Green Chemistry
Communication
Notes and references
1
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Fig. 6 Possible reaction mechanism.
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+
+
[
4CzIPN] [E1/2(PC /PC) = +1.52 V vs. a saturated calomel elec-
1
6
trode (SCE)]. The superoxide radical anion is capable of
abstracting hydrogen atoms from aldehyde 2a to generate an
acyl radical (A), driven by the polar effect in the transition
state. Then A is decomposed into an alkylradical (B) by de-
carbonylation. Radical addition of B to the charged 1a affords
the radical cation C. Finally, the sequential deprotonation of C
17
+
and single-electron oxidation by [4CzIPN] occur to yield the
final alkylated quinoline 3a.
Conclusions
In summary, we have developed aerobic photoredox decarbo-
nylative Minisci-type alkylations with aldehydes as the alkylat-
ing reagent. The present method was found to tolerate a range
of N-heteroarenes bearing various functionalities. Hence, sec-
ondary and tertiary alkylated N-heteroarenes were afforded
under ambient conditions. This protocol represents the first
photoredox decarbonylative C–C coupling. Mechanistically,
rather than the well-known ketyl radical mechanism of aldehydes
under photocatalysis, acyl radical formation by a highly oxidizing
photocatalyst is involved, which may inspire other cases of mild
decarbonylative C–C coupling with green O as an oxidant.
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7
(a) X. A. Liang, L. Niu, S. Wang, J. Liu and A. Lei, Org. Lett.,
Conflicts of interest
2019, 21, 2441–2444; (b) P. Nuhant, M. S. Oderinde,
There are no conflicts of interest to declare.
J. Genovino, A. Juneau, Y. Gagne, C. Allais, G. M. Chinigo,
C. Choi, N. W. Sach, L. Bernier, Y. M. Fobian,
M. W. Bundesmann, B. Khunte, M. Frenette and
O. O. Fadeyi, Angew. Chem., Int. Ed., 2017, 56, 15309–15313;
Acknowledgements
(
c) D. A. Dirocco, K. Dykstra, S. Krska, P. Vachal,
Support from the National Natural Science Foundation of
China (21502161 and 21602187), the Science and Technology
Planning Project of Hunan Province (2019RS2039), and the
Collaborative Innovation Center of New Chemical
Technologies for Environmental Benignity and Efficient
Resource Utilization is gratefully acknowledged.
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This journal is © The Royal Society of Chemistry 2019
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