418
h.K. tanuI et al.
121.2, 115.8, 86.6, 67.6, 19.8, 16.5, 11.9. HRMS (ESI-
TOF): m/z 509.2444 [M + H]+, calcd. for C32H33N2O4
509.2435.
The organic phase was dried over anhydrous NaHCO3 and
concentrated under reduced pressure. The crude mixture
was purified by flash column chromatography on silica
gel using hexane/ethyl acetate (7:1) as eluant. The prod-
uct (5c) was obtained (0.25 g) in 55% yield and recrys-
tallized from dichloromethane to give colorless crystals.
mp 45–47 °C. 1H NMR (250 MHz, CDCl3): δ, ppm 8.86
(1H, s), 8.83 (1H, s), 8.47 (1H, s), 7.53 (1H, d, J = 7.45
Hz), 7.45 (1H, d, J = 7.91 Hz), 7.24 (2H, m), 4.33 (2H,
q, J = 7.12 Hz), 4.23 (2H, q, J = 6.98 Hz), 2.37 (3H, s),
2.30 (3H, s), 2.11 (3H, s), 1.79 (3H, s), 1.39 (3H, t, J =
7.19 Hz), 1.32 (3H, t, J = 6.96 Hz). 13C NMR (63 MHz,
CDCl3): δ, ppm 9.9, 10.4, 10.7, 11.2, 14.7, 14.9, 60.3,
60.4, 105.9, 111.4, 119.5, 119.6, 120.0, 120.2, 121.3,
123.6, 124.6, 126.6, 128.1, 128.2, 128.8, 136.1, 161.6,
161.2. HRMS (ESI-TOF): m/z 448.2221 [M + H]+, calcd.
for C26H30N3O4 448.2231.
2,3-bis[2-(5-benzyloxycarbonyl-3,4-dimethyl-
pyrrolyl)]-indole (5a). Prepared using above method
from 4a in 54% yield and recrystallized from dichlo-
romethane to give colorless crystals. mp 53–54 °C.
1H NMR (250 MHz, CDCl3): δ, ppm 8.82 (1H, s), 8.80
(1H, s), 8.30 (1H, s), 7.34 (14H, m), 5.28 (2H, s), 5.18
(2H, s), 2.60 (2H, q, J = 7.56 Hz), 2.31 (3H, s), 2.34 (3H,
s), 2.23 (2H, q, J = 7.58 Hz), 1.11 (3H, t, J = 7.53 Hz),
0.82 (3H, t, J = 7.58 Hz). 13C NMR (63 MHz, CDCl3):
δ, ppm 10.6, 11.2, 15.2, 15.7, 18.1, 66.0, 106.1, 111.4,
119.5, 119.8, 123.6, 126.3, 127.3, 128.4, 128.5, 128.8,
128.9, 129.2, 136.0, 136.6, 161.7. HRMS (ESI-TOF): m/z
600.2889 [M + H]+, calcd. for C38H38N3O4 600.2863.
Cis-1,2-[2-(5-ethoxycarbonyl-4-ethyl-3-methylpyr-
rolyl)]ethene (6). Commercially available Lindlar’s cat-
alyst (5 wt.% Pd on CaCO3, poisoned with lead; 150 mg,
100 wt.%) was added to a solution of alkyne 4c (150 mg,
0.42 mmol) in dry ethyl acetate (15 mL). The flask was
evacuated and flushed with hydrogen gas (two freeze/
thaw cycles) and the mixture was stirred under hydrogen
gas for 12 h. The resulting mixture was then filtered over
a Celite cake and washed with ethyl acetate (2 × 30 mL).
The solvent was removed under reduced pressure and
the crude residue was purified by silica gel column chro-
matography eluting with ethyl acetate/dichloromethane/
hexanes (1:1:5) to yield the title product as a yellow oil
that solidified to a yellow powder (47 mg, 0.13 mmol,
31% yield). 1H NMR (450 MHz, CDCl3, 293 K): δ, ppm
8.73 (2H, s, NH), 6.33 (2H, s, CHCH), 4.26 (4H, q, CH2),
2.29 (6H, s, CH3), 1.99 (6H, s, CH3), 1.30 (6H, t, CH3).
HRMS (ESI-TOF): m/z 359.1965 [M + H]+, calcd. for
C20H27N2O4 359.1971.
1,2-bis[2-(5-benzyloxycarbonyl-3,4-dimethylpyr-
rolyl)]ethyne (4b). This compound was obtained in 54%
yield using the above method B and recrystallized from
1
dichloromethane to afford colorless crystals. H NMR
(250 MHz, CDCl3): δ, ppm 11.99 (2H, s), 7.47–7.32
(10H, m), 5.29 (4H, s), 2.2 (6H, s), 2.0 (6H, s). MS (EI):
m/z 480.129 [M]+.
1,2-bis[2-(5-ethoxycarbonyl-3,4-dimethylpyrro-
lyl)]ethyne (4c). This compound was obtained in 52%
yield using the above method B and recrystallized from
1
dichloromethane to afford colorless crystals. H NMR
(250 MHz, CDCl3): δ, ppm 8.80 (2H, s), 4.34 (4H. q, J =
7.01 Hz), 2.35 (6H, s), 2.10 (6H, s), 1.37 (6H, t, J = 7.05
Hz). 13C NMR (63 MHz, CDCl3): δ, ppm 10.3, 10.9, 14.9,
60.6, 86.0, 114.8, 120.3, 126.9, 160.6. HRMS (MALDI-
TOF): m/z 357.1807 [M + H]+, calcd. for C20H25N2O4
357.1808.
1,2-bis(N-tosylpyrrolyl)ethyne (4d). To a 50 mL round
bottom flask was added 2-bromo-1-tosyl-pyrrole (0.3 g,
1 mmol) followed by Pd(PPh)2Cl2 (0.042 g, 0.06 mmol)
and CuI (0.038 g, 0.2 mmol). The flask was sealed and
placed in a dry ice bath under N2. Trimethylsilylethyne
(0.072 mL, 0.5 mmol), DBU (0.9 mL, 6 mmol) and water
(0.0072 mL, 40 molar equiv.) were dissolved in benzene
(5 mL) and added to the reaction flask. After freezing the
mixture in a dry ice bath, the flask was evacuated and
nitrogen gas was added. The resulting reaction mixture
was allowed to warm slowly to room temperature and was
stirred until complete disappearance of the starting mate-
rial, as monitored by TLC. The mixture was worked up by
adding ethyl acetate (100 mL), and washing the organic
layer three times with brine. The organic phase was dried
over anhydrous Na2CO3 and concentrated under reduced
pressure. The crude mixture was purified by flash column
chromatography using hexane/ethyl acetate (5:1) for elu-
tion. The bispyrrolylethyne (4d) was obtained in 8.4%
yield (0.02 g) and recrystallized from dichloromethane
1
to afford colorless crystals. mp 185–186 °C. H NMR
(250 MHz, CDCl3,): δ, ppm 7.9 (4H, br), 7.4 (4H, br), 7.3
(2H, br, 2H), 6.71 (2H, br), 6.34 (2H, br), 2.42 (6H, s).
HRMS (MALDI-TOF): m/z 465.0939 [M + H]+, calcd.
for C24H21O4N2S2 465.0943.
2,3-bis[2-(5-ethoxycarbonyl-3-ethyl-4-methylpyr-
rolyl)]-indole (5c). 1,2-bis[2-(5-ethoxycarbonyl-3,4-
dimethylpyrrolyl)]ethyne (4c) (0.36 g, 1 mmol) was added
to a 100 mL reaction tube together with 2-iodoaniline
(0.44 g, 2 mmol), Pd(OAc)2 (0.02 g, 0.1 mmol), LiCl
(0.04 g, 1 mmol), and K2CO3 (1.38 g, 10 mmol) and dis-
solved in 25 mL of DMF. The mixture was placed in a
dry ice bath, evacuated, purged with nitrogen gas and
then allowed to warm to room temperature and heated at
80 °C for 2 d. The reaction was monitored by TLC. Ethyl
acetate (150 mL) was added to the reaction mixture and
the organic layer was washed with brine (3 × 100 mL).
1,2-bis[2-(5-benzyloxycarbonyl-3-ethyl-4-
methylpyrrolyl)]-dodecaborane (7). A mixture of
dodecaborane (2.44 g, 3.0 mmol) and Et2S (9.0 mL,
37 mmol) in 20 mL of dry toluene was heated at 40 °C for
2 h under Ar, then raised to 60 °C for 3 h. Then 4a (1.06 g,
2 mmol) in 20 mL toluene was added into the mixture
via a syringe, and the mixture was heated to 80 °C for
2 d under argon. After TLC indicated no 4a remained,
Copyright © 2011 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2011; 15: 418–420