M.Sc. (Chemistry) / This study was directed towards the investigation of oxidations by dimethyldioxirane, a new and versatile oxidant. To begin, the oxidation of various simple saturated hydrocarbons was examined. These oxidations gave alcohols in yields that varied considerably. This investigation showed that dimethyldioxirane reacts chemoselectively and that a preference is shown for tertiary C-H bonds and even more so for tertiary cis C-H bonds in bicyclic six-membered ring compounds and tertiary benzylic C-H bonds. A kinetic study of the oxidations of benzylic C-H bonds of various cumene derivatives by dimethyldioxirane confirmed the electrophilic nature of this reagent. In order to investigate the chemoselectivity of oxidations by dimethyldioxirane, the oxidation of eight steroids was examined. These oxidations were very selective and rarely gave more than two products. In all but one case, the oxidations selectively produced alcohols in good yields. The preference of dimethyldioxirane for tertiary cis C-H bonds in cyclic compounds and tertiary benzylic C-H bonds was confirmed by the oxidation' of an estrone derivative and two 5,8-5teroids. In all three cases the anticipated compounds were obtained as the major products. This oxidative method for the synthesis of 5,B-hydroxy steroids may provide a novel route for the synthesis of cardioactive steroids. The oxidation of a furo[2,3-b]benzofurane derivative was investigated to conclude this study of oxidations by dimethyldioxirane. The succesful oxidation of this compound at C-3a would furnish a synthon for aflatoxin M1 in a single step. Unfortunately, no product was obtained for the oxidation of the furo[2,3-b]benzofurane derivative by dimethyldioxirane. Futher studies into the source of this lack of reactivity are currently being undertaken.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:3880 |
| Date | 11 February 2014 |
| Creators | Dixon, John Thomas |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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