Verdazyl radicals are a family of multicoloured stable free radicals. Aside from the defining backbone of four nitrogen atoms, these radicals contain multiple highly modifiable sites that grant them a high degree of derivatization. Despite having been discovered more than half a century ago, limited applications have been found for the verdazyl radicals and little is known about their chemistry. This thesis begins with an investigation to determine whether verdazyl radicals have a future as mediating agents in living radical polymerizations and progresses to their application as substrates for organic synthesis, an application that to date has not been pursued either with verdazyl or nitroxide stable radicals. The first part of this thesis describes the successful use of the 1,5-dimethyl-3-phenyl-6-oxoverdazyl radical as a mediating agent for styrene and n-butyl acrylate stable free radical polymerizations. The study of other verdazyl derivatives demonstrated the impact of steric and electronic properties of the verdazyl radicals on their ability to mediate polymerizations. The second part of this thesis outlines the initial discovery and the mechanistic elucidation of the transformation of the 1,5-dimethyl-3-phenyl-6-oxoverdazyl radical into an azomethine imine, which in the presence of dipolarophiles, undergoes a [3+2] 1,3-dipolar cycloaddition reaction to yield unique pyrazolotetrazinone structures. The reactivity of the azomethine imine and the scope of the reaction were also examined. The third part of this thesis describes the discovery and mechanistic determination of a base-induced rearrangement reaction that transforms the verdazyl-derived pyrazolotetrazinone cycloadducts into corresponding pyrazolotriazinones or triazole structures. The nucleophilicity, or the lack thereof, of the base employed leading to various rearrangement products was examined in detail. The final part of this thesis demonstrates the compatibility of the verdazyl-initiated cycloaddition and rearrangement reactions with the philosophy of diversity-oriented synthesis in generating libraries of heterocycles. A library of verdazyl-derived heterocycles was generated in a short amount of time and was tested non-specifically for biological activity against acute myeloid leukemia and multiple myeloma cell lines. One particular compound showed cell-killing activity at the 250 mM range, indicating future potential for this chemistry in the field of drug discovery.

The emergence of verdazyl radicals as starting materials for organic synthesis is providing a unique opportunity to create a variety of distinctive heterocyclic scaffolds. These stable radicals have previously been used as spin probes, polymerization inhibitors, mediators of living radical polymerizations, and as substrates for molecular-based magnets. However, verdazyl radicals have never been employed to fulfill an organic synthetic role until recently. In an effort to pioneer the chemistry behind verdazyl radicals as novel organic substrates, our lab has been inspired to expand and explore the scope of reactions involving their synthetic utility. This thesis assesses the synthetic versatility of verdazyl radicals by constructing a library of structurally complex and diverse verdazyl-derived heterocycles in an approach called diversity-oriented synthesis. The synthetic versatility was further expanded to the preparation of a biphenyl-stacked biphenylophane, which exhibited interesting structural and conformational features as highlighted herein.

Les travaux de recherches présentés dans ce mémoire portent sur le développement de nouveaux ligands carbènes N -hétérocycliques anioniques et de leurs complexes organométalliques. Cette nouvelle famille de ligands, basée sur les ylures de N -iminoimidazolium, sont simples à synthétiser, faciles à purifier et forment des complexes stables et dotés de propriétés électroniques et dynamiques très intéressantes. Le premier chapitre porte sur la synthèse des ylures, ou proligands. Cette synthèse comprend trois grandes étapes, soit la formation des imidazoles N -substitués, suivie de l'amination de ces imidazoles pour finir avec l'addition de différents électrophiles, où il y a également la formation de l'ylure. Au total, c'est la synthèse de 16 ylures qui est présentée, regroupant des composés aux propriétés électroniques et d'encombrements stériques variés. Le second chapitre porte, quant à lui, sur la synthèse des complexes organométalliques. La synthèse des complexes d'argent, par métallation avec différentes sources d'argent, est détaillée. Par la suite, la synthèse de différents complexes de rhodium, de nickel et de cuivre, par transmétallation, est décrite. Au total, la synthèse de 16 complexes organométalliques est présentée incluant une analyse des structures de 9 complexes par diffraction de rayons X. Le dernier chapitre porte sur l'étude des propriétés des différents complexes. Dans un premier temps, l'effet a-donneur des ligands est analysé à travers les fréquences infrarouge de ligands carbonyles, à partir de complexes de rhodium. Par la suite, la labilité des ligands et la nature dynamique des complexes en solution est détaillée. Cette propriété dynamique a également été appliquée à des essais d'auto-assemblage à partir d'un diylure. Puis finalement, la réactivité des complexes d'argent a été analysée à travers leurs comportements face à un agent oxydant tel que l'iode, de même qu'à travers leur application en catalyse de cycloaddition (3+2) d'ylure d'azométhine.

Zugl.: Stuttgart, Univ., Diss., 2008

Darmstadt, Techn. Univ., Diss., 2001.

Universiẗat, Diss., 2000--Hannover.

Techn. Univ., Diss., 2001--Darmstadt

Techn. Universiẗat, Diss., 2003--Darmstadt.

Techn. Universiẗat, Diss., 2004--Berlin.

2,6-Disubstituted spiro[3.3]heptanes were synthesized to investigate and develop synthetic methods for preparation of these compounds. Possibilities for introducing different functionalities like nitriles and sulfonamides were also investigated.   Synthetic routes presented describe successive [2+2] cycloadditions between dichloroketene and olefins to give the sought after spiro compounds with low to moderate yields throughout the multi-step synthesis. [2+2] Cycloadditions offered low turnovers and chromatography was required for purification.   A synthetic route with cyclisations through double substitution reactions between di-electrophiles and di-nucleophiles resulting in a 2,6-disubstituted spiro[3.3]heptane is also described. This multi-step synthesis offered higher turnover and yields and often there was no need for purification through chromatography.