A New Sustainable Multistep Catalytic Process from Benzene to Caprolactam: Amination, Hydroximation and Beckmann Rearrangement Promoted and Catalyzed by Trifluoroacetic Acid

Here we report some results on a 3 steps benzene caprolactam process via amination, aniline Hydroxymation and Beckmann rearrangement. The amination proceeds with hydroxylamine trifluoroacetate, with 97% of conversion and selectivity of 90%, catalyzed by V compounds. We achieve 98% of conversion and 95% of selectivity in the hydroxymation of aniline in the presence of hydroxylamine trifluoroacetate, sulfonic resin and Pd/C. While in the absence of the resin, hydrogenation of hydroxylamine trifluoroacetate occurs readily to the ammonium salt. The reaction occurs likely by the exchanged hydroxylamine and the aniline reduction intermediate. The use of hydroxylamine trifluoroacetate, instead of the chloride, favors the sustainability of the process by avoiding the ammonium chloride formation. The absence of salt except those derived from the trifluoroacetic acid allows a complete reuse of the trifluoroacetic acid and the only byproduct is ammonium nitrate obtained by resin regeneration. Beckmann rearrangement of the so produced cyclohexanone oxime occurs easily after diethyl ether evaporation and additions of a solution trifluoroacetic acid acetonitrile in high yield and selectivity.[GRAPHICS]

Pd/C Catalyzed selective hydrogenation of nitrobenzene to cyclohexanone oxime in the presence of NH2OH·HCl: Influence of the operative variables and insights on the reaction mechanism

We studied the influence of temperature, solvent, pressure, catalysts type on the selectivity of nitrobenzene hydrogenation to cyclohexanone oxime (COX) in the presence of NH2OH. The best reaction conditions are: pressure 0.8 MPa, temperature 333 K, solvent ethers, and catalyst Pd/C5%. Other hydrogenation metal catalysts did not give comparable results. The amount of Pd/C influences the yield in COX, which rises above to 90 % at the highest load. The reaction profile shows that aniline is the reaction intermediate. Indeed, aniline as a substrate gives COX, though in lower yield than that achieved employing nitrobenzene. The NH2OH parallel hydrogenation to NH4Cl, influences positively the selectivity to COX. It has been observed that COX, cyclohexanone and N-cyclohexylideneaniline are in equilibrium in the reaction solution and all likely derive from nucleophilic substitutions to a common imine intermediate formed on the Pd surface, whose high activity does not need any further metal catalyst

Infections par des virus transmissibles par le sang chez des hémophiles en Tunisie

International audienceIn this work, we proposed to evaluate prevalences of hepatitis B and C viruses and Parvovirus B19 among 70 Tunisian haemophiliacs treated with clotting factors imported from Europe and/or locally produced cryoprecipitate; among them 6 (8.6%) are known HIV positive patients. HBs antigen, anti-HBc antibodies and anti-Parvovirus B19 antibodies were detected in 7.1%, 52.9% and 91.8%, respectively. HCV prevalence, defined as positive ELISA with positive Immunoblot and/or PCR was 50.0%. Prevalences of these viral infections in haemophiliacs are higher than prevalences detected among general population and in the control group of the study. HCV infection is less frequent in haemophiliacs born after 1985, the year of introduction of the inactivation procedures in the production of coagulation factors concentrates; it decreases more considerably after 1994, date of introduction of systematic screening of HCV among blood donors. In contrast, despite the inactivation of the factors concentrates and the systematic screening of the blood donations against HBs antigen, since 1973, the risk of HBV infection contamination remains high in the Tunisian haemophiliacs. The introduction in 1995 of hepatitis B vaccination in the national schedule of new-born vaccination may resolve in the future the problem of HBV infection in haemophiliacs and in the other categories of the Tunisian population.Dans ce travail, nous nous sommes proposés d'évaluer les prévalences des infections par les virus des hépatites B et C et le parvovirus B19 chez 70 hémophiles tunisiens traités avec les facteurs de coagulation importés d'Europe et/ou le cryoprécipité fabriqué localement ; parmi eux six patients (8,6 %) sont connus VIH positifs. L'antigène HBs, les anticorps anti-HBc et les anticorps anti-Parvovirus B19 ont été retrouvés chez 7,1, 52,9 et 91,8 % des patients, respectivement. La prévalence de l'infection par le VHC, définie par un test Elisa positif avec Immunoblot et/ou PCR positifs, a été de 50,0 %. Les prévalences de ces infections virales sont plus élevées chez les hémophiles que dans la population générale et la population témoin admise dans ce travail. L'infection à VHC est plus faible chez les sujets hémophiles nés après 1985, date d'introduction des procédés d'inactivation virale dans la fabrication des concentrés de facteurs de coagulation. Elle est encore plus faible chez les patients nés après 1994, date d'introduction du dépistage systémique du VHC chez les donneurs de sang tunisiens. En revanche, malgré l'inactivation des concentrés de facteurs et le dépistage systématique des dons du sang vis-à-vis de l'AgHBs depuis 1973, un risque élevé de contamination par le VHB persiste chez les hémophiles tunisiens. L'introduction depuis 1995 de la vaccination anti-hépatite B dans le calendrier national de vaccination des nouveau-nés devrait prochainement résoudre le problème de l'infection à VHB aussi bien chez les hémophiles que chez d'autres catégories de la population tunisienne

Hepatitis B genotypes, precore and core promoter mutants circulating in Tunisia

International audienceHepatitis B virus (HBV) is characterized by genetic heterogeneity, including genotypes and mutations. Eight genotypes (A-H) have been identified throughout the world with a characteristic geographical distribution. Previous studies also suggest that the viral genotypes may correlate with differences in clinical features of the infection. Two types of mutations were particularly described, precore and basal promoter mutations; they may play an important role in the clinical outcome of HBV infection. The aim of this study was to investigate the prevalence of HBV genotypes and HBV variants in Tunisia, and their eventual association with severity of liver disease. Using a molecular method, HBV genotypes, precore and basal core promoter mutations were determined in 56 asymptomatic carriers and in 82 patients with histologically verified chronic liver disease and hepatocellular carcinoma (HCC). Three genotypes (D, A, and E) were detected; the prevalence was 80%, 8%, and 9%, respectively. No significant difference was observed for genotype D with clinical status. HBV mutants were detected in 93% of cases, precore mutants were the most prevalent. Basal core promoter mutants were observed in 61% of cases, they were frequently characterized by a double mutation in 1762 and 1764. Co-infection by these two types of mutants was detected in 50% of cases. Genotype D was the most prevalent HBV genotype in Tunisia. High circulation of precore and basal core promoter mutants are common in chronic hepatitis B infection in Tunisia

Identification of adenoviruses serotypes implicated in haemorrhagic conjunctivitis in Tunisia

International audienceHuman adenoviruses (ADV) are distributed worldwide; they are associated with a variety of diseases. Some ADV can be implicated in large epidemics of conjunctivitis, gastroenteritis and respiratory infections. Classical diagnosis of ADV infections is based on virus isolation on cell culture and identification of the serotype by neutralization test or hemagglutination inhibition assay. However, these methods have a lack of rapidity that makes them impractical in clinical situations. With the advent of PCR, the diagnosis of ADV was improved. In this work, we have used molecular techniques for the identification of ADV serotypes implicated in conjunctivitis in Tunisia. A total of 199 conjunctival swabs received between October 2000 and May 2005 were investigated. Serotype identification was performed using a PCR followed by restriction enzyme analysis in the hexon gene. Typing by sequencing of the PCR product was used to confirm the serotype identification. Among the 199 tested clinical specimens, 24% were positive for ADV. Two different profiles were observed: one predominant corresponding to the majority of the detected ADV; this profile is in favour of two distinct serotypes, ADV37 or ADV8; the second profile was specific of ADV4 and was found in one case observed in 2005. Sequencing confirmed two serotypes: ADV8 with an endemoepidemically circulation in our country and ADV4 that appeared sporadic. The present work showed the importance of molecular techniques not only for ADV detection but also for identification of the circulating serotypes. These techniques are practical and interesting mainly for the rapid virological investigation during epidemics. (c) 2006 Elsevier Masson SAS. Toes droits reserves.Les adénovirus humains (ADV) sont des virus à ADN largement répandus dans le monde. Ils sont responsables d'infections très variées, le plus souvent bénignes. Certains ADV ont été incriminés dans des épidémies notamment de conjonctivites, gastroentérites ou d'infections respiratoires. Le diagnostic classique repose sur l'isolement viral sur cellules avec identification du sérotype par séroneutralisation ou inhibition de l'hémagglutination. Cette technique présente des inconvénients tels que le délai long d'obtention des résultats et la lourdeur de la manipulation. Dans ce travail, nous nous sommes proposés d'identifier, par des techniques moléculaires, les sérotypes d'ADV impliqués dans les conjonctivites en Tunisie. Au total, 199 prélèvements conjonctivaux reçus, d'octobre 2000 à mai 2005, ont été investigués. L'identification du sérotype a été réalisée par PCR au niveau du gène de l'hexon suivie d'une digestion enzymatique (RFLP) puis confirmée par séquençage partiel. Un ADV a été détecté dans 24 % des cas par PCR. Deux profils différents ont caractérisé les ADV circulants : un qui serait en faveur d'ADV37 ou 8 et un second spécifique d'ADV4. Le séquençage a permis de confirmer la présence d'ADV8 qui a circulé de façon endémoépidémique dans le pays et d'ADV4 responsable d'un seul cas sporadique. Ce travail constitue une première approche pour l'identification des ADV circulants dans le pays. Il démontre de l'importance des techniques moléculaires aussi bien pour la détection des ADV, mais aussi pour l'identification des sérotypes circulants. Ces techniques permettent une investigation virologique rapide des cas d'où l'intérêt de leur utilisation surtout en cours d'épidémies