Construction of Functionalized Annulated Sulfone via SO2/I Exchange of Cyclic Diaryliodonium Salts

Article abstract of DOI:10.1021/acs.orglett.7b02388

A straightforward protocol for diarylannulated sulfone construction is efficiently established via SO₂/I exchange of iodonium(III) salts. Readily available inorganic Na₂S₂O₅ was served as a safe and convenient SO₂ surrogate. Diverse functionalized diarylannulated sulfones were smoothly achieved in good to excellent yields with great functional group compatibility. Organic light emitting diodes (OLEDs) material molecules were subsequently established via this method in gram scale. The unsymmetrical conjugated systems with donor-acceptor groups and π-conjugation bridges motifs, which substantially communicate electron mobility in semiconductor material molecules, were successfully afforded under the facile conditions of the exchange strategy.

Full text of DOI:10.1021/acs.orglett.7b02388

Letter
pubs.acs.org/OrgLett
Construction of Functionalized Annulated Sulfone via SO2/I
Exchange of Cyclic Diaryliodonium Salts
Ming Wang,† Shihao Chen,† and Xuefeng Jiang*,†,‡
†Shanghai Key Laboratory of Green Chemistry and Chemical Process, School of Chemistry and Molecular Engineering, East China
Normal University, Shanghai 200062, P.R. China
‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, P.R. China
S
* Supporting Information
ABSTRACT: A straightforward protocol for diarylannulated sulfone construction is
efficiently established via SO2/I exchange of iodonium(III) salts. Readily available
inorganic Na2S2O5 was served as a safe and convenient SO2 surrogate. Diverse
functionalized diarylannulated sulfones were smoothly achieved in good to excellent
yields with great functional group compatibility. Organic light emitting diodes
(OLEDs) material molecules were subsequently established via this method in gram
scale. The unsymmetrical conjugated systems with donor-acceptor groups and π-
conjugation bridges motifs, which substantially communicate electron mobility in
semiconductor material molecules, were successfully afforded under the facile
conditions of the exchange strategy.
iarylannulated sulfones play a significant role in organic
efficient diarylannulated sulfones construction through direct
Dphotoconducting material chemistry for their unique SO2/I exchange of diaryliodonium salts with inorganic sodium
performance of electronic and optical properties.1 As shown in
metabisulfite (Na2S2O5) as a SO2 surrogate.
We commenced our study using the safe and commercially
available Na2S2O5 as a SO2 source, avoiding dangerous gaseous
SO2. Because Pd has exhibited great catalytic activation for SO2
coupling,6−9 diaryliodonium salt 2a and Na2S2O5 were first
conducted in the presence of Pd(OAc)2 and PPh3, which
disappointingly no desired dibenzannulated sulfone 3a was
detected (Table 1, entry 1). Nevertheless, 3a was afforded in 14%
yield when copper acetate and 1,10-phenanthroline was served as
the catalyst (Table 1, entry 2), which is a rare example of SO2
releasing from a salt without strong acid. Copper(II)
trifluoromethanesulfonate with the conjugated bidentate ligand
1,10-phenanthroline displayed a better result in 45% yield (Table
1, entries 3−5). TBAB, helping increase the solubility of salts,
drastically promoted the yield to 71% (Table 1, entry 6). A
stronger base Cs2CO3 inversely destroyed the transformation
(Table 1, entry 7). Potassium phosphate as the base was the best
choice, affording 3a in 82% yield (Table 1, entries 8−9). Other
SO2 sources, such as K2S2O5, DABSO, and NaHSO3, furnished
lower yields (Table 1, entries 10−12).
Figure 1A, diversiform diarylannulated sulfones molecules are
promising structures for organic light emitting diodes (OLEDs)
material due to the extraordinary photophysical properties of
diarylannulated sulfone in contrast with corresponding thio-
ether.2 The presence of an S,S-dioxides motif tremendously
lowers the energy of HOMO orbitals, enabling a requisite
increase in electron affinities and solid-state photoluminescence
(PL) efficiency.2c Conventionally, diarylannulated sulfones3
were achieved from oxidation of corresponding thioethers4
with strong oxidant after the coupling cyclization of problematic
thiols (Figure 1B). Furthermore, the strategy of straightforward
introduction of SO2 into organic frameworks is a challenge,
which has gained great attention due to its atom economy, step
economy, and recycling hazardous SO2.5 Great efforts have been
contributed by the Willis and Wu groups toward the introduction
of SO2 into aryl reagents and coupling partners, such as
hydrazines,6 alkyl halides,7 aryl halides,8 and electrophilic
fluorines,9 in which SO2 was employed as electrophile.
Diaryliodonium salt, as a mature and readily available reagent,
has been found to be one of the most efficient arylation reagents
in organic synthesis.10 The direct insertion of SO2 into
diaryliodonium salt will be highly efficient and pose a challenge
because the low-lying LUMO orbital of SO25b sharply decreases
the nucleophilicity of electron lone pair in a S atom and obstructs
the formation of two C-S bonds in one step. Despite the
electrophilic diaryliodonium salt not matching with the same
electrophilic ability of SO2, we envisioned that the radical
property of diaryliodonium(III) salt will drive SO2/I exchange
for two C-SO2 bond formations (Figure 1C). Here we disclose an
With the optimized conditions in hand, comprehensive SO2/I
exchange was shown in Scheme 1, which afforded a divergent
functionalized diarylannulated sulfones library. Because the
electrical characteristics are critical for adjusting a better charge
balance in the material molecules,1d a broad range of conjugated
diarylannulated sulfones substituted with electron-donating (for
the capture of hole carriers) (3b−3d) and electron-withdrawing
Received: August 1, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.7b02388
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Letter
Figure 1. Unsymmetrical conjugated sulfone synthesis.
molecular materials,1b was employed in the six-membered
substrates. Diarylannulated sulfones were also furnished when
copper(II) was replaced by dimethylethanediamine (DMEDA),
which initiated a radical process reported by Shi.12 Six-membered
diarylannulated sulfones bearing the electron-rich (4a), and
-deficient (4b−4c) groups at position 2 were readily achieved.
Diaryliodonium salts with two different substituents at positions
2 and 6/7 were all effectively tolerated regardless of electron-
donating or -withdrawing (4d−4k). The scope was further
demonstrated through the successful syntheses of fused ring and
multifunctionalized diarylannulated sulfones (4l−4m). By
replacing the gem-dimethyl with cyclopropyl group, the high
tension cyclic products 4n and 4o were efficiently afforded in
good yields.
To reveal the unique versatility and applicability of the
exchange protocol, the syntheses of functional semiconductor
material molecules were conducted. A gram scale synthesis of the
pivotal material molecule 3s with two easily modified bromides
in the structure was smoothly afforded, which could achieve the
diverse construction of OLED material molecules accordingly
(Scheme 2.1).13 Dibenzothiophene-S,S-dioxide with the sym-
metrical functional groups were well investigated, however, the
core with the unsymmetrical conjugated groups were arduous to
reach through the known methods. The compatibility of
demanding unsymmetrically substituted functional groups was
systematically probed in this SO2/iodine exchange strategy
(Scheme 2.2). The substituents at position 2 with a naphthalene
group and position 7 with a π-conjugation bridge type dimethyl-
fluorene group were well tolerated, affording the corresponding
product 3u in favorable yield. The other π-conjugated functional
groups, 9-anthracene (3v), 10-phenyl-9-anthracene (3w),
benzothiophene (3x), and phenylacetylene (3y), which always
display the excellent performances in organic material science,1,2
were also successfully accommodated even with different
electrical properties.
a
Table 1. Condition Optimization
yield
b
entry
catalyst, ligand
base
additive
“SO2”
(%)
1
2
3
4
5
6
7
8
9
Pd(OAc)2, PPh3
K2CO3
Na2S2O5
Na2S2O5
Na2S2O5
Na2S2O5
Na2S2O5
Na2S2O5
Na2S2O5
Na2S2O5
Na2S2O5
0
14
30
45
34
71
0
Cu(OAc)2, 1,10-phen K2CO3
CuI, 1,10-phen K2CO3
Cu(OTf)2, 1,10-phen K2CO3
Cu(OTf)2, bipyridine K2CO3
Cu(OTf)2, 1,10-phen K2CO3
Cu(OTf)2, 1,10-phen Cs2CO3
Cu(OTf)2, 1,10-phen DIPEA
TBAB
TBAB
TBAB
TBAB
55
82
Cu(OTf)2,
1,10-phen
K3PO4
10
11
12
Cu(OTf)2, 1,10-phen K3PO4
Cu(OTf)2, 1,10-phen K3PO4
Cu(OTf)2, 1,10-phen K3PO4
TBAB
TBAB
TBAB
K2S2O5
59
70
57
c
DABSO
NaHSO3
a
Reaction conditions: 2a (0.1 mmol), Na2S2O5 (0.2 mmol), catalyst
(0.01 mmol), ligand (0.012 mmol), base (0.2 mmol), additive (0.12
mmol), solvent (1 mL), 12 h. Isolated yield of 3a. DABSO is
b
c
DABCO·(SO2)2.
(for the capture of electron carriers) (3e−3j) at position 3 were
systematically furnished in good to excellent yields, whose
structure was further confirmed via X-ray diffraction analysis of
3e.11 The substituents on positions 1 (3k), 2 (3l), and 4 (3m)
with different electronic properties were also well tolerated. The
conjugated phenyl groups (3n−3p) and fused rings (3q), which
are beneficial for carrier mobility in semiconductor materials
molecules, were proved to be entirely compatible. Diary-
liodonium salts bearing the halogen moieties, which provide
the chances for further derivatization by the metal catalyzed
coupling reactions, were perfectly accommodated (3r). In
particular, 3s (CAS: 83834-12-2), which is a key pivot for
construction of organic electroluminescent materials molecules,
performed well through this strategy. Heteoaryl sulfone, derived
from the corresponding iodonium salt, was also afforded (3t).
Following the success establishment of planar five-membered
diarylannulated sulfones library, the six-membered diarylannu-
lated sulfones, which are confirmed nonplanar structures by X-
ray diffraction analysis of 4n,11 were further studied to exhibit a
more divergent synthesis for the potential OLEDs material
molecules via the current methodology (see Supporting
Information for conditions optimization). gem-Dimethyl, an
important contributor for charge transporting amorphous
Radical trapping experiments were conducted with the
assistance of 1,1-diphenylethylene under the standard con-
ditions. 2-Diphenylvinyl-2′-iodo-biphenyl 5 was isolated in 13%
yield, which provided the evidence of a aryl radical intermediate
involved in this transformation (Scheme 3a). To further confirm
the formation of electrophilic “SO2” precursor, morpholin-4-
amine (6) was tested in the exchange transformation, 2′-iodo-N-
morpholino-[1,1′-biphenyl]-2-sulfonamide 7 was observed in
moderate yield even without the Cu(II) and ligand (Scheme 3b).
B
DOI: 10.1021/acs.orglett.7b02388
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Organic Letters
Letter
a
Scheme 1. SO2/I Exchange
a
Reaction conditions: 2 (0.1 mmol), Na2S2O5 (0.2 mmol), TBAB (0.12 mmol), DMSO (1 mL), 12 h, isolated yields, n = 0, Cu(OTf)2 (0.01 mmol),
1,10-Phen (0.012 mmol), K3PO4 (0.2 mmol), 120 °C, n = 1, DMEDA (0.01 mmol), DIPEA (0.2 mmol), 110 °C.
Scheme 2. Syntheses of Sulfone-Containing Unsymmetrical
Organic Materials Molecules
Scheme 3. Mechanistic Study
Thus, a postulated reaction pathway was depicted in Scheme 3c.
Radical intermediate 8 was generated via oxidation of Cu(I)
species forming Cu(II), which has been proved in hypervalent
iodine chemistry.10 Subsequently, Na2S2O5 was captured by
radical intermediate 8 forming the syntonic SO2 radical anion
intermediate 9, followed by oxidation to intermediate 10 with
Cu(II) reduced to Cu(I) again. The oxidative addition of aryl
iodine with Cu(I) provided Cu(III) aryl species 11 as the Ullman
type intermediate, which underwent a intramolecular ligand
C
DOI: 10.1021/acs.orglett.7b02388
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Organic Letters
Letter
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ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.orglett.7b02388.
Experimental; NMR, X-ray, and analytical data (PDF)
Crystallographic data for 3e (CIF)
Crystallographic data for 3u (CIF)
Crystallographic data for 3x (CIF)
Crystallographic data for 3y (CIF)
Crystallographic data for 4n (CIF)
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2013, 52, 12679. (b) Chen, Y.; Willis, M. C. Chem. Sci. 2017, 8, 3249.
(9) Davies, A. D.; Curto, J. M.; Bagley, S. W.; Willis, M. C. Chem. Sci.
2017, 8, 1233.
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(b) Deprez, N. R.; Sanford, M. S. Inorg. Chem. 2007, 46, 1924.
(c) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2008, 108, 5299. (d) Merritt,
E. A.; Olofsson, B. Angew. Chem., Int. Ed. 2009, 48, 9052. (e) Kita, Y.;
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AUTHOR INFORMATION
■
Corresponding Author
*E-mail: xfjiang@chem.ecnu.edu.cn.
ORCID
Ming Wang: 0000-0003-0388-4473
Xuefeng Jiang: 0000-0002-1849-6572
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(11) CCDC nos. 1561668 (3e), 1561669 (4n), 1561670 (3u),
1561671 (3x), and 1561672 (3y).
We acknowledge financial support from NSFC (21722202,
21672069, 21472050, 21502054 for M.W.), DFMEC
(20130076110023), Fok Ying Tung Education Foundation
(141011), Program for Shanghai Rising Star (15QA1401800),
Professor of Special Appointment (Eastern Scholar) at Shanghai
Institutions of Higher Learning, and National Program for
Support of Top-Notch Young Professionals.
(12) Sun, C.-L.; Li, H.; Yu, D.-G.; Yu, M.; Zhou, X.; Lu, X.-Y.; Huang,
K.; Zheng, S.-F.; Li, B.-J.; Shi, Z.-J. Nat. Chem. 2010, 2, 1044.
(13) (a) Liu, J.; Zou, J.; Yang, W.; Wu, H.; Li, C.; Zhang, B.; Peng, J.;
Cao, Y. Chem. Mater. 2008, 20, 4499. (b) Grisorio, R.; Melcarne, G.;
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Gigli, G. J. Mater. Chem. 2010, 20, 1012. (c) Zhan, X.; Wu, Z.; Lin, Y.;
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DOI: 10.1021/acs.orglett.7b02388
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