Synthesis of precursors for the photochemical generation of substituted fluorenyl, phenyl and vinyl allene oxides

Allene oxides are structurally unique short-lived reactive intennediate molecules consisting of an epoxide and an exocyclic methylene group. The simplest form being 2,3-epoxypropene. Due to the high inherent instability of allene oxides, only a few have ever been isolated. Experimental studies have focused on examining the products obtained from the in situ generation of allene oxides by enzymatic, chemical or photochemical means from the appropriate precursors. As a result, these studies have firmly established the two fundamental reactions of allene oxides. First, the allene oxide may rearrange to a cyclopropanone via an oxyallyl intermediate, The second reaction, which is very prominent in hydrolytic solvents, is the addition of solvent molecules to the alpha-carbon, which opens the epoxide to generate an alpha-substituted ketone. These two fundamental reactions provide products that are distinct to allene oxides. This thesis focuses on the development of synthetic routes to obtain the target reactive intermediate allene oxides such that they or their products may be fully characterized. Five categories of precursor molecules were investigated: (i) introduction of electron donating groups placed at the 3 position of a fluorenyl moiety; (ii) introduction of alkyl groups placed on the alpha-carbon of the epoxide, also containing a fluorenyl moiety; (iii) introduction of a phenyl group containing methoxy groups at the meta and para positions; (iv) introduction of a vinyl spacer between the fluorenyl/phenyl and epoxy moieties; and (v) introduction of a vinyl group on the beta-carbon of gamma,delta-epoxy phenyl ketones. Photochemical and chemical studies were carried out on all five categories of precursor molecules using an array of solvents, including neat TFE, CH 3CN, and CH3OH as well as mixtures of TFE/H2O, CH3CN/H2O, and CH3CN/CH3OH under steady state irradiation at either 254 or 300 nm for periods varying from 1 min to 2.5 h. Analysis of the products from the reaction mixtures were performed using GC-MS and where possible 1H and 13C NMR spectroscopy. Results from the product studies of fluorenyl ring, a-substituted, phenyl core substituted and vinyl substituted allene oxide precursors were conclusive in determining that the allene oxide was indeed generated. In addition, varying the solvent and substituents were also found to affect the reactions ofthe allene oxides.