title: Synthesis, configuration, and (15)n NMR spectra of iminoaziridines. Synthons equivalent to three components of the Ugi reaction.
abstract: Monocyclic iminoaziridines and exo-endo diastereomers of spirocyclic iminoaziridines that are derived from norbornane are prepared in batches of up to 10 g to foster applications as building blocks in syntheses. N,N'-Disubstituted alpha-haloamidines, which are readily available in two steps from N-substituted alpha-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 1H-1H coupling and asymmetric solvent-induced shifts required that, in 13C NMR spectra, the observed gamma-effects of substitutents at the imino nitrogens were deshielding, contrary to the well-known shielding gamma-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 gamma-effects actually deshielding. The ranges of 15N NMR chemical shifts span more than 60 ppm. Neither the beta- nor the gamma-effects of substituents on both types of nitrogen follow a uniform increment pattern.
authors.affiliation: Institut für Organische Chemie der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany. hquast@uni-osnabrueck.de
authors.forename: Helmut
authors.initials: H
authors.lastname: Quast
authors.forename: Sven
authors.initials: S
authors.lastname: Aldenkortt
authors.forename: Bernd
authors.initials: B
authors.lastname: Freudenreich
authors.forename: Peter
authors.initials: P
authors.lastname: Schäfer
authors.forename: Manfred
authors.initials: M
authors.lastname: Hagedorn
authors.forename: Jens
authors.initials: J
authors.lastname: Lehmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Banert