Thesis (M.S.)--Florida State University, 2005. / Advisor: Dr. Igor Alabugin, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 19, 2005). Document formatted into pages; contains xv, 123 pages. Includes bibliographical references.

Title from second page of PDF document. Includes bibliographical references.

Thesis (Ph.D.)--Kent State University, 2005. / Title from PDF t.p. (viewed July 28, 2005). Author's first name appears on the abstract page as: Nataliya. Advisor: Paul Sampson. Keywords: b-hydroxysulfones; [beta]-hydroxysulfones; epoxide opening; intramolecular Diels-Alder reaction; vinylsulfones. Includes bibliographical references (p.194- 202).

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xv, 110, [139] p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 102-110).

Thesis (Ph.D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 263-272). Also available on the Internet.

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

The preparation of bicyclic systems containing an allylic, angular hydroxyl group (general structure 20 and compound 87b) is described. These materials have been prepared via a new annulation sequence involving (a) the alkylation of cyclic ketones with the bifunctional conjunctive reagents 129, 21 and 60, (b) the conversion of the alkylation products into keto vinyl iodides, and (c) cyclization of the keto vinyl iodides via low temperature metal halogen exchange with n-butyllithium. The cyclization process described in (c) has been employed in the first total synthesis of the diterpenoid (±)-ambliol B (94). Thus, 3,4-dimethyl-2-cyclohexen-l-one (96) was converted, in three steps, into the unstable enone 125. Reaction of this compound with the novel vinylgermane cuprate 110, followed by reaction of the resultant product with iodine, gave the cyclization precursor 106. Cyclization of 106 gave a single, trans-fused product (128) in high yield. The exocyclic methylene function of 128 was cyclopropanated and the vinyl substituent of the resultant cyclopropane was hydroborated to give the cyclopropane diol 149. Hydrogenolysis of the cyclopropane ring of compound 149 provided the required gem-dimethyl moiety. The resultant product was converted into (±)-ambliol B (94) via a four step sequence of reactions involving (a) oxidation of the primary alcohol function, (b) addition of 3-furyllithium to the so-formed unstable aldehyde, (c) acetylation of the secondary alcohol prepared in (b), and (d) reductive removal of the acetoxy function. A new annulation sequence which utilizes the vinylgermane cuprate 110 as a synthetic equivalent of the 1-butene a²,d⁴-synthon 153 is described. Thus, cyclic enones of the general structure 154 were treated with 110 to provide the keto vinylgermane intermediates 155. The latter materials were transformed into the corresponding keto vinyl iodides 156. Treatment of 156 with a palladium(0) catalyst and a base resulted in cyclization to provide the annulation products 157 or, when R₁ = H, the α,β-unsaturated ketones 185. [ Formulas omitted ] / Science, Faculty of / Chemistry, Department of / Graduate

The purpose of this investigation was to study the chemistry of the new and novel (trimethylsilyl)ketene. This ketene was synthesized by pyrolysis of (trimethylsilyl)ethoxyacetylene which was prepared from ethoxyacetylene and methyllithium. (Trimethylsilyl)ketene is a very stable and isolable ketene which does not dimerize and, therefore, provides an opportunity for some unique studies that have not been possible with other monosubstituted ketene.

This work describes mechanistic studies concerning the addition of the dienolate derived from ethyl 2-bromocrotonate 11 to enones and aldehydes to yield vinylcyc1opropanes 12 and 13, and vinyloxiranes 14 respectively. The conditions that affect the generation of the lithium dienolate 16 from croton ate 11 and the dienolate composition have been investigated. The possibility of asymmetric induction using chiral auxiliaries located either at the ester site or at the r- position of 11 was addressed. A new oxydihydrofuran annulation methodology was developed following the above investigation. The addition of the lithium dienolate generated from ethyl 2-bromo-4-[(tert-butyldimethylsilyl)oxy]-butenoate 105 to aldehydes provided vinyloxiranes of type 127 as single isomers. Vinyloxirane 127 was thermally rearranged to give dihydrofuran 141 as mixture of stereoisomers. Alternatively, 127 was converted to dihyrofuran via a new low temperature rearrangement. This rearrangement proceeded stereoselectively under mild conditions to give a single isomer of dihydrofuran 141 in good to excellent yields. Thus, the addition of the dienolate derived from 105 to aldehydes and the subsequent low temperature rearrangement of the vinyloxirane intermediate constitute a versatile new [2+3] dihydrofuran annulation. / Ph. D.

Ph. D.