Asymmetric aziridination of alkenes.

Abstract

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