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a) M. Julia, J. M. Paris, Tetrahedron Lett. 1973, 483. b) P. J.
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1
2
3
4
5
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7
8
of inseparable perylene photocatalyst, Sonogashira coupling
of 3b with 4-methoxyphenylethyne proceeded smoothly,
and the desired enyne 9 was isolated in a pure form (52%
yield) by column chromatography. The enyne 9 showed max
at 293 nm ( 6.29 x 104 L/molcm) in UV-vis absorption
spectrum (CHCl3, 10-5 mol/L), and 9 emitted fluorescence at
371 nm (F 0.20) in CHCl3 (CHCl3, 10-5 mol/L) and at 390
nm (0.57) in the powdery states.
a) F. Xu, T. Nishida, K. Shinohara, L. Peng, M. Takezaki, T.
Kamada, H. Akashi, H. Nakamura, K. Sugiyama, K. Ohta, A.
Orita, J. Otera, Organometallics, 2017, 36, 556. b) G. Mao, A.
Orita, L. Fenenko, M. Yahiro, C. Adachi, J. Otera, Mater. Chem.
Phys. 2009, 115, 378. c) D. Matsuo, X. Yang, A. Hamada, K.
Morimioto, T. Kato, M. Yahiro, C. Adachi, J. Otera, Chem. Lett.
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Nakanotani, A. Orita, J. Otera, M. Yahiro, C. Adachi, Jpn. J.
Appl. Phys. 2006, 45, L1331.
One-flask protocol: a) A. Orita, D. Hasegawa, T. Nakano, J.
Otera, Chem. Eur. J. 2002, 8, 2000. One-shot protocol: b) A.
Orita, H. Taniguchi, J. Otera, Chem. Asian J. 2006, 1, 430.
Several photoreductive desulfonylations of -sulfonylketones
were reported: for instance, M. Fujii, K. Nakamura, H. Mekata, S.
Oka, A. Ohno, Bull. Chem. Soc. Jpn. 1988, 61, 495. See also refs
20 for desulfonylation of N-sulfonylamine.
Although the ratios of geometric isomers (E/Z) in the ethenyl
sulfones 1 were determined by NMR analyses, neither isomer
was characterized in geometry. All the ethenyl sulfones were
recrystallized from the proper solvents before desulfonylation.
a) S. Okamoto, H. Tsujioka, A. Sudo, Chem. Lett. 2018, 47, 369.
b) S. Okamoto, K. Kojiyama, H. Tsujioka, A. Sudo, Chem.
Commun. 2016, 52, 11339.
6
7
9
10 Scheme 10. Synthesis of -expanded compound 9 from 3a.
11
8
9
12
In summary, we developed a new methodology for
13 desulfonylation of diarylethenyl sulfones using perylene
14 redox-catalyst under irradiation with UV/blue LEDs. This
15 protocol could be applied to ethenyl sulfones bearing
16 halogens, alkoxy and heteroaromatic rings. We also
17 succeeded to synthesize fluorescent -system expanded
18 enyne by Sonogashira coupling of bromostilbene which was
19 obtained in the desulfonylation. Further application of this
20 desulfonylation protocol to syntheses of expanded systems
21 and further investigation of the mechanism in the
22 photoreduction are under investigation.
80 10
81 11
82
See Supporting Information for details.
Although the SOMO level in radical anion of perylene should be
investigated for more precise prediction, we determined the
LUMO level for simplicity.
Because of low solubility of 1a in MeCN, the mixed solvents
MeCN/THF were used in the reductive desulfonylation.
The reaction temperature was kept at 50-60 °C by heat radiation
from the LEDs.
The yields of stilbenes 3 were determined by internal standard
method because it was difficult to separate 3 from the perylene
catalyst due to their similar Rf values.
The UV and blue LEDs emit at the centers of 398 nm and at 447
nm, respectively. Because perylene indicated the absorption band
at 350-450 nm, perylene catalyst would be photo-excited
efficiently by use of either UV or blue LED.
It is ambiguous that photo-excited perylene or perylene radical
anion would serve as reductant of 1a at this stage. See also
references 9.
It is possible that PhSO2 radical would eliminate from A or B to
provide 3a, and further investigation of the mechanism would be
required.
83
84 12
85
86 13
87
23
88 14
89
24 This work was supported by the Grant-in-Aid from JSPS
25 (JP18K05134 to A.O. and JP19K15574 to Y.O.), the Grant-
26 in-Aid for Scientific Research on Innovative Areas 2707
27 Middle Molecular Strategy (JP15H05850 to A.O.),
28 Okayama Prefecture Industrial Promotion Foundation
29 (A.O.), Okayama Foundation of Science and Technology
30 (Y.O.), Promotion and Mutual Aid Corporation for Private
31 Schools of Japan (Y.O.), OUS Research Project (OUS-RP-
32 29-1 to A.O. and Y.O., OUS-RP-19-4 to A.O. and Y.O.) and
33 OUS Faculty of Engineering Exploratory Research (Y.O.).
34 The authors thank Research Instruments Center, Okayama
35 University for the measurements of 300MHz NMR (LA300),
36 400MHz NMR (JNM-ECS400 and JNM-ECZ400S) and
37 MALDI-TOF MS (autoflex speed) measurements.
90
91 15
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95 16
96
97
98 17
99
100
101 18 F. B. Mallory, C. S. Wood, J. T. Gordon, J. Am. Chem. Soc. 1964,
102
86, 3094.
103 19 High polarity of methoxy-substituted ethene 3g enabled its easy
104
105
separation from the perylene redox-catalyst by column
chromatography.
106 20 This result is ascribable to preferential photo-induced elimination
38
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113
114
of the tosyl group. a) E. Hasegawa, Y. Nagakura, N. Izumiya, K.
Matsumoto, T. Tanaka, T. Miura, T. Ikoma, H. Iwamoto, K.
Wakamatsu, J. Org. Chem. 2018, 83, 10813. b) E. Hasegawa, N.
Izumiya, T. Miura, T. Ikoma, H. Iwamoto, S-y. Takizawa, S.
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X. Xie, J. Wan, Z. Zhang, J. Org. Chem. 2016, 81, 7036. d) C.
Liu, B. Zhang, RSC Adv. 2015, 5, 61199. e) L. Zheng, C. Yang,
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39 Supporting
40 http://dx.doi.org/10.1246/cl.******.
Information
is
available
on
41 References and Notes
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1
For a review of polyene, see: a) Carotenoids, Vol. 2. Synthesis,
ed. by G. Britton, S. Liaaen-Jensen, H. Pfander, Birkhäuser
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Devices, Synthesis Properties, and Applications, ed. by K.
Müllen and U. Scherf, Wiley-VCH, Weinheim, 2006, p. 215.
For reviews, see: a) P. R. Blakemore, J. Chem. Soc., Perkin
Trans. 1, 2002, 2563. b) D. Gueyrard, Synlett 2018, 29, 34.
a) Reductive desulfonylation by use of SmI2; G. E. Keck, K. A.
Savin, M. A. Weglarz, J. Org. Chem. 1995, 60, 3194. b) Julia-
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115 21 For reviews on photoreaction using flow microreactors, see: a) D.
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