This thesis covers the development of catalytic methodologies for the mild and chemoselective reductions of amides. The first part of the thesis describes the use of a Fe(II)/NHC catalyst for the deoxygenation of aromatic tertiary amides to corresponding amines. The protocol is characterized by low catalyst loading, mild reaction conditions and the use of air and moisture stable polymethylhydrosilaxane (PMHS) as the hydride source. The second part concerns the development of a protocol for the room temperature deoxygenation of a wide range of tertiary amides to amines using catalytic amounts of Et2Zn and LiCl together with PMHS. The system displayed high levels of chemoselectivity tolerating various reducible groups such as nitro, nitrile, and olefin functionalities, and was shown to be applicable for the reduction of aromatic, heteroaromatic and aliphatic tertiary amides. The attempts to expand the scope of the Fe-based protocol to accommodate benzylic tertiary amides led to the development of a transition metal-free catalytic system based on KOtBu for the formation of enamines. The final products constitute an important class of precursors for a wide range of valuable compounds in organic chemistry. Moreover, avoiding the use of transition metals in the protocol allowed the desired products to be obtained without the hazardous metal contaminants. The last chapter of the thesis describes the Mo(CO)6-catalyzed hydrosilylation of amides. The Mo-based catalyst was proven to mediate the deoxygenation of α,β-unsaturated tertiary and secondary amides to the corresponding allylamines without reduction of the olefinic bonds. Further development of the catalytic system revealed an unprecedented chemoselectivity in the hydrosilylation of aromatic and certain aliphatic tertiary amides in the presence of a variety of reducible groups along with aldehydes and imines that were tolerated for the first time. Moreover, it was possible to control the reaction outcome by variation of the reaction temperature to obtain either amines or aldehydes as the major products. The synthetic utility of the developed Mo(CO)6-catalyzed protocols was further demonstrated in the synthesis of the pharmaceuticals Naftifine and Donepezil.

This thesis concerns the preparation and use of diaryliodonium salts. In Project I various unsymmetrical diaryliodonium salts were reacted with three different nucleophiles in order to study the chemoselectivity of the reactions of the salts. The main focus of this project was to gain a deeper understanding of the underlying factors that affect the chemoselectivity in transition metal-free arylation reactions. They were found to be very nucleophile-dependent. Some nucleophiles were very sensitive to electronic effects, whereas others were sensitive to steric factors. Ultimately, some arenes are never transferred. A very interesting scrambling reaction was also observed under the reaction conditions, where unsymmetrical diaryliodonium salts form symmetrical salts in situ. Project II details the preparation of N-heteroaryliodonium salts via a one-pot procedure. The salts were designed so that the N-heteroaryl moiety was selectively transferred in applications both with and without transition metals. The chemoselectivity was demonstrated by selective transfer of the pyridyl group onto two different nucleophiles. The third project in the thesis discusses the synthesis of alkynyl(aryl)iodonium salts and alkynylbenziodoxolones from arylsilanes. This protocol could potentially be a very useful complement to the existing procedures, in which boronic acids are used. The last part of the thesis (Project IV) describes a C-2 selective arylation of indoles where diaryliodonium salts were used in combination with hetero-geneous palladium catalysis. This transformation was performed in water at ambient temperature to 50 °C, and tolerated variations of both the indole and the diaryliodonium salt. Importantly, several N-H indoles could be arylated. The MCF-supported Pd-catalyst showed very little leaching and it was demonstrated that the main part of the reaction occurred via heterogeneous catalysis. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted.</p>

This thesis describes new methods of carbon-carbon bond formation using metalated nitriles generated via metal exchange reactions. Sulfinylnitriles undergo a sulfinyl-metal exchange to yield lithiated, magnesiated and zincated nitriles, which can trap a range of electrophiles. The sulfinyl-metal exchange is effective with vinylic, quaternary and tertiary substitution patterns and addresses the long-standing problem of alkylating secondary nitriles. This method was then further extended to other oxidation states of sulfur, namely sulfonyl-metal exchange and relatively unknown sulfide-metal exchange. The sulfide metal exchange overcomes the problem related to the propensity of highly substituted sulfinylnitriles to eliminate. Sulfide-metal exchange is synthetically attractive because of the numerous methods for generating arylsulfides and the high tolerance of arylsulfides to numerous reagents. &lt;br&gt;A copper-catalyzed arylation reaction of aryl iodides and metalated nitriles was developed using catalytic Cu (I) and an amine ligand. A proof of principle has been established, providing a sound basis for developing the reaction. A new strategy has been developed for alkylation of alkenenitrile using LDA as base in presence of catalytic CuCN. Subsequent trapping with an electrophile, affords alkylated alkenenitriles in which the olefin is no longer in conjugation with the nitrile. &lt;br&gt;The distinct structural differences between N- & C-metalated nitriles have been harnessed in a series of chemoselective alkylations. Lithiated nitriles are found to be particularly reactive toward alkyl halides whereas magnesiated nitriles react selectively with oxygenated electrophiles. Using this strategy allows chemoselective alkylation of metalated nitriles. / Bayer School of Natural and Environmental Sciences; / Chemistry and Biochemistry / PhD; / Dissertation;

Esta tesis se ha centrado en el estudio de las reacciones de carbonilación de norborneno catalizada por metales. Este sustrato puede ser funcionalizado a través de este proceso, empleando sistemas catalíticos y condiciones de reacción adecuadas, en productos intermedios con aplicación en la industria de perfumes y química fina. En este trabajo se han llevado a cabo estudios en la reacción de metoxicarbonilación de norborneno catalizada por paladio empleando ligandos monofosfina y difosfina logrando un importante control de la selectividad hacia la formación del producto deseado. Algunos aspectos mecanísticos de esta reacción han sido desarrollados empleando métodos de resonancia magnética nuclear que incluyen experimentos de alta presión. Finalmente, se ha estudiado la reacción de hidroformilación asimétrica de norborneno catalizada por complejos de rodio usando ligandos difosfito derivados de carbohidrato. Estos sistemas catalíticos han mostrado alta actividad y selectividad con excesos enantioméricos moderados. / This thesis focuses on the study of the metal-catalyzed carbonylation of norbornene. The transformation of this substrate in esters and aldehydes offers potential applications for the production of valuable compounds in fine chemistry and perfumery industry. In this work we have performed studies on the palladium-catalyzed methoxycarbonylation of norbornene bearing monodentate and bidentate phosphine ligands achieving an important control of the selectivity towards the formation of the desired product. Mechanistic aspects of this reaction have been developed using nuclear magnetic resonance methods, including High-Pressure techniques. Finally, we have studied the asymmetric rhodium-catalyzed hydroformylation of norbornene using chiral 1,3-diphosphites ligands derived from carbohydrates. These catalytic systems have shown high activities with excellent stereoselectivities and moderate enantioselectivities.

Synthetic strategies for polysaccharide-protein conjugates, pH-responsive hydrogels, and amorphous solid dispersion (ASD) polymers were developed. Conjugating a polysaccharide to a protein drug via a covalent bond may improve its medical properties including solubility, stability, immunogenicity, circulation time, and targeting ability. Regioselectivity of conjugation is still challenging. We developed a strategy for regioselective conjugation of amino acid esters to polysaccharides, by employing 6-Br-polysaccharides in SN2 substitution reactions with amino acid esters. This work provides a good starting point for the regioselective conjugation of polysaccharides to proteins. Polysaccharides can also serve as hydrogel drug carriers. Most hydrogels employed in drug delivery work by incorporating the drug physically. We synthesized sustained and pH-responsive hydrogels using oxidized hydroxypropyl cellulose (Ox-HPC)/carboxymethyl chitosan (CMCS) crosslinked by imine bond. Phenylalanine as a model amine-containing drug was chemically bonded to the Ox-HPC hydrogel component and was observed to release faster at the pH of a tumor microenvironment. These hydrogels show promise as targeting cancer drug carriers. ASDs are polymeric systems to disperse poorly soluble drugs amorphously and enhance permeation from the gastrointestinal tract (GI tract) to the bloodstream. We synthesized potentially zwitterionic cellulose derivatives by reductive amination of Ox-HPC with ω-aminoalkanoic acids and obtained products with the degree of substitution (cation and anion) up to 1.6, which is difficult to attain using previous methods. The products showed manipulated amphiphilicity and excellent thermostability, exhibiting potential application in ASDs. We anticipate that these strategies will benefit future polysaccharide chemistry research and permit synthesis of a broad variety of more functional biomedical materials. / Doctor of Philosophy / Polysaccharides are long chains of individual sugars ("polymers"). Many natural-sourced polysaccharides are sustainable, biodegradable, and have low toxicity. Polysaccharide-based materials may improve the properties of current drugs, resulting in decreased cost, enhanced absorption efficiency, and continuous and/or targeted delivery. Protein drugs such as human insulin have a significant role in medicine. However, the residence time of a protein drug in the human body is short. To overcome this challenge, we designed a method to link polysaccharides to proteins at controlled reaction sites, and reported herein the first step of this route. The final polysaccharide-protein products will even have the ability to recognize and access target cells, like those of tumors. Tumor tissues are more acidic than normal tissue and can trigger faster release of drug from drug carriers. We developed polysaccharide-based hydrogels, which are gels that bind a great deal of water but won't dissolve in it, as acid-sensitive carriers. In addition, our hydrogels are also injectable, and can spontaneously repair themselves. These properties make our hydrogels promising as cancer targeting drug carriers. Most new drug candidates have poor water solubility and permeation through the gastrointestinal tract to reach the blood stream. Dispersing the insoluble drug into a properly designed polymer network can enhance dissolution, permeation, and absorption. We developed a new family of polymers designed for this purpose using two cheap starting materials. These polymers can interact with the drug, preventing it from forming crystals and simultaneously promoting slow drug release. Overall, we explored ways to modify polysaccharides to create harmless, effective medical materials. We aim to promote science and benefit human health via our research.

Cellulose ethers are valuable matrices for drug-delivery systems (DDS), namely amorphous solid dispersions (ASD). ASD are efficient vehicles that can solubilize and stabilize poorly soluble drugs by increasing the time that it takes for drugs to crystallize, thereby allowing higher drug concentrations and providing increased bioavailability. However, most commercially available cellulose derivatives were not specifically designed for this application, leading to gaps in understanding the key mechanisms by which ASD operate. This creates the need for polysaccharide derivatives specifically conceptualized for ASD and for elucidating structure-property relationships. In this dissertation, I successfully demonstrated regioselective and chemoselective techniques to functionalize cellulose to prepare new ASD as well as smart tracking devices. I efficiently and successfully create complex structures via appending bile salt substituents using olefin cross-metathesis. I ascertained that high performance crystallization inhibitors can be achieved with enhanced hydrophilicity by the marriage of two classes crystallization inhibitors (cellulose and bile salts), as illustrated with the commercial, fast crystallizing prostate cancer drug, enzalutamide. I obtained ketone-functionalized cellulose derivatives using oxidation chemistry to produce fluorescent poly- and oligosaccharides (hydroxypropyl cellulose, hydroxypropyl methylcellulose, and hydroxypropyl beta cyclodextrin). Schiff-base chemistry was then explored to append a commercially available fluorescent label, Nile Blue. Due to the dynamic nature and hydrolytic lability of Schiff-bases, I applied reductive-amination chemistry with either one pot, or two-step techniques and evaluated the efficiency of these approaches. I characterized the new fluorescent polymers, and with the objective of elucidating ASD mechanisms, I investigated their response in solvents of different polarities to probe environment-sensitivity. Flavonoids are interesting drug candidates; they have been explored for many biomedical applications, including as inducers of apoptosis and functioning as antioxidants by radical scavenging. I prepared high-performance ASD polymer candidates, then prepared and characterized ASDs with different loadings of the flavonoids, genistein and quercetin. I explored the performance of polymers with different functionalities, hydrophilicity/hydrophobicity, and carboxylic acid content (cellulose acetate glutarate, 5-carboxypentyl hydroxypropyl cellulose, and hydroxypropyl methyl cellulose acetate succinate as positive control) by using in vitro dissolution studies. In this screening process, I determined that cellulose acetate glutarate provides the most advantageous enhancement, possessing the appropriate amphiphilicity to increase drug concentration in this study, supported by the similarity of the polymer and drug solubility parameters. I was further able to confirm via polarized light microscopy that advantageous nanodroplet formation occurs during the drug-release process. / Doctor of Philosophy / As sources for future ecofriendly materials, derivatives from nature offer fertile ground. One group of natural materials that attracts increasing attention to fulfill both performance and sustainability are polysaccharides, long chains of carbohydrates, that can be found in plant cell walls, exoskeletons of bugs or oceanic bottom feeders, algae, and indeed in all living things. Cellulose derivatives provide biologically safe materials that are biomedically relevant, including in the field of oral drug delivery. While most orally administered drugs are not 100% effective or absorbable, a class of drug delivery systems named amorphous solid dispersions can improve drug absorption with the aid of polysaccharide derivatives. Although amorphous solid dispersions are highly effective, there is still much room for improvement, and important opportunities to learn about the precise mechanisms that make such systems work. With fluorescent markers, I can also explore the surrounding environment of the drug delivery systems in preliminary studies. By understanding the environment of such polysaccharides, I determined important insight into how they improve oral drug availability and performance. Herein, I explored new amorphous solid dispersion polysaccharide derivatives, and how I have attached fluorescent labels to track them to learn how they work.

The first part of this thesis describes the efficient synthesis of several hypervalent iodine(III) compounds. Electron-rich diaryliodonium salts have been synthesized in a one-pot procedure, employing mCPBA as the oxidant. Both symmetric and unsymmetric diaryliodonium tosylates can be isolated in high yields. An in situ anion exchange also enables the synthesis of previously unobtainable diaryliodonium triflates. A large-scale protocol for the synthesis of a derivative of Koser’s reagent, that is an isolable intermediate in the diaryliodonium tosylate synthesis, is furthermore described. The large-scale synthesis is performed in neat TFE, which can be recovered and recycled. This is very desirable from an environmental point of view. One of the few described syntheses of enantiopure diaryliodonium salts is discussed. Three different enantiopure diaryliodonium salts bearing electron-rich substituents are synthesized in moderate to high yields. The synthesis of these three salts shows the challenge in the preparation of electron-rich substituted unsymmetric salts. The second part of the thesis describes the application of both symmetric and unsymmetric diaryliodonium salts in organic synthesis. A metal-free efficient and fast method for the synthesis of diaryl ethers from diaryliodonium salts has been developed. The substrate scope is wide as both the phenol and the diaryliodonium salt can be varied. Products such as halogenated ethers, ortho-substituted ethers and bulky ethers, that are difficult to obtain with metal-catalyzed procedures, are readily prepared. The mild protocol allows arylation of racemization-prone a-amino acid derivatives without loss of enantiomeric excess. A chemoselectivity investigation was conducted, in which unsymmetric diaryliodonium salts were employed in the arylation of three different nucleophiles in order to understand the different factors that influence which aryl moiety that is transferred to the nucleophile. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 5: Submitted. Paper 6: Manuscript.</p>

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Chemoselective synthesis of ethyl 4-pirimidinecarboxylates and/or ethyl 5-pirimidineoxalates via cyclocondensation reaction of b-dimethylaminoenones [R1C(=O)C(=CNMe2)C(=O)CO2Et, where R1 = Ph, 4-MeC6H4, 4-MeOC6H4, 4-BrC6H4, 4-ClC6H4, 4-FC6H4, 4-O2NC6H4, 2-thienyl, benzo[b]furan-2-yl and CF3] with NCN 1,3- dinucleophiles such as benzamidine hydrochloride or 1H-1-pyrazolyl-carboxamidine hydrochloride (50-86%); utilization of ethyl 4-pirimidinecarboxylates (when R1 = Ph, 4-MeOC6H4, 4-FC6H4 and 2-thienyl) in the cyclization reaction with hydrazine monohydrate, leading to 7,8-dihydropyrimido[4,5-d]pyridazin-8-ones (81-92%). In this work it was also studied the condensation reaction of (3,5-dimethyl-1H-1- pyrazolyl)alkylketones with N,N-dimethylformamide dimethylacetal, with the aim to obtain b-dimethylaminoenones [PhC(=O)C(=CNMe2)(3,5-dimethyl-1H-1-pyrazolyl), PhC(=O)C(=CNMe2)(3,5-dimethyl-1H-1-pyrazolylmethyl) and MeC(=O)C(=CNMe2)(3,5-dimethyl-1H-1-pyrazolyl)] (92-98%); and synthesis of 1,4 -biazoles via cyclocondensation reaction of b-dimethylaminoenones with different 1,2-dinucleophiles such as hydrazine monohydrate, terc-butylhydrazine hydrochloride,phenylhydrazine hydrochloride, carboxymethylhydrazine or hydroxylamine hydrochloride (50-80%). The X-ray diffraction technique was used in the elucidation of the stereochemistry of PhC(=O)C(=CNMe2)(3,5-dimethyl-1H-1-pyrazolylmethyl) and regiochemistry of the cyclocondensation reactions. / Síntese quimiosseletiva de 4-pirimidinocarboxilatos de etila e/ou 5-pirimidinoxalatos de etila via reação de ciclocondensação de b-dimetilaminoenonas [R1C(=O)C(=CNMe2)C(=O)CO2Et, onde R1 = Ph, 4-MeC6H4, 4-MeOC6H4, 4-BrC6H4, 4-ClC6H4, 4-FC6H4, 4-O2NC6H4, 2-tienil, benzo[b]furan-2-il e CF3] com 1,3-dinucleófilos do tipo NCN, tais como cloridrato de benzamidina ou cloridrato de 1H-1-pirazolil-carboxamidina (50-86%); utilização de 4-pirimidinocarboxilatos de etila (quando R1 = Ph, 4-MeOC6H4, 4-FC6H4 e 2-tienil) na reação de ciclização com monoidrato de hidrazina, levando a 7,8-diidropirimido[4,5-d]piridazin-8-onas (81- 92%). Neste trabalho, também foi estudada a reação de condensação de (3,5-dimetil-1H-1-pirazolil)alquilcetonas com N,N-dimetilformamida dimetilacetal, visando a obtenção de b-dimetilaminoenonas [PhC(=O)C(=CNMe2)(3,5-dimetil-1H-1-pirazolil), PhC(=O)C(=CNMe2)(3,5-dimetil-1H-1-pirazolilmetil) e MeC(=O)C(=CNMe2)(3,5-dimetil-1H-1-pirazolil)] (92-98%); e síntese de 1,4 -biazóis via reação de ciclocondensação de b-dimetilaminoenonas com diferentes 1,2-dinucleófilos, tais como monoidrato de hidrazina, cloridrato de terc-butilidrazina, cloridrato de fenilidrazina, carboximetilidrazina ou cloridrato de hidroxilamina (50- 80%). A técnica de difração de raios-X foi utilizada na elucidação da estereoquímica de PhC(=O)C(=CNMe2)(3,5-dimetil-1H-1-pirazolilmetil) e regioquímica das reações de ciclocondensação.

The 'RNA World' hypothesis states that RNA was the first living system on the primitive Earth, where it carried out dual genotypic and phenotypic functions. Therefore, RNA must have self-assembled by purely chemical means from small prebiotic feedstock molecules. A plausible demonstration of the synthesis of RNA with the natural [5'→3'] phosphodiester linkage, and its self-replication has not been achieved so far. Some have speculated a 'simpler' informational polymer preceded it, and biology based on this polymer subsequently 'invented' RNA. The structurally simpler L-α-threofuranosyl nucleic acid (TNA) has been proposed as a primordial ancestor to RNA. A study into the potential self-assembly of TNA nucleotides was carried out. It is shown that as a direct result of TNA's structural simplicity, its generational chemistry is more difficult than RNA. The tetrose aminooxazolines are unstable under the conditions of its formation. The tetrose anhydronucleosides efficiently incorporate phosphate to form activated tetrose cytidine-2',3'-cyclic phosphates, but with the wrong stereochemistry. Strong support for the 'RNA world' hypothesis came from a report in 2009 of the prebiotic synthesis of activated pyridimine ribonucleoside-2',3'-cyclic phosphates. Oligomerisation studies were carried out on these activated monomers with various catalysts, and NMR studies were carried out to determine the aspects of their reactivity. It was found that only short oligomers are formed. However, nucleoside-2',3'-cyclic phosphates were found to selectively hydrolyse to a 2:1 mixture of 3' and 2'-monophosphates, and this observation was considered as etiologically relevant. Nucleoside-2' and 3'-monophosphates cyclise back to nucleoside-2',3'-cyclic phosphates upon phosphate activation, and so cannot be considered as direct candidates for oligomerisation. A chemistry that selectively uses the nucleoside-3'-phosphate for the synthesis of RNA, and recycles the unwanted 2'-phosphate would be highly desirable. Thus, a regio- and chemoselective reaction that selectively acetylates monomer and oligomer nucleoside-3'-phosphates at the 2'-hydroxyl in water is presented. Nucleoside-2'-phosphates are shown to acetylate less efficiently, and show a greater propensity to recyclise back to nucleoside-2',3'-cyclic phosphates. Purine nucleotides were also found to acetylate better than pyrimidines. This potentially primordial protecting group chemistry approach towards the prebiotic synthesis of RNA is conceptually novel, and has the potential to give a natural [5'→3'] phosphodiester linkage isomer. It is considered as a major step towards solving the long-standing problem of non-enzymatic self-replication of RNA.

<p> </p><p>A chemoselective catalyst is preferred in a chemical reaction where protecting groups otherwise are needed. The two lipases <em>Candida antarctica </em>lipase B and <em>Rhizomucor miehei</em> lipase showed large chemoselectivity ratios, defined as (<em>k_cat</em>/<em>K</em>_M)_OH/ (<em>k_cat</em>/<em>K</em>_M)_SH, in a transacylation reaction with ethyl octanoate as acyl donor and hexanol or hexanethiol as acyl acceptor (<strong>paper I</strong>). The chemoselectivity ratio of the uncatalyzed reaction was 120 in favour of the alcohol. Compared to the uncatalyzed reaction, the chemoselectivity was 730 times higher for <em>Candida antarctica </em>lipase B and ten times higher for <em>Rhizomucor miehei</em> lipase. The <em>K</em>_M towards the thiol was more than two orders of magnitude higher than the <em>K</em>_M towards the corresponding alcohol. This was the dominating contribution to the high chemoselectivity displayed by the two lipases. In a novel approach, <em>Candida antarctica </em>lipase B was used as catalyst for enzymatic synthesis of thiol-functionalized polyesters in a one-pot reaction without using protecting groups (<strong>paper II</strong>). Poly(e-caprolactone) with a free thiol at one of the ends was synthesized in an enzymatic ring-opening polymerization initiated with mercaptoethanol or terminated with either 3-mercaptopropionic acid or g-thiobutyrolactone.</p><p> </p>