Submitted by Franciele Moreira (francielemoreyra@gmail.com) on 2018-08-29T13:57:57Z No. of bitstreams: 2 Tese - Leandro Lima Carvalho - 2018.pdf: 15924313 bytes, checksum: a771fd37eef28f74a53a69978e8700f3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-08-29T14:14:18Z (GMT) No. of bitstreams: 2 Tese - Leandro Lima Carvalho - 2018.pdf: 15924313 bytes, checksum: a771fd37eef28f74a53a69978e8700f3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-08-29T14:14:18Z (GMT). No. of bitstreams: 2 Tese - Leandro Lima Carvalho - 2018.pdf: 15924313 bytes, checksum: a771fd37eef28f74a53a69978e8700f3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-08-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The management of the world energy matrix needs to be rethought, and in this context, the energy sector is, over all, the focus of this discussion, and the present, depends more and more on new strategies for energy production. In this way, the advances in the development of technologies about alternative sources of energy generation called Fuel Cells, mainly the electrochemical devices which working with ethanol as fuel (DEFCs). This work, the carbon supported Pt/C; Pd/C; Pt75Pd25/C; Pt75(PdOx)25/C; Pt50Pd50/C e Pt50(PdOx)50/C electrocatalysts with 20wt% of metal on carbon were prepared by fast reduction with sodium borohydride (NaBH4) followed by thermal treatment. The materials were characterized by X-ray diffraction (XRD) Transmission electron microscopy (TEM) and High resolution transmission electron microscopy (HRTEM), x-ray energy dispersive spectroscopy (EDS), cyclic voltammetry (VC) and Chronoamperometry. The EDS spectra showed e, experimental compositions of electrocatalysts are close to nominal, which suggest, high efficiency of the redactor agent BH4(aq) - /OH- (aq) for reducing the ions Pt+4 (H2PtCl6.6H2O) and Pd+2 (PdCl2.6H2O). The XRD analysis indicate the nanoparticle arrangement of the Platinum-Paladium with different content results in crystalline structure on carbon support, and the peaks assigned to Pt75(PdOx)25/C and Pt50(PdOx)50/C were observed indicating oxide formation from metal precursors Pt75Pd25/C e Pt50Pd50/C by thermal treatment method. The micrographs HRTEM showed homogenies particle size distribution on high area Vulcan XC-72 Carbon support. The particle size were determined as the maximum of Gaussian distribution of Pt/C; Pd/C e PtxPdy/C which showed electrochemical activity toward ethanol oxidation reaction in both, acid and alkaline, electrolyte. The exception is Pd in acid media. Moreover, the materials Pt75Pd25/C; Pt75(PdOx)25/C; Pt50Pd50/C e Pt50(PdOx)50/C with high Pd content, showed more better performance for ethanol oxidation reaction in alkaline media, with high anodic current density registered in the cyclic voltammetry and chronoamperometry experiments, in comparison with Pd/C e Pt/C catalysts. / O gerenciamento da matriz energética mundial precisa ser repensado. E, neste contexto, o setor energético é, sobretudo, o núcleo ativo desta discussão, que na atualidade, depende cada vez mais de novas estratégias para produção de energia. Desta forma, destacam-se os avanços no desenvolvimento de tecnologias ligadas às fontes alternativas de energia denominadas de “Células a Combustível”, principalmente os dispositivos eletroquímicos que operam com etanol como combustível (DEFCs). Neste trabalho, os eletrocatalisadores Pt/C; Pd/C; Pt75Pd25/C; Pt75(PdOx)25/C; Pt50Pd50/C e Pt50(PdOx)50/C, com 20% em massa de metal, foram preparados a partir do método de redução rápida por borohidreto de sódio (NaBH4) e de tratamento térmico. Os materiais obtidos foram caracterizados por Difração de Raios-X (DRX); Microscopia Eletrônica de Transmissão de Alta Resolução (HRTEM); Espectroscopia de Energia Dispersiva por Raios-x (EDS); Voltametria Cíclica (VC) e Cronoamperometria. Os espectros de EDS mostraram que as composições reais estão relativamente próximas das suas respectivas composições nominais, indicando que, o agente redutor BH4(aq) - /OH- (aq) é eficiente para reduzir tanto íons de Pt+4 (H2PtCl6.6H2O) como de Pd+2 (PdCl2.6H2O). As avaliações por DRX revelaram que a combinação de nanopartículas de “Platina-Paládio” em diferentes composições formaram estruturas cristalográficas no carbono suporte, e que picos difratográficos específicos foram observados para Pt75(PdOx)25/C e Pt50(PdOx)50C, confirmando a formação de óxidos metálicos através dos precursores Pt75Pd25/C e Pt50Pd50/C pelo método de tratamento térmico. As micrografias HRTEM mostraram distribuições de partículas homogêneas sobre o substrato de Carbono Vulcan XC-72 amorfo de alta área superficial, adotado como suporte. Os tamanhos médios das partículas foram tomados como os máximos das distribuições gaussianas. Pt/C; Pd/C e PtxPdy/C apresentaram atividades eletroquímicas para as reações de oxidação do etanol ROEs tanto em eletrólito ácido como básico, com exceção do Pd em meio ácido. E que, as composições Pt75Pd25/C; Pt75(PdOx)25/C; Pt50Pd50/C e Pt50(PdOx)50/C contendo maior teor de Pd, se mostraram mais ativas e promissoras para as ROEs em meio básico, apresentando melhores densidades de correntes anódicas registradas nos resultados voltamétricos e cronoamperométricos, quando comparadas aos materiais catalisadores de Pd/C e Pt/C.

Made available in DSpace on 2017-07-10T18:08:08Z (GMT). No. of bitstreams: 1 Fernando A P Voll.pdf: 745866 bytes, checksum: 24554e9ffb768c3450aabbf525840c64 (MD5) Previous issue date: 2008-02-14 / Fundação Araucária / Hydrogen peroxide decomposition is an undesirable reaction in the direct H2O2 synthesis process from H2 and O2. It s a desirable reaction for the generation of hydroxyl radicals (-OH) in the advanced oxidation processes. Thus, it is important to understand how the reaction medium conditions affect the H2O2 decomposition. In this work, the influence of the initial concentration of H2O2, the reaction temperature, the catalyst treatment with H2 and the catalyst deactivation (or activation) with H2O2 were studied. The catalysts studied in this work were a 5% Pd/C, a 0,5% Pd/C, a 1% Pd/g-Al2O3, and a 1% Pd/ZrO2. With the exception of the 1% Pd/ZrO2 catalyst, the apparent reaction rate constant (k) was affected by the initial concentration of H2O2 in the reaction medium, and in all cases where the reaction rate constant (k) was affected, its value decreased with the increase of the initial concentration of H2O2. The activation energy value was calculated for all the catalysts and varied between 25 and 55 kJ/mol. For all the catalysts tested, treatment with hydrogen resulted in a significant increase in the apparent reaction rate constant (k), and in a decrease in the activation energy for the reaction. All the reactions were well represented by a first order rate law. The effect of the treatment with H2O2 (realization of successive reactions of H2O2 decomposition, without catalyst exchange) was studied for the 5% Pd/C and 0,5% Pd/C catalysts (exposed to H2 or not). A small deactivation was observed in the 5% Pd/C catalyst (without prior exposure to H2) after four H2O2 decomposition reactions. A more significant deactivation was observed for the 5% Pd/C and 0,5% Pd/C (both treated with H2). For the 0,5% Pd/C catalyst not exposed to hydrogen, an activation of the catalyst occurred after successive reactions of H2O2 decomposition. / A decomposição do peróxido de hidrogênio é uma reação indesejável no processo de síntese direta do H2O2 a partir do H2 e O2. Por outro lado, é uma reação desejável para a formação dos radicais hidroxila (-OH) nos processos oxidativos avançados. Assim, é importante entender como as condições do meio de reação afetam a decomposição do H2O2. Neste estudo, foi verificada a influência de alguns fatores, tais como a concentração inicial de H2O2, a temperatura de reação, o tratamento do catalisador com H2 e a desativação (ou ativação) do catalisador com H2O2. Os catalisadores estudados nesse trabalho foram 5% Pd/C, 0,5% Pd/C, 1% Pd/γ -Al2O3 e 1% Pd/ZrO2. Com exceção do catalisador 1% Pd/ZrO2, a constante de velocidade aparente (k) da reação foi influenciada pela concentração inicial de H2O2 no meio reacional, e em todos os casos onde a constante de velocidade (k) foi afetada, seu valor diminuiu com o aumento da concentração inicial de H2O2. O valor da energia de ativação foi calculado para todos os catalisadores e variou entre 25 e 55 kJ/mol. Para todos os catalisadores testados, o tratamento com hidrogênio resultou em um aumento significativo no valor da constante de velocidade aparente (k), e em uma diminuição do valor da energia de ativação da reação. Todas as reações foram bem representadas por uma lei de velocidade de primeira ordem. O efeito do tratamento com H2O2 (realização de consecutivas reações de decomposição de H2O2, sem a troca do catalisador) foi verificado nos catalisadores 5% Pd/C e 0,5% Pd/C (tratados com H2 e não tratados). Uma pequena desativação foi observada no catalisador 5% Pd/C (não tratado) depois de algumas reações de decomposição do H2O2. Uma desativação mais significativa foi observada nos catalisadores 5% Pd/C e 0,5% Pd/C (ambos tratados com H2). Para o catalisador 0,5% Pd/C (não tratado com H2), ocorreu uma ativação do catalisador depois de sucessivas reações de decomposição do H2O2.

Palladium catalysed asymmetric hydroxy- and alkoxycarbonylation reactions of alkenes have the potential to deliver valuable chiral carboxylic acid and ester building blocks from cheap feedstocks: alkenes, carbon monoxide and water (alcohols in the case of alkoxycarbonylation). Despite the attractive nature of these reactions, extensive research has so far been unable to produce effective catalysts which are capable of controlling both regio- and enantioselectivity. Building on exciting recent results involving the use of highly enantioselective palladium catalysts derived from Phanephos-type ligands, this research focuses on paracyclophane-diphosphines and their use in asymmetric hydroxy- and alkoxycarbonylation reactions. An investigation into reaction conditions analysed several factors, including solvents, CO-pressure, acidic additives and halide sources, to provide optimal activity and selectivities. Two novel electron-poor paracyclophane-diphosphines and their mono- and di-palladium complexes were synthesised and shown to provide exceptional levels of regioselectivity while maintaining high levels of asymmetric induction. These are the first such examples of hydroxy- or alkoxycarbonylation catalysts to facilitate simultaneous control over both regio- and enantioselectivity. The most effective catalyst was used to promote the reactions of a selection of aryl alkenes and was shown to be tolerant of several different functional groups. A selection of non-symmetric paracyclophane-diphosphine ligands and their palladium complexes were also synthesised and assessed for their performance in hydroxy- and alkoxycarbonylation. We also report the use of Phanephos-type ligands to promote the highly enantioselective hydroxycarbonylation of N-(p-toluenesulfonyl)-3-pyrroline to deliver a chiral proline derivative in high ee.

Palladium based catalysts are widely used for C-C bonding reactions. This work describes the preparation of several such catalysts deposited onto siliceous, SBA-15 type support and common silica gel, whose surface was modified by organic chains with amine donor groups. The prepared catalysts have been tested in coupling reactions of organotin compounds and organic halides (Stille reactions) under various conditions.

A brief introduction explaining phosphine ligand properties, Pd catalysed cross-coupling reactions; the importance of the steps involved in the catalytic cycle (oxidative addition, transmetalation & reductive elimination), mechanistic studies and a comparison of various reactions will give an overview of important cross-coupling reactions and their limitations. The development of a “super-concentrated” (5M) Pd catalysed Kumada type coupling reaction has been developed for coupling a range of aryl bromide and chloride substrates with the Grignard reagents ((p-CF₃-C₆H₄)MgBr)) and PhMgBr in methyl-tetrahydrofuran (Me-THF). Using a range of bidentate ligands such as bis-phosphinoferrocenyl ligands, good conversions were achieved using small amounts of solvent; up to 10 times less than typical procedures in THF. The unsymmetrical Pt complexes of the form [Pt(P-P)Br₂], [Pt(P-P)(Ph)Br] and [Pt(P-P)Ph₂] have been synthesised and characterised. The variations of substituents on the ligand system and the steric bulk have been shown to have a dramatic effect on the rate of transmetalation. The results provide one explanation why 1,1’-bis(di tert-butylphosphino)ferrocene (dtbpf), an excellent ligand for certain Suzuki reactions, is quite poor in reactions where transmetalation is more difficult. Palladium dichloride complexes of the ferrocenylphosphine based ligands 1,1’-bis- (diphenylphosphino)ferrocene (dppf), 1,1’-bis-(diisopropylphosphino)ferrocene (dippf) and 1,1’-bis-(di-tert-butylphosphino)ferrocene (dtbpf) have been shown to be active in the Hiyama cross-coupling of p-bromoacetophenone and vinyltrimethoxysilane (CHCH₂Si(OMe₃)) in the presence of TBAF under thermal heating and microwave conditions. Ligands with the optimum balance for promoting the transmetalation, oxidative addition and reductive elimination steps along the reaction pathway have been identified. Competition experiments are consistent with slow transmetalation being an issue with the Hiyama reaction relative to the Suzuki coupling. A novel protocol has been developed for the synthesis of aryl-alkyl ethers via C-O bond activation under Pd catalysed conditions. Utilising the unsymmetrical 1-bis-(ditertbutyl-1’- bis-diphenylphosphino)ferrocene (dtbdppf) under optimised conditions with silicon based nucleophiles and NaOH or TBAF as an activator, the formation of methyl, ethyl, n-propyl and n-butyl ethers with a range of aryl halides was achieved in good yield.

Thesis (M. Tech. Chemistry, Dept. of Chemistry, Faculty of Applied and Computer Sciences)--Vaal University of Technology, 2010. / Membrane separation processes offer a promising alternative to energy-intensive separation processes such as distillation and solvent extraction. NF and RO are among the most investigated membrane processes with a potential use in the chemical industry. Carbon-carbon coupling reactions feature in the top ten most used reactions in the chemical industry. These reactions often use homogeneous palladium, nickel and other precious catalysts which are often difficult to separate from reaction products. This leads to potential product contamination and loss of active catalysts. This not only poses a threat to the environment but is also costly to the chemical industry. The purpose of this study was to investigate the efficiency of the recovery of the metal catalysts by selected membrane processes. Four commercial polymeric NF and RO membranes (NF90, NF270, BW30 and XLE) were selected for the study. Palladium catalysts commonly used in Heck and Suzuki coupling reactions were selected. These are Pd(OAc)2, Pd(OAc)2(PPh3)2, PdCl2 and Pd(PPh3)2Cl2. A range of organic solvents were also selected for the study. All the membranes were characterized for pure water permeability, pure solvent permeability, swelling, surface morphology and chemical structure. The chemical and catalytic properties of the catalysts were determined. Catalytic activity was investigated by performing coupling reactions. These catalysts generally performed well in the Heck coupling reaction with sufficient yields realized. The catalysts showed poor activities in the Suzuki and Sonogashira coupling reactions. These coupling reaction systems were affected by rapid palladium black formation. vi Catalyst retention studies showed the influence of membrane-solute interactions such as steric hindrance and size exclusion. The larger catalyst, Pd(OAc)2(PPh3)2 was rejected better by all the membranes irrespective of the solvent used. The smaller catalyst, Pd(OAc)2 was the most poorly rejected catalyst. This catalyst showed signs of instability in the selected solvents. An interesting finding from this study is that of higher rejections in water compared to other solvents for a particular catalyst. In this regard, the influence of solventsolute effects was evident. Generally, higher rejections were observed in solvents with higher polarity. This has been explained by the concept of solvation. It has been shown that solvents with different polarity solvate solutes differently, therefore leading to a different effective solute diameter in each solvent. Catalyst separation using NF90 membrane was attempted for the Heck coupling reaction system. The reaction-separation procedure was repeated for two filtration cycles with rapid activity decline evident. This was regarded as very poor showing of the catalyst separation efficiency of the membrane. Other authors in similar studies using SRNF membranes have reported reaction-separation processes of up to seven cycles. This observation shows the inferiority of polymeric membranes in organic solvent applications such as catalyst separation.

In this work, two groups of carbon supported Pt-Pd catalysts have been prepared in order to investigate the effect of Pd, as a second metal, and surfactants on the catalytic activity towards methanol and ethanol oxidation reactions used in the direct methanol and ethanol fuel cells. In the first group (group a), 1- hexanethiol was used as a stabilizing agent while in the second group (group b), 1,1 dimethyl hexanethiol was utilized. Cyclic voltammetry (CV), chronoamperometry (CA), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used in order to determine the nature of the catalysts. The average crystalline size of the metal particles in the catalysts was explored by XRD and TEM. TEM results revealed the uniform distribution of the metal nanoparticles on carbon support with a narrow size distribution in the range of 3.0 to 3.7 nm and the average crystalline sizes of metal particles for group &ldquo / b&rdquo / catalysts were larger than that of group &ldquo / a&rdquo / catalysts which can be explained by the surfactant effect. These results were in good agreement with XRD data. The oxidation states of platinum (Pt(0) and Pt(IV)) and palladium (Pd(0) and Pd(II)) and their ratios were investigated by XPS and for the most active catalyst, catalyst Ib, these ratios were found to be as 6.94 and 13.7, respectively. Electrochemical activities of the catalysts towards methanol and ethanol oxidation reactions were recorded and compared with that of Pt/C and the commercial Pt (ETEK 20 %wt) catalysts. The results indicated that the group &lsquo / b&rsquo / catalyst has greater catalytic activities than that of group &lsquo / a&rsquo / catalysts. Catalyst Ib comes into prominence as the most active catalyst due to its superior characteristics that it possess such as highest extent of alloying with respect to the palladium amount used, active surface area, CO-tolerance, stability and Pt (0) to Pt (IV) and Pd (0) to Pd (II) ratios.

N-heterocyclic carbenes (NHCs) have become a very popular class of ligands, which has found uses in numerous catalytic applications. The use of such compounds in combination with phosphorus-based ligands within metal complexes has enabled the design of very active yet robust catalytic systems. The following chapters will describe the design of novel well-defined palladium- and ruthenium-based pre-catalysts featuring a NHC and a phosphorus-based ligand, referred at as mixed ligand systems. Such species were employed in catalysis where their properties appeared highly beneficial, uses at low catalysts loading and under harsh conditions were then envisioned. The preparation of a series of well-defined palladium mixed NHC/phosphine species is presented in chapter 2. Their catalytic activity in the aqueous Suzuki-Miyaura reaction of aryl chlorides and boronic acids, using low catalyst loadings, is described. The observation of catalytic activity of the latter systems in the hydration of nitriles prompted us to further investigate this reactivity. This reaction appeared to be operative in the absence of palladium species and could be performed under base-catalysed conditions, which was studied in detail and depicted in chapter 3. The combination of a NHC and a phosphite ligand in ruthenium olefin metathesis pre-catalysts has been underexplored. Preliminary results showed that such species could be readily prepared and presented an unusual geometry and a high catalytic activity. Variations in phosphite-containing ruthenium olefin metathesis pre-catalysts are presented. Chapter 4 describes the investigation of various Schrock carbene moieties in such architectures, as well as their implications in structure and catalysis. Chapter 5 depicts attempts to design olefin metathesis Z-selective pre-catalysts by inserting a chelating NHC moiety within phosphite-containing ruthenium species. This dissertation concludes on the potential of such mixed species in catalysis, and armed with the new knowledge provided by this work, proposes potential developments of such chemistry in the design of always more robust and active catalytic systems.

Orientadores: Antonio José Gomez Cobo, César Augusto Moraes de Abreu / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-16T13:01:21Z (GMT). No. of bitstreams: 1 Freire_EleonoraMariaPereiradeLuna_D.pdf: 2485469 bytes, checksum: 5c15bdbbb73bd51d623eb4811e9d2248 (MD5) Previous issue date: 2005 / Resumo: Os catalisadores à base de paládio apresentam particular interesse para o tratamento de gases de exaustão automotiva, notadamente no caso da combustão do etanol. O presente trabalho tem o objetivo de estudar as propriedades físico- químicas de catalisadores Pd - Fe e Pd - Co suportados em alumina modificada pelo óxido de cério. Para tanto, catalisadores modelo foram preparados através do método de impregnação por via úmida, empregando-se sais precursores à base de nitrato dos metais, e os suportes Al2O3, CeO2 e CeO2/Al2O3. Os catalisadores obtidos tiveram seus teores metálicos determinados por meio de espectrofotometria de absorção atômica, tendo sido caracterizados através de adsorção de nitrogênio (método B.E.T), espectroscopia no infravermelho, difração de raio-X, redução à temperatura programada. Os sistemas preparados foram avaliados pela reação catalítica de oxidação do etanol em fase gasosa em um microreator tubular de leito fixo, operando a pressão atmosférica e a temperatura de 3500 C. Os catalisadores preparados apresentam frações mássicas em torno de 2 % para o Pd, e de 1% para os aditivos Fe ou Co. A adição de Pd, Pd-Fe e Pd-Co aos suportes Al2O3 e CeO2/Al2O3 não levou a modificações, nos volumes dos poros e nas áreas superficiais específicas. Esses resultados mostram que a adição dos metais pouco influenciam nas características texturais. Enquanto para os bimetálicos suportados em céria, há a hipótese da existência de microporos apesar de ter ocorrido diminuições relativas das áreas superficiais específicas os volumes dos poros permanecem constantes. Na reação de oxidação do etanol, os resultados das análises cromatográficas levam a concluir que a introdução dos aditivos cobalto e ferro ao paládio provoca redução de eficiência na conversão do etanol para os sistemas CeO2 e CeO2/Al2O3. A adição do cobalto ao paládio na alumina aumenta a conversão e apresenta alto rendimento para a oxidação do etanol e o catalisador paládio suportado em céria apresenta conversão menor do que o Pd-Co sobre alumina porém rendimentos semelhantes / Abstract: Palladium based catalysts have been, applied at the treatment of the automotive gas exhaustion, particularly in the case of ethanol combustion. In this context, the actual work has the aim to study the physical and chemical properties of the Pd, Pd-Fe and Pd-Co catalysts supported in alumina, ceria and alumina modified by the cerium oxide. The wet impregnation method was used to develop the model catalysts. Precursor salts metal nitrates as well as the supports Al2O3, CeO2 and CeO2/Al2O3, were used for this purpose. The catalysts were characterised by the methods of BET-N2, infrared spectroscopy (I.R), X- ray diffraction (XRD) and reduction at programmed temperature (TPR). The contents of the metal impregnated in the catalysts was quantified by atomic absorption spectrophotometry (A.A.S.). A fixed-bed tubular microreactor was used to evaluate the performance of the catalysts in the oxidation of ethanol in gas phase, at the atmospheric pressure and temperature of 350o C. The mass fractions observed for the palladium catalysts and those that had Fe and Co as additive, were around 2% and 1%, respectively. The addition of the Pd, Pd-Fe and Pd-Co to the alumina support and alumina modified by cerium oxide does not prove modification into they capacity of the porous and surface areas. This results prove that the addition of metals has no power to the textural characteristics. Whereas the supported bimetallic system in ceria has the theory of the existence of micropores despite of a relative decrease of specific surface areas, the capacity of porous remains stable. The ethanol oxidation reaction, and the results of the cromatographicas analysis conclude that the introduction of cobalt and iron into the palladium decreases the efficacy of ethanol conversion into the CeO2 and CeO2/Al2O3 systems. The addition of cobalt into the palladium in alumina increases the conversion and introduces high performance for the ethanol oxidation and the palladium catalyst supported by cerium shows minor , conversion than to the cobalt-palladium upom alumina, but with the same results / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

<p>  </p> <p>A historically important reaction, the Ueno-Stork reaction promotes, through the use of toxic organotin species, the cyclization of a haloacetal onto an alkene generating bicyclic acetals. This reaction has been used over the years in several total syntheses of biologically relevant natural products, especially the prostaglandin class of natural products. Herein, will be described the development of a novel nickel-catalyzed Ueno-Stork cyclization reaction, which no toxic organotin and radical promoters are used, and instead a greener, operationally friendly, and non-toxic earth abundant nickel catalyst is applied. Optimization studies, substrate scope, scalability, relative stereochemistry of the bicyclic acetals, as well as derivatization of the products were studied. Furthermore, the newly developed reaction was applied on the total synthesis of tricyclic-PGDM Methyl ester, a prostaglandin D2 metabolite of important clinical relevance that currently suffers from material supply issues.</p> <p>Cyclopropanol ring opening reactions have different reactivity modes. Either a metal homoenolate species or a b-keto radical species can be formed after ring opening depending on the reaction conditions applied. More specifically, hydroxycyclopropanols have been studied to access several important motifs present in an array of natural products and medicinally important molecules. The Dai group has used this strategy to access several motifs through intramolecular trapping of the homoenolate species with and without the presence of carbon monoxide to generate oxaspirolactones, THF/THP-fused bicyclic lactones, and disubstituted THF/THP heterocycles. Herein, it will be discussed the application of similar concepts to access new classes of heterocycles 4-ketovalerolactones and 3-furanones. The optimization of two reaction conditions to selectively synthesize each product starting from the same starting material was studied. Furthermore, the substrate scope, scale-up, and derivatization studies of each motif will be disclosed. </p>