J Fluoresc
50/50) to obtain 1-ethynylpyrene (353 mg, 87 %) as a white
powder. 1H-NMR (500 MHz, CDCl3): δ (ppm)=8.51 (d, J=
9.2 Hz, 1H), 8.13–8.06 (m, 4H), 8.00–7.90 (m, 4H), 3.59 (s,
1H). 13C-NMR (500 MHz, CDCl3): δ (ppm)=132.4, 131.5,
131.0, 130.8, 130.0,128.4, 128.3, 127.0, 126.1, 125.6, 125.6,
125.2, 124.3, 124.2, 124.0, 116.4, 82.7, 82.5.
by column chromatography (alumina, n-hexane/chloroform
=30/70) to obtain 4b (179 mg, 0.309 mmol). The compound
4b was dissolved in CH2Cl2 (10 ml), and DIEA (0.3 ml) and
BF3 Et2O complex (0.3 ml) were added to the reaction
solution, and stirred for 1 h at room temperature. The
reaction mixture was diluted with toluene, washed with
saturated NaHCO3 aqueous solution and brine, dried over
Na2SO4 and evaporated. The resulting residue was purified
by chromatography (silica gel, eluent: n-hexane/chloroform
=50/50 to 25/75) to obtain 5b as a yellow metallic solid
(112 mg, 40 % for 2 steps). 1H NMR (300 MHz, CDCl3): δ
(ppm)=7.88 (d, J=8.4 Hz, 2H), 7.83 (dd, J=1.2 Hz, 7.8 Hz,
4H), 7.50–7.42 (m, 6H), 7.33 (d, J=8.7 Hz, 2H), 7.01 (s,
2H), 6.27 (s, 2H). 13C NMR (500 MHz, CDCl3): δ (ppm)=
168.1, 153.9, 150.1, 141.1 139.3, 137.7, 133.8, 132.2,
130.3, 129.7, 129.1, 125.6, 103.2, 96.3, 95.6.
Compound 5a
2-Methyl-4H-furo[3,2-b]pyrrole-5-carboxylic acid 3a
(168 mg, 1.02 mmol, 2 eq.) was dissolved in TFA (2 ml)
and stirred at 50 °C for 40 min. 4-Iodobenzaldehyde
(118 mg, 0.509 mmol, 1 eq.) in TFA (2 ml) and
methanesulfonic acid (0.2 ml) were added to the reaction
mixture and stirred overnight at room temperature. p-
Chloranil (128 mg, 0.521 mmol, 1 eq.) was added to the
solution and the stirring was further continued for 90 min.
The reaction mixture was slowly poured into saturated
NaHCO3 aqueous solution (100 ml), and the resulting aque-
ous solution was extracted with CH2Cl2. The collected
organic phase was washed with water and brine, dried over
Na2SO4 and evaporated. The resulting residue was purified
by column chromatography (alumina, n-hexane/chloroform
=30/70) to obtain 4a (160 mg, 0.352 mmol). The compound
4a was dissolved in CH2Cl2 (10 ml), and TEA (0.5 ml) and
BF3 Et2O complex (0.5 ml) were added to the reaction
solution, and stirred for 2 h at room temperature. The
reaction mixture was diluted with toluene, washed with
saturated NaHCO3 aqueous solution and brine, dried over
Na2SO4 and evaporated. The resulting residue was purified
by chromatography (silica gel, eluent: n-hexane/chloroform
=50/50 to 25/75) to obtain 5a as a yellow metallic solid
(74.1 mg, 29 % for 2 steps). 1H NMR (300 MHz, CDCl3): δ
(ppm)=7.84 (d, J=8.1 Hz, 2H), 7.27 (d, J=8.4 Hz, 2H),
6.35 (s, 2H), 6.13 (s, 2H), 2.46 (s, 6H). 13C NMR
(500 MHz, CDCl3): δ (ppm)=169.5, 153.1, 150.3, 142.3,
137.5, 137.5, 133.8, 132.1, 103.1, 97.9, 96.1, 15.8.
Compound 5c
2-(2,4-Dimethoxyphenyl)-4H-furo[3,2-b]pyrrole-5-carboxylic
acid 3c (410 mg, 1.43 mmol, 2 eq.) was dissolved in TFA
(5 ml) and stirred at 40 °C for 20 min. 4-Iodobenzaldehyde
(165 mg, 0.713 mmol, 1 eq.) in TFA (2 ml) and
methanesulfonic acid (0.3 ml) were added to the reaction
mixture and stirred overnight at room temperature. p-
Chloranil (182 mg, 0.738 mmol, 1 eq.) was added to the
solution and the stirring was further continued for 1 h. The
reaction mixture was slowly poured into saturated NaHCO3
aqueous solution (200 ml), and the resulting aqueous solution
was extracted with CH2Cl2. The collected organic phase was
washed with water and brine, dried over Na2SO4 and evapo-
rated. The resulting residue was purified by column chroma-
tography (alumina, n-hexane/chloroform=30/70) to obtain 4c
(348 mg, 0.497 mmol). The compound 4c was dissolved in
CH2Cl2 (30 ml), and DIEA (0.7 ml) and BF3 Et2O complex
(0.7 ml) were added to the reaction solution, and stirred for
90 min at room temperature. The reaction mixture was diluted
with toluene, washed with saturated NaHCO3 aqueous solution
and brine, dried over Na2SO4 and evaporated. The resulting
residue was purified by chromatography (silica gel, eluent: n-
hexane/chloroform=40/60 to 20/80) to obtain 5c as a yellow
metallic solid (96.6 mg, 18 % for 2 steps). 1H NMR (500 MHz,
THF-d8): δ (ppm)=7.92 (d, J=8.3 Hz, 2H), 7.86 (d, J=8.9 Hz,
2H), 7.42 (d, J=8.6 Hz, 2H), 7.09 (s, 2H), 6.68 (d, J=2.3 Hz,
2H), 6.64 (dd, J=8.9 Hz, 2.3 Hz, 2H), 6.24 (s, 2H), 4.03 (s,
6H), 3.86 (s, 6H). 13C NMR (500 MHz, THF-d8): δ (ppm)=
166.7, 165.7, 160.0, 153.4, 151.6, 140.2, 140.0, 138.5, 135.5,
133.4, 129.0, 112.9, 106.7, 102.0, 99.5, 99.0, 96.4, 56.0, 55.8.
Compound 5b
2-Phenyl-4H-furo[3,2-b]pyrrole-5-carboxylic acid 3b
(202 mg, 0.89 mmol, 2 eq.) was dissolved in TFA (4 ml)
and stirred at 40 °C for 30 min. 4-Iodobenzaldehyde
(103 mg, 0.445 mmol, 1 eq.) in TFA (1 ml) and
methanesulfonic acid (0.1 ml) were added to the reaction
mixture and stirred overnight at room temperature. p-
Chloranil (118 mg, 0.481 mmol, 1.1 eq.) was added to the
solution and the stirring was further continued for 1 h. The
reaction mixture was slowly poured into saturated NaHCO3
aqueous solution (100 ml), and the resulting aqueous solu-
tion was extracted with CH2Cl2. The collected organic
phase was washed with water and brine, dried over
Na2SO4 and evaporated. The resulting residue was purified
PKF-1
Compound 5a (33.7 mg, 0.093 mmol, 1 eq.), 1-
ethynylpyrene (30.8 mg, 0.131 mmol, 1.5 eq.), and CuI(I)