A new synthesis of biologically active pyrroles: Formal synthesis of pentabromopseudilin,bimetopyrol, and several antitubercular agents

Although pyrroles have been synthesized from azido dienes, the corresponding reactions of structurally similar nitrodienes had not been investigated until it became the main focus of this study. This article describes the synthesis of several biologically active pyrroles and mechanistically intriguing results in connection with our new approach using nitrodienes in the presence of Ph₃P and a Mo catalyst, bis (acetylaceto)dioxomolybdenum (VI). The final precursor of pentabromopseudilin (PBP), pseudilin, was synthesized in four steps from o-hydroxycinnamaldehyde. An alternate pathway to PBP proceeded through o-methylpseudilin, prepared in two steps from o-methoxycinnamaldehyde. Both starting materials are commercially available. Similarly, bimetopyrol (2-methyl-4,5-bis(p-methoxyphenyl)pyrrole), a potent anti-inflammatory, was prepared using the new methodology. The remarkable conversion of nitrodienes 14 and 15 to bimetopyrol highlights the formation of a nitroso or nitrene intermediate. We also established that 14 and 15 interconvert in the presence of ambient light and each converts to bimetopyrol when reacted separately. The wide application of our synthetic methodology includes preparation of several antitubercular and Herpes Simplex 2 (HSV2) agents.     

Synthesis,Characterization and X-ray Structures of 2,6-Diacetylpyridinebis(benzenesulfonylhydrazide) and its Zinc(II) Complex

Abstract  2,6-Diacetylpyridinebis(benzenesulfonylhydrazide) (2,6-DAPBSH) and its zinc(II) complex have been synthesized and characterized by X-ray crystallography. The ligand crystallizes in the monoclinic crystal system, space group Cc, with cell parameter = 16.808(2) Ǻ, b = 16.328(2) Ǻ, c = 8.2670(11) Ǻ, β = 91.869(9)°, while the zinc(II) complex crystallizes in the orthorhombic crystal system, space group Pbcn, with cell parameters a = 14.5927(3) Ǻ, b = 9.6502(2) Ǻ, c = 20.5610(5) Ǻ. The metal center is seven-coordinate, with an approximate pentagonal bipyramidal configuration of the chelating ligand and two apically coordinated DMSO molecules. Graphical Abstract  X-ray crystallographic study on the [2,6-diacetylpyridine—bis(benzenesulfonylhydrazonato-κ⁵ N′N′′N′′′O′O′′)]bis(dimethyl sulfoxide-κO)zinc(II) (Fig. 1) shows that the complex is a seven-coordinate, with an approximate pentagonal bipyramidal configuration where the ligand coordinates to the zinc(II) ion as a pentadentate chelate via the pyridine nitrogen atom, the two azomethine nitrogen atoms and the two sulfonyl oxygen atoms.      

Dielectric behavior,conduction and EPR active centres in BiVO4 nanoparticles

Bismuth vanadate (BiVO₄) nanomaterials were synthesized by mechano-chemical ball milling method and complementary investigations were devoted to their structures, nanoparticle morphologies and electronic active centres. The dielectric and conductivity behaviour were analysed systematically in wide temperature and frequency ranges to correlate such physical responses with the peculiarities of the samples. Large interfacial polarisations favoured by high specific surfaces of nanoparticles account for a drastic enhancement of the dielectric function in the quasi-static regime. Exhaustive analyses of the dielectric experiments were achieved and account for the main features of dielectric functions and their related relaxation mechanisms. The electrical conductivity is thermally activated with energies in the range 0.1–0.6 eV depending on the sample features. DC conductivity up to 10^–3 S/cm was obtained in well crystallized nanoparticles. Vanadium ions reduction was revealed by EPR spectroscopy with higher concentrations of the active centres (V⁴⁺) in more agglomerated and amorphous nanopowders. The EPR spectral parameters of V⁴⁺ were determined and correlated with the local environments of reduced vanadium ions and the characteristics of their electronic configurations. An insight is also made on the role of active electronic centres (V⁴⁺) on the conduction mechanism in nanostructured BiVO₄.     

Effects of Ascorbic Acid on PVS2 Cryopreservation of Dendrobium Bobby Messina’s PLBs Supported with SEM Analysis

Regrowth of the cryopreserved protocorm-like bodies (PLBs) of Dendrobium Bobby Messina was assessed based on the plant vitrification solution 2 (PVS2) optimisation conditions. The optimized protocol obtained based on TTC spectrophotometrical analysis and growth recovery were 3–4 mm of PLBs size precultured in 0.2 M sucrose for 1 day, treated with a mixture of 2 M glycerol and 0.4 M sucrose supplemented with half-strength liquid MS media at 25 °C for 20 min and subsequently dehydrated with PVS2 at 0 °C for 20 min prior to storage in liquid nitrogen. Following rapid warming in a water bath at 40 °C for 90 s, PLBs were treated with unloading solution containing half-strength liquid MS media supplemented with 1.2 M sucrose. Subsequently, the PLBs were cultured on half-strength semi-solid MS media supplemented with 2 % (w/v) sucrose without any growth regulators and resulted in 40 % growth recovery. In addition, ascorbic acid treatment was used to evaluate the regeneration process of cryopreserved PLBs. However, growth recovery rates of non-cryopreserved and cryopreserved PLBs were 30 and 10 % when 0.6 mM ascorbic acid was added. Scanning electron microscopy analysis indicates that there are not much damages observed on both cryopreserved and non-cryopreserved PLBs in comparison to PLBs stock culture.     

Tandem Favorskii Intermediate/Cyclization Leading to Tricyclo[4.4.0.0]decanediones

The mechanism of dehydrobromination of the bromodiketone 8 leading to the unusual ring system of tricyclo[4.4.0.0]decanediones (9 and 10) is described. An entry into the ring system of the sesquiterpenoid hydrocarbons copaene and ylangene, 8 to 9, is achieved in three steps starting with enone 6. Compound 9 was either derived from a direct internal S_N2 cyclization of 8 or the Favorskii intermediate 8a. Formation of compound 10, on the other hand, can only occur via the Favorskii intermediate 8a. Structure assignments of 9 and 10 were determined using both one‐ and two‐dimensional NMR experiments.     

An effective ostrich oil bleaching technique using peroxide value as an indicator

Ostrich oil has been used extensively in the cosmetic and pharmaceutical industries. However, rancidity causes undesirable chemical changes in flavour, colour, odour and nutritional value. Bleaching is an important process in refining ostrich oil. Bleaching refers to the removal of certain minor constituents (colour pigments, free fatty acid, peroxides, odour and non-fatty materials) from crude fats and oils to yield purified glycerides. There is a need to optimize the bleaching process of crude ostrich oil prior to its use for therapeutic purposes. The objective of our study was to establish an effective method to bleach ostrich oil using peroxide value as an indicator of refinement. In our study, we showed that natural earth clay was better than bentonite and acid-activated clay to bleach ostrich oil. It was also found that 1 hour incubation at a 150 °C was suitable to lower peroxide value by 90%. In addition, the nitrogen trap technique in the bleaching process was as effective as the continuous nitrogen flow technique and as such would be the recommended technique due to its cost effectiveness.     

Direct Catalytic Conversion of Ethanol to C5+ Ketones: Role of Pd–Zn Alloy on Catalytic Activity and Stability

Ethanol can be used as a platform molecule for synthesizing valuable chemicals and fuel precursors. Direct synthesis of C₅₊ ketones, building blocks for lubricants and hydrocarbon fuels, from ethanol was achieved over a stable Pd‐promoted ZnO‐ZrO₂ catalyst. The sequence of reaction steps involved in the C₅₊ ketone formation from ethanol was determined. The key reaction steps were found to be the in situ generation of the acetone intermediate and the cross‐aldol condensation between the reaction intermediates acetaldehyde and acetone. The formation of a Pd–Zn alloy in situ was identified to be the critical factor in maintaining high yield to the C₅₊ ketones and the stability of the catalyst. A yield of >70 % to C₅₊ ketones was achieved over a 0.1 % Pd‐ZnO‐ZrO₂ mixed oxide catalyst, and the catalyst was demonstrated to be stable beyond 2000 hours on stream without any catalyst deactivation.     

Grafting of Polyester Fibers

Abstract

Polyester monofilaments were grafted with methacrylic acid monomer in order to improve the water absorption and dye uptake characteristics. Kinetic parameters like percent grafting and grafting efficiency were measured as a function of concentration of monomer, initiator concentration, time of reaction, and temperature. The results show that the rate of grafting is proportional to the 0.167 power of the monomer concentration and the 0.545 power of the initiator concentration. The activation energy for grafting, calculated from an Arrhenius plot, was found to be 11.12 kcal˙mol^?1. Water absorption and dye uptake were tremendously improved by grafting.