Asymmetric induction in addition of N-nitrenes to alkenes: oxidation of 3-amino-2-(1,2,2-trimethylpropyl)quinazolin-4(3H)-one in the presence of α-methylene-γ-butyrolactone: conformational analysis of the aziridines formed and comparison with alkanoylated cyclopropylamines

Abstract

Oxidation of the title N-aminoquinazolinone (11) in the presence of α-methylene-γ-butyrolactone yields the spiroaziridines (18a) and (18b) with virtually no asymmetric induction. The same oxidation carried out in the presence of 3.4 mol equiv. of trifluoroacetic acid yielded only a single stereoisomer (18a) whose relative configuration was determined by X-ray crystallography. This molecular structure also reveals an unexpected orientation around the N–N bond by comparison with other hydrazines. The n.m.r. spectra of compounds (18a) and (18b) show that both these aziridines exist in solution as single invertomers at nitrogen: (18b) shows the presence of both rotamers around the N–N bond but only one rotamer is evident for (18a).