The Journal of Organic Chemistry
ARTICLE
studies. Reactions that require anhydrous conditions were carried out under
nitrogen in oven-dried glassware. Tetrahydrofuran was distilled from
sodium/benzophenone. Melting points were determined with a capillary
degassed and purged with N2 for 15 min. The mixture was refluxed
overnight. After completion of the reaction (TLC), the flask was allowed
to cool to room temperature. The mixture was extracted with CH2Cl2,
and the organic layer was washed with brine, dried over MgSO4, and
filtered. The filtrate was evaporated to dryness under reduced pressure.
Flash chromatography over silica gel (97:3 hexane/ethyl acetate)
provided the coupled product 7 in 40% yield: mp >250 °C; 1H NMR
δ (300 MHz, CDCl3) 0.12 (s, 12H), 0.22 (s, 12H), 0.96 (s, 18H), 1.00
(s, 18H), 6.66-6.74 (m, 4H), 6.79 (s, 2H), 7.69-7.72 (m, 2H), 8.04 (s,
2H), 8.11-8.14 (m, 2H), 8.94 (s, 2H) 8.95 (s, 2H); 13C NMR δ (75.45
MHz, CDCl3) -4.1, -4.0, 18.4, 18.5, 25.91, 25.94, 120.6, 122.4, 122.9,
129.4, 129.5, 129.7, 130.1, 130.6, 130.7, 131.2, 133.8, 134.3, 135.2, 142.8,
146.5, 146.6, 182.9; MS (MALDI) m/z 981. Anal. Calcd for C58H78O6Si4:
C, 70.83; H, 7.99. Found: C, 70.80; H, 7.90.
Hexaquinone (8). Toa stirred solution of 7(155mg, 0.16 mmol) in
dry THF (2 mL) was added a solution of 1 M tetrabutylammonium
fluoride (TBAF) (206 mg, 0.79 mmol) under nitrogen atmosphere. The
mixture was stirred at room temperature for 2 h. After completion of the
reaction (TLC), dry pyridine (196 μL, 2.44 mmol) and trifluorometha-
nesulfonic anhydride (257 μL, 1.53 mmol) were slowly added to the
reaction mixture in situ at -20 °C. The flask was allowed to warm to room
temperature, and the mixture was stirred overnight. The reaction was
quenched by adding 2 N HCl solution. The aqueous layer was extracted
with tetrahydrofuran (THF). The organic layer was separated, dried over
MgSO4, and filtered. The filtrate was evaporated under reduced pressure to
get the crude which was purified by recrystallization from methanol and
dichloromethane to give the product in 45% yield: mp >250 °C; 1H NMR
δ (300 MHz, DMSO-d6) 7.52 (s, 2H), 7.64 (s, 2H), 8.65 (s,2H), 8.90 (s,
2H), 9.10 (s, 2H), 9.41 (s, 2H), 9.84 (s, 2H); 13C NMR (75.45 MHz,
DMSO-d6) 60, 95.4, 98.5, 101.8, 108.0, 110.0, 120.9, 123.2, 123.9, 128.7,
129.4, 129.9, 130.5, 131.4, 134.2, 145.6, 147.6, 168, 181.4; ESI MS m/z
1051. Anal. Calcd for C38H16F12O14S4: C, 43.35; H, 1.53. Found: C, 43.30;
H, 1.45.
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melting point apparatus and are uncorrected. H and 13C NMR spectra
were recorded on a 300 MHz spectrophotometer using CDCl3 as solvent
and TMS as internal standards. Data are reported as follows: chemical shifts
in ppm (δ), multiplicity (s = singlet, d = doublet, br = broad singlet, m =
multiplet), coupling constants (Hz), integration, and interpretation. Silica
gel 60 (60-120 mesh) was used for column chromatography.
2,3,9,10-Tetrakis(1,2-di-tert-butyldimethylsiloxyphenyl)-
6,13-pentacenequinone (3). To a mixture of 1 (270 mg, 0.43 mmol)
and tetrakis(triphenylphosphine)palladium(0) in toluene (20 mL) was
added a suspension of 2 (1 g, 2.15 mmol) in ethanol (5.2 mL) and 2 M
aqueous solution of K2CO3 (475 mg, 3.44 mmol). The mixture was
degassed and purged with N2 for 15 min. The mixture was refluxed
overnight. After completion of the reaction (TLC), the flask was allowedto
cool to room temperature. The mixture was extracted with CH2Cl2, and
the organic layer was washed with brine, dried over MgSO4, and filtered.
The filtrate was evaporated to dryness under reduced pressure. Flash
chromatography over silica gel (90:10 hexane/ethyl acetate) provided the
coupled product 3 in 40% yield: mp 165-170 °C; 1H NMR δ 0.13 (s,
24H), 0.22 (s, 24H), 0.96 (s, 36H), 1.00 (s, 36H), 6.69-6.74 (m, 8H),
6.79 (s, 4H), 8.06 (s, 4H), 8.95 (s, 4H); 13C NMR δ (75.45 MHz, CDCl3)
-4.1, -4.0, 18.4, 18.5, 25.9, 120.5, 122.4, 122.9, 129.5, 130.7, 131.2, 133.8,
134.3, 142.8, 146.5, 146.6; MS (FAB) m/z 1655. Anal. Calcd for
C94H142O10Si8: C, 68.14; H, 8.64. Found: C, 68.12; H, 8.55.
Heptaquinone (4). To a stirred solution of 3 (150 mg, 0.09
mmol) in dry THF (2 mL) was added a solution of 1 M tetrabutylam-
monium fluoride (TBAF) (237 mg, 0.90 mmol) under nitrogen atmo-
sphere which was accompanied by an immediate color change to dark
violet. The mixture was stirred at room temperature for 2 h. After
completion of the reaction (TLC), dry pyridine (231 μL, 2.88 mmol)
and trifluoromethanesulfonic anhydride (304 μL, 1.81 mmol) was
slowly added to the reaction mixture in situ at -20 °C. The flask was
allowed to warm to room temperature, and the mixture was stirred
overnight. The reaction was quenched by adding 2 N HCl solution. The
aqueous layer was extracted with tetrahydrofuran (THF). The organic
layer was separated, dried over MgSO4, and evaporated under reduced
pressure to obtain a solid residue, which was purified by recrystallization
from methanol and dichloromethane to give the pure product in 50%
yield: mp >250 °C; 1H NMR δ (300 MHz, DMSO-d6) 7.63 (s, 4H), 8.20
(s, 4H), 9.08 (s, 4H), 9.28 (s, 4H); 13C NMR (75.45 MHz, DMSO-d6)
25.5, 57.7, 67.4, 108.6, 110.7, 121.5, 123.9, 124.4, 129.8, 131.1, 132.2,
146.2, 148.2, 182.2; MS (MALDI) m/z 1790. Anal. Calcd for
C54H18F24O26S8: C, 36.13; H, 1.01. Found: C, 36.01; H, 0.98.
2,3,9,10-Tetrakis(1,2-dimethoxyphenyl)-6,13-pentacene-
quinone (10). To a mixture of 1 (575 mg, 0.92 mmol) and tetrakis-
(triphenylphosphine)palladium(0) in toluene (20 mL) was added a
suspension of 9 (1 g, 3.77 mmol) in ethanol (5.2 mL) and 2 M aqueous
solution of K2CO3 (1.01 mg, 7.37 mmol). The mixture was degassed and
purged with N2 for 15 min. The mixture was refluxed overnight. After
completion of the reaction (TLC), the flask was allowed to cool to room
temperature. The mixture was extracted with CH2Cl2 ,and the organic
layer was washed with brine, dried over MgSO4, and filtered. The filtrate
was evaporated to dryness under reduced pressure. Flash chromatogra-
phy over silica gel (85:15 hexane/ethyl acetate) provided the coupled
1
product 10 in 50% yield: mp 170-180 °C; H NMR δ (300 MHz,
CDCl3) 3.65 (s, 12H), 3.91 (s, 12H), 6.70 (s, 4H), 6.84-6.94 (m, 8H),
8.16 (s, 4H), 8.98 (s, 4H); 13C NMR δ (75.45 MHz, CDCl3) 15.7, 50.3,
55.7, 58.6, 110.9, 113.2, 122.0, 126.2, 129.5, 130.9, 133.1, 134.4, 142.6,
148.0, 148.4, 173.6; MS (FAB) m/z 853. Anal. Calcd for C54H46O10: C,
75.86; H, 5.42. Found: C, 75.80; H, 5.35.
2,3,9,10-Tetrakis(1,2-diprop-2-ynyloxyphenyl)-6,13-pen-
tacenequinone (5). K2CO3 (335 mg, 2.43 mmol) was added to a
solution of 11 (150 mg, 0.20 mmol) in dry DMF. The reaction mixture was
stirred for 5 min, and then propargyl bromide (217 μL, 2.43 mmol) was
added dropwise. The mixture was stirred overnight at 70-80 °C. After
completion of the reaction (TLC), the flask was allowed to cool to room
temperature, and thereafter, water was added to the reaction mixture. A
solidcompoundprecipitatedafteradditionofwater tothereactionmixture.
The solid compound was filtered and washed with methanol, and the solid
was recrystallized from dichloromethane to give compound 5 in 40% yield:
mp 140-150 °C; 1H NMR δ (300 MHz, CDCl3) 2.46 (s, 4H), 2.56 (s,
4H), 4.52 (s, 8H), 4.79(s, 8H), 6.89 (s, 4H), 6.98-7.07 (m, 8H), 8.15 (s,
4H), 8.97 (s, 4H); MS (FAB) m/z 1047. Anal. Calcd for C70H46O10: C,
80.29; H, 4.43. Found: C, 80.10; H, 4.30.
2,3,9,10-Tetrakis(1,2-dihydroxyphenyl)-6,13-pentacene-
quinone (11). BBr3 (2.87 mL, 2.87 mmol, 1 M in dichloromethane)
was added to a solution of 10 (200 mg, 0.23 mmol) in dry dichlorolo-
methane (5 mL) at -78 °C, and the mixture was stirred for 30 min. The
flask was allowed to warm to room temperature, and the mixture was stirred
overnight. The reaction was quenched with water. A solid compound
precipitated after addition of water to the reaction mixture. The solid
compound was filtered and used for further reaction without purification.
2,3-Bis(1,2-di-tert-butyldimethylsiloxyphenyl)-6,13-pen-
tacenequinone (7). To a mixture of 6 (435 mg, 0.93 mmol) and
tetrakis(triphenylphosphine)palladium(0) in toluene (20 mL) was
added a suspension of 2 (1 g, 2.15 mmol) in ethanol (5.2 mL) and
2 M aqueous solution of K2CO3 (475 mg, 3.45 mmol). The mixture was
’ ASSOCIATED CONTENT
S
Supporting Information. Characterization data includ-
b
ing melting point and 1H, 13C, and mass spectra. This material is
1582
dx.doi.org/10.1021/jo101996k |J. Org. Chem. 2011, 76, 1578–1583