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ARTICLE
Journal Name
DOI: 10.1039/C6CC02284G
K. Izawa, H. Liu, Chem. Rev. 2016, 116, 422.
Consequently, strong -donors originate significant red-shifts.
Interestingly, no significant blue-shifts can be traced in frozen
matrices at 77 K, even though the solvent molecules cannot
rearrange their dipole moments to stabilize the excited states.
It should be noted that a higher push-pull character has a
detrimental effect on the fluorescence quantum yield, which
can be related to a stronger solvent coupling both in the
excited as well as in the ground state. In the solid state, the
quantum yields drop significantly, which can be ascribed to
intermolecular interactions (see Table 2).
In summary, we have presented a straightforward access to 2-
alkylated indol-3-imines via reaction of (perfluoro)alkyl radicals
with two equivalents of an aryl isonitrile. The radical cascade
comprises three C-C bond formations. As radical precursors
perfluoroalkyl-iodine(III) reagents can be used and LiI is
applied as initiator for these electron-catalyzed processes.
Alternatively, AIBN or its derivatives can be applied as C-radical
precursors. Product imines show intense colour. The value of
the method has been documented by some follow-up
reactions. Importantly, hydrolysis of the exocyclic imine leads
to 3-oxindoles that show fluorescent properties.
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Recent examples: (a) V. M. Muzalevskiy, V. G. Nenajdenko, A. V.
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,
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This work was supported by the Deutsche Forschungsgemeinschaft
(DFG).
Notes and references
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Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149
Münster, Germany.
Email: studer@uni-muenster.de
Electronic Supplementary Information (ESI) available: Experimental
procedures, spectroscopic and crystallographic data as well as
computational details are included in the SI.
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8 the yield of a free radical is
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