A critical overview is presented on the use of charged tagged ligands (CTLs) as immobilising agents in organometallic catalysis and as probes for studying mechanisms through electrospray ionisation mass spectrometry (ESI-MS) based on the most recent literature.

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A system based on copper/1,10‐phenanthroline efficiently promotes the coupling between phenols or pyrazole with (E)‐bromostilbene. (E)‐1‐Aryloxy‐1,2‐diphenylethenes were obtained from the coupling with phenols in good to excellent yields (69–90%). The exception was the reaction involving a phenol containing an electron‐withdrawing cyano group that required a longer reaction time and gave only 49% yield. Kinetic studies indicated the participation of the vinyl halide in the rate‐determining step. Under the conditions employed, the activation of the vinyl halide via a radical pathway was discarded using a radical scavenger test. By using an ionically‐tagged 1,10‐phenanthroline derivative as the ligand, various copper‐based ions were detected through ESI(+)‐MS. These ions suggested that formation of the active species [phenCuOAr(HOAr)2] precedes the vinyl halide activation.

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A series of seven limonene β-amino alcohol derivatives has been regioselectively synthesised in moderate to good yields. Two of these compounds were found to be significantly effective against in vitro cultures of the Leishmania (Viannia) braziliensis promastigote form in the micromolar range. The activities found for 3b and 3f were about 100-fold more potent than the standard drug, Pentamidine, in the same test, while limonene did not display any activity. This is the first report of antileishmanial activity by limonene β-amino alcohol derivatives.Key words: limonene -β-amino alcohol -synthesis -leishmaniasis -Leishmania braziliensis -neglected diseases Parasitic diseases are the cause of much suffering and death throughout the world, mainly in underdeveloped areas like Africa, Asia and Latin America. In these regions, the economic and social impacts caused by these sicknesses are very high because the parasites infect millions of people. Among these parasites, the Protozoa genera are responsible for the principal sicknesses, and leishmaniasis is one of the strictest parasitic diseases caused by multiple species of Leishmania (WHO 2008). The disease is endemic in tropical regions, affecting over 12 million people in 88 countries and its clinical manifestations can occur in cutaneous, mucocutaneous and visceral forms (Croft & Yeardley 2002, Murray et al. 2005. The main health organisations are concerned about these statistics due to the significant number of cases (Nwaka & Hudson 2006). Despite this, the therapies currently available to treat this illness are deficient and outdated and most present several sideeffects. Moreover, the widespread development of resistance by certain strains of leishmaniasis to antimonial compounds contributes to poor health conditions in underdeveloped countries. Chemotherapy of leishmaniasis (Croft & Yeardley 2002, Nwaka & Hudson 2006 consists of using intravenous drugs like antimonial compounds as first-choice drugs and amphotericine B as second-choice. In countries where many resistance cases to the antimonial drugs are reported, this antibiotic is used as a first-choice. Intramuscular Pentamidine is administrated in patients infected with Leishmania panamensis and Leishmania braziliensis. Miltefosine and fluconazole are currently the only effective oral treatments for leishmaniasis. However, all of these treatments have significant drawbacks in terms of route of administration, length of treatment (21-28 days), toxicity and cost, which limit their use in endemic areas (Croft & Yeardley 2002, DNDI 2003, Murray et al. 2005. These arguments by themselves justify the search for new leishmanicidal drugs, which makes the search for new agents a priority for its erradication. In this context, the strategy of following new leads to treat neglected diseases starting from natural sources is widely used by medicinal chemists (Viegas et al. 2006, Newman & Cragg 2007.Limonene is a main constituent of essential oils of citrus plants, is abundant in nature and is available in both enantiomeri...

Um sistema catalítico composto por Pd(OAc) 2 e P(o-tol) 3 foi aplicado na reação de Heck entre brometos de arila e diariletenos. Utilizando-se K 2 CO 3 como base e DMF como solvente, olefinas triarilsubstituídas foram obtidas com rendimentos de bons a excelentes. Brometos de arila com substituintes eletroretiradores foram menos ativos para a reação de acoplamento Heck e levaram à formação de produto de homoacoplamento em quantidades substanciais, indicando que a adição oxidativa não deve ser a etapa lenta da reação. A presença de substituintes no diarileteno afetou drasticamente a seletividade da reação. Realizou-se também a dupla arilação do estireno, levando diretamente à olefina triarilsubstituída, com rendimento de 73%.A catalytic system composed of Pd(OAc) 2 and P(o-tol) 3 was found to be effective for the Heck reaction of aryl bromides with diarylethylenes. Using K 2 CO 3 as a base and DMF as a solvent, trisubstituted olefins were obtained in good to excellent yields. Aryl bromides containing an electron-withdrawing group in para position were less reactive for the Heck coupling reaction and gave substantial amount of homocoupling by-product suggesting that oxidative addition is not the rate-determining step. Electron withdrawing group substituent in the para position of stilbene affects the regioselectivity of the reaction. In this case, the phenyl group from the Ph-Pd complex migrates preferentially to the same carbon of the double bond to which the phenyl is bonded. Finally, a one pot sequential double Heck arylation of styrene was performed, giving trisubstituted olefin with an overall yield of 73%.Keywords: Heck reaction, palladium, trisubstituted olefins, double arylation IntroductionPalladium-catalyzed Heck cross-coupling reactions are one of the most efficient methods for the construction of C−C bonds and have found widespread use in organic synthesis.1 Most Heck reactions involves arylation of monosubstituted alkenes (especially acrylates and styrene derivatives) to allow synthesis of disubstituted olefins with regio and stereoselective control. In contrast, fewer studies have been conducted on the arylation of disubstituted olefins or double arylation of mono-substituted olefins, to yield trisubstituted products. Stereocontrol during the synthesis of highly substituted double bonds is a significant challenge in organic synthesis, 2 and the Heck reaction remains an important alternative. In this context, some examples of regio and stereoselective syntheses of trisubstituted α,β-unsaturated compounds, such as nitriles, 3,4 cinnamates 5-10 and aldehydes, 11 through either monoarylation of disubstituted olefins or direct diarylation of monosubstituted olefins, have been reported. Arylation of disubstituted alkenes without an electron-withdrawing group conjugated to the C=C double bond (e.g., α-or β-methylstyrene, 10,12 1,1-diphenylethene and transstilbene)13-15 has also been investigated. However, to the best of our knowledge, no example using substituted stilbenes has been described. Recently, we re...

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