Asymmetric Aziridination of Styrene Derivatives

Some p-substituted styrene derivatives were employed in the reaction to establish the generality of the present asymmetric synthesis. The pronounced effect of pyridine IV-oxide was also observed in the aziridination of mms-P-methylstyrene. While this compound was not aziridinated below room temperature in the absence of pyridine IV-oxide, the addition of the N-oxide to the reaction system resulted in both high yield and enantioselectivity of the aziridinated product, even at 0 °C (Table 6.3). 

In contrast, the aziridination of c/s-(J-methylstyrene was not observed at 0°C in spite of the presence of pyridine A-oxide. At room temperature, in the absence of the /V-oxide, the cis-aziridine was obtained in a poor yield and with a low ee value (Table 6.4). The addition of the JV-oxide improved the yield of the product, but did not cause a dramatic change in the ee value. 

It is noteworthy that high stereospecificity was observed in all the aziridinations of trans- and cis-1,2-disubstituted olefins, although such reactions in the presence of metal catalysts and PhI=NTs did not always show high stereospecificity [4,9a-j]. Other trans- substituted styrene derivatives were examined, and gave excellent en-antioselectivities, as shown in Table 6.5. 

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