Zhang et al.
JOCArticle
and reference electrode, respectively. The potential was cali-
brated against the ferrocene/ferrocenium couple. TGA was
carried out at a heating rate of 10 deg min-1 under nitrogen
flow. DSC was performed at a heating/cooling rate of 10 deg min-1
under nitrogen flow. The crystallographic data collection was
carried out at 293 K. Powder X-ray diffraction measurement
was performed at room temperature. SEM measurements were
carried out on a field emission scanning electron microanalyzer
at 5 kV. The samples for SEM were prepared by droping a drop
of dilute toluene solution of the TBC-C8 onto a Si wafer and the
solvent was allowed to evaporate slowly in a saturated toluene
atmosphere at room temperature. TEM measurements were
conducted at 200 keV. The saturated solutions of TBC-C8 in
hexane and toluene were aged for 3 days at room temperature
and then dropped onto 300 mesh copper TEM grids.
Synthesis of Thioketone 2a. Benzophenone (1a, 2.73 g, 15.0
mmol) and Lawesson’s reagent (0.6 eq, 3.60 g, 9.0 mmol) were
added to 120 mL of toluene. The solution was heated to 80 °C
under nitrogen atmosphere for 12 h. The dark blue solution was
allowed to cool to room temperature and 200 mL of a mixture
solvent of hexane and DCM (4:1, v/v) was added. The mixture
was filtrated through a plug of silica gel and washed with a
small amount of the same eluent. The solvent of the filtrate
was removed under vacuum and the crude product 2a was
isolated as a blue solid (2.90 g). Compound 2a is not stable so
the crude product was used for the next step immediately. 1H
NMR (300 MHz, CDCl3, 300 K, ppm) δ 7.81 (d, J=6.96 Hz,
4H), 7.59 (t, J=7.65 Hz, 4H), 7.49 (t, J=7.68 Hz, 2H). It is
hard to obtain 13C NMR spectra and MS spectra due to the
poor stability of 2a.
Synthesis of Thioepoxide 3a. A 1.2 equiv sample of 10-
diazoanthrone16 (3.30 g, 15.0 mmol) dissolved in THF (50 mL)
was added dropwise to a solution of thioketone 2a (2.55 g,
14.0 mmol) in THF (150 mL). After addition, the reaction
was stirred for 15 h. After romoval of solvent under vacuum,
the residue was purified by column chromatography (silica
gel, 4:1 hexane:DCM, Rf = 0.3) to give compound 3a as a
white solid (3.34 g, 57%), mp 230.2-231.5 °C. 1H NMR (500 MHz,
CDCl3, 300 K, ppm) δ 8.28 (d, J=7.55 Hz, 2H), 7.32 (t, J=
7.60 Hz, 2H), 7.25 (d, J=8.20 Hz, 2H), 7.10 (m, 6H), 6.95 (m,
6H). 13C NMR (125 MHz, CDCl3, 300 K, ppm) δ 184.8,
141.6, 139.8, 134.3, 131.9, 129.2, 128.9, 127.8, 127.6, 127.0,
126.7, 70.5, 56.6. MS (EI) calcd for C27H18OS (Mþ) 390.11,
found 390.10. Anal. Calcd for C27H18OS: C, 83.05; H, 4.65.
Found: C, 83.31; H, 4.52.
Synthesis of Ketone 4a. A solution of the thioepoxide 3a (3.00g,
7.68 mmol) and triphenylphosphine (2.40 g, 9.20 mmol) in
anhydrous toluene (120 mL) was heated at reflux under nitrogen
atmosphere for 24 h. After being cooled to room temperature,
the solvent was removed under reduced pressure. The solid
residue was purified by column chromatography (silica gel, 3:1
hexane: DCM, Rf=0.4) and ketone 4a was isolated as a light
yellow solid (2.60 g, 95%), mp 216.0-216.8 °C. 1H NMR (500 MHz,
CDCl3, 300 K, ppm) δ 8.20 (d, J=7.55 Hz, 2H), 7.30 (m, 12H),
7.19 (d, J=8.20 Hz, 2H), 7.12 (t, J=7.55 Hz, 2H). 13C NMR (125
MHz, CDCl3, 300 K, ppm) δ 186.0, 146.2, 143.0, 139.4, 133.0,
130.7, 130.5, 129.2, 129.1, 128.6, 127.2, 127.1, 126.4. MS (EI)
calcd for C27H18O (Mþ) 358.14, found 358.20. Anal. Calcd for
C27H18O: C, 90.47; H, 5.06. Found: C, 90.22; H, 5.03.
THF (50 mL). After addition, the reaction was stirred for 15 h.
After removal of solvents under vacuum, the residue was
purified by column chromatography (silica gel, 2:1 hexane:
DCM, Rf=0.3) to give compound 6a as a white solid (1.00 g,
89%), mp 254.3-255.5 °C. 1H NMR (500 MHz, CDCl3, 300
K, ppm) δ 7.47 (d, J=7.55 Hz, 4H), 7.42 (d, J=8.20 Hz, 2H),
7.38 (d, J=6.95 Hz, 4H), 7.25 (m, 6H), 7.16 (d, J=6.95 Hz,
2H), 7.10 (m, 6H), 6.86 (t, J=7.55 Hz, 2H), 6.77 (t, J=7.60 Hz,
2H). 13C NMR (125 MHz, CDCl3, 300 K, ppm) δ 142.2,
140.7, 139.9, 138.9, 136.3, 133.8, 130.4, 130.0, 128.5, 128.3,
128.0, 127.3, 126.8, 126.0, 125.8, 69.6, 63.7. MS (EI) calcd
for C40H28S (Mþ) 540.19, found 540.20. Anal. Calcd for
C
40H28S: C, 88.85; H, 5.22. Found: C, 88.52; H, 5.60.
Synthesis of 7a. The procedure for the synthesis of 4a was
followedtoprepare7a from 6a and triphenylphosphine. Compound
7a was obtained as a white solid in 87% yield, mp 309.4-
310.0 °C. 1H NMR (500 MHz, CDCl3, 300 K, ppm) δ 7.43 (d, J=
8.20 Hz, 8H), 7.30 (t, J=7.55 Hz, 8H), 7.22 (t, J=7.55 Hz, 4H),
7.00 (m, 4H), 6.73 (m, 4H). 13C NMR (125 MHz, CDCl3, 300 K,
ppm) δ 142.5, 139.8, 137.8, 135.6, 129.7, 128.2, 127.9, 126.6,
125.1. MS (EI) calcd for C40H28 (Mþ) 508.22, found 508.30. Anal.
Calcd. for C40H28: C, 94.45; H, 5.55. Found: C, 94.10; H, 5.66.
Synthesis of 8a. The photolysis setup has been previously
described.17 A mixture of compound 7a (508 mg, 1.00 mmol),
iodine (1.28 g, 5.00 mmol), and propylene oxide (20 mL) in
anhydrous benzene (250 mL) was irradiated with a 450 W
medium-pressure mercury vapor lamp in an immersion well,
under argon atmosphere. After 16 h of irradiation, the solvent
was removed under reduced pressure and a yellow powder
precipitate was collected. Compound 8a (389 mg, 77%) was
isolated by column chromatography (4:1 chloroform:THF, Rf=
0.6), mp 348.0-349.1 °C. 1H NMR (500 MHz, CDCl3, 300 K,
ppm) δ 9.14 (s, 2H), 9.00 (d, J=8.20 Hz, 2H), 8.03 (d, J=8.20 Hz,
2H), 7.76 (t, J=6.95 Hz, 2H), 7.60 (m, 10H), 7.50 (m, 4H), 6.76 (m,
2H). 13C NMR (125 MHz, CDCl3, 300 K, ppm) δ 141.7, 134.6,
133.6, 132.4, 131.9, 130.6, 129.5, 129.0, 127.8, 127.6, 127.4,
126.9, 126.5, 126.2, 125.7, 125.4, 122.8, 121.7. MS (EI) calcd
for C40H24 (Mþ) 504.19, found 504.30. Anal. Calcd. for C40H24:
C, 95.21; H, 4.79. Found: C, 94.84; H, 5.08.
Synthesis of TBC. Compound 8a (100 mg, 0.20 mmol) was
dissolved in dichloromethane (60 mL) in a 250-mL two-necked
round-bottomed flask. A constant stream of argon was bubbled
into the solution through a glass capillary. A solution of FeCl3
(0.74 g, 4.60 mmol) in CH3NO2 (10 mL) was then added
dropwise via syringe. Throughout the whole reaction, a constant
stream of argon was bubbled through the mixture to remove
HCl formed in situ. The reaction was stirred for 25 min and then
quenched by adding methanol (200 mL). The precipitate was
collected by filtration, washed with methanol, hexane, and
chloroform, and dried under vacuum to afford TBC as a yellow
solid (56 mg, 57% yield), mp >400 °C. It is hard to record 1H
NMR and 13C NMR spectra due to the poor solubility and
strong π-stacking of 2a. MS (EI) calcd for C40H20 (Mþ) 500.16,
found 500.30. HRMS (FABþ) calcd for C40H20 500.1565, found
500.1572 (error=1.4 ppm). Anal. Calcd. for C40H20: C, 95.97;
H, 4.03. Found: C, 95.81; H, 3.97.
Synthesis of TBC-C8:. Synthesis of Thioketone 2b The pro-
cedure for the synthesis of 2a was followed to prepare 2b from
4,40-dioctylbenzophenone (1b, see the synthesis in the Support-
ing Information) and Lawesson’s reagent. Compound 2b was
obtained as a dark blue oil in 95% yield. 1H NMR (300 MHz,
CDCl3, 300 K, ppm) δ7.65(d,J=8.40Hz, 4H),7.18(d,J=8.37 Hz,
4H), 2.65 (t, J=7.56 Hz, 4H), 1.63 (m, 4H), 1.30 (m, 20H), 0.89
(m, 6H). 13C NMR (75 MHz, CDCl3, 300 K, ppm) δ 147.8,
145.3, 129.9, 128.0, 36.0, 31.9, 31.0, 29.4, 29.3, 29.2, 22.6, 14.0.
MS (EI) calcd for C29H42S (Mþ) 422.30, found 422.40.
Synthesis of Thioketone 5a. The procedure for the synthesis of
2a was followed to prepare 5a from 4a and Lawesson’s reagent.
Compound 5a was obtained as a dark green solid in 91% yield.
1H NMR (300 MHz, CDCl3, 300 K, ppm) δ 8.34 (d, J=7.38 Hz,
2H), 7.23 (m, 12H), 7.10 (m, 4H). It is hard to obtain 13C NMR
spectra and MS spectra due to the poor stability of 5a.
Synthesis of Thioepoxide 6a. A 1.1 equiv sample of
diphenyldiazomethane12a dissolved in 20 mL of DCM was added
dropwise to a solution of thioketone 5a (1.12 g, 3.00 mmol) in
Synthesis of Thioepoxide 3b. The procedure for the synthesis
of 3a was followed to prepare 3b. Compound 3b was obtained as
8076 J. Org. Chem. Vol. 75, No. 23, 2010