-1
filtrates were further divided into a total of four portions and each
Pellet) 3169 cm (br s), 1697 cm-1 (s), 1491 cm-1 (s), 1399 cm-1 (m),
◦
1244 cm (s), 1203 cm-1 (s), 818 cm-1 (m).
-1
portion was diluted with 1.75 L of H
g of K CO
2
O and heated to 100 C. 175
was slowly added to each solution with stirring. When
2
3
2
,7-Dihydroxy-9-fluorenone (12). 10 g of anhydrous and
the addition was complete, and the gas evolution had stopped, the
mixtures were allowed to cool to room temperature and stand for
freshly fused ZnCl2 (s) was ground up with 5.0 g of 4,4-
dihydroxybiphenyl-2-carboxylic acid with a mortar and pestle.
This solid mixture was then placed in a 200 ml beaker and heated
to 210 C. The mixture was stirred until water vapour evolved and
a purple solid formed. The mixture was maintained at ~210 C
2
4 h, resulting in the precipitation 9H-fluorene-2,7-disulfonic acid
dipotassium salt as a white solid, which was collected by filtration.
◦
1
H NMR ((CD
J = 6.6 Hz), 3.96 (2H, s, CH
d 146. 86, 143.62, 141.35, 124.94, 122.86, 119.94, 36.87. FTIR
3
) SO, 300 MHz): d 7.8–7.9 (4H, m), 7.68 (2H, d,
2
◦
13
2
). C NMR ((CD ) SO, 75.5 MHz):
3
2
◦
for 10 min, and then allowed to cool to ~50 C. The mixture
was added to 50 mL of H O to dissolve the zinc salt, and 12
-
1
-1
-1
-1
2
(
(
1
KBr Pellet) 3554 cm (s), 3467 cm (s), 3060 cm (m), 2920 cm
was collected by suction filtration as a deep red solid. The crude
solid was recrystallized from 95% ethanol, yielding 4.17 g (90%)
of 12 as deep red crystals. Mp 326–329 C (lit. 338 C). H NMR
((CD CO, 300 MHz): d 8.78 (2H, s, ArO–H), 7.40 (2H, d, J =
7.9 Hz, Ar–H), 7.02 (2H, 2, J = 2.2 Hz, Ar–H), 6.96 (2H, dd, J =
7.9, 2.2 Hz, Ar–H). C NMR ((CD
158.01, 136.15, 135.62, 121.50, 121.42, 111.53. FTIR (KBr Pellet)
3391 (s), 1702 cm (s), 1601 cm (m), 1478 cm (s), 1408 cm (s),
1295 cm (s), 1236 cm-1 (s), 793 cm-1 (s).
m), 1643.7 cm (s), 1409 cm-1 (s), 1200 cm (s), 1099 cm (s),
-
1
-1
-1
034 cm- (s), 1002 cm-1 (s), 829 cm-1 (s), 703 cm (s), 623 cm (s).
-Oxo-9H-fluorene-2,7-disulfonic acid dipotassium salt. The
H-fluorene-2,7-disulfonic acid dipotassium salt from the previ-
1
-1
-1
◦
◦
6 1
9
)
3 2
9
1
3
ous step was divided into four portions, and to each was added
40 mL of H O and heated to dissolve the salt. Four solutions
3
2
) SO, 75.5 MHz): d 193.84,
4
2
-
1
-1
-1
-1
were prepared, each containing 52 g of KMnO
4
dissolved in
◦
-1
8
75 ml of H
2
O, and were heated to 80 C. Each hot potassium
permanganate solution was then slowly added to one of the 9H-
fluorene-2,7-disulfonic acid dipotassium salt (56) solutions over
2
CH
of NaBH
,7-Dihydroxy-9-fluorenol (9). To solution composed of 5 mL
CN, 5 mL H O, and 12 (0.30 g, 1.4 mmol) was added 10 equiv.
. The mixture was stirred at room temperature for 3 h,
3
2
1
h, resulting in the precipitation of a brown solid (MnO
mixtures were suction filtered to remove MnO , and the filtrates
were heated to reduce the volume to 1.125 L each. Any further
2
). The
4
2
and quenched by the addition of 30 ml of 10% HCl. The mixture
was diluted with 30 mL of water and extracted with 3 ¥ 20 ml of
diethyl ether. The combined organics were dried with MgSO
filtered. The ether was removed under reduced pressure yielding
(0.176 g, 58% yield). Mp 213–217 C. H NMR ((CD
00 MHz): d 9.33 (2H, s, ArO–H), 7.37 (2H, d, J = 7.8 Hz, Ar–H),
.94 (2H, s, Ar–H), 6.70 (2H, d, J = 7.8 Hz, Ar–H), 5.67 (1H, br
s, O–H), 5.27 (1H, s, C–H). C NMR ((CD
56.68, 148.61, 131.52, 119.78, 115.33, 112.8, 73.84. EIMS: 214
100), 213 (35), 198 (15), 197 (74), 168 (17), 157 (17), 141 (13), 128
MnO
2
was removed by filtration, and the filtrate was cooled to
4
and
◦
~
4 C for 20 h. 9-Oxo-9H-fluorene-2,7-disulfonic acid dipotassium
salt was collected as a bright yellow solid and was collected by
suction filtration. A second crop of this compound was obtained
by reducing the volume of each portion to 375 ml by boiling off
excess water, followed by cooling. After combining three crops
of the collected product from the four solutions, a total of 160
◦
1
9
3
6
3
2
) CO,
1
3
3
)
2
SO, 75.5 MHz): d
1
g of 9-oxo-9H-fluorene-2,7-disulfonic acid dipotassium salt was
(
(
(
1
collected (32% from fluorene). H NMR ((CD
3
2
) SO, 300 MHz): d
-
1
-1
-1
14). FTIR (KBr Pellet) 3221 cm (br s), 1613 cm (m), 1457 cm
s), 1242 cm (s), 813 cm (m).
7
7
.84 (2H, d, J = 7.5 Hz, Ar–H), 7.77 (2H, d, J = 7.5 Hz, Ar–H),
.76 (2H, s, Ar–H).
-
1
-1
1
3
C NMR ((CD
3
) SO, 75.5 MHz): d 150.33, 143.83, 133.88,
2
2,7-Dimethoxy-9-fluorenone (13). 1.0 g of NaOH pellets were
-
1
-1
1
32.75, 121.34. FTIR (KBr Pellet) 3425 cm (br w), 3054 cm
crushed with a mortar and pestle and added to 15 ml of DMSO
in a round-bottom flask. To this was added 12 (2.00 g, 9.4 mmol),
generating a dark purple solution. To this was added 4 equiv.
of iodomethane (5.3 g, 37.3 mmol) dropwise. The reaction vessel
was sealed with a rubber septum and the solution was stirred
for 3 h. The reaction was quenched by the addition of 50 mL
of 10% HCl, which precipitated a deep orange product, which
was collected by suction filtration. The product was then washed
with 0.1 M NaOH to remove traces of the starting material and
mono-substituted by-product, and then washed with water. 13
-
1
-1
-1
-1
(
1
w), 1715 cm (s), 1617 cm (m), 1604 cm (m), 1234 cm (s),
185 cm- (s), 1088 cm-1 (s), 1035 cm-1 (s), 729 cm-1 (s), 617 cm-1
1
(
s).
4,4¢-Dihydroxybiphenyl-2-carboxylic acid. 210 g of NaOH
pellets were placed in a stainless steel beaker and heated with
a Bunsen burner for several minutes and stirred until the NaOH
was completely molten. 105 g of 9-oxo-9H-fluorene-2,7-disulfonic
acid dipotassium salt was slowly added to the molten NaOH and
was carefully stirred with a glass rod. When the addition was
complete, the reaction mixture was cooled yielding a pink-brown
◦
1
was obtained in 65% yield (1.1 g). Mp 115–118 C. H NMR
(CD
2H, s, Ar–H), 7.09 (2H, d, J = 7.8 Hz, Ar–H), 3.82 (6H, s, OC–
(
(
H
1
(
(
1
3
)
2
SO, 300 MHz): d 7.58 (2H, d, J = 7.7 Hz, Ar–H), 7.11
solid. The solid was dissolved in 1.5 L H O, heated to near boiling,
2
and hot-filtered to remove a brown insoluble solid. The filtrate was
acidified by addition of 500 mL of conc. HCl, precipitating 4,4¢-
dihydroxybiphenyl-2-carboxylic acid as an off-white solid with a
1
3
3
). C NMR ((CD
3
) SO, 75.5 MHz): d 193.28, 160.18, 137.29,
2
-
1
35.62, 121.94, 120.77, 110.08, 56.14. FTIR (KBr Pellet) 2963 cm
w), 2931 cm (w), 2851 cm (w), 1712 cm (m), 1577 cm
s), 1475 cm (s), 1435 cm (m), 1289 cm (m), 1224 cm (m),
043 cm (m), 785 cm (m).
-
1
-1
-1
-1
◦
◦
6
yield of 52.6 g (91% yield). Mp 266–269 C (lit. 281–282 C).
-
1
-1
-1
-1
1
H NMR ((CD
1H, s, ArO–H), 9.44 (1H, s, ArO–H), 7.15 (1H, d, J = 7.0 Hz,
Ar–H), 7.08 (2H, d, J = 7.2 Hz, Ar–H), 7.07 (1H, s, Ar–H), 6.93
3
)
2
SO, 300 MHz): d 12.64 (1H, s, COOH), 9.77
-
1
-1
(
2,7-Dimethoxy-9-fluorenol (10). To a 250 mL round bottomed
flask was added CH
4.2 mmol), and NaBH
room temperature for 3 h. The reaction was quenched by addition
1
3
(
1H, d, J = 7.0 Hz, Ar–H), 6.77 (2H, d, J = 7.2 Hz, Ar–H).
NMR ((CD SO, 75.5 MHz): d 170.38, 156.72, 156.31, 133.57,
32.09, 131.95, 131.9, 129.74, 118.03, 115.77, 115.32. FTIR (KBr
C
3
CN (5 mL), H
2
O (5 mL), 13 (1.0 g,
3
)
2
4
(1.6 g), and the mixture was stirred at
1
9
28 | Photochem. Photobiol. Sci., 2011, 10, 920–930
This journal is © The Royal Society of Chemistry and Owner Societies 2011