Mukherjee et al.
JOCNote
0.56 g, 1.79 mmol) was added PtCl (0.023 mg, 0.089 mmol) in
(
2
argon, and the mixture was heated at 80 °C for 10 h. To this
solution was added water, and the organic layer was extracted with
diethyl ether. The extract was dried over MgSO4 and eluted
through a silica column to give 4-bromo-2-tert-butylphenanthrene
(
6) as a colorless oil (0.373 g, 1.19 mmol, 67%).
Synthesis of (2-tert-Butyl-4-ethynylphenanthrene) (7). To a
solution of CuI (0.006 g, 10 mol %) in Et N (6 mL) and piper-
3
idine (2 mL) was added 4-bromo-2-tert-butylphenanthrene
(
0.10 g, 0.32 mmol) and the mixture was degassed with nitrogen
for 15 min at 23 °C. To this resulting solution was added Pd-
PPh ) (0.025 g, 5 mol %), and the mixture was stirred for 15 min
(
3
4
before being treated with ethynyltrimethylsilane (0.053 mL,
0
.38 mmol) dropwise. The solution was heated at 80 °C for 10 h,
and then filtered through a Celite bed, concentrated, and eluted
through a silica column to give the crude coupling silyl pro-
2 2
duct (0.058 g, 0.21 mmol) in 66% yield. To a CH Cl /MeOH
solution (1/1, 20 mL) of this silyl species (0.058 g, 0.21 mmol)
was added K CO (0.043 g,0.317 mmol), and the mixture was
2
3
stirred at 23 °C for 2.5 h. The solution was filtered through a Celite
bed and purified through a silica column to obtain the desired 2-
tert-butyl-4-ethynylphenanthrene (7) (0.040 g, 0.158 mmol) in
76% yield.
Synthesis of 1,2-Bis(7-tert-butylphenanthren-4-yl)ethyne (8).
To a Et
0.0087gm, 10 mol %) was added compound 6 (0.144 g, 0.4614
mmol), and the mixture was degassed with nitrogen for 15 min at
3
N (6 mL) and piperidine (3 mL) solution of CuI
(
2
5
3 °C. To this resulting solution was added Pd(PPh
3 4
) (0.036 g,
mol %), and the mixture was stirred for 15 min before addi-
FIGURE 2. UV and PL spectra of tetrabenzo[de,hi,mn,qr]
naphthacenes 11, 14a, 14d, and 14e in CH Cl .
2 2
tion of compound 7 (0.143 g, 0.554 mmol). The solution was
heated at 80 °C for 10 h, filtered through a Celite bed, concen-
trated, and eluted through a silica column to give 1,2-bis(7-tert-
butylphenanthren-4-yl)ethyne (8) (0.14 g, 0.28 mmol) in 60%
yield.
In summary, we have developed a convenient new synth-
esis of tetrabenzo[de,hi,mn,qr]naphthacenes using readily
available 1,2-di(phenanthren-4-yl)ethynes through Bronsted
e
acid-mediated aromatization and FeCl oxidative coupling.
0
Synthesis of [5,5 -(1-Chloro-2-iodoethene-1,2-diyl)bis(2-tert-
butylphenanthrene)] (9). To a CH Cl solution (30 mL) of
3
2
2
Large substituents are more suitable for this approach
because of a decrease in undesired oligomerization. On the
basis of their photophysical properties, tetrabenzo[de,hi,mn,
qr]naphthacenes show an extensive π-conjugation, resulting
in a raise of the HOMO energy levels and a decrease of the
HOMO-LUMO energy gaps, compared to those of unsub-
stituted dibenzochrysene 1.
compound 8 (150 mg, 0.31 mmol) was added ICl (1.0 M in
CH Cl , 0.30 mL) at -78 °C, and the mixture was stirred at
2
2
-40 °C for 0.5 h before being quenched with sodium thiosul-
2 2
fate solution. The organic layer was extracted with CH Cl ,
dried over MgSO , and purified by column chromatography to
4
give compound 9 as white solid (123 mg, 0.19 mmol) in 62%
yield.
Synthesis of [(2-tert-Butyl-5-(2-tert-butylphenanthren-4-yl)-
pyrene] (10). To a CH Cl solution (140 mL) of compound 8
2
2
Experimental Section
(
0.50 g, 1.02 mmol) was added CF
0 °C, and the mixture was stirred for 10 min at 23 °C, giving a
dark violet solution. To this solution was added CF SO H
3
3 2
CO H (7.6 mL, 101 mmol) at
0
Synthesis of (2-Bromo-4-tert-butyl-2 -ethynylbiphenyl) (5). To
a solution of Na CO (5.95 g, 56.64 mmol) in toluene (45 mL),
2
3
3
ethanol (15 mL), and water (15 mL) was added 2-bromo-4-tert-
butyl-1-iodobenzene (3.19 g, 9.44 mmol) at room temperature,
and the solution was degassed with nitrogen. To this mixture
was added 2-[(trimethylsilyl)ethynyl]phenylboronic acid (2.26 g,
(0.152 mg, 1.02 mmol) dropwise; the resulting black colored
solution was stirred at 23 °C for 30 min before it was washed
3
with water and NaHCO solution. The organic layer was
separated, and the aqueous layer was extracted with CH
dried over MgSO , and purified by a silica column to give
compound 9 (0.34 g, 0.69 mmol) in 68% yield.
Cl ,
2
2
1
0.4 mmol) and Pd(PPh
3
)
4
(0.73 g, 5 mol %), and the result-
4
ing mixture was heated to 80 °C for 10 h. After completion of
the reaction, the solution was cooled to room temperature
and washed with water, and the organic layer was separated.
The aqueous layer was extracted with ethyl acetate, washed
Synthesis of (2,10-di-tert-butyltetrabenzo[de,hi,mn,qr]tetra-
cene) (11). Compound 10 (0.10 g, 0.204 mmol) was dissolved
in dry CH
for 20 min. To this solution was added dry CH
5.0 M, 1.01 mmol) and FeCl
quenched by adding methanol (50 mL) after 30 min. The solvent
was removed under reduced pressure and purified by a silica
column (46 mg, 47%). Compound 11 was obtained as a pale
2
Cl
2
(70 mL), and the solution was bubbled with argon
NO (0.20 mL,
dropwise at 23 °C; the reaction was
with brine solution, dried over MgSO , and concentrated. The
4
3
2
residues were eluted through a silica column to give the desired
0
3
0
[
(2 -bromo-4 -tert-butylbiphenyl-2-yl)ethynyl]trimethylsilane
(
0.54 g, 1.4 mmol) in 61% yield. To a solution of this silyl species
0.54 g, 1.4 mmol) in CH Cl (10 mL) and MeOH (10 mL) was
added K CO (0.29 g, 3.89 mmol), and the resulting mixture was
(
2
2
green crystalline solid after recrystallization from CH
MeOH (1:2).
Spectral data for 2,10-Di-tert-Butyltetrabenzo [de,hi,mn,qr]-
Cl -
2 2
2
3
stirred at room temperature for 2 h. The reaction mixture was
filtered through a Celite bed and purified on a silica column to
afford compound 5 (0.56 g, 1.79 mmol) in 69% yield.
-1
tetracene (11). Pale green solid; IR (neat, cm ) 3054 (m), 2918
(m), 1730 (w), 1365 (s), 1539 (s), 1130 (m), 862 (s), 769 (vs), 871
Synthesis of 4-Bromo-2-tert-butylphenanthrene (6). To a dichlor-
0
1
(s), 691 (vs), 545 (m); H NMR (600 MHz, CDCl
oethane (10 mL) solution of 2-bromo-4-tert-butyl-2 -ethynylbiphenyl
3
) δ 9.31
J. Org. Chem. Vol. 74, No. 16, 2009 6313