Application of Iron Complexes as Catalysts in C-O and C-C bond forming reactions

‘Green Chemistry’ is a philosophy that encourages chemists in research and industry to reduce toxic waste for cleaner and safer chemical production. Oxidation reactions are commonly used in industry and are traditionally achieved by methods that involve toxic metals (such as chromium) and solvents, generating considerable waste compared to the value of the final product. The Mukaiyama Aldol reaction is another organic reaction that utilizes metals as Lewis acid catalysts. The principles of Green Chemistry suggest that chemical reactions should be performed with a maximum of efficiency and with a minimum of side product formation, accompanied by a minimal use of the toxic reagents. The overall purpose of the PhD project was to replace toxic metals in catalyst systems by environmentally more benign iron. The research focused on synthesizing iron based organometallic complexes, that were fully characterized and then employed as catalysts, as compared to conventional in situ synthesis of catalytically active complexes (where the identification and modification of active sites is difficult due to lack of knowledge of the exact structure of the metal complex). Iron complexes of the general formula [BrCpFe(CO)(L)] (1) where L is a monodentate phosphoramidite, [Fe(L)2(OTf)2] (2) where L is bidentate α-iminopyridine and OTf is triflate, and [Fe2(L)Cl6] (3) where L is a tris-dentate α-diiminopyridine were synthesized and characterized by various instrumental methods such as multinuclear NMR, IR, Mass-spectrometry, UV-VIS spectroscopy, elemental analyses, and single crystal X-ray diffraction methods. Complexes 1 and 2 were successfully employed as catalyst precursor in oxidation reactions of activated methylene groups and secondary alcohols to obtain the corresponding ketones in 21-91% yield. Complex 3 was successfully employed as catalysts after activation using AgSbF6 in Mukaiyama Aldol reactions to give silyl protected β-hydroxyketones in 43-91% yield

Evaluation of the effects of passion fruit peel flour (Passiflora edulis fo. flavicarpa) on metabolic changes in HIV patients with lipodystrophy syndrome secondary to antiretroviral therapy

AbstractThis study evaluated the effects of using passion fruit peel flour together with diet therapy and counseling in 36 patients with HIV lipodystrophy who were in an ambulatory clinic in a university hospital. The patients were divided into two groups. One received 30g of passion fruit peel flour daily for 90 days and diet therapy counseling. The other group received only diet therapy counseling. The metabolic changes were analyzed before and after the intervention, with a significance level predetermined at p≤0.05. The use of passion fruit peel flour was effective in reducing total cholesterol and triacylglycerides after 30 days. The concentrations of LDL-C decreased, while HDL-C increased in the blood of lipodystrophy patients after 90 days passion fruit peel flour treatment. No significant differences in food consumption were seen between groups. The use of 30g of passion fruit peel flour for 90 days together with diet therapy counseling was effective in improving plasma concentrations of total cholesterol, LDL-C, HDL-C and triacylglycerides

New Bis(Imino)Pyridine Complexes of Iron(II) and Iron(III), and Their Catalytic­ Activity in the Mukaiyama Aldol Reaction

New iron(II) and iron(III) complexes bearing bis(imino)pyridine ligands were synthesized and successfully applied to the Mukaiyama aldol reaction. The two complexes [FeCl2 L] (L = bis(imino)pyridine ligand, 55% isolated yield) and [LFe(μCl)3FeCl3] (76%) were obtained employing FeCl2 and FeCl3 iron sources, respectively, and characterized by elemental analyses, mass spectrometry, IR spectroscopy and, one example, by X-ray diffraction. The two new iron complexes were subsequently employed as catalysts in the Mukaiyama aldol reaction after abstraction of two chlorides by AgSbF6 to obtain the aldol products in 43% to virtually quantitative yield (CH2Cl2 solvent, room temperature, 3.5 to 16 h reaction time). The impact of the oxidation state of the iron center on the reaction rate and the diastereomeric ratios of the products was investigated

The Role of the Nrf2/ARE Antioxidant System in Preventing Cardiovascular Diseases

It is widely believed that consuming foods and beverages that have high concentrations of antioxidants can prevent cardiovascular diseases and many types of cancer. As a result, many articles have been published that give the total antioxidant capacities of foods in vitro. However, many antioxidants behave quite differently in vivo. Some of them, such as resveratrol (in red wine) and epigallocatechin gallate or EGCG (in green tea) can activate the nuclear erythroid-2 like factor-2 (Nrf2) transcription factor. It is a master regulator of endogenous cellular defense mechanisms. Nrf2 controls the expression of many antioxidant and detoxification genes, by binding to antioxidant response elements (AREs) that are commonly found in the promoter region of antioxidant (and other) genes, and that control expression of those genes. The mechanisms by which Nrf2 relieves oxidative stress and limits cardiac injury as well as the progression to heart failure are described. Also, the ability of statins to induce Nrf2 in the heart, brain, lung, and liver is mentioned. However, there is a negative side of Nrf2. When over-activated, it can cause (not prevent) cardiovascular diseases and multi-drug resistance cancer

Active Palladium Colloids via Palladacycle Degradation as Efficient Catalysts for Oxidative Homocoupling and Cross-Coupling of Aryl Boronic Acids

Active palladium colloids formed upon degradation of a palladacyclic complex (Herrmann–Beller <b>1</b>) have been isolated for the first time and thoroughly characterized with techniques such as transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure spectroscopy. The synthesized palladium colloids have been utilized as efficient catalysts for the oxidative homocoupling of aryl boronic acids. Cross-coupling of two different aryl boronic acids has also been made possible using these active palladium colloids. This is the first report of this kind of coupling between aryl boronic acids

New Chiral Phosphoramidite Complexes of Iron as Catalytic Precursors in the Oxidation of Activated Methylene Groups

New phosphoramidite complexes of iron were synthesized and structurally characterized. Reaction of the known chiral phosphoramidites (RO)2PNR’2 (R = binaphthyl, R’ = CH3, 1a; R = binaphthyl, R’ = benzyl, 1b) with [FeBr(Cp)(CO)2] afforded the title compounds [FeBr(Cp)(CO)(1a,b)] (4a,b) in 34 and 65 % isolated yields as mixtures of diastereomers, since both the metal and the ligand are stereogenic. Similarly, reaction of 1b with [Fe(Cp)I(CO)2] in the presence of catalytic [Fe(Cp)(CO)2]2 afforded [Fe(Cp)I(CO)(1b)] (5b) in 81% yield as a mixture of diastereomers. The molecular structures of 4a, 4b and 5 were determined, revealing a pseudo octahedral coordination geometry about the iron center. The new metal complexes are catalytically active in the oxidation of benzylic methylene groups to the corresponding ketones, utilizing t-BuOOH as oxidant (2 mol% catalyst, 36 h, room temperature, 31−80% yield)