Chemistry - A European Journal
10.1002/chem.201802478
FULL PAPER
Acknowledgements
The comparison of the Mayer bond orders of the four allylic
systems implies that the electronic structure of the
Marcel Schlegel and Peter Coburger are grateful to the European
Social Fund (ESF) and the Studienstiftung des Deutschen Volkes,
respectively, for predoctoral fellowships. We thank Evonik and
BASF for the generous donation of chemicals.
-(N-methoxy)imino carbocation 12 resembles the allyl cation 11
more closely than 13 or 14. It is noteworthy that replacing the
methoxy group of 12 by a methyl group (13) results in an
electronic structure that is intermediate between a 1-azaallyl
cation and a -imino carbocation. These interpretations are
supported by the energies and compositions of the Kohn-Sham
orbitals, which represent the allylic systems of these cations and
display the same trends. Our results are in agreement with previ-
ous wavefunction theory calculations by Creary et al. who have
already mentioned the almost identical electronic nature of the
allyl cation 11 and the -(N-methoxy)imino carbocation 12.[15] The
exact same trends can be derived for the indanone-based
systems (see SI for more details). These results indicate that the
reactive intermediates in the present work can be considered as
Keywords: tertiary alcohols • Lewis acid catalysis • 1-azaallyl
cations • multicomponent reactions • aza-Friedel-Crafts reaction
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General procedure for compounds 4: 2-Hydroxy oxime ether 1 (0.20 mmol,
1
(
.0 equiv), a 1,3-dicarbonyl compound (0.24 mmol, 1.2 equiv), Sc(OTf)
20 mol, 0.10 equiv) and 4 Å molecular sieves (50 mg) were placed in an
oven dried and sealable DURAN® test tube. Absolute CHCl (1 mL) was
3
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and it was stirred for the indicated time at 90 °C. The reaction mixture was
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quenched with sat. NaHCO
3
-solution and extracted twice with CH
2 2
Cl . The
combined organic phases were dried over Na
2
SO , filtered and the solvent
4
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was removed under reduced pressure. The crude products were purified
by flash column chromatography (MTBE/hexane). Compounds 4 were
dried in vacuo (~0.1 mbar) at 60 °C overnight.
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