Synthetic routes to a C(48)H(12) fullerene fragment and to the parent fullerene

Although over fifteen years have past since the first discovery of C₆₀, a total rational synthesis of isolable amounts of the parent fullerene has yet to be achieved. The completion of such a synthesis could lead to a general strategy for synthesis of the larger, more sought-after fullerenes and nanotubes.; Our first target molecule is a C₄₈H₁₂ hydrocarbon that maps onto the surface of C₆₀ (Chapter 1). The strategy was first to synthesize a planar polycyclic aromatic hydrocarbon (PAH) precursor that contains the 48-carbon framework, and then subject it to flash vacuum pyrolysis (FVP) conditions. The high temperatures in the FVP would provide the energy necessary to induce the curvature and inherent strain in the target molecule. We have attempted to incorporate halogen atoms into the precursors, located at the sites desired for ring closure. The incorporation of halogen atoms has been shown to facilitate reaction in the FVP at a temperature lower than that of the hydrocarbon.; Chapter 2 presents an extension of the C₄₈H₁₂ route to a C₆₀H₃₀ compound which, under laser desorption conditions, formed the parent fullerene. This compound was proven to be a molecular precursor to C₆₀ by control experiments and 13C labelling of the starting material. A macroscopic total synthesis of C₆₀ was approached using PAHs that incorporate halogen atoms at the sites desired for ring closure.; A new generation of pyrolysis precursors is presented in Chapter 3. These FVP precursors incorporate halogen atoms, but at sites remote from those desired for ring closure. These precursors to C₆₀ and C₄₈H ₁₂ are readily made via the aldol trimerization method. A remote halogen atom is expected to cleave in the FVP reaction, leaving an aryl radical which can participate in a 1,2-hydrogen shift and ultimately form a bond in the desired location.; Chapter 4 discusses the aldol trimerization method used in the synthesis of our C₃-symmetric PAH pyrolysis precursors. Although the reaction has been known for more than a century, it is not well understood. Some ketones form a trimeric product readily, while others result in intermediate dimers, higher oligomers, or intractable mixtures of products. In an attempt to predict which cases would be favorable, calculations were used to relate the structure of the favored dimeric intermediate with the ability of its monomeric ketone to trimerize. While this prediction proved to be correct in most cases, it was found that the correlation is not universal.