1906 J . Org. Chem., Vol. 64, No. 6, 1999
Zajc
(2.040 g, 7.5 mmol) in benzene (440 mL) at 5 °C was added a
solution of N-bromosaccharin (1.965 g, 7.5 mmol) in benzene
(250 mL), cooled to just above the freezing point, over 30 min.
The reaction mixture was stirred for an additional hour at 5
°C and then for 24 h at room temperature. The mixture was
diluted with ethyl acetate; washed with aqueous Na2S2O5,
aqueous NaHCO3, and water; dried over anhydrous sodium
sulfate; and evaporated. Dry column chromatography (SiO2,
eluted with methylene chloride) gave 6-bromo-7,8,9,10-tet-
rahydrobenzo[a]pyren-7-ol 2 as a pale yellow powder (1.952
g, 74%); mp (THF) 213-215 °C; 1H NMR (CDCl3) δ 8.52 (d, 1
H-5, J ) 9.3 Hz), 8.26 (d, 1 H-11, J ) 9.3 Hz), 8.22-8.17 (m,
2 H-1, H-3), 8.13 (d, 1 H-12, J ) 9.3 Hz), 8.09 (d, 1 H-4, J )
9.3 Hz), 8.01 (t, 1 H-2, J ) 7.6 Hz), 5.57 (broad t, 1 H-7, J app
) 3.0 Hz), 3.70 (ddm, 1 H-10eq, J ) 17.5, 5.3 Hz), 3.26 (ddd, 1
H-10ax, J ) 17.7, 12.0, 6.0 Hz), 2.79 (broad s, OH), 2.43 (dm,
1 H-8eq, J ) 13.7 Hz), 2.31 (qm, 1 H-9ax, J ) 13.6 Hz), 2.12 (m,
1 H-9eq), 1.97 (tt, 1 H-8ax, J ) 13.7, 3.4 Hz); 13C NMR (CDCl3)
δ 135.20 (C-6a), 133.24 (C-10a), 131.16, 131.09 (C-3a, C-12a),
128.74, 128.71 (C-5a, C-10b), 128.46 (C-4), 127.92 (C-12),
126.54 (C-2, C-5), 125.80 (C-1), 125.60 (C-3), 125.48 (C-12c),
124.29 (C-6), 123.90 (C-12b), 122.86 (C-11), 67.66 (C-7), 30.54
23.29 (d, C-10, J ) 3.0 Hz), 22.85 (s, C-9); 19F NMR (CDCl3) δ
-133.23 (broad s); HRMS m/e calcd for C20H13F 272.1001,
found 272.1010. Anal. Calcd for C20H13F: C, 88.21; H, 4.81.
Found: C, 87.96; H, 4.65.
tr a n s-7,8-Diben zoyloxy-6-flu or o-7,8,9,10-tetr ah ydr oben -
zo[a ]p yr en e (5). Silver benzoate (138.9 mg, 0.607 mmol) was
suspended in dry benzene (5 mL) and finely powdered iodine
(77 mg, 0.303 mmol) was added. The reaction mixture was
protected from light and stirred at room temperature for 2 h.
6-Fluoro-9,10-dihydrobenzo[a]pyrene 4 (75 mg, 0.276 mmol)
was added with 1 mL of benzene. The stirring was continued
for 22 h at room temperature and then under reflux for another
10 h. The reaction mixture was filtered hot through Celite,
the Celite was washed with hot benzene, and the filtrate was
evaporated. The crude product was purified by preparative
TLC (SiO2, 2 mm, 20 cm × 20 cm, using 20% n-hexane in
benzene) to yield white crystalline trans-7,8-dibenzoyloxy-6-
fluoro-7,8,9,10-tetrahydrobenzo[a]pyrene 5 (65 mg, 46%): mp
(benzene) at 148 °C, a gradual transformation of original
crystals into needlelike crystals started, along with the forma-
tion of liquid droplets; the transformation was complete at
approximately 200 °C, and the needles melted at 207-210 °C;
1H NMR (CDCl3) (′: C-7 benzoyloxy; ′′: C-8 benzoyloxy) δ 8.27
(d, 1 H-11, J ) 9.3 Hz), 8.21 (d, 1 H-5, J ) 9.1 Hz), 8.20 (broad
d, 1 H-1, J ) 7.5 Hz), 8.16 (broad d, 1 H-3, J ) 7.2 Hz), 8.12
(d, 1 H-12, J ) 9.3 Hz), 8.09-7.99 (m, 4 H-2′, H-6′, H-4, H-2),
7.93-7.88 (m, 2 H-2′′, H-6′′), 7.53 (tt, 1 H-4′, J ) 7.4, 1.3 Hz),
7.47 (tt, 1 H-4′′, J ) 7.4, 1.3 Hz), 7.39 (tm, 2 H-3′, H-5′, J )
7.4 Hz), 7.31 (tm, 2 H-3′′, H-5′′, J ) 7.4 Hz), 7.04 (d, 1 H-7, J
) 3.5 Hz), 5.84-5.79 (m, 1 H-8), 3.76 (ddd, 1 H-10, J ) 17.6,
5.6, 4.0 Hz), 3.57 (ddd, 1 H-10, J ) 17.6, 10.2, 6.1 Hz), 2.70-
2.50 (m, 2 H-9); 13C NMR (CDCl3) δ 165.51 (s, CO′′), 165.11 (s,
CO′), 155.77 (d, C-6, J ) 254.7 Hz), 133.18 (s, C-4′), 133.13 (s,
C-4′′), 132.42 (d, C-10a, J ) 3.2 Hz), 131.58 (s, C-3a), 131.24
(s, C-12a), 129.94 (s, 2 C-2′, C-6′), 129.86 (s, C-1′), 129.81 (s,
C-1′′), 129.73 (s, 2 C-2′′, C-6′′), 128.39 (s, 2 C-3′, C-5′), 128.36
(s, 2 C-3′′, C-5′′), 127.45 (d, C-4, J ) 2.6 Hz), 126.88 (d, C-12,
J ) 2.8 Hz), 126.81 (s, C-2), 125.91 (d, C-12c, J ) 6.4 Hz),
125.55 (d, C-1, J ) 2.3 Hz), 125.37 (d, C-3, J ) 1.8 Hz), 125.06
(d, C-10b, J ) 3.3 Hz), 124.43 (d, C-12b, J ) 3.8 Hz), 122.58
(d, C-11, J ) 2.1 Hz), 119.37 (d, C-5, J ) 5.2 Hz), 117.51 (d,
C-6a, J ) 15.4 Hz), 117.34 (d, C-5a, J ) 15.4 Hz), 69.64 (s,
C-8), 65.72 (d, C-7, J ) 4.7 Hz), 23.12 (s, C-9), 21.87 (d, C-10,
J ) 2.1 Hz); 19F NMR (CDCl3) δ -127.36 (broad s); HRMS
m/e calcd for C34H23O4F 514.1580, found 514.1588.
(C-8), 27.16 (C-10), 17.06 (C-9). HRMS m/e calcd for C20H15
-
BrO 350.0306, found 350.0315. Anal. Calcd for C20H15BrO: C,
68.39; H, 4.30. Found: C, 68.91; H, 4.77. IR (5 mM solution in
CCl4: 3601 cm-1 (OH).
6-Br om o-9,10-d ih yd r oben zo[a ]p yr en e (3). To a stirred
suspension of 6-bromo-7,8,9,10-tetrahydrobenzo[a]pyren-7-ol
2 (1.769 g, 5.03 mmol) in benzene (120 mL) was added
p-toluenesulfonic acid monohydrate (190 mg, 1 mmol). The
suspension was heated at 70 °C for 2.5 h, cooled, and diluted
with ethyl acetate. The mixture was washed with aqueous
NaHCO3 and dried, and the solvent was evaporated. The crude
product was purified by dry column chromatography (SiO2,
eluted with benzene). 6-Bromo-9,10-dihydrobenzo[a]pyrene 3
was obtained as a yellow powder (1.558 g, 93%); mp (acetone)
1
187-189 °C; H NMR (CDCl3) δ 8.50 (d, 1 H-Ar, J ) 9.3 Hz),
8.19 (d, 1 H-Ar, J ) 9.3 Hz), 8.11 (m, 2 H-Ar), 8.02 (m, 2 H-Ar),
7.94 (t, 1 H-Ar, J ) 7.6 Hz), 7.40 (dt, 1 H-7, J ) 9.9, 1.8 Hz),
6.40 (dt, 1 H-8, J ) 9.9, 4.5 Hz), 3.46 (t, 2 H-10, J ) 8.3 Hz),
2.51 (tdd, 2 H-9, J ) 8.3, 4.5, 1.8 Hz); 13C NMR (CDCl3) δ
131.45, 131.23, 131.04, 130.89, 128.64, 128.42, 128.04, 127.63,
127.32, 126.80, 126.18, 125.42, 125.36, 125.30, 124.25, 122.85,
120.90, 24.30, 22.71; HRMS m/e calcd for C20H13Br 332.0201,
found 332.0206.
6-F lu or o-9,10-d ih yd r oben zo[a ]p yr en e (4). A stirred so-
lution of 6-bromo-9,10-dihydrobenzo[a]pyrene 3 (225 mg, 0.676
mmol) in dry toluene (15 mL) under argon was cooled in an
ice bath, and tert-butyllithium (1.351 mL, 1.5 M in pentane,
2.03 mmol) was added. Stirring was continued for 2.5 h, and
N-fluorobenzenesulfonimide (467 mg, 1.481 mmol) in dry
toluene (8.6 mL) was added to the reaction mixture. After
addition, the ice bath was removed, and the reaction was
allowed to proceed at room temperature for 1.5 h. Subse-
quently, saturated aqueous NH4Cl was added, and the reaction
mixture was diluted with ethyl acetate. The ethyl acetate layer
was washed three times with saturated aqueous sodium
carbonate and dried over anhydrous sodium sulfate. After
evaporation of the solvent and purification on a SiO2 column
using hexane/benzene (96:4), the product 6-fluoro-9,10-dihy-
drobenzo[a]pyrene 4 (138 mg, 75%) was obtained as an off-
tr a n s-7,8-Diben zoyloxy-6-flu or o-7,8-d ih yd r oben zo[a ]-
p yr en e (6). trans-7,8-Dibenzoyloxy-6-fluoro-7,8,9,10-tetrahy-
drobenzo[a]pyrene 5 (115 mg, 0.224 mmol) was placed into a
three-neck round-bottom flask equipped with a thermometer,
water condenser, and argon inlet. CCl4 (33.6 mL) was added,
the mixture was stirred and carefully heated with a tungsten
halogen lamp (50 W), while argon was bubbled through the
solution. When the temperature of the solution reached 60 °C,
NBS (47 mg, 0.264 mmol) and AIBN (1.5 mg) were simulta-
neously added to the reaction mixture. The reaction was
carefully monitored every few minutes by TLC (SiO2, 25% ethyl
acetate in n-hexane), and after 10 min, only trace amounts of
the starting compound were left. The heating was therefore
discontinued after 13 min, and the flask quickly immersed into
ice-water. After cooling, a small amount of decolorizing carbon
was added to the mixture, and the suspension filtered through
Celite. The Celite was washed thoroughly with CCl4, and the
filtrate was carefully evaporated at room temperature. Finally,
the reaction mixture was dried in vacuo. The crude product
was dissolved in dry toluene (25.8 mL), NEt3 (168 µL) and
NaHCO3 (674 mg) were added, and the reaction mixture was
1
white powder: mp (i-PrOH) 128-129 °C; H NMR (CDCl3) δ
8.18 (d, 1 H-5, J ) 9.1 Hz), 8.11 (d, 1 H-11, J ) 9.3 Hz), 8.06
(d, 2 H-1, H-3, J ) 7.6 Hz), 7.96 (d, 1 H-4, J ) 9.1 Hz), 7.94-
7.88 (m, 2 H-12, H-2), 7.13 (dtd, 1 H-7, J ) 9.8, 1.8, 0.6 Hz),
6.31 (dt, 1 H-8, J ) 9.8, 4.4 Hz), 3.43 (t, 2 H-10, J ) 8.3 Hz),
2.55 (tdd, 2 H-9, J ) 8.3, 4.4, 1.8 Hz); 13C NMR (CDCl3) δ
152.40 (d, C-6, J ) 252.6 Hz), 131.30 (d, C-3a, J ) 1.1 Hz),
130.99 (s, C-12a), 130.84 (d, C-10a, J ) 4.1 Hz), 129.82 (d, C-8,
J ) 2.5 Hz), 126.85 (d, C-4, J ) 2.6 Hz), 126.27 (d, C-12, J )
2.7 Hz), 126.08 (d, C-2, J ) 1.0 Hz), 125.13 (d, C-12c, J ) 5.9
Hz), 124.97-124.85 (two d, 2 C-1, C-3), 124.80 (d, C-12b, J )
3.9 Hz), 124.37 (d, C-10b, J ) 3.1 Hz), 122.67 (d, C-11, J ) 2.2
Hz), 120.59 (d, C-7, J ) 7.1 Hz), 119.44 (d, C-5, J ) 5.5 Hz),
119.23 (d, C-6a, J ) 14.3 Hz), 117.23 (d, C-5a, J ) 15.7 Hz),
refluxed under
a small flux of argon. The reaction was
monitored by TLC (SiO2, benzene). After 7 h, the heating was
discontinued, and the reaction mixture was cooled and filtered
through Celite. After evaporation of the filtrate, the product
was purified by preparative TLC (SiO2, 2 mm, 20 cm × 20 cm,
using benzene (30%)/n-hexane (65%)/ethyl acetate (4%)/NEt3
(1%), developed twice). Pure trans-7,8-dibenzoyloxy-6-fluoro-
7,8-dihydrobenzo[a]pyrene 6 (57 mg, 50%) was isolated as a
yellow solid: 1H NMR (CDCl3) (′: C-7 benzoyloxy; ′′: C-8