Aerial oxidation of bisnaphthols to spironaphthalenones by a recyclable magnetic core-sell nanoparticle-supported TEMPO catalyst

Aerial oxidative cyclization of bisnaphthols to their corresponding mixture of two isomeric spirans 3 and 4 has been carried out using a catalytic amount of magnetic core-shell nanoparticle-supported TEMPO (MNST) combined with a small amount of FeCl₃·6H₂O. This catalytic system consistently has the advantages of moderate to good yields, low reaction times, mild and convenient conditions, simple experimental and work-up procedure, and of being environmentally benign and highly economic. The magnetically separable MNST catalyst makes it possible for it to be recovered and recycled for several times without significant loss of activity.     

Green and diasteroselective oxidative cyclization of bisnaphthols to spirans

Hydrogen peroxide/MoO₃, as an efficient and clean oxidizing system was used to afford diasteroselective oxidative cyclization of bisnaphthols to spirans in ethanol at 60 °C with high yields. Bisnaphthols were prepared by the reaction of a series of aldehydes and 2-naphthol in the presence of a catalytic amount of H₃[P(Mo₃O₁₀)₄].nH₂O (HPa) in refluxing dichloromethane.     

Retrievable magnetic copper ferrite nanoparticles: an efficient catalyst for air oxidative cyclization of bisnaphthols

Herein, a green and efficient heterogeneous and photocatalytic system for the oxidation of bisnaphthols in acetonitrile under light-emitting diode will be presented. In this reaction, aerial oxygen and H₂O₂ have been used as oxidant in the presence of copper ferrite nanoparticles and N-hydroxyphthalimide as an organic co-catalyst. Copper ferrite nanoparticles were magnetically separated, the efficiency of which remained nearly unchanged up to five cycles. Magnetic copper ferrite nanoparticles were synthesized by sol–gel method and characterized by XRD, FT-IR, SEM, TEM, VSM and DRS analysis. In this project, both sets of diastereomers were formed.

Graphical abstract

Catalytic system for the oxidation of bisnaphthols.

     

One-step novel synthesis of methylene bisphenols and methylene bisnaphthols using Lewis acid mediated rearrangement

Mono- and di-substituted isomeric methylene bisphenols and methylene bisnaphthols have been synthesized by rearrangement of the corresponding O-methoxyacetyl derivatives of phenols and naphthols, respectively, in presence of aluminium chloride under dry conditions. The chemistry observed is different from the usual Fries rearrangement reaction and involves an intermolecular rearrangement. The reactions reported here also reflect the influence of substituents present in the substrate as is supported by the substitution of the bridging methylene at a position meta to the phenolic hydroxyl in some of the minor products formed along-side the majorly formed ortho substituted products.     

Oxidation of Alkynyl Boronates to Carboxylic Acids,Esters, and Amides

A general efficient protocol was developed for the synthesis of carboxylic acids, esters, and amides through oxidation of alkynyl boronates, generated directly from terminal alkynes. This protocol represents the first example of C(sp)−B bond oxidation. This approach displays a broad substrate scope, including aryl and alkyl alkynes, and exhibits excellent functional group tolerance. Water, primary and secondary alcohols, and amines are suitable nucleophiles for this transformation. Notably, amino acids and peptides can be used as nucleophiles, providing an efficient method for the synthesis and modification of peptides. The practicability of this methodology was further highlighted by the preparation of pharmaceutical molecules.     

Oxidation of Alkynyl Boronates to Carboxylic Acids,Esters, and Amides

A general efficient protocol was developed for the synthesis of carboxylic acids, esters, and amides through oxidation of alkynyl boronates, generated directly from terminal alkynes. This protocol represents the first example of C(sp)?B bond oxidation. This approach displays a broad substrate scope, including aryl and alkyl alkynes, and exhibits excellent functional group tolerance. Water, primary and secondary alcohols, and amines are suitable nucleophiles for this transformation. Notably, amino acids and peptides can be used as nucleophiles, providing an efficient method for the synthesis and modification of peptides. The practicability of this methodology was further highlighted by the preparation of pharmaceutical molecules.     

Reversibility of cadmium sorption to calcite revisited

Cadmium sorption to calcite was studied in aqueous solution at calco-carbonic (CO(2)-H(2)O-CaCO(3)) equilibrium and at concentrations below the solubility product of otavite (<10(-7) mol L(-1)). Experiments were conducted in a stirred flow-through reactor, lasting for 15 and 60 h at flow rates of 1.6 and 0.5 mL min(-1), respectively. Under both flow conditions, the cadmium breakthrough curves reached steady state after a flow time of about 50 reactor volumes, but different calcite saturation levels were achieved, which implied time-dependent sorption rates. Desorption of cadmium was induced by switching from Cd-containing to Cd-free solution in the reactor inflow. Reversibility of sorption was then evaluated by comparing amounts sorbed and desorbed over identical time intervals. On average, the desorption/sorption ratio was 95±10%. Desorption rates were close to those for sorption and showed the same time dependency: Initially, rates were fast and slowed down with time. "Irreversible" surface reactions such as solid-solution formation could not be inferred. In previous research, cadmium sorption was often shown to be partly irreversible. We surmise that calcite surface ripening is conditioned by the concentration of lattice-building ions in the EDL. At calco-carbonic equilibrium, these ion concentrations at the surface are lowest. Therefore, irreversible binding of cadmium is not favoured.     

Hydrocarbon plasma emission as a means to monitor plasma polymerization,revisited

The degree of aromaticity of toluene plasma polymer is shown to decrease with decreasing toluene flow rate into the plasma (constant rf power). Optical emission spectroscopy (OES) of the plasma is predictive; a plasma emitting a higher relative benzyl radical signal results in the deposition of a more aromatic plasma polymer. Such results have been earlier reported in the literature. However, in this work the geometry of OES observation assured that only plasma emissions from the vicinity of the deposition site were observed. Under these conditions it is found that plasma pressure must be kept constant for the predictive nature of OES results to hold.     

Oxidation of Benzylamines to Amides

A convenient method for the conversion of tertiary benzylamines to benzamides by phase transfer oxidation is described. Yields are good. Regioselectivities are reported.     

Co-MCM-41催化氧化二苯甲烷制备二苯甲酮的反应条件

系统地研究了Co掺杂MCM-41用于液相催化氧化二苯甲烷的反应,并探讨了不同溶剂及溶剂用量、反应时间、反应温度、催化剂用量等对二苯甲烷氧化反应的影响;并得出较优的反应条件:m(二苯甲烷)∶m(催化剂)=10∶1;V(二苯甲烷)∶V(冰醋酸)=1∶10;温度为100℃,时间为10 h,二苯甲烷的转化率21%,二苯甲酮的选择性95.8%。     

Oxidation of polyethylene,polypropylene, and copolymers

This investigation of the autoxidation of ethylene–propylene copolymers and polyethylene–polypropylene mixtures was undertaken to determine whether reactivity is a linear function of composition. The copolymers and the mixtures were autoxidized in a trichlorobenzene solution at 100°C in the presence of 1,1′-azodicyclohexanecarbonitrile, and the rates of oxygen absorption were determined. The reactivity of the copolymers and the mixtures, after the underlying absorption of oxygen by initiator radicals is accounted for, is a nearly linear function of composition; however, the polymer mixtures and copolymers oxidized somewhat less readily than predicted by a straight line relationship. Several additional oxidations were performed on solutions of polypropylene so that the effects of initiation rate and substrate concentration could be evaluated. The oxidation kinetics of polypropylene even in dilute solution, are complex; titratable hydroperoxide yields are low. Further work will be required to specify the mechanism of oxidation.     

Vibrational energy levels of ozone up to dissociation revisited

Two recent papers presented calculations of the highly excited vibrational states of ozone. The nature and energies of these states may hold the key to the anomalous isotopic distribution of ozone in the atmosphere. Even though the same potential energy surface of Babikov et al. was used in both calculations, the number of bound van der Waals states reported below dissociation differed significantly. In order to resolve the issue we present here the results of an independent computation of all the bound vibrational states of (16)O(16)O(16)O and (16)O(16)O(18)O up to dissociation. Our methods differ from both earlier calculations since we use hyperspherical coordinates and a direct product discrete variable representation of the Hamiltonian. The results of present work support the existence of several van der Waals states for J=0 on this potential energy surface.     

From parity to chirality: chemical implications revisited

Parity violation represents an essential property of particle and atomic handedness used to cope with the complex phenomenon of asymmetry in the universe. At the molecular level, however, numerous experiments suggest that parity-violating energy differences have not determined the amplification and propagation of homochirality. Asymmetric transformations conducted under far-from-equilibrium conditions reveal the existence of non-linear autocatalysis which is stochastic in nature. In any event and, globally considered, chirality appears as a unifying characteristic of our visible environment with evolutionary implications, thereby suggesting areas for productive research.     

Mendeleyev revisited

Despite the periodic table having been discovered by chemists half a century before the discovery of electronic structure, modern designs are invariably based on physicists’ definition of periods. This table is a chemists’ table, reverting to the phenomenal periods that led to the table’s discovery. In doing so, the position of hydrogen is clarified.