804
A. L. POLISHCHUK ET AL.
a solution of 1-lithiobiphenylene prepared as described
above. A slight exotherm was generated upon addition.
The resulting dark-red solution was stirred at room
temperature under an argon atmosphere, exposed to light,
for 2 h. The solution was then transferred to a 125 ml
separating funnel, the reaction flask was rinsed with
diethyl ether (20 ml) and the rinse was added to the
product mixture. The resulting solution was washed
with saturated NaHSO3 (2 ꢂ 30 ml) and deionized water
(2 ꢂ 30 ml). The red–orange organic layer was dried over
anhydrous MgSO4, filtered and concentrated to yield ca
3 ml of a dark-red oil, which by GC–MS contained 1-
iodobiphenylene (parent ion mass 287) as the major
product, with unreacted starting material and several
other impurities as minor constituents. This material
was chromatographed through a 60 ꢂ 3.5 cm diameter
silica gel column using hexanes as eluent. The product
appeared as the third overall band (colorless), immedi-
ately following a yellow–green band that gradually
turned purple after isolation. Only fractions that were
pure by TLC were combined and concentrated into solid
1-iodobiphenylene (0.23 g, 26% yield). The product was
bands and washing with acetone yielded 1-phenylbiphe-
nylene (0.123 g, ꢃ100% yield) as a pale-yellow, low-
melting oil (lit.17 m.p. 46.5 ꢀC). The product was ana-
1
lyzed by GC–MS, H,1H COSY and 13C NMR spectro-
scopy and high-resolution mass spectrometry. GC–MS
1
shows a single peak with a parent ion mass of 228. H
NMR (CDCl3), ꢂ: 6.62 (dd, J ¼ 6.8, 0.7 Hz, 1H), 6.68 (m,
1H), 6.77 (m, 3H), 6.86 (dd, J ¼ 8.5, 6.8 Hz, 1H), 7.01
(dd, J ¼ 8.5, 0.7 Hz, 1H), 7.35 (dd, J ¼ 7.4, 7.4 Hz, 1H),
7.46 (dd, J ¼ 7.4, 7.2 Hz, 2H), 7.60 (dd, J ¼ 8.4, 1.3 Hz,
2H). 13C NMR (CDCl3), ꢂ: 116.12, 117.30, 117.80,
126.42, 126.95, 127.69, 128.20, 128.43, 128.78, 129.26.
MS (ESI), calculated for C18H12: 228.09390. Found:
228.09472.
Preparation of 2-bromobiphenylene.29 2-Bromobipheny-
lene was synthesized according to the method of Baker
et al.29 Biphenylene (250 mg, 1.6 mmol) was added to a
100 ml round-bottomed flask. A solution of bromine
(0.5 ml, 9.8 mmol) in carbon tetrachloride (25 ml) was
prepared and 4.5 ml of this solution were added to the
flask containing biphenylene. The resulting blood-red
mixture was placed under an argon atmosphere and two
drops of pyridine were added while the mixture was
stirred at room temperature. A cloud of yellow–orange
vapor was generated immediately upon pyridine addition.
The mixture was stirred at room temperature for 10 min.
Next, an additional 2.5 ml of the bromine–CCl4 solution
was added, the reaction flask was immersed in a 90 ꢀC oil
bath and stirring under argon at the elevated temperature
was continued for an additional 15 min, after which
almost all solvent had evaporated through the gas outflow.
The remaining yellow–red residue was dissolved in 30 ml
of CCl4 and washed with saturated NaHCO3 solution
(1 ꢂ 30 ml), followed by 5% NaHCO3 solution
(1 ꢂ 30 ml). The pale-yellow organic layer was dried
over anhydrous MgSO4 and removal of solvent yielded
0.71 g of pale-yellow crude product. This material was
spotted on to two 20 ꢂ 20 cm, 1000 mm thick silica gel
plates, which were eluted with hexanes. Following devel-
opment, the top bands were cut out from each plate,
washed with acetone and concentrated to yield 2-bromo-
biphenylene as a white–yellow solid (70 mg), slightly
contaminated with starting material by NMR but appear-
1
characterized by GC–MS and H NMR spectroscopy.
GC–MS analysis shows a single peak with parent ion
1
mass of 287. H NMR (CDCl3), ꢂ: 6.47 (dddd, J ¼ 8.2,
6.8, 0.6, 0.6 Hz, 1H), 6.59 (dd, J ¼ 6.8, 0.6 Hz, 1H), 6.67
(br ddd, J ¼ 6.7, 3.5, 0.6 Hz, 1H), 6.82 (m, 3H), 6.96 (dd,
J ¼ 8.6, 0.6 Hz, 1H).
Preparation of 1-phenylbiphenylene (21).17 The coupling
of 1-iodobiphenylene with phenylboronic acid as de-
scribed below was performed according to Miyaura
et al.25 To a 100 ml two-necked round-bottomed flask
fitted with a condenser were added phenylboronic acid
(77 mg, 0.68 mmol), sodium carbonate monohydrate
(156 mg, 1.3 mmol), tetrakis(triphenylphosphine)palla-
dium (37 mg, 0.032 mmol), and 1-iodobiphenylene
(151 mg, 0.52 mmol). This mixture of solids was imme-
diately dissolved in toluene (25 ml) and absolute ethyl
alcohol (2.5 ml). The bright-yellow suspension was
warmed to 80 ꢀC over 2 h while stirring under an argon
atmosphere. Once the warm-up was complete, deionized
water (2.3 ml) was added to the yellow–orange suspen-
sion and the mixture was stirred under an argon atmo-
sphere for 10 h, at which point the hot reaction mixture
was quenched with 50 ml of cold deionized water. No
significant change in color was observed over the course
of the reaction. The resulting mixture was stirred until
cool and extracted into diethyl ether (60 ml). The organic
layer was washed with 5% sodium bicarbonate solution
(1 ꢂ 70 ml) and saturated NaCl solution (2 ꢂ 70 ml).
Drying over anhydrous MgSO4 and removal of solvent
yielded 0.173 g of crude product. This material was
separated into two equal fractions and each was purified
by preparative TLC on a 20 ꢂ 20 cm, 1000 mm thick silica
gel plate. Elution with hexane, isolation of the middle
band (yellow, dark under UV light) from a total of five
1
ing clean by GC–MS. H NMR (CDCl3), ꢂ: 6.50 (d,
J ¼ 7.3 Hz, 1H), 6.66 (m, 2H), 6.77 (t, J ¼ 0.8 Hz, 1H),
6.78 (m, 2H), 6.91 (dd, J ¼ 7.3, 1.5 Hz, 1H).
Preparation of 2-phenylbiphenylene (22).17 The coupling
of 2-bromobiphenylene with phenylboronic acid was
performed according to Miyaura et al.25 To a 100 ml
two-necked round-bottomed flask fitted with a condenser
were added 2-bromobiphenylene as obtained in the pre-
vious synthesis (49 mg, 0.21 mmol), phenylboronic acid
(31 mg, 0.25 mmol), sodium carbonate monohydrate
(63 mg, 0.51 mmol) and tetrakis(triphenylphosphine)pal-
ladium (18 mg, 0.016 mmol). This mixture of solids was
Copyright # 2004 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2004; 17: 798–806