Synthesis, configuration, and (15)n NMR spectra of iminoaziridines. Synthons equivalent to three components of the Ugi reaction.

Monocyclic iminoaziridines and exo-endo diastereomers of spirocyclic iminoaziridines that are derived from norbomane are prepared in batches of up to 10 g to foster applications as building blocks in syntheses. N,N'-Disubstituted α-haloamidines, which are readily available in two steps from N-substituted α-halocarboxamides, are 1,3-dehydrohalogenated by strong bases such as alkali-metal hydrides or tert-butoxides to afford distillable oils or low-melting solids, which consist of slowly interconverting E-Z diastereomers of the title compounds. The scope and limitations are outlined for this reaction. The configurations E and Z that were assigned on the basis of homoallylic 1 H- 1 H coupling and asymmetric solvent-induced shifts required that, in 13 C NMR spectra, the observed γ-effects of substitutents at the imino nitrogens were deshielding, contrary to the well-known shielding γ-effects in all other types of C=N compounds. However, an NOE NMR study demonstrated unequivocally that the previous assignments are correct and hence the observed γ-effects actually deshielding. The ranges of 15 N NMR chemical shifts span more than 60 ppm. Neither the β- nor the γ-effects of substituents on both types of nitrogen follow a uniform increment pattern.