DIASTEREOSELECTIVE AZIRIDINATION OF ALKENES USING ETOXYAMINO-2-(1-HYDROXYALKYL)QUINAZOLIN-4(3H)-ONES IN THE PRESENCE OF TITANIUM(IV) TERT-BUTOXIDE

-1-hydroxy-2,2-dimethylpropyl]quinazolin-4(3H)-one 9 (Q(2)NH) was prep ared in four steps from (S)-tert-leucine in 43% yield without the need for chromatography. The corresponding 3-acetoxyaminoquinazolinone 10 (Q(2)NHOAc), prepared in dichloromethane solution by reaction of 9 wit h lead tetraacetate, reacts with alkenes in the presence of titanium(I V) tert-butoxide to give the corresponding aziridines diastereoselecti vely. With styrene and butadiene the corresponding aziridines 12a (65% ) and 15a (85%) are obtained completely diastereoselectively. Indene g ave the expected endo-N-invertomer of aziridine 16a as the kinetically -formed product (86%) also completely diastereoselectively: equilibrat ion to give a 8:1 ratio of exo:endo N-invertomers occurs above 0 degre es C. From an X-ray structure determination of aziridine 12a, the sens e of diastereoselectivity in its formation is in agreement with the tr ansition state model 14. Aziridinations of methyl acrylate and of tert -butyl acrylate give respectively 23a (65%) and 24a (53%), highly dias tereoselectively (dr greater than or equal to 20:1) and with the same sense of diastereoselectivity as identified by an X-ray crystal struct ure determination on 24a and chemical correlation of esters 23a and 24 a via the acid 25. Aziridinations of alpha-methylstyrene and methyl me thacrylate are less completely diastereoselective; isoprene reacts com pletely diastereoselectively at its unsubstituted double bond but with little diastereoselectivity at its methyl-substituted double bond and the regioselectivity of aziridination on the two double bonds is 1.4: 1 respectively by comparison to 1:4.7 in the absence of titanium(IV) t ert-butoxide.