Radical induced fragmentation in a benzoxocane ring system: application to the synthesis of elvirol and a formal synthesis of 7,8-dihydroxycalamenene

A novel radical induced fragmentation in a benzoxocane ring system has been employed for a synthesis of elvirol 8 and an advanced intermediate in the synthesis of 7,8-dihydroxycalamenene 20. The coumarins 9, 22 were taken through a sequence of reactions to the benzoxocanols 16, 30, which when subjected to Barton’s deoxygenation conditions involving conversion to the corresponding thionocarbonates 17, 31 followed by exposure to tri-n-butyltin hydride, underwent a radical induced fragmentation to furnish elvirol 8 and the curcuphenol derivative 32, which was converted to the dimethoxy compound 33. This had served as an advanced intermediate in a previous synthesis of dihydroxycalamenene.     

An efficient one-pot organocatalytic synthesis of 9-(1H-indol-3-yl)-xanthen-4-(9H)-ones under mild aqueous micellar conditions

An efficient and facile l-proline-catalyzed three-component coupling of 2-hydroxybenzaldehyde, 5,5-dimethyl-1,3-cyclohexanedione (dimedone), and indole has been accomplished under mild aqueous micellar conditions to deliver a small library of 9-(1H-indol-3-yl)-xanthen-4-(9H)-ones of potential biological relevance. Under optimized conditions [10 mol % of l-proline, water (2 mL), SDS (23 mg, 0.08 mmol), rt], the reaction was highly selective toward the target compound and essentially free from competitive two-component byproduct formation.     

Relationship between wood color parameters measured by the CIELab system and extractive and phenol content in Acacia mangium and Vochysia guatemalensis from fast-growth plantations

The heterogeneity of color distribution between sapwood and heartwood limits the market for wood from fast-growth plantations of tropical species. Wood color is associated with wood extractives contents. This study presents the relationship between wood color parameters measured by the CIELab color system and total amount of extractives and phenolic-type extractives in ethanol-toluene and hot water extracts of wood from two fast-growth plantation species. The results demonstrated that the difference in sapwood and hardwood color in Vochysia guatemalensis and Acacia mangium is caused by lower concentrations of extractives in sapwood of both species. Additionally, variations in total extractive and phenolic content have different effects on the color parameters (L*, a* and b*) of both species studied. In Vochysia guatemalensis wood, parameter L* decreases as total extractive and phenolic content increases; however, parameter a* increases as the content of extractives and phenols increases. In Acacia mangium, the amount of phenols showed no relationship with the color parameters. The ethanol-toluene total extractive content, however, shows a relationship with several color parameters. An increase in the content of total extractives in water and ethanol-toluene increases parameter a*, but decreases parameter L*.     

Structure-charge transport relationship of 5,15-dialkylated porphyrins

5,15-Dialkyl-substituted porphyrins that are symmetrically capped with ethyl (C(2)-Por), butyl (C(4)-Por) and hexyl (C(6)-Por) were synthesized and characterized. Molecular structure versus physical property relationship has been established through the analysis of planar charge transport using thin film transistor (TFT) structure.     

Nanostructured layered double hydroxide aerogels with enhanced adsorption properties

Aerogels of layered double hydroxides were prepared by a simple and eco-friendly method involving a quick coprecipitation followed by supercritical CO(2) drying. Such aerogels display high surface areas and enhanced adsorption behavior.     

Highly oriented surface-growth and covalent dye labeling of mesoporous metal-organic frameworks

Mesoporous amino-functionalized metal-organic framework thin films with the UiO-68 topology were grown in a highly oriented fashion on two different self-assembled monolayers on gold. The oriented MOF films were covalently modified with the fluorescent dye Rhodamine B inside the pore system, as demonstrated with size-selective fluorescence quenching studies. Our study suggests that mesoporous metal-organic frameworks are promising hosts for the covalent attachment of numerous functional moieties in a molecularly designed crystalline environment.     

First example of a heterobimetallic 'Pd-Sn' catalyst for direct activation of alcohol: efficient allylation, benzylation and propargylation of arenes, heteroarenes, active methylenes and allyl-Si nucleophiles

Arenes, heteroarenes, 1,3-dicarbonyls and organosilicon nucleophiles undergo highly efficient alkylation with allylic, propargylic and benzylic alcohols in the presence of a new 'Pd-Sn' bimetallic catalyst in nitromethane; water being the sole byproduct. The plausible mechanism of alkylation and the intermediacy of ether has been enumerated.     

Zinc and cadmium 2-pyrazinephosphonates: syntheses, structures and luminescent properties

Three new metal(II) 2-pyrazinephosphonates have been synthesized by hydrothermal reactions based on 2-pyrazinephosphonic acid (C(4)H(3)N(2)PO(3)H(2)1) as ligand, namely, Zn(C(4)H(3)N(2)PO(3)) (2), Cd[(C(4)H(3)N(2)PO(3))(H(2)O)] (3) and Cd[(C(4)H(3)N(2)PO(3)H)Cl]·H(2)O (4). In compound 2, the O-P-O bridged inorganic layers are pillared by pyrazinyl groups into a three-dimensional network. In compound 3, the {CdO(5)N} and {CPO(3)} polyhedra are interconnected via edge and corner-sharing into a metal phosphonate layer. In compound 4, the {Cd(2)Cl(2)} dimers are linked by O-P-O bridges into a one-dimensional double chain, and the chains are joined into a layer by pyrazinyl groups. Here we employ pyrazinephosphonic acids as structure directing motifs to form extended structures and materials with interesting luminescent properties. The luminescent properties studied have also been described.