PAPER
Synthesis and Resolution of Cyclotribenzylenes
661
H2O, (5:1, 50 mL). The resulting suspension was stirred for 2 h at
r.t. before evaporation of the MeOH. The aq suspension was then
extracted with CH2Cl2 (5 25 mL), the combined organic layers
were washed with H2O (3 20 mL), brine (20 mL) and dried with
MgSO4. After evaporation to dryness, the residue was recrystallised
from MeOH yielding 18 as yellow crystals (3.64 g, 12.8 mmol, 89%
after consecutive work-up of the mother liquids); mp 107–108 °C.
1H NMR (300 MHz, DMSO-d6): = 3.97 (s, 2 H, bibenzylic CH2),
4.44, 4.46 (2 s, 4 H, benzylic CH2OH), 5.14 (t, J = 5.5 Hz, 1 H,
benzylic CH2OH), 5.23 (t, J = 5.5 Hz, 1 H, benzylic CH2OH), 6.86–
7.45 (m, 7 H, ArH).
13C NMR (75.5 MHz, DMSO-d6): = 33.3 (bibenzylic CH2), 60.3,
60.9 (benzylic CH2OH), 119.9, 126.5, 127.1, 127.3, 129.0, 129.1,
129.2, 131.3, 136.7, 140.0, 140.37, 140.4 (Ar C).
IR (CsI): 1718, 1617, 1597, 1580, 1560, 1477, 1328, 1276, 835,
823, 728, 497 cm–1.
1H NMR (300 MHz, CDCl3): = 6.97, 7.06 (2 d, J = 12.1 Hz, 2
H, olefinic CH), 7.37–7.72 (m, 5 H, ArH), 8.17–8.20 (m, 1 H, ArH),
8.34 (d, J = 2.2 Hz, 1 H, ArH).
13C NMR (75.5 MHz, CDCl3): = 106.1, 107.4 (olefinic CH2),
123.2, 129.1, 130.4, 130.6, 131.0, 132.3, 132.4, 132.9, 134.9, 138.1,
138.3, 139.7 (ArC), 191.4 (C=O).
MS (EI): m/z = 290, 288 [M – H2O]+ (5), 272, 270 [M – 2H2O]+
(20), 259, 257 [M+ H2O CH2OH] (10), 209 (25), 191 (30), 178
(100), 165 (25), 152 (10), 91 (25).
HRMS (EI): m/z [M – H2O]+ calcd for C15H15BrO2 – H2O: 288.015;
found: 288.014.
Anal. Calcd for C15H15BrO2: C, 58.65; H, 4.92. Found: C, 58.75; H,
4.82.
MS (EI): m/z = 286, 284 [M]+ (100), 258, 256 [M – CO]+ (85), 207
2-Bromo-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene (12a)
A soln of compound 20 (305 mg, 0.99 mmol) in anhyd benzene (100
mL) was added dropwise over 30 h to a mixture of concd H2SO4 (20
mL) and of anhyd benzene (20 mL) at r.t. After additional stirring
for 48 h the reaction mixture was poured into ice H2O (150 mL).
The aq layer was extracted with CH2Cl2 (3 100 mL) and the com-
bined organic layers were washed with a sat. aq soln of NaHCO3
(100 mL), H2O (100 mL), brine (100 mL), and dried with MgSO4.
After evaporation of solvent to dryness, the residue was purified by
column chromatography (SiO2, hexane acetone, 20:1; Rf 0.42)
yielding 12a as a colorless crystalline powder (225 mg, 0.65 mmol,
65%); mp 230 °C.
[M – Br]+, 176 [M – CO – Br]+ (50), 151 (15), 88 (10).
HRMS (EI): m/z calcd for C15H9BrO: 283.9836; found: 283.983.
3-Bromo-5H-dibenzo[a,d]cycloheptene (19)
A mixture of ketone 18 (0.50 g, 1.75 mmol) and aluminium triiso-
propylate (1.07 g, 5.26 mmol) was heated to 275 °C for 3 h in an at-
mosphere of Ar until the melt had become solid. After cooling to r.t.
the precipitate was suspended in 2 N HCl (15 mL)and stirred for 1
h. The aq suspension was then extracted with CH2Cl2 (5 20 mL).
The combined organic layers were evaporated to dryness, and the
residue was purified by column chromatography (SiO2, hexane
CH2Cl2, 5:1; Rf 0.59) yielding 19 as a slightly yellow crystalline
powder (0.42 g, 1.55 mmol, 89%); mp 128–129 °C.
IR (CsI): 3059, 3018, 2929, 1586, 1492, 1482, 1476, 1447, 1104,
778, 751, 720 cm–1.
IR (CsI): 2959, 1653, 1583, 1483, 1420, 1076, 906, 836, 812, 794,
765, 732, 512, 447 cm–1.
1H NMR (300 MHz, CDCl3): = 3.67 (s, 2 H, benzylic CH2), 6.91–
1H NMR (500 MHz, benzene-d6): = 3.21–3.42 (3 d, J = 11–13
Hz, 3 H, 3 benzylic CHH), 4.33–4.43 (3d, J = 13 Hz, 3 H, 3 benzylic
CHH), 6.75–7.17 (m, 10 H, ArH), 7.39 (d, J = 2.2 Hz, 1 H, ArH).
13C NMR (125.8 MHz, benzene–d6): = 36.6, 36.8, 37.1 (benzylic
CH2), 120.6 (ArCBr), 127.1, 127.25, 127.29, 127.3, 130.1, 130.2 (2
C), 130.3, 130.4, 132.0, 132.9, 138.7, 138.8, 139.2, 139.6, 139.8,
142.0 (ArC).
MS (EI): m/z = 350, 348 [M]+ (60), 335, 333 [M – CH3]+ (10), 269
[M – Br]+ (45), 252 (25), 191 (20), 178 (100), 165 (15), 126 (5), 91
(15).
7.05 (2 d, J = 11.6 Hz, 2 H, olefinic CH), 7.11–7.32 (m, 7 H, ArH).
13C NMR (75.5 MHz, CDCl3): = 41.1 (benzylic CH2), 126.3,
127.9, 128.15, 128.17, 128.7, 129.02, 129.04, 129.5, 130.3, 130.4,
130.63, 130.64, 132.1 (olefinic C, ArC).
MS (EI): m/z = 272, 270 [M]+ (100), 191, [M – Br]+ (40), 163 (5),
95 (10), 82 (5).
HRMS (EI): m/z calcd for C15H11Br: 270.0044; found: 299.004.
HRMS (EI): m/z calcd for C21H17Br: 348.051; found: 348.051.
Anal. Calcd for C15H11Br: C, 66.44; H, 4.09. Found: C, 66.45; H,
4.10.
Anal. Calcd for C21H17Br: C, 72.22; H, 4.91. Found: C, 72.11; H,
4.91.
5-Bromo-2,2´-bis(hydroxymethyl)diphenylmethane (20)
A stream of O2/O3 was bubbled through a solution of compound 19
(0.42 g, 1.55 mmol) in anhyd CH2Cl2 (15 mL) for 2 h at –78 °C. Af-
ter 1 h the blue color of unreacted ozone was noticeable. The reac-
tion mixture was allowed to warm to r.t., and Ar was bubbled
through to remove any dissolved ozone. BH3 S(CH3)2 (6.20 mL of
a 1 M soln in CH2Cl2, 6.20 mmol) was slowly added via a syringe,
and the reaction mixture was stirred for additional 24 h resulting in
a yellow soln containing some flaky precipitate. To decompose ex-
cess of borane, aq EtOH (10 mL ) followed by 5% HCl (0.5 mL )
were dropwise added followed by stirring for 1 h at r.t. The pH was
adjusted at 5–6 by adding solid NaHCO3, and the resulting mixture
was dried with MgSO4. After evaporation of the solvent, the residue
was purified by column chromatography (SiO2, CH2Cl2
EtOAc,1:1; Rf 0.48) yielding 20 as a colorless crystalline powder
(0.42 g, 1.36 mmol, 88%); mp 109–110 °C.
2-Iodo-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene (21)
Compound 12a (930 mg, 2.66 mmol, dried under high vacuum) was
dissolved in anhyd THF (93 mL) under Ar, and the soln was cooled
to –78 °C. n-BuLi (1.6 M in hexane, 5.0 mL, 8.0 mmol) was added
via a syringe. After stirring for 30 min at –78 °C I2 (2.03 g, 7.99
mmol, dried over P2O5) was added in one portion and the cooling
bath was removed. After stirring overnight, the organic solvent was
removed under vacuum and the resulting red oil was dissolved in
CH2Cl2 (100 mL). The organic layer was washed with sat. aq sodi-
um hydrogensulfite soln (3 100 mL) and dried with MgSO4. After
evaporation to dryness, the residue was purified by column chroma-
tography (SiO2, hexane acetone, 20:1; Rf 0.44) to afford 21 as a
white solid (784 mg, 1.98 mmol, 75%); mp 214–215 °C.
IR (CsI): = 3057, 3017, 2928, 2362, 1475, 1445, 1099, 749, 718
cm–1.
IR (CsI): 3313, 2922, 1593, 1478, 1445, 1399, 1049, 1017, 1007,
754 cm–1.
1H NMR (300 MHz, CDCl3): = 3.65–3.76 (3 d, J = 13.5 Hz,
J = 13.4 Hz, J = 13.7 Hz, 3 H, 3 benzylic CHH), 4.79–4.85 (m, 3 H,
3 benzylic CHH), 7.06–7.13 (m, 5 H, ArH), 7.29–7.40 (m, 5 H,
ArH), 7.69 (d, J = 1.9 Hz, 1 H, ArH).
Synthesis 2002, No. 5, 655–663 ISSN 0039-7881 © Thieme Stuttgart · New York