| This thesis describes reliable synthetic routes to small carbon-rich halocarbons such as haloalkynes, halocumulenes, and haloenynes, and their potential applications as precursors to new conjugated organic molecules and materials.; This thesis also describes a new synthesis of octatetrayne and dodecahexayne rods from 1,4-diiodo-1,3-butadiyne (C4I2) using successive Stille coupling and iodination reactions. By adding diiodobutadiyne and trimethyltin alkynes slowly to the palladium and copper catalysts, both the random polymerization of diiodobutadiyne and the formation of homo-coupling products in the coupling reactions had been limited.; The work described here also includes studies of the chemistry of perhalocumulenes C4Br4, C4I4 and C4Br 2I2 in palladium-catalyzed couplings and Diets-Alder reactions. The Suzuki reaction of C4Br4 gives an undesirable mixture of cumulene and enyne products, depending on the solvent, the temperature and the amount of phenyl boronic acid used. In benzene solution this reaction affords 14% yield of monophenylcumulene after isolation, and comparable amounts of several products that display allylic rearrangement. However, C4Br 4 forms a Diels-Alder adduct in high yield. Suzuki coupling reaction of this adduct led to phenyl addition to the hydrofuran ring, rather than insertion in the C-Br bonds.; This thesis also includes the synthesis of asymmetrically end-capped butadiynes such as 1-bromo-4-iodobutadiyne and 1-triisopropylsilyl-4-trimethylsilyl-1,3-butadiyne. A forth project involved studying the selective halogenation reactions of diphenylbutadiyne, producing haloenynes as monomers for polymerization to polyacenes. |
