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Chemistry has been defined by some as an art, by others as a science and people have gone as far as dismissing it as pure alchemy. Overall, however, one cannot help but come to the conclusion that chemistry is a unique blend of all three. The work contained within this manuscript is an attempt to delve deep into the mysteries of but one type of transformation - a ¡¥simple¡¦ cyclisation step in which one couples two different moieties to form a cyclobutane ring with the aid of SmI2. There are two opposing forces of nature which control the outcome of this reaction, namely elimination and cyclisation and it is the contest between these two driving forces that ultimately decides the fate of these transformations. This work was born from previous attempts in RAU¡¦s laboratories to synthesise chiral cyclobutane derivatives from carbohydrates as well as the apparent discrepancies in two independent scientists¡¦ publications on the effect of SmI2 on reactions utilising 1,4-diketones. Hoffmann from Germany had managed to form 1,2-cyclobutanediols from a pinacol reaction promoted by SmI2 while Ghosh in India had experienced fragmentation products under similar conditions. The information contained herein provides a bird¡¦s eye view of cyclisation vs. fragmentation in 1,4-disubstituted compounds as well as an insight into how one might avoid or exploit the particular reaction pathways. The effects of various moieties in a ¡§ƒ×¡¨ disposition to the ketone have been investigated to obtain a broader understanding of the scope of the cyclobutane ring formation. These findings also provide the information necessary for effecting cyclobutane ring closures within the realm of carbohydrate chemistry. One will learn that the ¡¥geminal¡¦ effect is not the only efficacious method for the coupling of a ketyl radical and an activated alkene to form a four-membered ring. The thesis concludes with a strategic route towards the synthesis of a potential antiviral compound containing the cyclobutane substructure, originating from the simple sugar D-ribose. / Prof. D.B.G. Williams

Indirect nuclear spin-spin coupling constants in high resolution nuclear magnetic resonance (NMR) spectroscopy provide the most powerful method for determining conformations and structures of molecules in solution. The research described in this dissertation establishes the conformational and substituent dependencies of several new types of nuclear spin-spin coupling for use in structural studies. It was also of interest to determine the electronic factors which lead to the observed experimental trends. Geminal, vicinal, and four-bond carbon-carbon nuclear magnetic resonance coupling constants were studied experimentally with fifty carbon-13 enriched alicyclic compounds. Because of the small magnitudes of many of these coupling constants it ~vas necessary to modify existing Fourier transform NMR equipment to perform J-resolved two-dimensional NMR experiments. With the greater spectral resolution it was possible to determine 56 intercarbon geminal (²J(cc)), 107 vicinal (³J(cc)) and 26 four-bond (⁴J(cc)) coupling constants. These data represent the largest collection of ²J(cc), the only known data for ⁴J(cc), and the most accurate compilation of vicinal ¹³C-¹³C coupling constants. In combination with molecular orbital methods, the relevant conformational and substituent trends in each of these series were elucidated. Because of the great amount of interest in the importance of bridgehead interactions in "strained" molecules, a study is presented of coupling transmitted via nonbonded interactions between the bridgehead carbons in a series of l-substituted-bicycloalkanes. The two-dimensional Fourier transform methods were again used to obtain the experimental coupling constants and molecular orbital methods were used to determine the importance of the intercarbon bridgehead interactions on ¹H-¹H, ¹³c-¹H, ¹³C-¹³C, ¹³c-¹⁹F , and ¹H-¹⁹F coupling constants. In all cases the nonbonded interactions increased dramatically as the separation between the bridgehead carbons decreased. Further understanding of mechanisms of "through space" coupling were based on NMP. studies of the long range coupling constants (⁵J(HF) and ⁴J(HF)) in N-methyl-8-fluoroquinolinium halides. The X-ray structure of N-methyl-8-fluoroquinolinium chloride was determined in an attempt to calculate the observed ⁵J(HF) and ⁴J(HF). A selective population inversion mIR method was used to show that the sign of ⁵J(HF) in N-ethyl-8- fluoroquinolinium iodide is positive.

The purpose of this work was to investigate the reaction of allena and phenyl azide, in order to gain greater insight into the reaction of aryl azides with allenes.

A major purpose of this research was to investigate the mechanism of aryl azide addition to allenes. Much evidence has accumulated in support of a concerted mechanism for aryl azide additions to simple alkenes. Consistent with these findings, this addition is a symmetry allowed process. The analagous aryl azide additions to allenes have received little mechanistic study. The approach taken in this work was to probe the mechanism by using optically active 1,2-cyclonanadiene, observing the stereochemistry of the adduct formed upon addition of phenyl azide. Another goal was to investigate the isomerization of the phenyl azide-1,2-cylononadiene adduct, 10-phenyl-10,11,12-triaza-△ 11 -bicyclo [7. 3. 0] duodec-1-ene (7) to the previously unknown aromatic isomer 4,5-heptamethylene-1-phenyl-1,2,3-triazole (14).