Desilylative elimination of the quinazolinone ring from 1-(4-oxoquinazolin-3-yl)-2-silylaziridines; Preparation of an N-H aziridine in high enantiomeric excess by in situ nucleophilic addition to the derived azirine

Aziridination of vinylsilanes PhCH=CHSiR(3) (R = Me, Pt, Ph) with enantiopure 3-acetoxyaminoquinazolinone 11 gives the corresponding aziridines 12 [diastereoisomer ratio (dr) 10:1], 18(dr 13:1) and 20 (dr 2:1). Desilylative elimination of the quinazolinone from these aziridines by caesium fluoride in the presence of cyanide gives aziridine 14 by cyanide addition to the 3-unsubstituted azirine 13, produced in situ. Acylation of aziridine 14 with (S)-acetoxypropionyl chloride gives N-acylaziridine 16; the good correlation between the diastereoisomer ratios of aziridines 12, 18 and 20 and those of the N-acylaziridine 16 produced in each case suggests that intermediate azirine 13 is configurationally stable.