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Asymmetric aziridination of alkenesTughan, Garfield Cecil January 1987 (has links)
The work contained in this thesis is essentially concerned with the development of methods for the asymmetric aziridination of prochiral alkenes using N-nitrenes. The studies carried out are a necessary first step in a strategy directed towards the enantiospecific functionalization of alkenes. The addition of the N-nitrenes derived by oxidation of the chiral 1-amino-2-(l ,2,2-trimethylpropyl) benzimidazole and chiral 3-amino-2-(l,2,2-trimethylpropyl)quinazolin-4 (3H)-one (in the presence of TFA) to prochiral alkenes are found to proceed with moderate to high diastereoselectivities. The asymmetric inductions obtained are rationalized in most cases by a transition state geometry for the addition of the N-nitrene to the alkene. A method of carrying out chiral oxoquinazolinyl nitrene additions to alkenes both at low temperature (-60°C) (with the expected increase in diastereoselectivity) and with ~ molar equivalents of the alkene (with little loss of yield of the aziridine) is also developed. Conformational studies on the 7-(3,4-dihydro-2-(l,2,2-trimethyl- propyl) -4-oxoquinazolin-3-yl) -2-oxa-7-aza-spiro [4,2] -heptane-1-one are also carried out and reveal an unexpected orientation around the N-N bond, by comparison with other hydrazines, both in the crystal and in solution.
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