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 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.
Quast
Helmut
H
Institut für Organische Chemie der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany. hquast@uni-osnabrueck.de
Aldenkortt
Sven
S
Freudenreich
Bernd
B
Schäfer
Peter
P
Hagedorn
Manfred
M
Lehmann
Jens
J
Banert
Klaus
K