Reaction of nitrile ylides with isatins and o-benzoquinones: formation of novel spirooxazoline derivatives
作者:Vijay Nair、D Sethumadhavan、Smitha M Nair、S Viji、Nigam P Rath
DOI:10.1016/s0040-4020(02)00182-5
日期:2002.4
Nitrileylide generated by the base catalysed reaction of imidoyl chlorides underwent dipolar cycloaddition with isatins, phenanthrenequinone and acenaphthenequinone to afford novel spirooxazoline derivatives.
The reaction of N-benzylbenzamides 6 with SOCl2 under reflux gave the corresponding N-benzylbenzimidoyl chlorides 7. Further treatment with KSeCN in dry acetone yielded imidoyl isosclenocyanates 3 (Scheme 2). These compounds, obtained in satisfying yields, proved to be stable enough to be purified and analyzed. Reaction of 3 with morpholine in dry acetone led to the corresponding selonourea derivatives 8. On treatment with Et3N, the 4-nitrobenzyl derivatives of type 3 were transformed into bis(2,4-diarylimidazol-5-yl) diselenides 9 (Scheme 3). This transformation takes place only when the benzyl residue bears an NO2 group and the phenyl group is not substituted with a strong electron-donating group. A reaction mechanism for the formation of 9 is proposed in Scheme 4. The key structures have been established by X-ray crystallography.