Azomethine ylides generated by reaction of difluorocarbene with N-alkyl-and N-arylimines derived from benzaldehyde and benzophenone react with N-benzylidenebenzenesulfonamide in a regioselective fashion, yielding the corresponding imidazolidin-4-ones via 1,3-dipolar cycloaddition at the C=N bond. Ylides generated from benzaldehyde imines give rise to mixtures of stereoisomeric 2,5-diphenyl-1-(phenylsulfonyl)imidazolidin-4-ones, the cis isomer prevailing.

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Imidazole derivatives R 0190 1,3-Dipolar Cycloaddition of Fluorinated Azomethine Ylides at the C=N Bond. -It is noteworthy that the intermediately formed geminal difluoro compounds hydrolyze during chromatography. The structure of compound (IVa) is determined by X-ray analysis. -(NOVIKOV, M. S.; KHLEBNIKOV, A. F.; EGARMIN, M. A.; KOPF, J.; KOSTIKOV, R. R.; Russ.