Corannulene. A Three-Step Synthesis
J. Am. Chem. Soc., Vol. 119, No. 45, 1997 10967
Proton and carbon NMR chemical shifts are reported in ppm downfield
from tetramethylsilane with chloroform as the reference standard, unless
otherwise specified. Preparative thin layer chromatographies were
performed on 20 × 20 cm Analtech Uniplate Taper plates, Silica Gel
GF. For column chromatographies, Silica Gel 60-200 mesh and
aluminum oxide (activated, neutral, Brockmann I, ca. 150 mesh) were
used. High-resolution mass spectrometry (HRMS) was performed by
the Midwest Center for Mass Spectrometry at the University of
Nebraska-Lincoln and by the Mass Spectrometry Laboratory, School
of Chemical Sciences, University of Illinois.
(dd, 2H, J ) 8.1 and 6.9 Hz), 7.47 (s, 2H). 13C NMR (100 MHz,
CDCl3): δ 137.0, 136.0, 135.9, 132.7, 132.1, 130.1, 128.5, 127.9, 127.7,
123.7, 94.0. MS (EI, 70 eV) m/z (rel abundance) 574 (2), 572 (8),
570 (13), 568 (9), 566 (2), 492 (6), 490 (17), 488 (18), 486 (7), 412
(10), 410 (18), 408 (11), 330 (21), 328 (23), 250 (100), 249 (47), 248
(59). HRMS Calcd for C20H10Br4: 565.7518. Found: 565.7517.
7,10-Diethynylfluoranthene (3). To a mixture of diisopropylamine
(1.44 g, 14.4 mmol) in 20 mL of dry THF under nitrogen at -78 °C
was added n-BuLi in hexane (2.5 M, 5.6 mL, 14 mmol). After 15
min, a solution of tetrabromide 8 (2.00 g, 3.50 mmol) in 10 mL of
THF was added, and the reaction mixture was stirred at -78 °C for 5
h. The resulting mixture was poured into 50 mL of water, the aqueous
solution was extracted with 3 × 50 mL of ether, the combined organic
layers were washed with 30 mL of 5% aqueous hydrochloric acid and
30 mL of 10% aqueous sodium bicarbonate and dried over magnesium
sulfate, and the solvent was removed under reduced pressure. The crude
product was purified by column chromatography on silica gel with use
of 9:1 hexane/ethyl acetate as eluant to give 719 mg (80%) of 3 as
pale yellow crystals: mp 143.0-145.0 °C. 1H NMR (400 MHz,
CDCl3): δ 8.62 (d, 2H, J ) 6.9 Hz), 7.94 (d, 2H, J ) 9.0 Hz), 7.71
(dd, 2H, J ) 9.0 and 6.9 Hz), 7.47 (s, 2H), 3.63 (s, 2H). 13C NMR
(100 MHz, CDCl3): δ 140.2, 135.0, 132.6, 131.6, 129.8, 128.2, 127.6,
123.9, 117.2, 83.4, 82.4. MS (EI, 70 eV) m/z (rel abundance): 251
(22), 250 (100, M+), 249 (22), 248 (30), 125 (8), 124 (10). HRMS
Calcd for C20H10: 250.0782. Found: 250.0781.
Dimethyl Fluoranthene-7,10-dicarboxylate (5). A mixture of
acenaphthenequinone (5.00 g, 24.7 mmol), dimethyl 1,3-acetone
dicarboxylate (9.0 mL, 65 mmol), and glycine (4.5 g, 60 mmol) in 75
mL of 2,5-norbornadiene was stirred at reflux for 3.5 days. The reaction
flask was equipped with a modified Hickman still reflux condenser
(or a Dean-Stark trap) to remove the water generated from the reaction.
Excess solvent was removed at the end of the reaction either by simple
distillation or by evaporation under reduced pressure to give a brown
solid which was chromatographed on silica gel with 2:2:1 benzene/
hexane/ethyl acetate as eluant. The product was further purified by
crystallization from methanol to give 7.51 g (86%) of light brown to
pale peach colored solid: mp 144-145 °C, lit.6a mp 147-148 °C.
7,10-Bis(hydroxymethyl)fluoranthene (6). A solution of diester
5 (1.00 g, 3.2 mmol) in 30 mL of dry THF was added dropwise with
stirring to a solution of lithium aluminum hydride (1.21 g, 32 mmol)
in 30 mL of dry THF at 0 °C. The reaction mixture was stirred at
room temperature for 6 h and then hydrolyzed with 15 mL of water,
15 mL of 10% aqueous sodium hydroxide, and 15 mL of water. The
mixture was subsequently extracted with 3 × 50 mL of 1:1 ether/THF.
Note: Diol 6 is not sufficiently soluble in pure ether to be efficiently
extracted with ether alone. The combined organic layers were washed
with 50 mL of water, then dried over magnesium sulfate. Removal of
the solvents under reduced pressure gave a brown oil that was purified
by column chromatography on silica gel with 6:4 ethyl acetate/hexane
as eluant. The material thus isolated was crystallized from anhydrous
ether to give 800 mg (95%) of white crystals: mp 213-215 °C, lit.6a
mp 217-220 °C. 13C NMR (100 MHz, DMSO-d6): δ 133.7, 132.3,
131.8, 127.8, 125.6, 124.5, 122.9, 122.6, 120.6, 57.8 (not previously
reported).
7,10-Diformylfluoranthene (7). A mixture of diol 6 (800 mg, 3.0
mmol) and pyridinium chlorochromate (2.15 g, 10 mmol) in 15 mL of
dry THF was stirred at room temperature for 5 h. The resulting brown
solution was then diluted with 50 mL of ether to give a brown
precipitate. The organic layer was separated, and the brown residue
was washed with 2 × 30 mL of ether. The combined ethereal solutions
were filtered through a short pad of florisil to give a light yellow
solution, which was concentrated under reduced pressure to give 530
mg (70%) of 7 as yellow crystals: mp 195 °C dec. 1H NMR (400
MHz, CDCl3): δ 10.75 (s, 2H), 8.75 (d, 2H, J ) 7.2 Hz), 8.02 (d, 2H,
J ) 8.1 Hz), 7.99 (s, 2H), 7.74 (dd, 2H, J ) 8.1 and 7.2 Hz). 13C
NMR (100 MHz, CDCl3): δ 191.6, 140.9, 136.0, 134.0, 133.0, 132.0,
130.1, 129.5, 128.5, 127.7. IR (KBr): 1722 cm-1 (CdO). MS (EI,
70 eV) m/z (rel abundance) 258 (74, M+), 230 (21), 229 (34), 202
(100), 201 (70), 200 (84), 100 (53). HRMS Calcd for C18H10O2:
258.0680. Found: 258.0688.
7,10-Diacetylfluoranthene (17). A 1000-mL round-bottomed flask,
equipped with a magnetic stirrer and a modified Hickman still reflux
condenser to remove the water generated from the reaction, was charged
with acenaphthenequinone (20.0 g, 0.11 mol), glycine (8.24 g, 0.11
mol), and 100 mL of toluene. This reaction mixture was heated with
stirring over a period of 20 min to a temperature of approximately 100
°C, at which point 2,4,6-heptanetrione27 (15.60 g, 0.11 mol) was added
all at once. After another 30 min at 100 °C, 2,5-norbornadiene (250
mL) was introduced to the flask, and the solution was brought to reflux
in a 120 °C oil bath. After 24 h, a second equivalent of 2,4,6-
heptanetrione (15.60 g, 0.11 mol) was added. This brown solution
was maintained at reflux with stirring for a total of 72 h. At the end
of this period, the mixture was cooled, then diluted with 200 mL of
methylene chloride and washed 3 × 300 mL of water and 3 × 300 mL
of saturated sodium chloride solution. The combined organic layers
were dried over magnesium sulfate, filtered, and concentrated on the
rotory evaporator. The crude solid was digested in 100 mL of acetone
and put in the freezer overnight. Filtration gave relatively pure 17 as
a yellow solid. More 17 was obtained from the acetone solution by
chromatography on silica gel with use of 1:1 hexane/ethyl acetate as
eluant to give a combined yield of 22.70 g (72%): mp 193-194 °C.
1H NMR (400 MHz, CDCl3): δ 8.34 (d, J ) 7.2 Hz, 2H), 7.93 (d, J
) 8.1 Hz, 2H), 7.64 (dd, J ) 8.0, 7.2 Hz, 2H), 7.59 (s, 2H), 2.77 (s,
6H). 13C NMR (100 MHz, CDCl3): δ 202.83, 138.75, 138.31, 134.38,
133.67, 130.46, 129.15, 128.52, 126.82, 126.30, 30.81. IR (neat): 3059
(w), 3002 (w), 1688 (s), 1428 (s), 1360 (m), 781 (s) cm-1. MS (EI, 70
eV) m/z (rel abundance): 286 (62, M+), 271 (100), 243 (26), 228 (10).
HRMS: Calcd for C20H14O2: 286.0994. Found: 286.1001.
7,10-Bis(1-chlorovinyl)fluoranthene (18). To a solution of 7,10-
diacetylfluoranthene (10.0 g, 0.034 mol) in 150 mL of toluene at 90-
100 °C under a nitrogen atmosphere was added phosphorus pentachlo-
ride (18.9 g, 0.090 mol) in small portions with stirring. Stirring was
maintained at the same temperature for 7 h; then the reaction mixture
was chilled and hydrolyzed by careful addition of crushed ice (3.0 g).
The cold toluene layer was quickly washed with 2 × 150 mL of water,
dried immediately over magnesium sulfate, and concentrated to dryness
under vacuum. The residue was chromatographed on silica gel with
use of 5:1 hexane/benzene as eluant to afford 9.40 g (83%) of 18 as
light yellow crystals: mp 137-138 °C. 1H NMR (400 MHz, CDCl3):
δ 8.32 (d, J ) 7.2 Hz, 2H), 7.89 (d, J ) 8.1 Hz, 2H), 7.64 (dd, J )
8.1, 7.2 Hz, 2H), 7.30 (s, 2H), 5.88 (d, J ) 1.4 Hz, 2H), 5.72 (d, J )
1.4 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 138.81, 137.20, 136.08,
135.23, 133.28, 130.56, 128.74, 128.59, 128.25, 125.04, 117.94. IR
(neat): 3100 (w), 3052 (m), 1628 (s), 1427 (s), 1345 (m), 891 (s), 827
(s) cm-1. MS (EI, 70 eV) m/z (rel abundance): 326 (3, M++4), 324
(20, M++2), 322 (31, M+), 289 (13), 287 (40), 252 (40), 251 (100),
7,10-Bis(2,2-dibromovinyl)fluoranthene (8). A mixture of zinc
powder (2.08 g, 31.8 mmol), triphenylphosphine (8.24 g, 31.5 mmol),
and carbon tetrabromide (8.80 g, 27.5 mmol) in 150 mL of methylene
chloride was stirred under nitrogen for 36 h, during which time a pink
color developed.21 A solution of dialdehyde 7 (2.08 g, 8.06 mmol) in
methylene chloride was then added, and the reaction mixture was stirred
at room temperature for 8 h. The reaction mixture was poured into
100 mL of hexane to give a milky solution with a brown residue. The
organic layer was separated, and the brown residue was dissolved in
25 mL of methylene chloride. The methylene chloride solution was
poured into another 100 mL of fresh hexane to give another milky
solution with a brown residue. The organic layer was again separated
and combined with the first one and filtered through a short pad of
florisil to give a clear solution. Removal of the solvent gave pale
crystals which were recrystallized from methanol to give 2.77 g (60%)
of white crystals: mp 188-190 °C. 1H NMR (400 MHz, CDCl3): δ
7.95 (s, 2H), 7.95 (d, 2H, J ) 6.9 Hz), 7.91 (d, 2H, J ) 8.1 Hz), 7.69