Solvent and ligand effects on α-pinene epoxidation with Methyltrioxorhenium/hydrogen peroxide system (MTO/H2 O2 )

RESUMEN: Se estudiaron varios ligandos como cocatalizadores para la epoxidación de α-pineno con el sistema MTO/H2O2. La piridina es un buen cocatalizador usando diclorometano como solvente, pero se requieren grandes cantidades de piridina para obtener altos rendimientos al epóxido. El surfactante Aromox es más atractivo ya que se evita el uso de solventes clorados, los cuales son menos amigables ambientalmente. Además, se requieren cantidades relativamente pequeñas de este ligando para obtener alta actividad y selectividad al epóxido.ABSTRACT: Several ligands were studied as co-catalysts for α-pinene epoxidation with MTO/H2O2. Pyridine is an efficient co-catalyst with dichlorometane, tetrahydrofuran or ethyl acetate. However, large amounts of pyridine are required. In contrast, with relatively small amounts of the Aromox surfactant, high activity and selectivity to α-pinene epoxide are obtained. The latter system has the additional advantage of requiring no chlorinated solvents which are environmentally less friendly

Epoxidation of cyclohexene and indene with hydrogen peroxide in the presence of WO5 onto hydroxyapatite as catalyst

Epoxidation of cyclohexene and indene with hydrogen peroxide was performed with peroxotungstic species complexed with phosphate groups at the surface of hydroxyapatite. Hydroxyapatite (HAp) was prepared from calcium acetate, diammonium phosphate, and ammonia in water. Tungsten was deposited on HAp using two procedures. In procedure A, HAp was suspended in different volumes of peroxotungstic acid either at room temperature or in an autoclave at 90 or 120 degreesC. In the later case, the peroxo form was regenerated by heating the catalyst suspension with 30% H2O2 for 6 h at 60 degreesC. In procedure B, HAp was suspended in a solution of (AliQ(+))(2)W2O11 in dichloromethane. The resulting materials were isolated by filtration, washed with CH,02, and dried overnight under vacuum. Some of the catalysts were lipophilized and buffered by a partial exchange with R4N+ from NBu4Cl. The catalytic materials were characterized by adsorption-desorption isotherms of N-2 at -196 degreesC, FT-IR, XRD, P-31 CP/MAS NMR, and XPS. The stability of the catalysts was checked by leaching and recycling tests. (C) 2003 Elsevier B.V. All rights reserved

Catalyzed ring opening of epoxides: Application to bioplasticizers synthesis

International audienceThe ring opening of mono, di or tri-substituted epoxides by acetic anhydride to corresponding diacetates is catalyzed by weak bases such as hydrotalcite in the carbonated form. This reaction is performed at 423 K without solvent and the solid catalyst is reused after simple regeneration for 4 runs with constant conversion. Ring-opening of methyl oleate epoxide leads to the formation of useful diacetate methyl oleate. Starting from vegetable oils, polyacetate derivatives are prepared in three catalytic steps (methanolysis, epoxidation then ring opening). Plastisol was prepared by mixing these products with PVC and their rheological properties were evaluated. The recorded data show that they can act as bioplasticizer with similar behaviour as phthalate reference. (c) 2010 Elsevier B.V. All rights reserved

Structure-activity relationships in platelet-activating factor. Part 14: Synthesis and biological evaluation of piperazine derivatives with dual anti-PAF and anti-HIV-1 activity

As HIV-associated dementia prevalence has risen with the lifespan of HIV-infected individuals, there is an important need for antiretroviral and anti-inflammatory drugs targeting the central nervous system. Platelet-activating factor, a mediator of inflammation, is an HIV-induced neurotoxin secreted in the infected brain. In this work, we developed piperazine derivatives bearing a heterocyclic moiety as PAF-antagonists and HIV-1 replication inhibitors with micromolar potency. (c) 2006 Elsevier Ltd. All rights reserved