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W.-Y. Chai et al.
PAPER
4-tert-Butyl-2-ethynylphenyl Acetate (9)14
(1 mL), and extracted with CH2Cl2 (3 × 10 mL). The combined or-
ganic layers were dried (MgSO4) and concentrated under reduced
pressure. The residue was dissolved in MeOH (10 mL) and treated
with NaOH (34 mg, 0.85 mmol). The reaction mixture was stirred
at reflux overnight (monitored by TLC, eluent: PE–CH2Cl2, 5:1),
quenched with aq 1 M HCl (1 mL), and extracted with CH2Cl2
(3 × 10 mL). The combined organic layers were dried (MgSO4) and
concentrated under reduced pressure. Flash column chromatogra-
phy of the residue on silica gel (PE–CH2Cl2, 3:1) gave 1 (52 mg,
49%) as a pale-yellow solid; mp 252–253 °C.
To a stirred solution of 8 (0.16 g, 0.56 mmol) in THF (5 mL) was
added AcOH (0.064 mL) and TBAF (0.26 g, 0.82 mmol). The reac-
tion mixture was stirred for 1 h at r.t., quenched with sat. aq NH4Cl
(2 mL), and extracted with CH2Cl2 (3 × 10 mL). The combined or-
ganic layers were dried (MgSO4) and concentrated under reduced
pressure. Flash column chromatography of the residue on silica gel
(PE–EtOAc, 30:1) afforded 9 (0.11 g, 92%) as a colorless solid; mp
61–62 °C.
IR (KBr): 3284, 2964, 2220 (C≡C), 1763, 1493, 1368, 1206, 1183,
1123, 1011, 893, 842 cm–1.
IR (KBr): 2960, 2863, 1737, 1458, 1369, 1261, 1163, 877, 812 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.32 (s, 9 H, 3 × CH3), 2.34 (s, 3
H, COCH3), 3.24 (s, 1 H, ≡CH), 7.02 (d, J = 8.8 Hz, 1 H, ArH), 7.39
(dd, J = 8.8, 2.4 Hz, 1 H, ArH), 7.56 (d, J = 2.4 Hz, 1 H, ArH).
13C NMR (100 MHz, CDCl3): d = 20.9 (CH3), 31.2 (CH3), 34.5 (C),
79.2 (C, ≡CH), 81.2 (C, ≡C), 115.4 (C), 121.7 (CH), 127.3 (CH),
130.6 (CH), 148.8 (C), 149.8 (C), 169.1 (C).
1H NMR (400 MHz, CDCl3): d = 1.44 (s, 36 H, 12 × CH3), 6.77 (s,
4 H, 4 × H-3¢), 7.43 (dd, J = 8.8, 2.0 Hz, 4 H, ArH), 7.48 (d, J = 8.8
Hz, 4 H, ArH), 7.61 (d, J = 1.2 Hz, 4 H, ArH), 8.33 (s, 2 H, ArH-
3,6).
13C NMR (100 MHz, CDCl3): d = 31.8 (CH3), 34.7 (C), 106.4 (CH,
C-3¢), 110.7 (CH), 117.4 (CH), 122.8 (CH), 128.6 (C), 129.2 (C),
131.1 (CH), 146.0 (C), 153.0 (C), 154.0 (C).
HRMS (ESI): m/z [M + NH4]+ calcd for C14H20NO2: 234.1489;
found: 234.1484.
HRMS (MALDI): m/z [M + Na]+ calcd for C54H54O4 + Na:
789.3914; found: 789.3918.
1,2,4,5-[Tetrakis(2-acetyloxy-5-tert-butyl)phenylethynyl]ben-
zene (10)
6,7-Bis(5-tert-butylbenzo[b]furan-2-yl)bis(5-tert-butylben-
zo[b]furan-2-yl)[2,3-a:3¢,2¢-c]naphthalene (2)
Method A: Compound 1 (20 mg, 0.026 mmol) was dissolved in
CH2Cl2 (10 mL), and then exposed to UV light for 20 min. The mix-
ture was then concentrated under reduced pressure. Flash column
chromatography on silica gel (PE–CH2Cl2, 10:1) gave 2 (19 mg,
95% brsm) as a pale-yellow solid; mp 236–237 °C.
To a stirred solution of 12 (0.27 g, 0.46 mmol) and Et3N (10 mL) in
THF (5 mL) was added PdCl2(PPh3)2 (35 mg, 0.05 mmol), CuI (20
mg, 0.10 mmol), and 9 (0.60 g, 2.78 mmol). The reaction mixture
was stirred under argon at 40 °C for 48 h. Et2O (10 mL) and aq 0.1
N HCl (2 mL) were added. The organic layer was separated, washed
with H2O (10 mL), dried (MgSO4), and concentrated under reduced
pressure. Flash column chromatography of the residue on silica gel
(PE–EtOAc, 10:1) afforded 10 (0.39 g, 91%) as a pale-yellow solid;
mp 135–136 °C.
Method B: To a stirred solution of 1 (20 mg, 0.026 mmol) in CH2Cl2
(20 mL) was added a solution of FeCl3 (26 mg, 0.16 mmol) in anhyd
MeNO2 (1 mL) dropwise under argon at 0 °C. Stirring was contin-
ued at this temperature for 3 min, and the reaction mixture was
quenched with MeOH (1 mL). The solvent was removed under re-
duced pressure. Flash chromatography of the residue on silica gel
(PE–CH2Cl2, 3:1) afforded 2 (18 mg, 90%) as a pale-yellow solid;
mp 236–237 °C.
IR (KBr): 2962, 2870, 2212 (C≡C), 1769, 1450, 1367, 1194, 1122,
1010, 898, 838 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.29 (s, 36 H, 12 × CH3), 2.26 (s,
12 H, 4 × COCH3), 7.04 (d, J = 8.8 Hz, 4 H, ArH), 7.39 (dd, J = 8.8,
2.4 Hz, 4 H, ArH), 7.66 (d, J = 2.4 Hz, 4 H, ArH), 7.71 (s, 2 H, ArH-
3,6).
13C NMR (100 MHz, CDCl3): d = 20.7 (CH3), 31.1 (CH3), 34.4 (C),
90.9 (C, ≡C), 91.1 (C, ≡C), 116.0 (C), 121.7 (CH), 125.0 (C), 127.3
(CH), 130.3 (CH), 135.2 (CH), 148.8 (C), 149.2 (C), 169.0 (C).
IR (KBr): 2958, 2867, 1741, 1471, 1363, 1253, 1203, 1121, 1067,
871, 811 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.43 (s, 18 H, 6 × CH3), 1.59 (s,
18 H, 6 × CH3), 6.77 (s, 2 H, 2 × H-3¢), 7.42 (d, J = 8.8 Hz, 2 H,
ArH), 7.51 (d, J = 8.8 Hz, 2 H, ArH), 7.60 (s, 2 H, ArH), 7.64 (d,
J = 8.8 Hz, 2 H, ArH), 7.73 (d, J = 8.8 Hz, 2 H, ArH), 8.62 (s, 2 H,
ArH-4¢¢), 8.97 (s, 2 H, ArH).
HRMS (ESI): m/z [M + H]+ calcd for C62H63O8: 935.4517; found:
935.4519.
Hexakis[(2-acetyloxy-5-tert-butyl)phenylethynyl]benzene (11)
According to the preceding procedure for the preparation of alkyne
10, perbromobenzene (13; 0.08 g, 0.15 mmol) and alkyne 9 (0.26 g,
1.20 mmol) provided compound 11 (0.15 g, 74%) as a pale-yellow
solid; mp 174–175 °C.
13C NMR (100 MHz, CDCl3): d = 31.9 (CH3), 32.0 (CH3), 34.8 (C),
35.0 (C), 106.2 (CH, C-3¢), 110.7 (CH), 111.5 (CH), 115.6 (C),
117.5 (CH), 118.8 (CH), 119.4 (C), 122.6 (CH), 123.3 (CH), 124.3
(C), 124.7 (CH), 127.3 (C), 128.9 (C), 146.0 (C), 146.2 (C), 149.0
(C), 153.1 (C), 154.6 (C), 155.0 (C).
IR (KBr): 2961, 2871, 2207 (C≡C), 1762, 1491, 1364, 1186, 1120,
HRMS (MALDI): m/z [M + Na]+ calcd for C54H52O4 + Na:
787.3758; found: 787.3752.
1008, 893, 829 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.26 (s, 54 H, 18 × CH3), 1.99 (s,
18 H, 6 × COCH3), 7.03 (d, J = 8.8 Hz, 6 H, ArH), 7.41 (dd, J = 8.8,
2.4 Hz, 6 H, ArH), 7.71 (d, J = 2.4 Hz, 6 H, ArH).
13C NMR (100 MHz, CDCl3): d = 20.5 (CH3), 31.1 (CH3), 34.4 (C),
90.4 (C, ≡C), 95.4 (C, ≡C), 116.3 (C), 121.9 (CH), 127.4 (CH),
127.5 (C), 131.0 (CH), 148.7 (C), 149.4 (C), 169.3 (C).
Tetrakis(5-tert-butylbenzo[b]furan-2-yl)[2,3-a:3¢,2¢-c:2¢¢,3¢¢-
f:3¢¢¢,2¢¢¢-h]anthracene (3)
Method A: To a stirred solution of 1 (20 mg, 0.026 mmol) in CH2Cl2
(20 mL) was added a solution of FeCl3 (34 mg, 0.21 mmol) in anhyd
MeNO2 (1 mL) dropwise under argon at 0 °C. Stirring was contin-
ued at this temperature for 3 min, and the reaction mixture was
quenched with MeOH (1 mL). The solvent was removed under re-
duced pressure. Flash chromatography of the residue on silica gel
(PE–CH2Cl2, 3:1) afforded 3 (10 mg, 50%) as a pale-yellow solid;
mp >380 °C.
HRMS (ESI): m/z [M + H]+ calcd for C90H91O12: 1363.6505; found:
1363.6501.
1,2,4,5-Tetrakis(5-tert-butylbenzo[b]furan-2-yl)benzene (1)
To a stirred solution of 10 (0.13 g, 0.14 mmol) in CH2Cl2 and
MeOH (1:1 v/v) was added NaOH (34 mg, 0.85 mmol). The reac-
tion mixture was stirred at r.t. overnight, quenched with aq 1 M HCl
Method B: To a stirred solution of 2 (20 mg, 0.026 mmol) in CH2Cl2
(20 mL) was added a solution of FeCl3 (13 mg, 0.08 mmol) in anhyd
Synthesis 2012, 44, 439–445
© Thieme Stuttgart · New York