Sunlight Induced Oxidative Photoactivation of N-Hydroxyphthalimide
(
(
3
broad s, 1H), 8.34 (d, 2H), 8.21 (d, 2H), 8.14 (d, 1H), 7.99
s, 1H), 7.69 (t, 2H), 7.67 (s, 1H), 4.47 (t, 2H), 4.33 (t, 2H),
.90 (t, 2H), 3.86 (t, 2H)
2008, 120, 4868–4874; Angew. Chem. Int. Ed. 2008, 47,
4790–4796; d) S. Coseri, Catal. Rev. 2009, 51, 218–292;
e) L. Melone, C. Punta, Beilstein J. Org. Chem. 2013, 9,
1296–1310. Some recent contributions in the field: f) R.
Spaccini, L. Liguori, C. Punta, H.-R. Bjørsvik,
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Polym. 2013, 91, 502–507; i) Y. Amaoka, S. Kamaijo, T.
Hoshikawa, M. Inoue, J. Org. Chem. 2012, 77, 9959–
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Pꢁre, Chem. Phys. Lett. 2012, 534, 67–71; k) K. Chen,
Y. Sun, C. Wang, J. Yao, Z. Chen, H. Li, Phys. Chem.
Chem. Phys. 2012, 14, 12141–12146; l) A. Dhakshina-
moorthy, M. Alvaro, H. Garcia, J. Catal. 2012, 289,
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The compound NI8 was obtained with the same proce-
dure as for NI7 but using EtNH in place of NH OH·HCl.
Purified by chromatography on silica gel using hexane:E-
2
2
tOAc 7:3 (v:v) as eluent (R : 0.42); yield: 90%; mp 1298C.
f
1
H NMR (400 MHz, DMSO): d=8.56 (d, 2H), 8.31 (s, 1H),
8
(
(
.24 (dd, 1H), 8.204 (d, 2H), 7.76 (d, 1H), 7.74 (3, 2H), 5.54
m, 1H), 5.03 (dd, 1H), 4.85 (dd, 1H), 3.69 (q, 2H), 2.31
m, 1H), 2.07 (m, 1H), 1.23 (t, 3H), 0.99 (t, 3H).
Carb-NHPI was synthesized similarly to NI7, by preparing
the ester from MeOH and trimellitic anhydride chloride and
then forming the N-hydroxyimide using NH OH·HCl. Puri-
fied by chromatography on silica gel using CHCl :MeOH
9
exposed to NH ); yield: 94%; mp 172.08C. H NMR
(
8
2
3
:1 (v:v) as eluent (R : 0.60 – orange-coloured spot if TLC is
f
1
3
400 MHz, acetone-d ): d=9.95 (broad s, 1H), 8.43 (d, 1H),
6
.28 (s, 1H), 7.96 (d, 1H), 3.98 (s, 3H).
Photo-assisted Oxidations
[3] a) I. Hermans, J. Peeters, P. Jacobs, Top. Catal. 2008, 50,
1
24–132; b) I. Hermans, E. S. Spier, U. Neuenschwan-
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174.
The sunlight aerobic oxidations were performed by dissolv-
ing 5 mmol of hydrocarbon in 10 mL of MeCN with 5%
NHPI and 5% NI (molar basis) (more details in the figures
and tables) using a glass test tube with an oxygen balloon
and a thermometer. The apparatus was exposed to the solar
light (behind a glass window) under stirring and using a fan
1
[
4] a) L. Melone, C. Gambarotti, S. Prosperini, N. Pastori,
F. Recupero, C. Punta, Adv. Synth. Catal. 2011, 353,
1
47–154; b) L. Melone, C. Gambarotti, S. Prosperini, N.
Pastori, F. Recupero, C. Punta, J. Mol. Catal. A: Chem.
012, 355, 155—160.
[19]
as cooling system in order to minimize the heating effects.
2
Similar experiments were repeated under artificial light irra-
diation using a quartz test tube (F: 20 mm) and a ventilated
Rayonet reactor equipped with 4 lamps Philips Blacklight
Blue TL8W/08F8T5/BLB emitting in the UV range (maxi-
mum at 365 nm).
[
5] M. Lucarini, F. Ferroni, G. F. Pedulli, S. Gardi, D. Laz-
zari, G. Schlingloff, M. Sala, Tetrahedron Lett. 2007, 48,
5
331–5334.
[
6] P. Zhang, Y. Wang, J. Yao, C. Wang, C. Yan, M. Anto-
nietti, H. Li, Adv. Synth. Catal. 2011, 353, 1447–1451.
7] a) F. Wꢃrthner, M. Stolte, Chem. Commun. 2011, 47,
[
5
109–5115; b) X. Zhan, A. Facchetti, S. Barlow, T. J.
Acknowledgements
Marks, M. A. Ratner, M. R. Wasielewski, S. R. Marder,
Adv. Mater. 2011, 23, 268–284; c) X. Guo, F. S. Kim,
M. J. Seger, S. A. Jenekhe, M. D. Watson, Chem. Mater.
2012, 24, 1434–1442; d) L. Han, L. Qin, L. Xu, Y.
Zhou, J. Sun, X. Zou, Chem. Commun. 2013, 49, 406–
408; e) H. F. Higginbotham, R. P. Cox, S. Sandanayake,
B. A. Graystone, S. J. Langford, T. D. M. Bell, Chem.
Commun. 2013, 49, 5061–5063.
We thank MIUR and University of Bologna for continual
support of our free-radical (PRIN 2010-2011, project
2
2
010PFLRJR 005) and organic (FIRB-Future in Research
008, project RBFR08XH0H 001) chemistry. Prof. Chiara
Castiglioni and Dott. Luigi Brambilla from Politecnico di
Milano are kindly acknowledged for the use of their fluores-
cence spectrophotometer. Lucio Melone dedicates this work
to the memory of his father.
[8] a) A. Samanta, G. Saroja, J. Photochem. Photobiol. A
1994, 84, 19–26; b) P. Kucheryavy, R. Khatmullin, E.
Mirzakulova, D. Zhou, K. D. Glusa, J. Phys. Chem. A
2
011, 115, 11606–11614.
[
9] The mechanism reported in Scheme 1 focuses mainly
on the role of NI in the photoactivation of the NHPI-
based hydrocarbons oxidation. A more complete set of
reactions classically considered in the NHPI-based oxi-
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