One-step stereoselective synthesis of (2Z,4Z,6Z,8Z)-decatetraene diketone from pyrylium salts

Article abstract of DOI:10.1002/ejoc.201301685

A strategy for the stereoselective synthesis of (2Z,4Z,6Z,8Z)-decatetraene diketone by the one-step metal reduction of pyrylium salts is described. Reduction of α-active pyrylium salts (at least one H at the α-C positon) leads to only linear decatetraene

Full text of DOI:10.1002/ejoc.201301685

FULL PAPER
DOI: 10.1002/ejoc.201301685
One-Step Stereoselective Synthesis of (2Z,4Z,6Z,8Z)-Decatetraene Diketone
from Pyrylium Salts
Lijian Yang,[a] Junwei Ye,*[a] Yuan Gao,[a] Dai Deng,[a] Yuan Lin,[a] and Guiling Ning*[a]
Keywords: Synthetic methods / Polyenes / Ketones / Dimerization / Reduction
A strategy for the stereoselective synthesis of (2Z,4Z,6Z,8Z)-
The reaction conditions were optimized, and a reaction
decatetraene diketone by the one-step metal reduction of py- mechanism was proposed. Single-crystal structures of deca-
rylium salts is described. Reduction of α-active pyrylium salts
(at least one H at the α-C positon) leads to only linear decate-
traene diketone derivatives, whereas reduction of α-non-
active pyrylium salts (no H at the α-C position) generates two
unexpected structures and one linear decatetraene diketone.
tetraene diketone derivatives demonstrate the twisted con-
figuration of the backbones and the all-(Z) geometry of the
double bonds. In addition, the thermal, optical, and electro-
chemical properties of these compounds were studied in de-
tail.
salts have been widely used in synthesizing carbocyclic and
heterocyclic compounds through ring transformations.[27–30]
In contrast, ring-opening reactions of pyrylium salts have
been rarely studied. For example, Balaban et al. and Mar-
vell et al.[31,32] independently reported that 2,4,6-trialkylpyr-
ylium salts could be converted into dienones upon treat-
ment with sodium borohydride. In our continuing research
on the synthesis, optical properties, and reactivity of pyryl-
ium salts,[33–36] we became interested in constructing deca-
tetraene diketone derivatives by dimerization of pyrylium
salts. In this paper, we report a facile and efficient strategy
for the stereoselective synthesis of decatetraene diketone de-
rivatives by metal reduction of α-active and α-non-active
pyrylium salts. By following this strategy, a series of
Introduction
Conjugated polyenes are basic skeletons in a variety of
natural products such as isotretinoin,[1,2] pheromones,[3,4]
and carotenoids.[5–8] Recently, these compounds have at-
tached growing interest as a result of their unique electronic
structures and optoelectronic properties.[9–11] Considerable
efforts have been devoted to the development of synthetic
approaches to polyene derivatives.[12–14] Traditional meth-
ods are based on Wittig and Horner–Emmons–Wadsworth
conversions[15,16] and transition-metal-(especially Pd)-cata-
lyzed cross-coupling reactions.[17–19] However, these meth-
ods often need multistep procedures or expensive catalysts,
and the products are usually not totally chemo- and stereo-
selective.[20] Recently, Takahashi et al. reported the regiose-
lective formation of trienes and tetraenes from different alk-
ynes by using a Zr/Cr or Zr/Cu system.[21,22] Wu et al. ex-
plored the nickel-catalyzed tetramerization of alkynes to
construct conjugated tetraenes.[23] Xi and co-workers syn-
thesized all-cis octatetraenes by dimerization of 1,4-dicop-
per-1,3-butadienes and subsequent Pd-catalyzed cross-cou-
pling.[24] In this context, it is desired to develop new, facile,
and efficient methods for the stereoselective synthesis of
conjugated polyenes.
(2Z,4Z,6Z,8Z)-decatetraene-1,10-diketone
compounds
were stereoselectively synthesized. A reaction mechanism
was proposed, and crystal structures were investigated.
Furthermore, the thermal, optical, and electrochemical
properties of these compounds were studied.
Results and Discussion
Metal Reduction of α-Active Pyrylium Salts
Ring opening of cyclic and heterocyclic compounds pro-
vides an effective approach to linear π-conjugated sys-
tems.[25,26] As a class of important intermediates, pyrylium
In previous work, metal reduction of 2,4,6-triarylpyryl-
ium salts (α-non-active) was shown to produce pyran γ-rad-
icals at the C4 site, which led to pyran-4,4Ј-dimers.[37–39]
However, researchers speculated that this result deviated
from the nature of pyran radicals. It is believed that pyran
α-radicals (at the C2/C6 sites) can be obtained by changing
the reaction conditions. In our previous report,[33] α-active
pyrylium salts were efficiently prepared from triarylcyclo-
pentadienes. Compared to α-non-active pyrylium salts, α-
active pyrylium salts have lower steric hindrance and
unique reactivity at the C2/C6 sites. Encouraged by these
[a] State Key Laboratory of Fine Chemicals and School of
Chemical Engineering, Faculty of Chemical, Environmental
and Biological Science and Technology, Dalian University of
Technology,
2 Linggong Road, Dalian 116024, P. R. China
E-mail: junweiye@dlut.edu.cn;
ninggl@dlut.edu.cn
http://ceb.dlut.edu.cn/
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201301685.
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L. Yang, J. Ye, Y. Gao, D. Deng, Y. Lin, G. Ning
FULL PAPER
discoveries, the metal reduction reactions of α-active 2,4,5-
triarylpyrylium salts were investigated. As illustrated in
Table 1, a series of linear π-conjugated decatetraene diket-
one derivatives were obtained in good yields.
Table 1. Synthesis of decatetraene diketone derivatives from α-
active pyrylium salts.
Scheme 1. Proposed mechanism for metal reduction reactions of
1a–g.
Entry
1
R1
R2 R3
R4
2: Yield
[%]
Metal Reduction of α-Non-Active Pyrylium Salts
1
2
3
4
5
6
7
1a Ph
H
H
H
H
H
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
2a: 83.3
2b: 80.4
2c: 81.2
2d: 85.4
2e: 84.8
To examine the universality of this synthetic route, re-
duction reactions of three types of α-non-active pyrylium
salts 3a–c under the similar conditions were performed. As
shown in Table 3, only reduction of 3c generated
(2Z,4E,6E,8Z)-decatetraene diketone 6. Products 4 and 5
without decatetraene chains were obtained and purified by
recrystallization in methanol. The characterization results
imply that a radical centered at C6 on the pyrylium cations
was generated, which led to the fabrication of the pyran
dimers. In comparison with the results we previously re-
ported,[34] the yields of the reduction reactions of 3a–c in-
creased in the CH3CN/Mg system. According to the results
of the reduction reactions of the α-active and α-non-active
pyrylium salts, we can draw the following conclusions:
(1) Pyran α-radicals can be generated in THF or CH3CN.
(2) The reduction reactions reach high yields in the
CH3CN/Mg system. (3) The reduction of α-active pyrylium
salts leads to linear decatetraene diketone structures; how-
ever, reduction of α-non-active pyrylium salts generates two
other compounds without the all-(E)-decatetraene chains.
As shown in Scheme 2, the mechanism of formation of 4
1b 4-FC6H4
1c 4-BrC6H4
1d 2-naphthyl
1e 4-PhC6H4
1f Ph
4-PhC6H4 4-PhC6H4 2f: 86.0
Ph 2g: 80.6
1g Ph
Ph Ph
To achieve optimum reaction conditions, the effects of
reductant, solvent, and atmosphere were explored. Because
of the poor stability of pyrylium salts in water and their
poor solvability in nonpolar solvents, THF and CH3CN
were selected to dissolve the pyrylium salts. Taking 1a as
an example, the reaction details are summarized in Table 2.
First, the reducing capacity of Mg, Zn, Fe, and Al was
evaluated in CH3CN. The yield of polyene diketone was the
highest in Mg/CH3CN. However, no conversion from the
pyrylium salt into the decatetraene diketone was detected
upon using Al as the reductant, probably because of the
generation of a shielding film on the metal particles. Sec-
ond, the reaction in Mg/THF was finished in a compara-
tively longer time and lower yield than the one in Mg/
CH3CN because of the higher boiling point of CH3CN.
Third, an inert atmosphere such as Ar2 was necessary, be-
cause the absence of oxygen could avoid the partial quench-
ing of the intermediate pyran radical. As a result, the opti-
mum reaction conditions for the synthesis of decatetraene
diketones 2a–g involved the use of Mg as the metal, aceto-
nitrile as the solvent, and Ar2 as an inert atmosphere with
a reaction time of about 5 h. A possible reaction mechanism
is proposed in Scheme 1. The decatetraene diketones were
obtained by double Claisen rearrangement of pyran-6,6Ј-
dimers, which were generated by pyran α-radicals from α-
active pyrylium salts.
Table 3. Synthesis of polyene diketone derivatives from α-non-
active pyrylium salts.
Table 2. Optimization of the reaction conditions.
Entry Reductant M:1a Solvent
Time [h] 2a:Yield [%]
1
2
3
4
5
Mg
Zn
Al
Fe
Mg
50:1 CH3CN
50:1 CH3CN
50:1 CH3CN
50:1 CH3CN
50:1 THF
4
5
12
8
83.3
70.8
–
52.3
77.6
Entry
3
Solvent
Metal
Time [h] Product: yield [%]
1
2
3
3a CH3CN
3b CH3CN
3c CH3CN
Mg
Mg
Mg
5
5
5
4: 45.8
5: 55.1
6: 83.1
6
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One-Step Stereoselective Polyene Diketone Synthesis
Scheme 2. Proposed mechanism for metal reduction reactions of 3a and 3b.
and 5 is speculated to occur through dimerization of pyran ene diketones 2a–c, 2e, and 2f were prepared for X-ray dif-
α-radicals, which is followed by complicated transforma- fraction experiment by vaporizing mixed solvents of
tions including Claisen rearrangement and Diels–Alder ad- CH2Cl2/CH3OH at room temperature. The crystal data and
dition. The proposed mechanism implies that there is po- structure refinements are tabulated in Table 4. Selected
tential for the large-scale synthesis of pyran α-radicals by bond lengths and angles for these compounds are listed in
metal reduction of pyrylium cations. The mechanism for the Table S2 (Supporting Information).
reduction of 3c is similar to that of 1a–g (Scheme 1).
The molecular structures of 2a–c, 2e, and 2f and their
packing arrangements are shown in Figures 1, 2, 3, 4, and
5. As shown in the ORTEP drawings in Figures 1–5, the
Crystal Structures of Decatetraene Diketones
To investigate the spatial structures and the relations be- double bonds in these compounds have all-(Z) geometry.
tween structures and properties, single crystals of decatetra- Another noteworthy feature of these molecules in the crys-
Table 4. Crystallographic data and structure refinement for 2a–c, 2e, and 2f.
2a
2b
2c
2e
2f
Empirical formula
Formula weight
Crystal system
Space group
a [Å]
C46H34O2
618.73
monoclinic
P2/n
12.969(4)
8.948(2)
15.068(4)
1745.1(8)
2
C46H32F2O2
654.72
C46H32Br2O2
776.54
monoclinic
P21/c
9.630(8)
22.534(18)
8.563(7)
1857(3)
2
C59H44Cl2O2
855.84
C70H50O2
923.10
monoclinic
C2/c
28.8673(7)
11.6645(2)
18.6634(4)
5020.52(18)
4
triclinic
triclinic
¯
¯
P1
P1
8.5673(11)
12.0055(18)
18.147(2)
1757.1(4)
2
1.237
0.082
10.4943(5)
10.8997(5)
21.0623(10)
2284.39(19)
2
1.244
0.186
b [Å]
c [Å]
Volume [Å3]
Z
Dcalcd. [mgm–3]
1.178
0.071
1.389
2.220
1.221
0.072
μ [mm–1]
F(000)
Rint
652
0.0471
1.014
0.0544
0.1289
0.1306
0.1625
684
0.0297
0.990
0.0674
0.1863
0.1450
0.2362
788
0.0502
1.005
0.0639
0.1620
0.1755
0.2065
896
0.0262
1.051
0.0661
0.1831
0.1012
0.2091
1944
0.0409
1.257
0.0806
0.2143
0.1317
0.2430
GOF on F2
R1 [IϾ2σ(I)][a]
wR2 [IϾ2σ(I)][a]
R1(all data)[a]
wR2 (all data)[a]
2
2 2
[a] R1 = Σ||Fo|–|Fc||/Σ|Fo|; wR2 = {Σ[w(Fo – Fc ) ]/Σ[w(Fo2)]2}1/2
.
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L. Yang, J. Ye, Y. Gao, D. Deng, Y. Lin, G. Ning
FULL PAPER
Figure 1. (a) ORTEP drawing of 2a with 30% probability thermal ellipsoids. (b) Schematic C–H···π hydrogen-bonding interactions; the
interaction distance and the angle of the C–H···π center for I are 2.93 Å and 154°, respectively, and for II these values are 3.54 Å and
136°, respectively. (c) Stacking images of 2a.
Figure 2. (a) ORTEP drawing of 2b with 30% probability thermal ellipsoids. (b) Schematic C–H···π hydrogen-bonding interactions; the
interaction distance and the angle of the C–H···π center for I are 3.10 Å and 152°, respectively; for II these values are 3.07 Å and 149°,
respectively; for III these values are 2.99 Å and 144°, respectively; for IV these values are 3.07 Å and 149°, respectively; and for V these
values are 2.69 Å and 172°, respectively. (c) Stacking images of 2b.
Figure 3. (a) ORTEP drawing of 2c with 30% probability thermal ellipsoids. (b) Schematic C–H···π hydrogen-bonds interactions. The
interaction distance and the angle of the C–H···π center for I are 2.84 Å and 145°, respectively; for II these values are 2.83 Å and 146°,
respectively; for III these values are 3.60 Å and 125°, respectively; and for IV these values are 2.73 Å and 161°, respectively. (c) Stacking
images of 2c.
tal is torsion conformation, which is due to the large steric cules are packed into different crystal systems with different
hindrance of the aryl groups linking to the double bonds. space groups, the stacking images are very similar, except
For example, the decatetraene chains of these compounds for different intra- and intermolecular interactions. The mo-
are not linear but have the twisted “S” configuration. As lecules are packed into molecular layers on the basis of C–
shown in Table 5, the torsion angles between double bonds H···π interactions. The twisted configuration and large
and adjacent carbonyl [θ(0,1,2,3)] groups are distributed from steric hindrance make the π–π interaction impossible. The
41 to 50°, and the torsion angle between the double bonds origin of non-fluorescence and low fluorescence efficiency
with the two adjacent aryl rings [θ(2,3,4,5) and θ(6,7,8,9)] are in of these compounds in solution and in the solid state are
the 27–42° and 16–89° range, respectively. θ(4,3,7,8) is clearly related to such a twisted configuration and the correspond-
larger, from 64 to 74°. Intra- and intermolecular interac- ing motion of the aryl groups linked to the single bond.
tions and the molecular packing arrangements in the crys- The optical properties of these compounds will be discussed
tals are also shown in Figures 1–5. Although these mole- in the following section.
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One-Step Stereoselective Polyene Diketone Synthesis
Figure 4. (a) ORTEP drawing of 2e with 30% probability thermal ellipsoids. (b) Schematic C–H···π hydrogen-bonding interactions. The
interaction distance and the angle of the C–H···π center for I are 3.10 Å and 142°, respectively; for II these values are 3.41 Å and 117°,
respectively; for III these values are 2.88 Å and 158°, respectively; for IV these values are 3.17 Å and 152°, respectively; and for V these
values are 3.03 Å and 156°, respectively. (c) Stacking images of 2e.
Figure 5. (a) ORTEP drawing of 2f with 30% probability thermal ellipsoids. (b) Schematic C–H···π hydrogen-bonding interactions in 2f.
The interaction distance and the angle of the C–H···π center for I are 3.22 Å and 137°, respectively; and for II these values are 3.36 Å
and 156°, respectively. (c) Stacking images of 2f.
Table 5. Selected torsion angles in 2a–c, 2e, and 2f.
calorimetry (DSC) and thermogravimetric analysis (TGA).
The DSC curves were recorded during the second heating
runs at a scan rate of 10 °Cmin–1. As shown in Figure S3
and Table 6, 2d, 2f, 2g, and 6 exhibit a glass transition peak,
and the glass transition temperatures (Tg) are 80, 85, 82 and
81 °C, respectively. The decomposition temperature (Td) is
defined as the temperature at which 5% weight loss occurs
during heating under a N2 atmosphere. As shown in Table 6
and Figure S4, the compounds are stable, as they start to
decompose at 240–320 °C. By comparing the values of Td
for these compounds, the introduction of bulky aryl groups
and an increase in the quantity of aryl groups increase the
thermal stability of this class of compounds.
Compound Torsion angle [°]
θ(0,1,2,3)
θ(2,3,4,5)
θ(6,7,8,9)
θ(4,3,7,8)
The optical properties of 2a–g and 6 in CH2Cl2 (5ϫ
10–5 m) were investigated by UV/Vis absorption spec-
troscopy (UV) and photoluminescence (PL) spectroscopy.
The maximum absorption wavelengths (λabsmax) were in the
range from 301 to 381 nm (Figure 6 and Table 6), which
2a
2b
2c
2e
2f
44
41
48
49
50
42
34
27
33
35
41
16
29
88
89
64
68
70
75
74
was caused by π–π transitions. Compared to 2a–g, the clear
max
redshift of λabs
for 6 to 381 nm is indicative of a more
planar configuration in 6. In dilute solution, these com-
pounds barely exhibit emissions because of the vibration
Thermal, Optical, and Electrochemical Properties
The thermal properties of decatetraene diketone deriva- and rotation of the abundant single bonds, isomerization
tives 2a–g and 6 were investigated by differential scanning of the double bonds, and the twisted configuration of the
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Table 6. Thermal, optical properties, and energy levels of decatetraene diketones.
max
opt
Compound
Tg
Td
λabs
λem
ΔEg
EHOMO
ELUMO
[°C]
[°C]
[nm]
[nm]
[eV]
[eV]
[eV]
2a
2b
2c
2d
2e
2f
2g
6
–
–
–
85
–
82
80
81
257
266
267
308
290
320
240
280
311
310
309
301
308
337
324
381
465
409
476
590
547
549
527
437
2.54
2.53
2.56
2.58
2.57
2.50
2.63
2.66
–5.43
–5.37
–5.43
–5.47
–5.47
–5.45
–5.56
–5.58
–2.89
–2.84
–2.87
–2.89
–2.90
–2.95
–2.93
–2.92
backbones, but the normalized PL spectra in Figure 7 illus- tion, respectively. As shown in Table 6, the ΔEg values of
trate the tunable emission properties of these compounds. the compounds were in the 2.50–2.66 eV range and the
As expected, no or very weak fluorescent emission was ob- HOMO values ranged from –5.37 to –5.58 eV.
served in solid powders and in the crystals because of the
twisted configuration.
Conclusions
In summary, a strategy for the stereoselective synthesis
of (2Z,4Z,6Z,8Z)-decatetraene diketone through the one-
step metal reduction of pyrylium salts was developed. Re-
duction of α-active pyrylium salts led only to linear decate-
traene diketone derivatives, whereas reduction of α-non-
active pyrylium salts led to decatetraene diketone deriva-
tives as well as other cyclic compounds. The crystal struc-
tures of these decatetraene diketones confirmed the twisted
configuration of the backbones and the all-(Z) geometry of
the double bonds. The predictability, stereoselectivity, and
high yields illustrate the potential applications of this reac-
tion. Moreover, the reaction conditions were optimized,
Figure 6. The normalized UV/Vis absorption spectra of decatetra-
ene ketones in CH2Cl2.
and a reaction mechanism was proposed. Further studies
are expanded to other heterocyclic salts to fabricate func-
tional conjugated polyenes by metal reduction reactions.
Experimental Section
General Methods: All solvents were distilled before use unless
otherwise stated. THF was distilled from sodium/benzophenone,
and CH3CN was distilled from P2O5 under a nitrogen atmosphere.
1H NMR and 13C NMR spectra were recorded at 400 and
100.6 MHz, respectively. Mass spectra and high-resolution mass
spectra (HRMS) were measured with a UPLC/Q-Tof. UV and fluo-
rescence spectra were measured in 1 cm cells in CH2Cl2. DSC
curves and TGA were obtained at a heating rate of 10 °Cmin–1
under an atmosphere of N2. Cyclic voltammetry (CV) measure-
ments were performed in a three-electrode cell with a Pt disk work-
ing electrode, a Ag/AgNO3 reference electrode, and a glassy carbon
counter electrode. All CV measurements were performed under an
atmosphere of N2 with supporting electrolyte of 0.01 m tetra-n-bu-
Figure 7. The normalized PL spectra of decatetraene ketones in
CH2Cl2.
tylammonium hexafluorophosphate in CH3CN at a scan rate of
100 mVs–1 by using ferrocene (Fc) as a standard.
It is well known that the highest occupied molecular or-
Single-Crystal X-ray Crystallography: The X-ray diffraction data
bital (HOMO), the lowest unoccupied molecular orbital
(LUMO), and the energy band gaps (ΔEg) are three impor-
tant parameters for organic semiconductor materials.[40] On
the basis of cyclic voltammetry (CV) and the UV spectra,
the HOMO levels and the values of ΔEg were obtained by
using the onset oxidation potential obtained from the CV
were collected at 100 K by using graphite monochromated Mo-
Kα radiation (λ = 0.71073 Å). The structures were solved by direct
methods and refined on F2 by full-matrix least-squares methods
with SHELXTL. All non-hydrogen atoms were refined anisotropi-
cally.
CCDC-957385 (for 2a), -957386 (for 2b), -957387 (for 2c), -957388
curves (Figure S5) and the onset wavelength of UV absorp- (for 2e), -957389 (for 2f), -957383 (for 5), and -957384 (for 6) con-
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One-Step Stereoselective Polyene Diketone Synthesis
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
(400 MHz, CDCl3): δ = 8.52 (s, 2 H), 8.04 (d, J = 8.0 Hz,2 H), 7.82
(m, 7 H), 7.64 (s, 2 H), 7.56 (m, 2 H), 7.50 (m, 2 H), 7.39 (d, J =
6.8 Hz,4 H), 7.27 (m, 4 H), 7.02 (d, J = 7.2 Hz,4 H), 6.95 (d, J =
7.2 Hz, 2 H), 6.88 (m, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 190.9, 151.3, 141.7, 139.4, 138.8, 135.6, 135.4, 132.5, 130.4, 129.5,
129.4, 128.8, 128.5, 128.4, 128.1, 127.8, 127.4, 126.8, 126.7, 126.2,
125.6, 124.2 ppm. HRMS (ESI-TOF): calcd. for C54H38O2Na [M
+ Na]+ 741.2770; found 741.2744. C54H38O2 (718.89): calcd. C
90.22, H 5.33; found C 90.19, H 5.39.
Synthetic Procedure for Pyrylium Perchlorates: Pyrylium perchlo-
rates 1a–g and 3c were synthesized according to our published
method.[33,36]
A mixture of the cyclopentadiene derivatives
(0.62 mmol) and perchloric acid (70%, 1 mL) in toluene/acetoni-
trile (3:1, 15 mL) was stirred at room temperature for 3 d. Diethyl
ether (30 mL) was poured into the mixture. Then, the precipitate
was obtained by filtration and washed with diethyl ether (3ϫ
15 mL). The crude product was recrystallized from acetic acid for
purification. Pyrylium perchlorates 3a and 3b were synthesized ac-
cording to the published procedure.[41]
(2Z,4Z,6Z,8Z)-1,10-Di(4,4Ј-biphenyl)-3,4,7,8-tetraphenyldeca-
tetraene-1,10-dione (2e): Compound 1e (0.48 g, 1 mmol) was
treated with Mg (1.2 g, 50 mmol) to yield 2e (0.33 g, 0.42 mmol,
84.8%) as a yellow amorphous solid (silica gel, CH2Cl2/hexane =
1
1:1). H NMR (400 MHz, CDCl3): δ = 7.94 (d, J = 8.0 Hz, 4 H),
General Procedures for Metal Reduction of Pyrylium Salts: A
100 mL flask was charged with pyrylium perchlorate (1 mmol), Mg
(50 mmol), and anhydrous CH3CN (30 mL). The mixture was
heated at reflux for 4–6 h under an atmosphere of Ar2 and then
cooled to room temperature. Magnesium and the magnesium salt
were removed by filtration and washed with CH2Cl2 (3ϫ 30 mL).
The crude product was obtained after the solvent was removed
under reduced pressure. Purification was performed by recrystalli-
zation from methanol or flash column chromatography (silica gel,
CH2Cl2/n-hexane). The crystals were prepared in CH2Cl2/CH3OH.
7.79 (d, J = 8.4 Hz,2 H), 7.70–7.67 (m, 2 H), 7.53 (d, J = 8.4 Hz,4
H), 7.48 (d, J = 8.0 Hz,6 H), 7.45 (s, 2 H), 7.42–7.36 (m, 8 H) 7.11–
7.02 (m 12 H), 6.78 (s, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 190.5, 151.5, 145.5, 141.6, 140.0, 136.9, 130.5, 129.5, 129.1, 128.9,
128.5, 128.4, 128.2, 128.1, 127.8, 127.4, 127.279, 127.1, 126.7,
125.8, 125.7 ppm. HRMS (ESI-TOF): calcd. for C58H42O2Na [M
+ Na]+ 793.3083; found 793.3043. C58H42O2 (770.97): calcd. C
90.36, H 5.49; found C 90.42, H 5.56.
(2Z,4Z,6Z,8Z)-1,10-Diphenyl-3,4,7,8-tetra(4,4Ј-biphenylyl)deca-
tetraene-1,10-dione (2f): Compound 1f (0.56 g, 1 mmol) was treated
(2Z,4Z,6Z,8Z)-1,3,4,7,8,10-Hexaphenyldecatetraene-1,10-dione
(2a): Compound 1a (0.41 g, 1 mmol) was treated with Mg (1.2 g, with Mg (1.2 g, 50 mmol) to yield 2f (0.40 g, 0.43 mmol, 86.0%) as
50 mmol) to yield 2a (0.26 g, 0.42 mmol, 88.3 %) as a yellow
amorphous solid (silica gel, CH2Cl2/hexane = 1:1). 1H NMR
(400 MHz, CDCl3): δ = 7.97 (d, J = 6.8 Hz, 4 H), 7.52 (s, 2 H),
7.47 (t, J = 8.0 Hz, 2 H), 7.40 (m, 8 H), 7.30 (m, 6 H), 7.08 (s, 10
H), 6.84 (s, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 190.8,
151.7, 141.6, 138.0, 132.8, 129.5, 128.8, 128.5, 128.5, 128.3, 128.2,
127.4, 126.7, 125.7, 125.4 ppm. HRMS: (ESI-TOF): calcd. for
a yellow amorphous solid (recrystallization from methanol twice).
1H NMR (400 MHz, CDCl3): δ = 8.05 (d, J = 7.6 Hz,4 H), 7.67
(s, 2 H), 7.59–7.55 (m,12 H), 7.49–7.27 (m, 30 H), 7.00 (s, 2 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 190.7, 151.3, 142.5, 140.7,
140.3, 140.2, 138.2, 133.0, 131.1, 129.8, 129.0, 128.9, 128.700,
128.6, 128.4, 127.9, 127.7, 127.3, 127.2, 127.1, 127.1, 127.0, 126.9,
126.7 ppm. HRMS (ESI-TOF): calcd. for C70H50O2Na [M + Na]+
945.3709; found 945.3743. C70H50O2 (923.16): calcd. C 91.07, H
5.46; found C 91.15, H 5.56.
C
46H34O2Na [M + Na]+ 641.2457; found 641.2473. C46H34O2
(618.77): calcd. C 89.29, H 5.54; found C 89.44, H 5.20.
(2Z,4Z,6Z,8Z)-1,10-Di(4-flourophenyl)-3,4,7,8-tetraphenyldeca-
tetraene-1,10-dione (2b): Compound 1b (0.43 g, 1 mmol) was
treated with Mg (1.2 g, 50 mmol) to yield 2b (0.26 g, 0.40 mmol,
80.4%) as a yellow amorphous solid (recrystallization from meth-
1,2,3,4,7,8,9,10-Octaphenyldecatetraene-1,10-dione (2g): Com-
pound 1g (0.48 g, 1 mmol) was treated with Mg (1.2 g, 50 mmol)
to yield 2g (0.31 g, 0.40 mmol, 80.6%) as a yellow amorphous solid
(2ϫ recrystallization from methanol). 1H NMR (400 MHz,
CDCl3): δ = 8.01 (d, J = 6.8 Hz, 2 H), 7.91 (d, J = 7.2 Hz, 2 H),
7.44 (t, J = 7.6 Hz, 1 H), 7.33 (m, 6 H), 7.1–6.9 (m, 26 H), 6.75 (d,
J = 6.4 Hz, 4 H), 6.51 (d, J = 11.6 Hz, 1 H), 6.35 (d, 11.6 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 197. 6, 196.6, 147.5, 146.4,
143.9, 142.5, 140.8, 139.3, 139.0, 138.3, 138.2, 137.8, 137.6, 137.0,
132.8, 132.7, 131.2, 130.6, 130.4, 130.2, 130.1, 130.0, 129.9, 128.4,
128.2, 127.8, 127.7, 127.5, 127.4, 127.3, 127.2, 127.1 ppm. HRMS
(ESI-TOF): calcd. for C58H42O2Na [M + Na]+ 793.3083; found
793.3100. C58H42O2 (770.97): calcd. C 90.36, H 5.49; found C
90.27, H 5.64.
1
anol twice). H NMR (400 MHz, CDCl3): δ = 7.96–7.92 (m, 4 H),
7.44 (m, 6 H), 7.34 (m, 6 H), 7.10–7.00 (m, 14 H), 6.80 (s, 2 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 189.4, 151.8, 141.6, 139.4,
134.5, 134.5, 131.1, 131.0, 130.4, 129.7, 129.2, 128.9, 128.2, 127.4,
126.6, 125.6, 125.4, 115.6, 115.4 ppm. HRMS (ESI-TOF): calcd.
for C46H32O2F2Na [M + Na]+ 677.2268; found 677.2313.
C46H32F2O2 (654.75): calcd. C 84.38, H 4.93; found C 84.44, H
4.90.
(2Z,4Z,6Z,8Z)-1,10-Di(4-bromophenyl)-3,4,7,8-tetraphenyl deca-
tetraene-1,10-dione (2c): Compound 1c (0.49 g, 1 mmol) was
treated with Mg (1.2 g, 50 mmol) to yield 2c (0.32 g, 0.41 mmol,
81.2%) as a yellow amorphous solid (silica gel, CH2Cl2/hexane =
Dimer Derivate of 2,4,6-Tetraphenylpyrylium Salts (4): Compound
3a (0.41 g, 1 mmol) was treated with Mg (1.2 g, 50 mmol) to yield
4 (0.14 g, 0.23 mmol, 45.8%) as a yellow amorphous solid (2ϫ
recrystallization from methanol). 1H NMR (400 MHz, CDCl3): δ
= 7.68 (d, J = 7.6 Hz, 2 H), 7.57 (d, J = 7.6 Hz, 2 H), 7.40 (d, J =
7.2 Hz, 2 H), 7.34 (m, 4 H), 7.19–7.13 (m, 4 H), 7.06–7.00 (m, 6
H), 6.87–6.72 (m, 8 H), 6.74 (d, J = 7.2 Hz, 2 H), 6.54 (s, 1 H),
5.55 (s, 1 H), 5.15 (d, J = 10 Hz, 1 H), 4.56 (d, J = 9.6 Hz, 1 H),
4.03 (d, J = 17.2 Hz, 1 H), 2.87 (d, J = 17.2 Hz, 1 H) ppm. 13C
1
1:1). H NMR (400 MHz, CDCl3): δ = 7.77 (d, J = 8.4 Hz,4 H),
7.48–7.35 (m, 16 H), 7.11–7.06 (m, 10 H), 6.77 (s, 2 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 189.8, 152.28, 141.6, 1394, 136.9,
131.7, 130.0, 129.8, 128.9, 128.3, 127.7, 127.4, 126.6, 125.6,
125.1 ppm. HRMS (ESI-TOF): calcd. for C46H32O2Br2Na [M +
Na]+ 797.0667; found 797.0670. C46H32Br2O2 (776.57): calcd. C
71.15, H 4.15; found C 71.19, H 4.23.
1,10-Di(2-naphthyl)-3,4,7,8-tetraphenyldecatetraene-1,10-dione (2d): NMR (100 MHz, CDCl3): δ = 204.1, 201.74 (s), 142.9, 140.4, 139.6,
Compound 1d (0.46 g, 1 mmol) was treated with Mg (1.2 g, 139.2, 138.1, 137.8, 133.1, 132.4, 132.0, 131.7, 129.0, 128.7, 128.6,
50 mmol) to yield 2d (0.31 g, 0.43 mmol, 85.4 %) as a yellow 128.3, 128.3, 128.2, 128.1, 128.0, 127.7, 127.5, 127.3, 127.2, 127.0,
amorphous solid (silica gel, CH2Cl2/hexane = 2:1). 1H NMR
126.5, 55.7, 49.7, 44.9, 37.2 ppm. MS (API-ES): m/z = 621.3 [M +
Eur. J. Org. Chem. 2014, 515–522
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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521

L. Yang, J. Ye, Y. Gao, D. Deng, Y. Lin, G. Ning
FULL PAPER
1]+. C46H36O2 (620.79): calcd. C 89.00, H 5.85; found C 89.16, H
5.94.
[9] T. C. Lin, J. M. Cole, A. P. Higginbotham, A. J. Edwards, R. O.
Piltz, J. Perez-Moreno, J. Y. Seo, S. C. Lee, K. Clays, O. P.
Kwon, J. Phys. Chem. C 2013, 117, 9416–9430.
[10] B. W. Domagalska, K. A. Wilk, R. Zielin´ski, J. Photochem.
Photobiol. A: Chem. 2006, 184, 193–203.
[11] K. Staub, G. A. Levina, S. Barlow, T. C. Kowalczyk, H. S.
Lackritz, M. Barzoukas, A. Fort, S. R. Marder, J. Mater.
Chem. 2003, 13, 825–833.
[12] J. H. Delcamp, P. E. Gormisky, M. C. White, J. Am. Chem. Soc.
2013, 135, 8460–8463.
[13] J. Burghart, R. Brückner, Eur. J. Org. Chem. 2011, 150–165.
[14] T. Kondo, M. Niimi, Y. Yoshida, K. Wada, T. A. Mitsudo, Y.
Kimura, A. Toshimitsu, Molecules 2010, 15, 4189–4200.
[15] M. Zeeshan, H. R. Sliwka, V. Partali, A. Martínez, Org. Lett.
2012, 14, 5496–5498.
Dimer-Derivate of 2,3,4,6-Tetraphenylpyrylium Salts (5): Com-
pound 3b (0.48 g, 1 mmol) was treated with Mg (1.2 g, 50 mmol)
to yield 5 (0.21 g, 0.28 mmol, 55.1%) as a yellow amorphous solid
(2ϫ recrystallization from methanol). 1H NMR (400 MHz,
CDCl3): δ = 7.52 (d, J = 7.6 Hz, 2 H), 7.46 (m, 2 H), 7.26 (m, 18
H), 6.90 (m, 8 H), 6.81 (t, J = 8.0 Hz, 3 H), 6.72 (t, J = 8.0 Hz, 3
H), 6.59 (d, J = 7.6 Hz, 2 H), 6.05 (d, J = 8.0 Hz, 2 H), 4.97 (s, 1
H), 4.36 (s, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 198.2,
148.1, 147.4, 147.1, 143.3, 142.2, 140.4, 140.0, 139.5, 138.1, 137.1,
136.92 (s), 134.9, 131.9, 131.2, 130.2, 129.6, 1328.3, 128.0, 127.6,
127.3, 127.1, 126.8, 126.6, 126.3, 126.0, 87.5, 83.4, 68.5, 58.2 ppm.
MS (API-ES): m/z = 771.3 [M + 1]+. C58H42O2 (770.97): calcd. C
90.36, H 5.49; found C 90.45, H 5.44.
[16] N. R. Cichowicz, P. Nagorny, Org. Lett. 2012, 14, 1058–1061.
[17] C. Oger, L. Balas, T. Durand, J. M. Galano, Chem. Rev. 2012,
113, 1313–1350.
[18] E. Shirakawa, H. Yoshida, Y. Nakao, T. Hiyama, J. Am. Chem.
Soc. 1999, 121, 4290–4291.
[19] N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457–2483.
[20] R. Jana, T. P. Pathak, M. S. Sigman, Chem. Rev. 2011, 111,
1417–1492.
(2Z,4E,6E,8Z)-Decaphenyldecatetraene-1,10-dione (6): Compound
3c (0.56 g, 1 mmol) was treated with Mg (1.2 g, 50 mmol) to yield
6 (0.38 g, 0.42 mmol, 83.1%) as a yellow amorphous solid (silica
1
gel, CH2Cl2/hexane = 1:1). H NMR (400 MHz, CDCl3): δ = 7.51
(d, J = 7.6 Hz, 10 H) 7.30–7.20 (m, 30 H), 7.16 (m, 10 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 197.6, 149.3, 145.6, 145.0, 143.2,
142.5, 142.0, 141.0, 138.0, 136.2, 131.4, 130.7, 129.6, 129.6, 128.0,
127.4, 127.3, 127.2, 126.7, 126.6, 126.4, 126.0, 125.9, 125.6 ppm.
HRMS (ESI-TOF): calcd. for C70H50O2Na [M + Na]+ 945.3709;
found 945.3748. C70H50O2 (923.16): calcd. C 91.07, H 5.46; found
C 91.27, H 5.54.
[21] K. Kanno, E. Igarashi, L. Zhou, K. Nakajima, T. Takahashi,
J. Am. Chem. Soc. 2008, 130, 5624–5625.
[22] T. Takahashi, Y. H. Liu, A. Iesato, S. Chaki, K. Nakajima, K.
Kanno, J. Am. Chem. Soc. 2005, 127, 11928–11929.
[23] T. C. Wu, J. J. Chen, Y. T. Wu, Org. Lett. 2011, 13, 4794–4797.
[24] J. Wei, Z. Wang, W. X. Zhang, Z. Xi, Org. Lett. 2013, 15, 1222–
1225.
[25] V. V. Burlakov, P. Arndt, W. Baumann, A. Spannenberg, U.
Rosenthal, Organometallics 2004, 23, 5188–5192.
[26] C. Dell’Erba, A. Mugnoli, M. Novi, M. Pertici, G. Petrillo, C.
Tavani, Eur. J. Org. Chem. 1999, 431–435.
[27] A. C. Carrasco, E. A. Pidko, A. M. Masdeu-Bultó, M. Lutz,
A. L. Spek, D. Vogt, C. Müller, New J. Chem. 2010, 34, 1547–
1550.
Supporting Information (see footnote on the first page of this arti-
cle): Copies of the 1H NMR and 13C NMR spectra, MS and
HRMS spectra, DSC curves, TGA curves, and CV curves, and X-
ray crystallographic data.
[28] C. Mahler, U. Muller, W. M. Muller, V. Enkelmann, C. Moon,
G. Brunklaus, H. Zimmermann, S. Hoger, Chem. Commun.
2008, 4816–4818.
Acknowledgments
[29] A. T. Balaban, I. Ghiviriga, E. W. Czerwinski, P. De, R. Faust,
J. Org. Chem. 2004, 69, 536–542.
[30] P. Lainé, F. Bedioui, P. Ochsenbein, V. Marvaud, M. Bonin, E.
Amouyal, J. Am. Chem. Soc. 2002, 124, 1364–1377.
[31] A. T. Balaban, G. Mihai, C. D. Nenitzesco, Tetrahedron 1962,
18, 257.
This work was supported by the National Natural Science Founda-
tion of China (NSFC) (grant numbers 51003009 and 20772014),
Specialized Research Fund for the Doctoral Program of Higher
Education, and the Fundamental Research Funds for the Central
Universities of China.
[32] E. N. Marvell, T. Gosink, J. Org. Chem. 1972, 37, 3036–3037.
[33] L. Yang, J. Ye, Y. Gao, D. Deng, W. Gong, Y. Lin, G. Ning,
Tetrahedron Lett. 2013, 54, 2967–2971.
[34] X. Zhang, J. Ye, S. Wang, W. Gong, Y. Lin, G. Ning, Org. Lett.
2011, 13, 3608–3611.
[35] T. Xu, W. T. Gong, J. W. Ye, Y. Lin, G. L. Ning, Organometal-
lics 2010, 29, 6744–6748.
[36] W. T. Gong, G. L. Ning, X. C. Li, L. Wang, Y. Lin, J. Org.
Chem. 2005, 70, 5768–5770.
[1] B. D. Cox, D. D. Muccio, T. P. Hamilton, Comput. Theor.
Chem. 2013, 1011, 11–20.
[2] M. Salman, S. J. Babu, V. K. Kaul, P. C. Ray, N. Kumar, Org.
Process Res. Dev. 2005, 9, 302–305.
[3] D. Kong, M. J. Lee, S. Lin, E. S. Kim, J. Ind. Microbiol. Bio-
technol. 2013, 40, 529–543.
[4] R. Yamakawa, N. Do, M. Kinjo, Y. Terashima, T. Ando, J.
Chem. Ecol. 2011, 37, 105–113.
[37] M. J. Shaw, J. Mertz, Organometallics 2002, 21, 3434–3442.
[38] H. Kawata, Y. Suzuki, S. Niizuma, Tetrahedron Lett. 1986, 27,
4489–4492.
[5] S. Krawczyk, R. Luchowski, Chem. Phys. Lett. 2013, 564, 83–
87.
[6] Y. Yamano, M. V. Chary, A. Wada, Org. Biomol. Chem. 2012,
10, 4103–4108.
[7] J. He, F. Chen, J. Li, O. F. Sankey, Y. Terazono, C. Herrero, D. [41] J. A. VanAllan, G. A. Reynolds, J. Org. Chem. 1968, 33, 1102–
Gust, T. A. Moore, A. L. Moore, S. M. Lindsay, J. Am. Chem.
Soc. 2005, 127, 1384–1385.
[8] S. K. Guha, S. Koo, J. Org. Chem. 2005, 70, 9662–9665.
[39] K. Conrow, P. C. Radlick, J. Org. Chem. 1961, 26, 2260–2263.
[40] Y. Liu, M. S. Liu, A. K. Y. Jen, Acta Polym. 1999, 50, 105–108.
1105.
Received: November 9, 2013
Published Online: December 17, 2013
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Eur. J. Org. Chem. 2014, 515–522