Synthesis of a Crowded Naphthalene
J. Am. Chem. Soc., Vol. 123, No. 44, 2001 10925
g, 0.30 mol) was dissolved in tert-butyl alcohol (1 L). The clear crystals
collected previously were added, and the reaction mixture was heated
under argon at 40 °C until its color turned dark red. Workup and column
chromatography as before yielded a second fraction of 15. The
combined fractions containing 15 were concentrated to dryness, and
the bright red-orange oil soon crystallized to give pure 15 (2.76 g, 11.1
mmol, 4.7%): mp 53.5-54 °C (lit.21 53-53.5 °C); 1H NMR (CDCl3)
δ 1.13 (s, 9 H), 1.307 (s, 9 H), 1.311 (s, 9 H), 6.66 (s, 1 H); 13C NMR
(CDCl3) δ 29.4, 31.6, 31.8, 32.6, 33.2, 33.9, 132.5, 138.8, 140.6, 156.9,
205.5 (11 of 11 expected resonances); MS (EI) m/z 248 (M+, 27), 192
(M - C4H8, 46), 177 (M - CH3 - C4H8, 100).
(br s, 1 H), 6.62 (t, J ) 7.5 Hz, 1 H), 6.72-7.08 (m, 16 H), 7.42 (s,
1 H); 13C NMR (CDCl3) δ 33.1, 33.8, 34.4, 36.8, 39.7, 40.8, 125.0,
125.1, 126.0, 126.1, 126.3, 126.4, 126.6, 126.8, 127.3 (br), 130.5 (br),
130.7, 131.6, 132.0, 132.8, 133.0, 133.4 (br), 134.0 (br), 134.2, 135.6,
135.7, 136.2, 137.5, 139.5, 141.37, 141.42, 141.8, 144.7, 144.8, 145.0,
150.2 (36 resonances observed; 32 resonances are expected in the fast
exchange limit, but 40 are possible if there is restricted phenyl rotation,
as is evident from the broadened aryl resonances); MS (EI) m/z 600
(M+, 7), 543 (M - C4H9, 13), 487 (M - C4H8 - C4H9, 26), 431 (M
- 2C4H8 - C4H9, 100); exact mass 600.3774, calcd for C46H48
600.3758. Single crystals of 2 were obtained upon solidification of the
neat oil after the final step of the purification.
3,4,6-Tri(tert-butyl)phthalic Anhydride (17). A mixture of 15 (1.00
g, 4.0 mmol), bromomaleic anhydride (1.07 g, 6.0 mmol), and
bromobenzene (3 mL) was heated to reflux under argon for 2 h. After
cooling, most of the bromobenzene was removed by vacuum distillation,
and the residue was fractionated on a silica gel column (16:1 hexanes-
ethyl acetate) to give crude 17 as a yellow oil (0.91 g). Crystallization
from hexanes-EtOAc gave colorless 17 (0.73 g, 2.3 mmol, 58%): mp
The material with Rf 0.32 proved to be the fluoranthene 20 (8 mg,
0.015 mmol, 37%): mp 246.5-247.5 °C; 1H NMR (CDCl3) δ 1.04 (s,
9 H), 1.76 (s, 9 H), 6.45 (d, J ) 7 Hz, 1 H), 6.66 (m, 2 H), 6.86 (m,
3 H), 6.92 (m, 3 H), 7.02 (m, 3 H), 7.11 (m, 2 H), 7.21 (m, 2 H), 7.94
(s, 1 H), 8.19 (d, J ) 8 Hz, 1 H); 13C NMR (CDCl3) δ 31.2, 33.6,
36.1, 37.7, 123.6, 125.4, 126.0, 126.42, 126.47, 126.6, 126.7, 126.9,
127.3, 128.0, 128.8, 129.1, 130.1, 131.3, 131.6, 133.2, 133.7, 135.7,
136.0, 138.2, 138.5, 140.0, 140.1, 140.4, 141.6, 144.0, 147.2, 150.2
(32 of 32 expected resonances); MS (EI) m/z 542 (M+, 37), 471 (23),
429 (20), 105 (100); exact mass 542.2969, calcd for C42H38 542.2975.
Single crystals of 20 were obtained from dichloromethane-methanol.
1
111.5-113 °C; H NMR (CDCl3) δ 1.49 (s, 9 H), 1.52 (s, 9 H), 1.61
(s, 9 H), 7.83 (s, 1 H); 13C NMR (CDCl3) δ 29.8, 33.0, 34.1, 35.2,
38.9, 40.8, 126.5, 133.9, 135.0, 147.2, 153.1, 161.9, 162.9, 163.9 (14
of 14 expected resonances); MS (EI) m/z 316 (M+, 41), 301 (M -
CH3, 100), 259 (M - C4H9, 39); exact mass 316.2027, calcd for
C20H28O3 316.2038.
When refluxing toluene was employed as the solvent for the
decomposition of the norbornadienone 3, the yield of the naphthalene
2 was nearly quantitative.
3,4,6-Tri(tert-butyl)phthalimide (18). Compound 17 (0.73 g, 2.3
mmol) and finely groud urea (10 g) were placed in a 250-mL round-
bottom flask fitted with an air condenser. The mixture was heated to
170 °C for 36 h; periodically, sublimed urea was returned to the flask.
After cooling, water (100 mL) was added to dissolve the unreacted
urea, and the resulting mixture was extracted three times with
chloroform. The combined extracts were washed with water and dried
over Na2SO4. The solvent was evaporated, and the residue was
recrystallized from chloroform-ethanol to give colorless 18 (343 mg,
5,6,8-Tri(tert-butyl)-2,3-bis(4-bromophenyl)-1,4-diphenylnaph-
thalene (26). The synthesis of 26 was essentially the same as that of
2. Compound 15 (0.40 g, 1.6 mmol) was dissolved in 1,2-dichloroethane
(24 mL), and the solution was heated to reflux. Isoamyl nitrite (1.00
mL, 7.5 mmol) was added, followed by the slow addition of a solution
of 4,5-bis(p-bromophenyl)-3,6-diphenylanthranilic acid (25, 0.97 g, 1.6
mmol) in 1,2-dichloroethane (80 mL) over 30 min. After heating for
another hour, ethanol (18 mL) and 1% NaOH (54 mL) were added to
quench the reaction. The reaction mixture was extracted with chloro-
form, the extract was washed with saturated NaHCO3, and it was dried
over Na2SO4. The solvent was removed, and the residue was fraction-
ated by silica gel column chromatography (8:1 hexanes-benzene) to
yield the norbornadienone intermediate (Rf 0.26, 8:1 hexanes-benzene),
which was not characterized. This material was dissolved in toluene
(10 mL), and the solution was heated at reflux for 24 h. Removal of
the solvent left pure 26 (134 mg, 0.177 mmol, 11%): mp 204-205
°C; 1H NMR (CDCl3) δ 0.78 (s, 9 H), 0.88 (s, 9 H), 1.48 (s, 9 H), 5.98
(br s, 1 H), 6.14 (dd, J ) 8 Hz, 2 Hz, 1 H), 6.76 (dd, J ) 8 Hz, 2 Hz,
1 H), 6.77 (br d, J ) 8 Hz, 1 H), 6.78-7.18 (m, 14 H), 7.50 (s, 1 H);
13C NMR (CDCl3) δ 33.0, 33.8, 34.3, 36.9, 39.8, 40.8, 119.5, 119.6,
126.4, 126.5, 126.8, 127.0 (br), 127.1, 127.6 (br), 129.7, 129.8 (br),
130.1, 130.2 (br), 131.1, 132.2 (br), 132.9, 133.0, 133.1, 133.3 (br),
133.5, 133.9 (br), 134.1, 134.5 (br), 135.8, 135.9, 136.5, 139.6, 140.2,
140.3, 141.9, 144.1, 144.3, 145.2, 150.6 (39 resonances observed; 32
resonances are expected in the fast exchange limit, but 40 are possible
if there is restricted aryl group rotation, as is evident from the broadened
aryl resonances); MS (EI) m/z 758 (M+, 37), 701 (M - C4H9, 35), 645
(M - C4H8 - C4H9, 100), 589 (M - 2C4H8 - C4H9, 96), 510 (78);
exact mass 758.1922, calcd for C46H46Br2 758.1948. Single crystals of
26 were obtained from ethanol.
1
1.09 mmol, 47%): mp 137-139 °C; H NMR (CDCl3) δ 1.48 (s, 9
H), 1.50 (s, 9 H), 1.60 (s, 9 H), 7.70 (s, 1 H); 13C NMR (CDCl3) δ
29.8, 33.5, 34.0, 34.8, 38.5, 40.2, 127.4, 133.1, 135.2, 145.5, 151.3,
159.4, 168.0, 169.7 (14 of 14 expected resonances); MS (EI) m/z 315
(M+, 14), 300 (M - CH3, 43), 258 (M - C4H9, 41), 244 (100); exact
mass 315.2200, calcd for C20H29NO2 315.2198.
1,2,4-Tri(tert-butyl)-5,6,7,8-tetraphenyl-9-oxo-1,4-dihydro-1,4-
methanonaphthalene (3). Compound 15 (0.25 g, 1.0 mmol) was
dissolved in 1,2-dichloroethane (15 mL), and the solution was heated
to reflux. Isoamyl nitrite (0.67 mL, 5.0 mmol) was added, followed by
the slow addition of a solution of 3,4,5,6-tetraphenylanthranilic acid
(0.28 g, 0.63 mmol) in 1,2-dichloroethane (50 mL) over 30 min. After
heating for another hour, ethanol (12 mL) and 1% NaOH (36 mL) were
added to quench the reaction. The reaction mixture was extracted with
chloroform, the extract was washed with saturated NaHCO3, and it was
dried over Na2SO4. Removal of the solvent left 0.64 g of material, and
this was fractionated by silica gel column chromatography (4:1
hexanes-benzene). The first component to elute was unreacted 15, the
second was 1,2,3,4-tetraphenylbenzene (Rf 0.40, 4:1 hexanes-benzene),
and the third was 3 (71 mg, 0.113 mmol, 11%; Rf 0.32): 1H NMR
(CDCl3) δ 1.15 (s, 9 H), 1.20 (s, 9 H), 1.31 (s, 9 H), 5.23 (s, 1 H),
6.78-6.92 (m, 10 H), 7.08-7.17 (m, 10 H); 13C NMR (CDCl3) δ 26.6,
28.3, 30.0, 32.0, 36.2, 37.8, 40.1, 53.7, 125.9, 126.5, 127.0, 127.2, 127.3,
127.7, 127.8, 128.0, 129.7, 130.0, 130.2, 130.3, 130.7, 131.3, 131.6,
131.8, 133.7, 140.2, 140.6, 141.2, 142.1, 158.7, 192.6 (31 of 33 expected
resonances); MS (EI) m/z 600 (M - CO, 4), 544 (M - CO - C4H8,
13), 487 (M - CO - C4H8 - C4H9, 19), 431 (M - CO - 2C4H8 -
C4H9, 100). Single crystals of 3 were obtained from chloroform-
methanol-ethylene glycol.
General X-ray Crystallographic Procedures. X-ray data were
collected by using graphite-monochromated Mo KR radiation (0.710 73
Å) on a Nonius KappaCCD diffractometer. The diffraction data were
processed by using the program DENZO.28 All structures were solved
by direct methods using Siemens SHELXTL,29 and all were refined
by full-matrix least squares on F2 using SHELXTL. All non-hydrogen
atoms were refined anisotropically, and hydrogens were included with
a riding model. The structure of 20 contain a highly disordered
dichloromethane of crystallization; for this reason, the SQUEEZE/
5,6,8-Tri(tert-butyl)-1,2,3,4-tetraphenylnaphthalene (2) and 4,6-
Di(tert-butyl)-1,2,3-triphenylfluoranthene (20). Freshly purified 3 (25
mg, 0.040 mmol) was dissolved in xylenes (5 mL), and the solution
was heated at reflux for 12 h. The solvent was evaporated to leave a
yellow residue which was fractionated by preparative silica gel TLC
(8:1 hexanes-benzene) to give two major components. The material
with Rf 0.41 proved to be the naphthalene 2 (12 mg, 0.020 mmol,
(28) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307-
326.
(29) Sheldrick, G. M. SHELXTL, Version 5. Siemens Analytical X-ray
Instruments, Madison, WI, 1996.
1
50%): mp 155.0-155.5 °C; H NMR (CDCl3) δ 0.80 (s, 9 H), 0.90
(s, 9 H), 1.49 (s, 9 H), 6.06 (br s, 1 H), 6.21 (d, J ) 7.5 Hz, 1 H), 6.60