Convenient Phenacene Synthesis by Sequentially Performed Wittig Reaction and Mallory Photocyclization Using Continuous-Flow Techniques

Article abstract of DOI:10.1055/s-0036-1588775

Various phenacenes possessing chrysene, picene, and fulminene frameworks were prepared by using a continuous-flow synthetic protocol in which Wittig reaction affording diarylethenes and their Mallory photocyclization producing phenacene skeletons were sequentially performed. The Wittig reaction solution, containing the diaryl ethene obtained from an arylaldehyde and an arylmethyltriphenylphosphonium salt, was mixed with an iodine solution in the flow system and, subsequently, the solution was subjected to the photoreaction. Desired phenacenes were obtained with high to moderate chemical yield. For the present protocol, isolation of the intermediary diarylethene, which is the key precursor of the phenacene, is unnecessary. The approach provides a convenient method to supply a variety of phenacene samples, which are needed for initial systematic surveys in material science.

Full text of DOI:10.1055/s-0036-1588775

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2017, 49, A–I
paper
A
en
H. Okamoto et al.
Paper
Synthesis
Convenient Phenacene Synthesis by Sequentially Performed
Wittig Reaction and Mallory Photocyclization Using Continuous-
Flow Techniques
Hideki Okamoto*a
Haruhiko Takahashia
Takamitsu Takanea
Yasuhiro Nishiyamab
Kiyomi Kakiuchib
Shin Gohdac
Minoru Yamajid
a Division of Earth, Life, and Molecular Sciences, Graduate
School of Natural Science and Technology, Okayama
University, Tsushima-Naka 3-1-1, Okayama 700-8350,
Japan
b Graduate School of Materials Science, Nara Institute of
Science and Technology (NAIST), 8916-5 Takayama,
Ikoma, Nara 630-0192, Japan
c Material Science Research Group, NARD Institute, Ltd.,
Nishinagasu-cho 2-6-1, Amagasaki, Hyogo 660-0805,
Japan
d Division of Molecular Science, Graduate School of
Science and Engineering, Gunma University, Kiryu,
Gunma 376-8515, Japan
hokamoto@okayama-u.ac.jp
Received: 18.02.2017
Accepted after revision: 13.03.2017
Published online: 24.04.2017
DOI: 10.1055/s-0036-1588775; Art ID: ss-2017-f0100-op
n-2
n-2
[n]phenacene
Abstract Various phenacenes possessing chrysene, picene, and fulmi-
[n]acene
nene frameworks were prepared by using a continuous-flow synthetic
protocol in which Wittig reaction affording diarylethenes and their
Mallory photocyclization producing phenacene skeletons were sequen-
tially performed. The Wittig reaction solution, containing the diaryl-
ethene obtained from an arylaldehyde and an arylmethyltriphenylphos-
phonium salt, was mixed with an iodine solution in the flow system and,
subsequently, the solution was subjected to the photoreaction. Desired
phenacenes were obtained with high to moderate chemical yield. For
the present protocol, isolation of the intermediary diarylethene, which
is the key precursor of the phenacene, is unnecessary. The approach
provides a convenient method to supply a variety of phenacene sam-
ples, which are needed for initial systematic surveys in material science.
Figure 1 General structures of [n]acene and [n]phenacene; n depicts
the number of the benzene rings in the compounds
Acenes have attracted much attention as an active layer
of OFET and they have been widely studied4,6 since the dis-
covery of high-performance p-channel OFET operation of
pentacene-based devices.11 However, the chemical instabil-
ity of acenes prevents them from being used in practical
electronic devices. In contrast, phenacenes have been much
less investigated as functional materials in organic elec-
tronics. Recently, it has been disclosed that phenacenes are
promising materials for the active layer of p-channel
OFET.12–16 It is notable that increasing the number of ben-
zene rings n in phenacenes tends to systematically increase
in charge mobility of OFET devices fabricated with phen-
acene single-crystals.16 Furthermore, upon doping with al-
kali or alkali-earth metals, picene ([5]phenacene) exhibits
superconductivity.7 Phenacenes are quite stable and robust
against exposure to both oxygen and light. Therefore, they
are considered to be promising materials for applications in
practical organic electronic devices.
Key words phenacene, flow reaction, Mallory photocyclization, Wittig
reaction, photochemistry
Aromatic molecules possessing extended π-conjugation
are becoming an important class of materials because of
their potential applications in organic electronics, such as
organic field effect transistors (OFET)1–4 and organic light-
emitting diodes (OLED),5,6 and even as organic supercon-
ductors.7–10 There are several structural categories of π-ex-
tended aromatic compounds, typified by acenes and phen-
acenes, which consist of, respectively, linear- and zigzag-
fusion of benzene rings (Figure 1).
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H. Okamoto et al.
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Synthesis
Apart from the potential applications, fundamental
photophysical features of phenacenes would be of addition-
al interest. Picene fluoresces from the second singlet excit-
ed state (S2) in the gas phase, demonstrating that it has
non-Kasha photoluminescence properties.17
As for synthesis of phenacene frameworks, since phen-
acenes are old compounds extracted from coal tar,18 there
are many reported synthetic routes to them. However, little
information is available on efficient and systematic phen-
acene synthesis. Therefore, the development of a facile syn-
thetic protocol for the preparation of various phenacene
frameworks is desired to promote phenacene-based mate-
rial sciences and organic electronics.
hν
I2, air
PPh3X
CHO
KOH
CH2Cl2/H2O
+
flow
photolysis
coil
diaryethene
substrate
phenacene
(isolated by column chromatography)
Scheme 2 Two-step phenacene synthesis by using flow photolysis
were thus obtained in good to moderate chemical yields
with shortened overall experimental time.
One of the most versatile synthetic strategies is photo-
cyclization of diarylethenes followed by oxidative aromati-
zation; the so-called Mallory photocyclization.19 A general
scheme for the reaction is shown in Scheme 1.
We first investigated the Wittig–Mallory sequential
phenacene synthesis targeting 1-methylchrysene (1MeCH)
because methyl-substituted phenacenes serve as building
blocks for constructing larger phenacene frame-
works.15,16,26–29 Details of the experimental setup is illus-
trated in Figure 2. In the Wittig reaction, we chose tetrabu-
tylammonium hydroxide (Bu4NOH) as the base because it
could be used in the homogeneous organic phase and
trapped by a silica gel column incorporated in the flow sys-
tem (see below).
hν
oxidative
aromatization
H
H
stilbene
(diarylethene)
phenenthrene
(phenacene)
Scheme 1 General reaction scheme for the Mallory photocyclization
Conventionally, batch photolysis has been used for syn-
thetic photoreactions. However, the reaction scale is limit-
ed by the size of photolysis vessels, and overreaction form-
ing undesired side products can cause problems. In con-
trast, continuous-flow photolysis can be used to exclude
these drawbacks.20–22 It has been reported that a continu-
ous-flow photolysis technique was successfully adapted to
the Mallory photocyclization for the preparation of
phenanthrene and helicene frameworks.23,24 In our previ-
ous study,15,25 we successfully applied the continuous-flow
photolysis to the Mallory photocyclization starting from di-
arylethenes as the substrates and obtained [n]phenacenes
possessing benzene rings up to n = 8. Therefore, continu-
ous-flow photolysis has great potential for facile phenacene
synthesis.
The diarylethene substrates can be easily prepared by
Wittig reaction between arylaldehydes and (arylmeth-
yl)triphenylphosphonium salts in the presence of a base. In
our previous phenacene synthesis,25 we isolated the sub-
strates by column chromatography and subsequently car-
ried out their Mallory photocyclization and it took several
hours to complete the two-step synthesis (Scheme 2).
In the present study, we planned to more conveniently
synthesize phenacenes by modifying the two-step synthe-
sis. The Wittig diarylethene synthesis and the Mallory pho-
tocyclization were sequentially performed without isola-
tion of the diarylethene substrates by using continuous-
flow reaction techniques. Various [n]phenacenes (n = 4–6)
Figure 2 Schematic diagram of the sequentially performed Wittig re-
action and Mallory photocyclization for phenacene synthesis. The in-
serted picture displays the flow photolysis coil part.
A representative experimental procedure is as follows.
To a 1.1:1 mixture of tolualdehyde and (1-naphthylmeth-
yl)triphenylphosphonium chloride (NpTPCl) in CH2Cl2 was
added Bu4NOH (1.4 equiv) during 12 min and the mixture
was stirred at room temperature for an additional 18 min to
form 1-(1-naphthyl)-2-(o-tolyl)ethene (diarylethene) (Fig-
ure 2, a). The resulting mixture was flowed by pump 1
through a silica gel column (b) in which excess Bu4NOH and
a part of Ph3PO, generated in the Wittig reaction, were
trapped. The resulting solution containing the diarylethene
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H. Okamoto et al.
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Synthesis
was then mixed with a toluene solution of I2 (c) supplied by
pump 2 at the ‘T’-shaped connector (d). The final concen-
tration of I2 was set to 10 mol% of the initial concentration
of NpTPCl. The mixture was photolyzed with a 450 W high-
pressure mercury arc lamp while being flowed through the
photolysis coil (e) made of fluorinated ethylene-propylene
copolymer (FEP). The obtained reaction solution (f) was
concentrated and the residual crude product was washed
with MeOH to afford 1MeCH.
The reaction conditions were optimized by modifying
two parameters; namely, initial concentration of the reac-
tant NpTPCl (substrate concentration), and residence time
(irradiation time) of the flow photolysis. Figure 3 summa-
rizes the results of the product yields as a function of these
two parameters. At the same residence time, the yield of
1MeCH increased with a decrease in substrate concentra-
tion. Lower substrate concentration is, thus, beneficial for
phenacene formation. As for the residence-time dependen-
cy, at a high concentration (26 mM), longer residence time
resulted in higher product yield; 33% and 50% at 3 min and
9 min residence time, respectively. In contrast, at a lower
substrate concentration (6 mM), the product yield reached
a maximum at 6 min residence time (78%) and decreased
after longer irradiation (9 min, 65%).
ene and xylenes in the presence of oxygen.30 It is concluded
that oxidative photodegradation is partly responsible for
the lower yield observed after longer illumination time;
thus, prolonged irradiation should be avoided.
Based on the results, we determined to use the optimal
conditions for the present phenacene synthesis; namely,
6 min residence time and 6 mM substrate concentration.
NpTPCl and (1-phenanthrylmethyl)triphenylphosphonium
bromide (PhenTPBr) were used as the Wittig reactants and
systematic phenacene synthesis was investigated. The re-
sults, together with the product structures and abbrevia-
tions, are summarized in Table 1.
Starting from NpTPCl and either benzaldehyde or 1-
naphthaldehyde, the parent CH and PIC were obtained in
excellent isolated yields, 84% and 86%, respectively (Table 1,
entries 1 and 2). Reactions of PhenTPBr with benzaldehyde
and 1-naphthaldehyde gave PIC (71%) and FUL (74%), re-
spectively (entries 10 and 11). These chemical yields are
comparable to those previously observed for flow photoly-
sis of diarylethenes.25
When o-substituted benzaldehydes were used as sub-
strates, the corresponding 1-substituted chrysenes and 4-
substituted picenes were obtained; thus, the corresponding
methyl, bromo, and cyano derivatives could be prepared in
moderate to high yields (Table 1, entries 3–5 and 12–14).
Furthermore, by using p-substituted benzaldehydes, 3-sub-
stituted chrysenes (entries 7 and 8) and 2-substituted pi-
cenes, respectively, were efficiently prepared (entries 16
and 17).
Nitro derivatives (1NO2CH, 4NO2PIC) were not obtained
by using the present procedure, and complex reaction mix-
tures were formed (Table 1, entries 6 and 15). It has been
noted that 2-nitrostilbene was photolabile and generates
resinous products.31 π-Extension of the phenyl moiety in 2-
nitrostilbene to 1-naphthyl (entry 6) or 1-phenanthryl (en-
try 15) groups was not effective in promoting the desired
Mallory photocyclization.
For the reaction between NpTPCl and m-bromobenzal-
dehyde, two isomeric products, 2BrCH and 4BrCH, are pos-
sible through photocyclization of two conformers; that is,
exo- and endo-A (Scheme 3). Experimentally, 2BrCH (34%)
and unsubstituted CH (34%) were obtained, whereas the
expected product 4BrCH was not detected in the present
sequential synthesis (Table 1, entry 9). Formation of the de-
hydrobrominated product CH was unexpected.
For the reaction between PhenTPBr and m-bromobenz-
aldehyde, dehydrobrominated product PIC was detected
along with expected cyclization products, 1BrPIC and
3BrPIC (Table 1, entry 18); 3BrPIC/1BrPIC/PIC = 30:21:35%.
From the product mixture, 1BrPIC was isolated by ex-
traction with toluene. As PIC and 3BrPIC were not com-
pletely separated from each other by chromatography be-
cause of their low solubility in common solvents, their
yields were determined by the integral ratio of 1H NMR sig-
nals of the product mixture (cf. Table 1, entry 18).
Figure 3 Isolated yields of 1MeCH obtained by the sequential phen-
acene synthesis plotted as a function of residence time and substrate
concentration
We examined the factors decreasing the yield of 1MeCH
upon prolonged irradiation, namely at the low substrate
concentration, with respect to photodegradation of the
photoproduct. A solution of 1MeCH (5 mM in CDCl3) was ir-
radiated under aerated conditions with a small amount of I2
and the photolysate was analyzed by 1H NMR spectroscopy.
Upon 30 min irradiation, 29% of the initial 1MeCH was con-
sumed, while 1-chrysenecarbaldehyde was observed (7%)
as a detectable photoproduct (Figure S1 in the Supporting
Information). Photo-oxidative degradation of methyl-sub-
stituted aromatics has been observed for photolysis of tolu-
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Table 1 Synthesis of Phenacenes by Wittig–Mallory Sequential Reactions in the Flow System
Entry Substrate
Phosphonium salt
Product
Abbreviation Isolated yield
mg (μmol) Arylaldehyde
mg (μmol)
mg (μmol)
%
CH2PPh3Cl
1
CHO
2
1
55 (125)
15 (138)
CH
24 (110)
84
4
3
NpTPCl
CHO
CH2PPh3Cl
CH2PPh3Cl
CH2PPh3Cl
CH2PPh3Cl
CH2PPh3Cl
1
2
4
3
2
3
4
5
6
55 (125)
23 (140)
16 (130)
26 (138)
19 (142)
23 (149)
PIC
30 (110)
24 (97)
34 (110)
20 (79)
86
78
87
63
0
CHO
55 (125)
1MeCH
1BrCH
1CNCH
1NO2CH
Br
CHO
55 (125)
Br
CN
CHO
55 (125)
CN
NO2
CHO
a
55 (125)
–
NO2
CH2PPh3Cl
CH2PPh3Cl
CHO
7
8
55 (125)
26 (142)
19 (141)
3BrCH
33 (110)
85
60
Br
Br
CHO
55 (125)
3MeOCH
19 (75)
13 (42)
MeO
OMe
2BrCH
4BrCH
CH
34
0
Br
CHO
CH2PPh3Cl
9b
55 (125)
26 (137)
–
a
Br
Br
10 (42)
25 (90)
34
CH2PPh3Br
CHO
10
67 (127)
15 (138)
PIC
71
PhenTPBr
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Table 1 (continued)
Entry Substrate
Product
Abbreviation Isolated yield
Phosphonium salt
mg (μmol) Arylaldehyde
mg (μmol)
mg (μmol)
%
CHO
CH2PPh3Br
11
67 (127)
23 (140)
FUL
31 (94)
74
CH2PPh3Br
CH2PPh3Br
CH2PPh3Br
CH2PPh3Br
CHO
CHO
12
13
14
15
67 (127)
67 (127)
67 (127)
67 (127)
16 (130)
26 (138)
19 (142)
22 (148)
4MePIC
4BrPIC
28 (96)
39 (100)
13 (44)
75
87
35
0
Br
Br
CHO
4CNPIC
4NO2PIC
CN
CN
CHO
a
–
NO2
NO2
Br
CH2PPh3Br
CH2PPh3Br
CHO
16
17
67 (127)
67 (127)
26 (142)
19 (141)
2BrPIC
41 (120)
17 (56)
92
44
Br
OMe
CHO
2MeOPIC
3BrPIC
MeO
Br
3BrPIC/
1BrPIC/
PIC
Br
CHO
CH2PPh3Br
18c
67 (127)
25 (137)
36 mgd
35 mge
30:21:35
27:45:5
1BrPIC
PIC
Br
a Not detected.
b The products were separated by preparative chromatography (reversed-phase silica gel, MeOH).
c Product yield was determined by integration of the 1H NMR spectra.
d Weight of the crude product mixture and the product ratio obtained under photolysis conditions at r.t.
e Weight of the crude product mixture and the product ratio obtained under photolysis conditions at 0 °C.
It was found that the product distribution for the se-
quential reaction of m-bromobenzaldehyde with PhenTPBr
was affected by the temperature of the photoreaction step.
When the reaction between PhenTPBr and m-bromobenz-
aldehyde was carried out under the ice-cooled photolysis
conditions, the product yields were 3BrPIC/1BrPIC/PIC =
27:45:5% at 0 °C. Thus, under the low-temperature photoly-
sis conditions, the yield of PIC decreased while that of
1BrPIC increased (cf. Table 1, entry 18). In contrast, for the
reaction of NpTPCl and m-bromobenzaldehyde, when the
sequential synthesis was conducted by cooling the photoly-
sis coil with ice, yields of 2BrCH/CH = 45:34% were compa-
rable to those observed for the reaction performed at r.t. (cf.
Table 1, entry 9). These results suggest that a thermal pro-
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Synthesis
CHO
PPh3X
+
Br
NpTPCl
PhenTPBr
Bu4NOH
Br
H
Br
Br
exo-A
hν
endo-A
E
O2 / – H-O2
or
[H]
hν
I / – HI
1
2
4b
4a
Br
H
3
H H
H H
4
Br
H
Br
B
C
D
two-fold [1,5] H-shift
or
[1,9] H-shift
[O]
[O]
– HBr
Br
Br
2BrCH
3BrPIC
4BrCH
1BrPIC
CH
PIC
Scheme 3 Plausible mechanism for formation of CH and PIC in the sequential reaction of m-bromobenzaldehyde with NpTPCl and PhenTPBr
cess was involved in the dehydrobromination process and
the activation barrier was considered to be higher for the
formation of PIC than that for the formation of CH.
In summary, various phanacenes were prepared
through sequentially performed Wittig reaction and Mallory
photocyclization by using continuous-flow photolysis tech-
niques. Isolation of the diarylethene precursors generated
in the Wittig reaction was not necessary and drastically
shortened total operation time (<1.2 h) was attained for the
present reaction scale. The results indicate that several
hundred milligrams of phenacenes will be obtained by one-
day operation of the flow system. Furthermore, the substi-
tuted phenacenes can be converted into various functional-
ized derivatives through an appropriate functional-group
transformation.32 Therefore, the present synthetic protocol
is expected to promote phenacene-based material sciences
by rapid supply of various samples needed for initial sys-
tematic surveys.
Several pathways of thermally occurring dehydrobromi-
nation are expected: (1) sigmatropic hydrogen shift of H4b
in intermediate C via two-fold [1,5] shift or direct [1,9]
shift33,34 forming D, followed by elimination of HBr,
(2) extraction of H4b in intermediate C mediated by the dis-
solved molecular oxygen or iodine radical subsequent to
hydrogen re-abstraction of radical E, which finally aroma-
tizes to afford the unsubstituted products CH, PIC. It has
been noted that [1,5] H-shift is not important in the 4a,4b-
dihydrophenanthrene system.19 Theoretical calculations
suggest that a [1,9] H-shift from C to D is energetically unfa-
vorable compared with the two-fold [1,5] H-shift (Figure S1
in the Supporting Information). Therefore, we deduce that
the formation of the dehydrobrominated products might be
derived through abstraction of H4a of intermediate C fol-
lowed by hydrogen reabstraction by radical E and the final
elimination of HBr. During the conversion from E into D, a
C(sp3)–H bond of 1,3-cyclohexadiene is produced. By con-
sidering bond-dissociation energy of the C(sp3)–H bond in
1,3-cyclohexadiene (73 kcal mol–1),35 H–I (71 kcal mol–1),36
and H–O2• (47 kcal mol–1),36 the transformation from E into
D is expected to be exothermic. Further experimental and
theoretical investigations to reveal the mechanism of HBr
elimination are under way.
1H and 13C NMR spectra were collected with VARIAN Mercury 300
(300 MHz), VARIAN 400MR (400 MHz) or VARIAN NMR System 600
(600 MHz) spectrometers. IR spectra were measured with a SHIMADZU
IR Prestige-21 spectrophotometer. Elemental analyses were per-
formed with a Perkin–Elmer 2400II at the Micro Elemental Analysis
Laboratory of Okayama University.
The flow reaction apparatus consisted of two ceramic micro-plunger
pumps (Yamazen, MSP-101), a 450 W high-pressure mercury arc
lamp (USHIO, UM-452), and FEP tubing (2 mm i.d. × 10 m) (cf. Figure
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H. Okamoto et al.
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2). A syringe-type disposable silica gel column (Yamazen, W826–02)
was incorporated in the flow system (Figure 2, b) and was replaced
for each run.
3-Bromochrysene (3BrCH)
[CAS Reg. No. 56158-60-2]
Colorless crystals; mp 182–183 °C (Lit.39 182.5–183 °C).
1H NMR (400 MHz, CDCl3): δ = 8.91 (d, J = 1.2 Hz, 1 H), 8.76 (d, J =
8.0 Hz, 1 H), 8.72 (d, J = 9.2 Hz, 1 H), 8.60 (d, J = 9.2 Hz, 1 H), 8.45–7.98
(m, 2 H), 7.95 (d, J = 9.2 Hz, 1 H), 7.85 (d, J = 8.8 Hz, 1 H), 7.76–7.69
(m, 2 H), 7.66 (ddd, J = 8.0, 6.8, 1.2 Hz, 1 H).
Wittig–Mallory Sequential Phenacene Synthesis; Typical Proce-
dure
To a solution of (1-naphthylmethyl)triphenylphosphonium chloride
(55 mg, 125 μmol) and o-tolualdehyde (16 mg, 130 μmol) in CH2Cl2
(10 mL) was added dropwise a solution of Bu4NOH (34 mM in CH2Cl2,
5 mL, 175 μmol) over 12 min. The solution was diluted with CH2Cl2 (5
mL) and stirred at r.t. for 18 min. The resulting Wittig reaction mix-
ture was introduced into the flow reaction apparatus (Figure 2). The
excess Bu4NOH, H2O, and a part of triphenylphosphine oxide in the
reaction mixture were trapped with a silica gel column. The solution
that flowed out from the column was mixed with the same volume of
solution of I2 (16 mg, 64 μmol) in toluene (100 mL) through a ‘T’-
shaped connector and irradiated with a 450 W high-pressure mercu-
ry arc lamp. The residence time in the photoreaction coil was set to
6 min (cf. Figure 2). The finally obtained reaction solution was con-
centrated under reduced pressure and the residual crude product was
washed with MeOH to afford 1MeCH (24 mg, 78 %).
3-Methoxychrysene (3MeOCH)
[CAS Reg. No. 36288-19-4]
Colorless crystals; mp 147–148 °C (Lit.40 145–146 °C).
1H NMR (300 MHz, CDCl3): δ = 8.79 (d, J = 8.1 Hz, 1 H), 8.64 (d, J =
9.3 Hz, 1 H), 8.60 (d, J = 9.0 Hz, 1 H), 8.12 (d, J = 2.4 Hz, 1 H), 8.05–7.94
(m, 3 H), 7.91 (d, J = 8.7 Hz, 1 H), 7.71 (ddd, J = 8.4, 6.9, 1.2 Hz, 1 H),
7.67–7.59 (m, 1 H), 7.30 (dd, J = 8.7, 2.4 Hz, 1 H), 4.07 (s, 3 H).
1-Cyanochrysene (1CNCH)
[CAS Reg. No. 68723-52-4]
Colorless crystals; mp 232–235 °C (Lit.41 228–229 °C).
1H NMR (300 MHz, CDCl3): δ = 9.04 (d, J = 9.0 Hz, 1 H), 8.96 (d, J =
9.3 Hz, 1 H), 8.83 (d, J = 8.1 Hz, 1 H), 8.70 (d, J = 9.3 Hz, 1 H), 8.43 (d,
J = 9.3 Hz, 1 H), 8.09 (d, J = 9.3 Hz, 1 H), 8.05 (dd, J = 7.2, 1.2 Hz, 1 H),
8.04 (dd, J = 7.8, 1.2 Hz, 1 H), 7.82–7.73 (m, 2 H), 7.71 (ddd, J = 7.8, 6.9,
1.2 Hz, 1 H).
In the above protocol, the products were isolated after washing the
crude reaction mixture with MeOH. In some cases, the final products
were isolated by column chromatography (Table 1, entries 9 and 18)
or recrystallization (Table 1, entry 17).
1-Methylchrysene (1MeCH)
Picene (PIC)
[CAS Reg. No. 3351-28-8]
Colorless crystals; mp 252–253 °C (Lit.37 250–253 °C).
[CAS Reg. No. 213-46-7]
Colorless crystals; mp >300 °C (Lit.42 >366–367 °C).
1H NMR (400 MHz, CDCl3): δ = 8.81 (d, J = 8.4 Hz, 1 H), 8.77 (d, J =
9.6 Hz, 1 H), 8.75 (d, J = 9.2 Hz, 1 H), 8.69 (d, J = 8.4 Hz, 1 H), 8.22 (d,
J = 9.6 Hz, 1 H), 8.01 (d, J = 9.2 Hz, 1 H), 8.00 (d, J = 8.0 Hz, 1 H), 7.70
(ddd, J = 8.4, 6.8, 1.2 Hz, 1 H), 7.68–7.57 (m, 2 H), 7.49 (d, J = 7.2 Hz,
2 H), 2.83 (s, 3 H).
1H NMR (300 MHz, CDCl3): δ = 8.97 (s, 2 H), 8.87 (d, J = 8.4 Hz, 2 H),
8.80 (d, J = 9.3 Hz, 2 H), 8.08–7.99 (m, 4 H), 7.75 (ddd, J = 8.4, 6.6,
1.5 Hz, 2 H), 7.67 (ddd, J = 7.8, 6.6, 1.2 Hz, 2 H).
4-Methylpicene (4MePIC)
Chrysene (CH)
[CAS Reg. No. 117868-02-7]
[CAS Reg. No. 218-01-9]
Colorless crystals; mp 259–259.5 °C (Lit.38 256 °C).
1H NMR (300 MHz, CDCl3): δ = 8.80 (d, J = 8.4 Hz, 1 H), 8.74 (d, J =
9.0 Hz, 1 H), 8.02 (d, J = 9.0 Hz, 1 H), 8.00 (dd, J = 8.1, 1.5 Hz, 1 H), 7.72
(ddd, J = 8.4, 6.9, 1.5 Hz, 1 H), 7.64 (m, J = 8.1, 6.9, 1.5 Hz, 1 H).
Colorless crystals; mp >300 °C (Lit.43 >370–372 °C).
1H NMR (400 MHz, CDCl3): δ = 8.98 (d, J = 9.6 Hz, 1 H), 8.95 (d, J =
9.6 Hz, 1 H), 8.87 (d, J = 8.4 Hz, 1 H), 8.83 (d, J = 9.2 Hz, 1 H), 8.81 (d,
J = 8.8 Hz, 1 H), 8.76 (d, J = 8.4 Hz, 1 H), 8.24 (d, J = 9.2 Hz, 1 H), 8.08–
7.99 (m, 2 H), 7.75 (ddd, J = 8.4, 6.8, 1.2 Hz, 1 H), 7.69 (ddd, J = 8.0, 6.8,
1.2 Hz, 1 H), 7.64 (dd, J = 8.4, 7.2 Hz, 1 H), 7.52 (d, J = 7.2 Hz, 1 H), 2.85
(s, 3 H).
1-Bromochrysene (1BrCH)
[CAS Reg. No. 76670-38-7]
Colorless crystals; mp 242–243 °C (Lit.39 240–241 °C).
1H NMR (600 MHz, CDCl3): δ = 8.83 (d, J = 9.3 Hz, 1 H), 8.80 (d, J =
8.4 Hz, 1 H), 8.78 (d, J = 7.8 Hz, 1 H), 8.69 (d, J = 9.0 Hz, 1 H), 8.46 (d,
J = 9.3 Hz, 1 H), 8.04 (d, J = 9.0 Hz, 1 H), 8.01 (d, J = 8.1 Hz, 1 H), 7.93
(d, J = 7.8 Hz, 1 H), 7.75 (ddd, J = 8.4, 7.2, 1.2 Hz, 1 H), 7.70–7.65 (m,
1 H), 7.55 (t, J = 7.8 Hz, 1 H).
4-Bromopicene (4BrPIC)
Colorless crystals; mp >300 °C.
IR (neat): 3047, 1581, 1427, 1273, 1209, 1051, 797, 766, 748, 698 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.99 (d, J = 9.2 Hz, 1 H), 8.93 (d, J =
9.2 Hz, 1 H), 8.90 (d, J = 9.6 Hz, 1 H), 8.87 (d, J = 8.8 Hz, 1 H), 8.86 (d,
J = 8.4 Hz, 1 H), 8.80 (d, J = 9.2 Hz, 1 H), 8.48 (d, J = 9.6 Hz, 1 H), 8.07
(d, J = 9.2 Hz, 1 H), 8.03 (d, J = 8.0 Hz, 1 H), 7.95 (dd, J = 7.6, 1.2 Hz,
1 H), 7.61 (ddd, J = 8.4, 6.8, 1.6 Hz, 1 H), 7.69 (ddd, J = 8.0, 6.8, 1.2 Hz,
1 H), 7.58 (dd, J = 8.4, 7.6 Hz, 1 H).
13C NMR (151 MHz, CDCl2CDCl2, 80 °C): δ = 132.3, 132.2, 130.8, 130.6,
130.5, 129.2, 128.8, 128.7, 128.6, 128.0, 127.2, 127.1, 127.0, 126.0,
123.8, 123.3, 123.2, 123.0, 122.4, 121.7, 121.5, 120.4.
2-Bromochrysene (2BrCH)
[CAS Reg. No. 55120-48-4]
Colorless crystals; mp 265–265.5 °C (Lit.39 261–262 °C).
1H NMR (300 MHz, CDCl3): δ = 8.83–8.69 (m, 2 H), 8.64 (d, J = 9.0 Hz,
1 H), 8.63 (d, J = 9.0 Hz, 1 H), 8.14 (d, J = 2.1 Hz, 1 H), 8.08–7.96 (m,
2 H), 7.91 (d, J = 9.0 Hz, 1 H), 7.77 (dd, J = 9.0, 2.1 Hz, 1 H), 7.73 (d, J =
8.4, 6.9, 1.5 Hz, 1 H), 7.66 (d, J = 8.1, 6.9, 1.2 Hz, 1 H).
Anal. Calcd for C22H13Br: C, 73.96; H, 3.67. Found: C, 73.76; H, 3.55.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–I

H
H. Okamoto et al.
Paper
Synthesis
3-Bromopicene (3BrPIC)
1H NMR (400 MHz, CDCl3): δ = 9.11 (d, J = 8.4 Hz, 1 H), 9.03 (d, J =
9.2 Hz, 1 H), 9.01 (d, J = 9.2 Hz, 1 H), 8.93 (d, J = 9.2 Hz, 1 H), 8.87 (d,
J = 8.0 Hz, 1 H), 8.80 (d, J = 9.2 Hz, 1 H), 8.44 (d, J = 9.2 Hz, 1 H), 8.10
(d, J = 9.2 Hz, 1 H), 8.08–8.00 (m, 2 H), 7.84 (m, 2 H), 7.71 (ddd, J = 8.0,
6.8, 1.2 Hz, 1 H).
13C NMR (151 MHz, CDCl2CDCl2, 80 °C): δ = 132.4, 132.3, 131.8, 130.8,
130.4, 129.4, 129.1, 128.7, 128.6, 128.4, 128.3, 128.2, 127.22, 127.18,
126.0, 124.9, 123.7, 123.2, 123.0, 121.3, 121.2, 118.0, 110.9.
Colorless crystals; mp >300 °C.
IR (neat): 3051, 1429, 1273, 1263, 880, 806, 752 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.97 (d, J = 9.2 Hz, 1 H), 8.92–8.84 (m,
2 H), 8.81 (d, J = 9.2 Hz, 1 H), 8.76 (d, J = 9.2 Hz, 1 H), 8.71 (d, J =
8.8 Hz, 1 H), 8.16 (d, J = 2.0 Hz, 1 H), 8.05 (d, J = 9.2 Hz, 1 H), 8.02 (d,
J = 8.0 Hz, 1 H), 7.94 (d, J = 9.2 Hz, 1 H), 7.81 (dd, J = 8.8, 2.0 Hz, 1 H),
7.78–7.72 (m, 1 H), 7.72–7.63 (m, 1 H).
13C NMR (151 MHz, CDCl2CDCl2, 80 °C): δ = 133.4, 132.1, 130.7, 130.5,
130.0, 129.2, 129.0, 128.74, 128.70, 128.6, 128.5, 127.9, 127.1, 126.9,
126.4, 125.0, 123.2, 123.0, 122.3, 121.5, 121.4, 120.8.
Anal. Calcd for C23H13N: C, 91.06; H, 4.32; N, 4.62. Found: C, 90.66; H,
4.32; N, 4.62.
Fulminene (FUL)
Anal. Calcd for C22H13Br: C, 73.96; H, 3.67. Found: C, 73.73; H, 3.31.
[CAS Reg. No. 217-37-8]
Colorless crystals; mp >300 °C (Lit.44 >300 °C).
2-Bromopicene (2BrPIC)
1H NMR (600 MHz, CDCl2CDCl2, 65 °C): δ = 9.05 (d, J = 9.6 Hz, 1 H),
9.01 (d, J = 9.6 Hz, 1 H), 8.90 (d, J = 7.2 Hz, 1 H), 8.89 (d, J = 9.0 Hz,
1 H), 8.11 (d, J = 9.0 Hz, 1 H), 8.07 (d, J = 7.8 Hz, 1 H), 7.79 (t, J = 7.2 Hz,
1 H), 7.72 (t, J = 7.8 Hz, 1 H).
Colorless crystals; mp >300 °C.
IR (neat): 3047, 1431, 1259, 1078, 827, 798, 754 cm–1
1H NMR (400 MHz, CDCl3): δ = 9.02–8.94 (m, 2 H), 8.88 (d, J = 8.0 Hz,
1 H), 8.86 (d, J = 9.2 Hz, 1 H), 8.81 (d, J = 9.2 Hz, 1 H), 8.77 (d, J =
9.2 Hz, 1 H), 8.05 (d, J = 9.2 Hz, 1 H), 8.02 (d, J = 8.0 Hz, 1 H), 7.99 (d,
J = 8.8 Hz, 1 H), 7.88 (d, J = 8.4 Hz, 1 H), 7.80–7.72 (m, 2 H), 7.68 (ddd,
J = 8.0, 6.8, 1.2 Hz, 1 H).
.
Funding Information
13C NMR (151 MHz, CDCl2CDCl2, 80 °C): δ = 132.2, 132.0, 130.6, 130.5,
130.1, 130.0, 129.20, 129.16, 128.6, 127.9, 127.8, 127.1, 127.00,
126.95, 126.0, 123.3, 122.3, 122.2, 121.54, 121.50, 121.3, 120.4.
Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Sci-
entific Research (KAKENHI JP26288032)
Anal. Calcd for C22H13Br: C, 73.96; H, 3.67. Found: C, 73.65; H, 3.51.
Acknowledgment
1-Bromopicene (1BrPIC)
Financial support from the Okayama Foundation of Science and Tech-
nology (H.O.) and Grant-in-Aid for Scientific Research (KAKENHI
JP26288032) from JSPS (M.Y.) are gratefully acknowledged. H.O. and
M.Y. thank Prof. Fumito Tani (Kyushu University) for support in in-
strumental analyses through the Cooperative Research Program of
the Network Joint Research Center for Materials and Devices. The au-
thors are grateful to the Micro Elemental Analysis Team of Okayama
University for the combustion analysis of novel compounds.
Colorless crystals; mp 238–239 °C.
IR (neat): 3046, 1429, 1421, 1266, 823, 813, 794, 745 cm–1
1H NMR (300 MHz, CDCl3): δ = 10.13 (d, J = 9.6 Hz, 1 H), 8.96–8.84 (m,
2 H), 8.82 (d, J = 9.0 Hz, 1 H), 8.76 (d, J = 9.3 Hz, 1 H), 8.07 (d, J =
9.3 Hz, 1 H), 8.07 (dd, J = 7.5, 1.2 Hz, 1 H), 8.03 (d, J = 9.3 Hz, 1 H), 8.02
(dd, J = 7.8, 1.2 Hz, 1 H), 7.99–7.92 (m, 2 H), 7.76 (ddd, J = 8.4, 6.9,
1.5 Hz, 1 H), 7.68 (ddd, J = 7.8, 6.9, 1.2 Hz, 1 H), 7.45 (t, J = 7.8 Hz, 1 H).
.
13C NMR (151 MHz, CDCl3): δ = 135.0, 132.3, 130.59, 130.57, 129.4,
129.1, 128.8, 128.7, 128.6, 128.4, 127.8, 127.6, 127.06, 127.03, 126.8,
125.5, 123.6, 122.98, 122.97, 121.9, 119.9, 119.8.
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0036-1588775.
Anal. Calcd for C22H13Br: C, 73.96; H, 3.67. Found: C, 74.06; H, 3.58.
S
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2-Methoxypicene (2MeOPIC)
Colorless crystals; mp 275–276 °C.
IR (neat): 2994, 1610, 1431, 1221, 1034, 826, 799, 752, 525 cm–1
References
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–I