Date of Award
Program or Major
Doctor of Philosophy
Richard P Johnson
The photoaddition of 1,2-cyclononadiene to naphthalene gives para adducts as the primary products, accompanied by a minor amount of the meta cycloadduct. Photolysis of naphthalene and 1,2-nonadiene did not yield any addition products, nor did irradiation of anthracene and 1,2-cyclononadiene, indicating that the reaction is sensitive to the structure of both the allene and arene.
Dichlorocarbene can be cleanly generated photochemically by irradiation of 7,7-dichlorodibenzo (a;c) bicyclo (4.1.0) heptane. This new method of producing dichlorocarbene permitted the first measurement of the absolute rate constants for the addition of dichlorocarbene to a series of olefins. Additional studies on this carbene included irradiation of the precursor with benzophenone, a triplet sensitizer. This protocol, however, did not lead to formation of triplet dichlorocarbene. The carbene was found to insert into the methine bond of 2-methylpentane, but no insertion products were detected with cyclohexane. The dichlorocarbene precursor was subsequently modified, yielding potential progenitors to chlorocarbene, benzylchlorocarbene, and chloromethylcarbene.
1,2,3-Cyclooctatriene was generated through fluoride-induced elimination of 2-chloro-3-trimethylsilyl-1,3-cyclooctadiene. The highly reactive butatriene was trapped as its 1,3-diphenylisobenzofuran adduct. Synthesis of the eight-membered ring completes the C6-C10 series of cyclic butatrienes. The intermediate 1,2,3-cyclooctatriene was not directly detected by NMR spectroscopy.
1,2-Cyclopentadiene remains an elusive molecule. A logical precursor to this compound, 1-chloro-5-trimethylsilylcyclopentene, decomposes in the polar solvents typically employed in $\beta$-elimination reactions of halosilanes. Synthesis of a substituted 1,2-cyclopentadiene, 1-phenyl-1,2-cyclopentadiene, has also proven unsuccessful. The precursor to this strained allene rearranges at $-$78$\sp\circ$C.
The existence of 1,2-cyclobutadiene was examined using ab initio calculations. This intermediate was viewed as forming through the degenerate rearrangement of vinylacetylene. Results of this study suggest that 1,2-cyclobutadiene is best represented as a planar diradical, rather than as a chiral allene.
Kirchhoff, Mary Morgan, "Mechanistic and exploratory organic photochemistry and the synthesis of strained cyclic cumulenes" (1992). Doctoral Dissertations. 1711.