Flash vacuum pyrolysis (FVP) of 2-azido-1-(1-methyl-2-pyrryl)ethanone and 2-azido-1- (2-benzo[b]thienyl)ethanone gave nitrene by elimination of one nitrogen molecule. When 2-azido-1-(1-methyl-2-pyrryl)ethanone as a precorsor, the reactive nitrene readily underwent self-condensation to give 2-(1-methyl-2-formylpyrryl)-4-(1-methyl-2- pyrryl)imidazole, it¡¦s isomer and 2,4,5-tri(1-methyl-2-formylpyrryl) imidazole. While 2-azido-1-(2-benzo[b]thienyl)ethanone as a precorsor, the reactive nitrene readily underwent self-condensation to give 2-2-formylbenzo[b]thienyl-5-(2-benzo[b]thiophen-2-yl)imidazole. The mechanism for the formation of products of self-condensation reaction from FVP of 2-azido-1-(1-methyl-2-pyrryl)ethanone and 2-azido-1-(2-benzo[b]thienyl) ethanone will be discussed.

Hohenheim, Univ., Diss., 2007. / Enthält u.a. drei Zeitschriftenaufsätze.

Flash vacuum pyrolysis (FVP) of azidomethylthiophene, via a nitrene intermediate, gave a trimer (N,N`-trifurfurylidene-furfurylidene diamine). Use three kinds of methods to synthies benzofuran compound and gain the product by using the third method.

The diversity of transition metal complexes allows for a wide range of chemical processes to be mediated by the metal, from catalysis to surface chemistry. Investigations into the structure and electronic configuration of transition metal complexes allow for tuning of desired species by modifications to the ligands and/or metals to achieve more efficient thermodynamics and kinetics for the process of interest. Transition metals, often used in catalysts for a number of important processes, require detailed descriptions of intermediates, transition states and products to fully characterize a reaction mechanism(s) in order to design more active and efficient catalysts. Computational investigations into inorganic catalysts are explored with the aim of understanding the activity of each species and how modifications of supporting ligands, co-ligands and metals vary the interaction along the reaction pathway. Reported results give important insight into the development of the most active complexes in addition to determining the least active complexes to aid experimental development. This report first investigates the mechanisms of two unique transfer reactions: 1) formation of low coordinate nickel-nitrene ((P~P)Ni=NR; P~P = 1,2-bis(dihydrophosphino)-ethane or 1,2-bis(difluoromethylphosphino)-ethane) complexes as catalysts for nitrogen atom transfer and 2) oxidation of a triphosphorus niobium complex, [(η2-P3SnPh3)Nb(OMe)3], for the transfer of the phosphorus synthon, Ph3SnP3. These reactions have utility in the synthesis of nitrogen and phosphorus containing molecules, respectively, and the results presented provide mechanistic insight into the synthesis of the organometallic intermediates. Additionally, a computational approach towards rational catalyst design was performed on the ruthenium based hydroarylation catalyst TpRu(CO)(Ph) [Tp = hydrido-tris(pyrazolyl)borate]. Targeted modifications at the Tp, metal and co-ligand (CO) sites were studied in order to tune the electronics and sterics of the catalyst. Modifications, through computational methods, provided a more cost- and time-efficient way to study the impact of modifications, which provided direct input into attractive synthetic targets. The research described heir in highlights the use of computational chemistry methodologies, specifically DFT, in collaboration with experimental results, for the accurate description of reaction geometries and factors influencing the thermodynamics and kinetics of the systems. Valuable insight is gained by treating inorganic complexes with theoretical methods and additionally provides a fast, cheap way to predict and understand the chemistry of such complex systems.

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<div><p>Nitrenes are reactive intermediates that are known to generate high interest organic molecules. Due to their inherent instability, nitrenes are often stabilized by introducing them to transition metal complexes. Many transition metal stabilized nitrenes (M=NR₂) have been reported and some of these complexes have been shown to control nitrene reactivity and selectivity. Transition metal nitrene reactivity can be categorized into two main groups: bond-insertion and group transfer reactions. In the reference to the former, chapter one of this dissertation highlights using unique dinuclear Nicatalysts to generate nitrenes from aromatic azides. These Ni₂ nitrenes are used towards selective C(sp²)−H bond amination in order to generate indole and carbazole derivatives. This work highlights the unique properties of the Ni₂ imide that enable a 1,2-addition pathway, which contrasts known bimetallic nitrene insertion reactions. A detailed mechanistic study, primarily using density functional theory (DFT) is the focus of this chapter.</p> <p>Chapter two of this dissertation focuses on nitrene group transfer. In particular, this chapter highlights the ability of the dinuclear Nicatalyst [<i>ⁱ</i>^-PrNDI]Ni₂(C₆H₆) to react with aromatic azides to perform N=N coupling. A large scope of functional groups are tolerated in high yield with short reaction times. Catalyst comparison studies, studies on relevant catalytic intermediates for N=N coupling and reaction kinetics are shown in this chapter. Lastly, chapter three showcases the expansion of the nitrene group transfer ability of [<i>ⁱ</i>^-PrNDI]Ni₂(C₆H₆) to generate high molecular weight azopolymers from aromatic diazides. These azopolymers are generated from monomers often used in organic semi-conducting materials. End group control and post polymer functionalization are highlighted in this chapter. Lastly, this work showcases a new polymer, polyazoisoindigo, as the first organic semiconducting material that reversibly transitions from a colored to colorless state upon reduction.</p><br></div>

1. Generation of nitrenes by means of photolysis of arylmethylazides and its derivatives have been studies. Pyrolysis of 2-azidomethylthiophene¡]44a¡^ gave 2-thiophenecarboxaldehyde¡]77a¡^and (2-thienylmethylidene)-2-thienylamine¡]45a¡^, and pyrolysis of 2-azidomethylbenzo[b]thiophene¡]44b¡^gave the corresponding products. Pyrolysis of 2-azido-1-(2-thienyl)ethanone¡]52a¡^gave 2-thiophenecarboxaldehyde¡]77a¡^, 2-acetylthiophene¡]80a¡^and 2-(thiophene-2-carbonyl)amino-1-(2-thienyl)ethanone¡]83a¡^, and pyrolysis of 2-azido-1-(2-benzo[b]thienyl)ethanone¡]52b¡^gave the corresponding products. 2. Pyrolysis of 3-cyclohexeno[b]furylmethyl benzoate¡]35¡^gave cyclohexeno-4-methylenecyclobuten-3-one¡]25¡^via highly reactive carbene intermediate. At high temperature, compound 25 can continue the reaction of elimination and ring opening to give benzene¡]43¡^, fulvene¡]46¡^, 2-ethylnylcyclohex-1-ene carbaldehyde¡]44¡^ and 4,5-dimethylenecyclopent-2-enone¡]45¡^.

¤@¡BPyrolysis of 2-azido-1-(4-methoxyphenyl)ethanone (69) and 2-(2-azidoethyl)furan (85) gave nitrene intermediate to study. There is 2-(4-methoxybenzoyl)-4-(4- methoxyphenyl)imidazole (81) ¡B2-(4-methoxybenzoyl)-5-(4-methoxyphenyl) imidazole] (81¡¦)¡B2,3-di(4-methoxybenzoyl)-5-(4-methoxyphenyl) pyrazine] (82) and 3,5-di(2-furyl) pyridine (92) for pyrolysis products. ¤G¡BPyrolysis of3-methyl-2-cyclohexen[b] furylmethyl benzoate) (50) gave carbene intermediate to study. There is 2,3-dimethylene cyclohexen[b]furan (59) for pyrolysis products.

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