt metathesis reaction mixing this compound with sodium tert-butoxide, the sodium congener Me(8)Cr(2)[Na(OEt(2))](4) has been synthesized as a green crystalline compound and isolated in 51% yield. Its solid-state structure was determined by single-crystal X-ray diffraction. Exhibiting exact crystallographic C(4h) symmetry, this heavier alkali-metal chromate structure is also dimeric, formally comprising a (Me(8)Cr(4))(4-) tetranionic core with four peripheral Na(+) cations carrying supporting ether ligands. Its salient feature is the long Cr···Cr distance of 3.263(2) ?, which is remarkably elongated compared to that in the lithium THF-solvated congener [1.968(2) ?]. With respect to the methyl C atoms, the Cr coordination is distorted-square-planar. Each Na(+) interacts with four methyl C atoms, and there are also some short Na···H(C) contacts. Unlike for lithium chromate, no NMR spectroscopic data could be obtained for sodium chromate. The paramagnetic character of sodium chromate was confirmed by variable-temperature magnetization measurements, which indicated antiferromagnetic behavior.     

Conformations of 2-phenylethanol and its singly hydrated complexes: UV–UV and IR–UV ion-dip spectroscopy

The structures of 2-phenylethanol and its 1:1 water complexes have been investigated by UV–UV holeburning and IR–UV ion-dip spectroscopy, coupled with ab initio computation. The most populated molecular conformer is stabilized by an intramolecular π-type H-bond and its rotational band contours suggest the incidence of vibronic coupling involving motion of the side chain. Its 1:1 water complexes are associated with two distinct structures – water binds either as a proton donor or an acceptor. In the latter, the intramolecular H-bond is disrupted and the water molecule inserts between the OH and the aromatic ring. A second, extended anti conformer can also be detected.     

Air microwave-induced plasma: Relation between ion density and atomic oxygen density

Electron temperature and ion density are measured in an air microwave-induced plasma (2450 MHz) by means of a floating double probe. A 'cinetic scheme for ion formation and decay is set up, and a relationship between atomic oxygen and ion densities is obtained. From this relationship an order-of-magnitude of atomic oxygen concentration in the discharge is derived and compared with results obtained by optical actinometry in another work.     

Molten sodium nitrite—potassium nitrite eutectic: the reaction of some compounds of molybdenum

Molybdenum(VI) oxide, ammonium molybdate and molybdic acid reacted in molten sodium nitrite—potassium nitrite eutectic to form orthomolybdate, nitrogen dioxide and nitric oxide (with nitrate as a secondary product), a more polymerised polymolybdate being formed as an intermediate product. Tungsten(VI) oxide reacted similarly but less rapidly. Molybdenum and tungsten metals reacted to form the orthoxyanion and nitrogen, the latter metal reacting considerably faster and forming smaller amounts of nitric oxide and nitrous oxide. Reaction temperatures and stoichiometries are given and reaction pathways suggested.     

Synthesis of 1,4‐Diaryl‐piperazine‐2,5‐diones: New Behavior of N,N‐Dimethylformamide Dimethyl Acetal (DMFDMA)

Reactions of chloroacetamides (5) with N,N‐dimethylformamide dimethyl acetal gave 1,4‐diaryl‐piperazine‐2,5‐diones 11a–e in good yield, rather than 1,5‐diaryl‐3,7‐dimethoxy‐1H,5H‐[1,5]diazocine‐2,6‐diones (9a–e).     

Thermally Rearranged Polymer Membranes Containing Tröger's Base Units Have Exceptional Performance for Air Separations

The influence of segmental chain motion on the gas separation performance of thermally rearranged (TR) polymer membranes is established for TR polybenzoxazoles featuring Tröger's base (TB) monomer subunits as exceptionally rigid sites of contortion along the polymer backbone. These polymers are accessed from solution‐processable ortho‐acetate functionalized polyimides, which are readily synthesized as high‐molecular‐weight polymers for membrane casting. We find that thermal rearrangement leads to a small increase in d‐spacing between polymer chains and a dramatic pore‐network reconfiguration that increases both membrane permeability and O₂/N₂ selectivity, putting its performance above the 2015 upper bound.