Surface properties and catalytic activity of ferrospinels of nickel, cobalt and copper, prepared by soft chemical methods

Ferrospinels of nickel, cobalt and copper and their sulphated analogues were prepared by the room temperature coprecipitation route to yield samples with high surface areas. The intrinsic acidity among the ferrites was found to decrease in the order: cobalt> nickel> copper. Sulphation caused an increase in the number of weak and medium strong acid sites, whereas the strong acid sites were left unaffected. Electron donor studies revealed that copper ferrite has both the highest proportion of strong sites and the lowest proportion of weak basic sites. All the ferrite samples proved to be good catalysts for the benzoy lation of toluene with benzoyl chloride. copper and cobalt ferrites being much more active than nickel ferrite. The catalytic activity for benzoylation was not much influenced by sulphation, but it increased remarkably with calcination temperature of the catalyst. Surface Lewis acid sites, provided by the octahedral cations on the spinel surface, are suggested to be responsible for the catalytic activity for the benzoylation reaction.

Surface properties and catalytic activity of phosphate modified zirconia

Preparation and physico-chemical characterization or phosphate modified zirconia systems and their application to Friedel-Crafts benzylation and benzoylation of toluene have been reported. The influence of transition metals on the surface properties and catalytic activity has also been discussed.

Catalysis by Transition Metal Modified Ceria and Ceria-Zirconia Mixed Oxides Prepared via Sol-Gel Route

The aim of catalysis research is to apply the catalyst successfully in economically important reactions in an environmentally friendly way. The present work focuses on the modification of structural and surface properties of ceria and ceria-zirconia catalysts by the incorporation of transition metals. The applications of these catalysts in industrially important reactions like ethylbenzene oxidation, alkylation of aromatics are also investigated.Sol-gel method is effective for the preparation of transition metal modified ceria and ceria-zirconia mixed oxide since it produces catalyst with highly dispersed incorporated metal. Unlike that of impregnation method plugging of pores is not prominent for sol-gel derived catalyst materials. This prevents loss of surface area on metal modification as evident for BET surface area measurements.The powder X-ray diffraction analysis confirms the cubic structure of transition metal modified ceria and ceria-zirconia catalysts. The thermal stability is evident from TGA/DTA analysis. DR UV-vis spectra provide information on the coordination environment of the incorporated metal. EPR analysis ofCr, Mn and Cu modified ceria and a ceria-zirconia catalyst reveals the presence of different oxidation states of incorporated metal.Temperature programmed desorption of ammonia and thermogravimetric desorption of 2,6-dimethyl pyridine confirms the enhancement of acidity on metal incorporation. High a-methyl styrene selectivity in cumene cracking reaction implies the presence of comparatively more number of Lewis acid sites with some amount of Bronsted acid sites. The formation of cyclohexanone during cyclohexanol decomposition confirms the presence of basic sites on the catalyst surface.Mn and Cr modified catalysts show better activity towards ethylbenzene oxidation. A redox mechanism through oxometal pathway is suggested.All the catalysts were found to be active towards benzylation of toluene and a-xylene. The selectivity towards monoalkylated products remains almost 100%. The catalytic activity is correlated with the Lewis acidity of the prepared systems.The activity of the catalysts towards methylation of phenols depends on the strength acid sites as well as the redox properties of the catalysts. A strong dependence of methylation activity on the total acidity is illustrated.

Structural tuning of Montmorillonite clays by pillaring: Designing of shape selective solid acid catalysts and PANI - Montmorillonite nanocomposites

Green chemistry boots eco-friendly,natural clays as catalysts in the chemical as well as in the pharmaceutical industry.Industry demands thermal stability,mechanical strength etc for the catalyst and there the modification methods becomes important.Pillaring tunes clays as efficient catalytic templates for shape selective organic synthesis.Here pillared clays are used as promising alternatives for the environmentally hazardous homogeneous catalysts in some industrially important Friedel-Crafts alkylation reactions of arenes with lower alchohols and higher olefins.The layer structure is enhanced upon pillaring and allows the nanocomposite formation with polyaniline to develop today’s nanoscale diameter devices.Present work gives an entry of pillared clays to the world of conducting composite nanofibers.

Alkylation of Benzene with higher olefins over zeolites: A green route for lab synthesis.

The objective of the present work is to improve the textural and structural properties of zeolite-Y through ion exchange with rare earth metals. We meant to obtain a comparative evaluation of the physicochemical properties and catalytic activity of rare earth modified H-Y, Na-Y, K-Y, and Mg-Y zeolites. Friedel-Crafts alkylations of benzene with higher 1- olefins such as 1-octene, 1-decene, and 1dodecene for the synthesis of linear alkylbenzene (LAB) have been selected for the present study. An attempt has also been directed towards the correlation of the enhancement in 2-phenylalkane formation to the improvement in the textural and structural properties upon rare earth modification for the zeolite-Y. The present method for LAB synthesis stands as an effective Green alternative for the existing hydrofluoric acid technology

"Catalysis by pillared montmorillonites exchanged with transition metals"

The present work is oriented to obtain a comparative evaluation of the physicochemical properties and catalytic activities of iron, aluminium and iron aluminium mixed pillared montmorillonites and their transition metal exchanged analogues. Reactions of industrial importance like Friedel Crafts alkylations, catalytic wet peroxide oxidation of phenol and MTBE synthesis have been selected for the present study. The thesis is structured into seven chapters. First chapter deals with a brief introduction and literature survey on pillared clays. Second chapter explains the materials and methods employed in the work. Results and discussions on the characterisation techniques are described in the third chapter. The subsequent three chapters describe the catalytic activities of pillared clays in the industrially important reactions. Last chapter comprises the summary of the investigations and the conclusions drawn from the earlier chapters

‘‘catalysis by nano sulfated titania modified by transition metals"

in the present study, we have prepared and evaluated the physical and chemical properties and catalytic activities of transition metal loaded sulfated titania via the sol-gel route. Sol-gel method is widely used for preparing porous materials having controlled properties and leads to the formation of oxide particles in nano range, which are spherical or interconnected to each other. Characterization using various physico-chemical techniques and a detailed study of acidic properties are also carried out. Some reactions of industrial importance such as Friedel-Crafts reaction, fen-butylation of phenol,Beckmann rearrangement of cyclohexanone oxime, nitration of phenol and photochemical degradation of methylene blue have been selected for catalytic activity study in the present venture. The work is organized into eight chapters

One-pot synthesis and characterization of soluble poly(aryl ether-ketone)s having pendant carboxyl groups

Aromatic poly(ether-ketone)s having pendant carboxyl groups have been obtained by direct, one-pot, Friedel-Crafts copolycondensation of 4,4'-diphenoxybenzophenone with a mixture of terephthaloyl chloride (TC) and trimellitic anhydride acid chloride (TAAC), over a wide range of TAAC/TC molar ratios, in the presence of anhydrous aluminum chloride. The syntheses were performed as precipitation-polycondensations, and the polymers were obtained in particulate form. Besides globular particles of polymer, small quantities of elongated, needlelike particles were observed when the mole ratio TAAC/TC was less than 1. Use of X-ray microdiffraction with synchrotron radiation has revealed that the needlelike material consists of a cyclic compound containing 10 phenylene units, i.e., the crystals are of a [2 + 2] macrocyclic dimer. The polymers obtained are soluble in strong acids and in mixtures of methanesulfonic acid or trifluoroacetic acid with chlorinated hydrocarbons. The molecular structures of the polymers were confirmed by H-1 and C-13 NMR spectroscopy. Reaction of TAAC with 4,4'-diphenoxybenzophenone produced mainly meta-orientation of the resulting ketone linkages. The size of the polymer particles, their molecular weights, and the melting behavior of the products obtained depend on the TAAC/TC ratio used. Ortho-keto acid residues, formed during reaction of anhydride groups of TAAC with 4,4'-diphenoxybenzophenone, exhibit ring-chain tautomerism. A carboxyl-containing aromatic polyketone derived from p-terphenyl, and thus having with no ether linkages in the main chain, was prepared by analogous chemistry, and functional derivatives of carboxy-substituted polyketones were also obtained and characterized.

Preparação e caracterização estrutural de complexos quirais de nióbio, utilizando álcoois terpênicos quirais como ligantes

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Terpenos e lignanas de Aristolochiaceae

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Stereoselective Catalytic Processes for the Synthesis of Polycyclic Aromatic Compounds

In this PhD-thesis, two methodologies for enantioselective intramolecular ring closing reaction on indole cores are presented. The first methodology represents a highly stereoselective alkylation of the indole N1-nitrogen, leading to 3,4-dihydro-pyrazinoindol-1-ones – a structural class which is known for its activity on the CNS and therefore of high pharmacological interest concerning related diseases. In this approach, N-benzyl cinchona-alkaloids were used for the efficient catalysis of intramolecular aza-Michael reactions. Furthermore, computational studies in collaboration with the research group Prof. Andrea Bottoni (Department of Chemistry “G. Ciamician”, Bologna) were accomplished in order to get insight into the key interactions between catalyst and substrate, leading to enantiomeric excesses up to 91%. The results of the calculations on a model system are in accordance with the experimental results and demonstrate the high sensibility of the system towards structural modifications. The second project deals with a metal catalyzed, intramolecular Friedel-Crafts (FC)-reaction on indolyl substrates, carrying a side chain which on its behalf is furnished with an allylic alcohol unit. Allylic alcohols are part of the structural class of “π-activated alcohols” – alcohols, which are more easily activated due to the proximity to a π-unit (allyl-, propargyl-, benzyl-). The enantioselective intramolecular cyclization event is catalyzed efficiently by employment of a chiral Au(I)-catalyst, leading to 1-vinyl- or 4-vinyl-tetrahydrocarbazoles (THCs) under the formation of water as byproduct. This striking and novel process concerning the direct activation of alcohols in catalytic FC-reactions was subsequently extended to similar precursors, leading to functionalized tetrahydro-β-carbolines. These two methodologies represent highly efficient approaches towards the synthesis of scaffolds, which are of enormous pharmaceutical interest and amplify the spectra of enantioselective catalytic functionalisations of indoles.

Design and development of new green catalytic methodologies for the synthesis of enantiomerically enriched molecules

The following Ph.D work was mainly focused on catalysis, as a key technology, to achieve the objectives of sustainable (green) chemistry. After introducing the concepts of sustainable (green) chemistry and an assessment of new sustainable chemical technologies, the relationship between catalysis and sustainable (green) chemistry was briefly discussed and illustrated via an analysis of some selected and relevant examples. Afterwards, as a continuation of the ongoing interest in Dr. Marco Bandini’s group on organometallic and organocatalytic processes, I addressed my efforts to the design and development of novel catalytic green methodologies for the synthesis of enantiomerically enriched molecules. In the first two projects the attention was focused on the employment of solid supports to carry out reactions that still remain a prerogative of omogeneous catalysis. Firstly, particular emphasis was addressed to the discovery of catalytic enantioselective variants of nitroaldol condensation (commonly termed Henry reaction), using a complex consisting in a polyethylene supported diamino thiopene (DATx) ligands and copper as active species. In the second project, a new class of electrochemically modified surfaces with DATx palladium complexes was presented. The DATx-graphite system proved to be efficient in promoting the Suzuki reaction. Moreover, in collaboration with Prof. Wolf at the University of British Columbia (Vancouver), cyclic voltammetry studies were reported. This study disclosed new opportunities for carbon–carbon forming processes by using heterogeneous, electrodeposited catalyst films. A straightforward metal-free catalysis allowed the exploration around the world of organocatalysis. In fact, three different and novel methodologies, using Cinchona, Guanidine and Phosphine derivatives, were envisioned in the three following projects. An interesting variant of nitroaldol condensation with simple trifluoromethyl ketones and also their application in a non-conventional activation of indolyl cores by Friedel-Crafts-functionalization, led to two novel synthetic protocols. These approaches allowed the preparation of synthetically useful trifluoromethyl derivatives bearing quaternary stereocenters. Lastly, in the sixth project the first γ-alkylation of allenoates with conjugated carbonyl compounds was envisioned. In the last part of this Ph.D thesis bases on an extra-ordinary collaboration with Prof. Balzani and Prof. Gigli, I was involved in the synthesis and characterization of a new type of heteroleptic cyclometaled-Ir(III) complexes, bearing bis-oxazolines (BOXs) as ancillary ligands. The new heteroleptic complexes were fully characterized and in order to examine the electroluminescent properties of FIrBOX(CH2), an Organic Light Emitting Device was realized.

Nuovi processi catalitici per la sintesi di prodotti ad attività farmacologica

The transition metal-catalyzed allylic alkylation (Tsuji-Trost type reaction) is a powerful tool for C-C, C-N, and C-O bond formation, which has been widely applied to organic chemistry over the last decades. Typical substrates for this transformation are activated allylic compounds such as halides, esters, carbonates, carbamates, phosphates, and so on. However, use of these substrates is associated with the disadvantage of generating a stoichiometric amount of chemical waste. Furthermore, these starting materials have to be prepared in an extra step from the corresponding allylic alcohol. Thus, ideal substrates would be the allylic alcohols themselves, with water being the only byproduct in this case. However, the scarse propensity of the hydroxyl moiety to act as good leaving group has significantly limited their use so far. During the last decade significant efforts have been made in order to develop more atom-economical and environmentally-friendly allylic alkylation protocols by employing allylic alcohols directly. In this PhD dissertation two main projects addressing this topic are presented. “Project 1” deals with the development of new metal-catalyzed intramolecular Friedel-Crafts (FC) allylic alkylations of electron-rich (PAPER A), as well as challenging electron-poor arenes (PAPER B) with alcohols. In “Project 2”, gold(I)-catalyzed intramolecular and stereoselective allylic alkylation reactions are reported. In particular, a FC alkylation of indole-containing allylic alcohols is presented in PAPER C. While, an O-alkylation of aminol-containing allylic alcohols is reported in PAPER D. To the best of knowledge, these reports represent the first example of gold(I)-catalyzed stereoselective alkylations with alcohols.

Synthese von optisch aktivem 9,14-Methylen-Lipoxin A 4

In der vorliegenden Arbeit wurde die Synthese von optisch aktivem 9,14-Methylen-Lipoxin A4 untersucht. Lipoxin A4 und seine Derivate leiten sich von der Arachidonsäurekaskade ab wie die Prostaglandine, Prostacycline, Thromboxana und Leucotriene. Alle diese Verbindungen sind biologisch aktive Eicosanoide, die aus 20 C-Atomen bestehen. Lipoxine können im Organismus auf verschiedenen Biosynthesewegen entstehen: über die Lipoxygenase sowie über die Zell-Zell-Wechselwirkungen. Untersuchungen ergaben, dass die Lipoxine selektive biologische Wirkungen zeigen, die eine wichtige Rolle vor allem in Entzündungsprozessen und Infektabwehr zeigen. Da aber diese Moleküle rasch isomerisieren, sind diese hohen Aktivitäten mit einer sehr geringen Stabilität gekoppelt. Aufgrund dieser Instabilität konnte die biologisch aktive Konformation des Lipoxin A4 am Rezeptor nicht eindeutig bestimmt werden. Zur besseren Untersuchung der Lipoxinrezeptor-Anordnung wurden deshalb stabile Analoga synthetisiert. Die biologische Aktivität des nach Nokami et al hergestellten Lipoxin A4-Analogons weicht sehr stark von der des Lipoxins ab. Angeregt durch diese Arbeiten wurde in der Arbeitsgruppe Nubbemeyer die Idee entwickelt, das konjugierte Tetraensystem des Lipoxin A4-Moleküls durch das Cycloheptatrien nachzuahmen. Die CH2-Gruppe bildet eine Brücke, die die Isomerisierung vom aktiven cis-Isomer zu den inaktiven trans-Isomeren verhindern soll. Mit diesem Cycloheptatriengerüst als Lipoxin A4-Analogon hoffen wir das Lipoxingerüst unwesentlich zu verändern und die damit verbundene biologische Aktivität zu erhalten. Die Synthese des 9,14-Methylen-LXA4 soll möglichst konvergent erfolgen, so dass gegebenenfalls auf Bausteine zurückgegriffen werden kann, deren Aufbau bereits optimiert wurde. Eine derartige Strategie ermöglicht darüber hinaus die Herstellung einer großen Zahl von weiteren potentiell interessanten Verbindungen ohne komplettes Umstellen der Synthese. Wichtige Reaktionen im Verlauf dieser Synthese sind: bei der Synthese des C8-C20-Bausteins: Friedel-Crafts-Acylierungen, Haloform-Reaktion, Veresterung mittels Standardmethoden, enantioselektive Reduktion mit dem chiralen CBS-Katalysator und Schutzgruppenoperation. bei der Synthese des C1-C7-Bausteins: ex-chiral-pool-Synthese aus 2-Desoxy-D-ribose, Wittig-Reaktion, Hydrierung mit Pd/C, Schutzgruppenoperation, Abspaltung von Schutzgruppen und Swern-Oxidation zum Aldehyd. Die Schlüsselreaktion der ganzen Synthese ist die Eintopf-Variante der Julia-Olefinierung nach Kocienski: selektiver Aufbau des trans-Olefins durch Verknüpfung der beiden Bausteine. Nach weiteren Schutzgruppenoperationen (und Öffnung des Valerolactons) wird der Methylester des 9,14-Lipoxin A4 erhalten, dessen biologische Aktivität zweifelsfrei bewiesen wurde.

Reazioni tandem organocatalitiche enantioselettive di derivati indolici e nitroetene: un accesso diretto a precursori di alcaloidi dell'Ergot

Il lavoro discusso in questa tesi è lo sviluppo di un metodo sintetico basato sulla catalisi asimmetrica che consente di ottenere precursori di alcuni alcaloidi dell’Ergot in forma enantioarricchita. La reazione sviluppata consiste in un processo domino Friedel-Crafts/nitro-Michael fra indoli sostituiti in posizione 4 con un accettore di Michael e nitroetene. I catalizzatori utilizzati sono in grado di attivare il nitroetene per la Friedel-Crafts mediante legami a idrogeno e di indurre stereoselezione nella successiva ciclizzazione di Michael intramolecolare. Mediante la procedura ottimizzata è possibile ottenere una serie di indoli policiclici, potenziali precursori sintetici di alcaloidi dell’Ergot, con buone rese ed enantioselezioni.