Studies on aziridinations using 3-acetoxyaminoquinazolinones.

Aziridination of some vinyl silanes and vinyl stannanes using 2-substituted 3-acetoxyaminoquinazolinones are reported. The desilylation and destannylation of two of the resultant aziridines with caesium fluoride in the presence of potassium cyanide proceeds with loss of the quinazolinone unit via an azirine intermediate; subsequent addition of the cyanide ion furnishes a nitrile-substituted aziridine. This aziridine-azirine-aziridine transformation was also accomplished using an enantiopure 2-substituted-3-acetoxyaminoquinazolinone to provide an optically active aziridine of unknown enantiopurity. Attempts to bring about the above aziridine-azirine-aziridine conversion by deprotonation of 1-(quinazolinone-3-yl)-2-ester- and 1-(quinazolinone-3-yl)-2-nitrile-substituted aziridines are reported. The synthesis of 3-amino-2-trifluoromethylquinazolinone and the anomalous stability of the derived 3-acetoxyaminoquinazolinone are reported. This stability of 3-acetoxyamino-2-trifluoromethylquinazolinone leads to unusually high yields in its aziridination reactions with alkenes compared to those obtained using 2-alkyl-3-acetoxyaminoquinazolinones. In aziridination of cyclohexenol, this 2-trifluoromethyl-3-acetoxyaminoquinazolinone gives the syn aziridination product completely stereoselectively. To probe the origin of this unexpected stability of 2-trifluoromethyl-3-acetoxyaminoquinazolinone, the stability of a number of other 3-acetoxyaminoquinazolinones bearing electron-withdrawing substituents in the 2-position was examined. From these investigations and from the deleterious effects of acetic acid upon the stability of 3-acetoxyaminoquinazolinones an explanation for the greater stability and greater yields obtained in aziridinations using 2-trifluoromethyl-3-acetoxyaminoquinazolinones is offered.