Beilstein Journal of Organic Chemistry 2009, 5, No. 47.
1H NMR spectra were recorded on Bruker 500 MHz (at [silica gel/pet. ether (60–80 °C) and ethyl acetate mixture, 19:1]
Chemgen Pharma, Kolkata) and Bruker 400 MHz (at Chembi- to furnish 65 mg (71%) of 12 as a light yellow solid, m.p.,
otek International, Kolkata) and Bruker 300 MHz (IACS, 175–177 °C. IR (KBr) νmax 3235, 3302 cm−1; 1H NMR (500
Kolkata) NMR spectrometer respectively. ESI mass spectra MHz, CDCl3) δ: 5.47 (1H, s), 7.04 (1H, br s), 7.58 (1H, t, J =
were recorded on a micro mass Q-TOF mass spectrometer 7.4 Hz), 7.63 (1H, t, J = 7.5 Hz), 7.75 (1H, d, J = 8.8 Hz), 7.78
(serial no. YA 263) at IACS, Kolkata. IR spectral data were (1H, br s), 7.85 (1H, s), 7.91 (1H, d, J = 7.8 Hz), 8.22 (1H, d, J
obtained from a JASCO FT/IR680 PLUS Spectrometer.
= 8.8 Hz), 8.55 (1H, d, J = 8.2 Hz) ppm.
[2-(Furan-2-yl)-naphthalen-1-yl]acetic acid
Phenanthro[1,2-b]furan-10,11-dione (13)
methyl ester (8)
To a stirred solution of potassium nitrosodisulfonate (Fremy’s
A mixture of compound 7 (150 mg, 0.54 mmol), furan-2- salt) (170 mg, 0.65 mmol) in 12 mL 1/6 (M) Na2HPO4 solution
boronic acid (75 mg, 0.64 mmol) and Et3N (0.5 mL, 3.6 mmol) taken in a 50 mL round bottomed flask, a solution of the
was degasified with argon for 25 minutes. Now to it the cata- furonaphthol derivative 12 (50 mg, 0.21 mmol) in 6 mL meth-
lyst Pd(PPh3)4 (~15 mg, 2 mol %) was added. The mixture was anol was added drop wise. Stirring was continued at 0–5 °C for
then heated with stirring under argon at 110 °C till the reaction 2 h and then left overnight in freeze. The dark red solid separ-
was completed (~53 h). After cooling to room temperature, the ated was filtered and purified by column chromatography [silica
mixture was poured into cold water and extracted with ether. gel/ pet. ether (60–80 °C) and ethyl acetate, 10:1]. An analyt-
Organic layer was washed successively with NaHCO3 solution, ical sample was prepared further by recrystallisation from pet
5% brine and dried (Na2SO4) and solvent removed. Crude ether–ethyl acetate mixture. Yield, 25 mg (48%), m.p.,
product thus obtained was then purified by column chromato- 178–180 °C. IR (KBr) νmax 1686, 1667 cm−1; 1H NMR (500
graphy [silica gel/ pet. ether (60–80 °C) and ethyl acetate MHz, CDCl3) δ: 6.87 (1H, br s), 7.53 (1H, d, J = 7.5 Hz), 7.55
mixture, 10:1]. Compound 8 was obtained as a white solid (110 (1H, br s), 7.70 (1H, br t, J = 7.5 Hz), 7.81–7.85 (2H, a doublet
mg) in 77% yield, m.p., 109–111 °C. IR(KBr) νmax : 1737.6 and a triplet merged together), 8.12 (1H, d, J = 8.5 Hz), 9.40
cm−1; 1H NMR (400 MHz, CDCl3) δ: 3.72 (3H, s), 4.33 (2H, s), (1H, d, J = 8.5 Hz) ppm; 13C NMR (125 MHz, CDCl3) δ:
6.53 (1H, dd, J = 1.7 and 3 Hz), 6.67 (1H, d, J = 3 Hz), 7.50 109.11, 119.16, 120.79, 122.88, 126.66, 127.66, 129.20, 130.07,
(1H, t, J = 7.2 Hz), 7.56 (1H, d, J = 7.2 Hz), 7.57 (1H, br s), 131.20, 132.47, 134.65, 137.33, 145.54, 161.31, 174.53, 183.07
7.72 (1H, d, J = 8.6 Hz), 7.82 (1H, d, J = 9.4 Hz), 7.84 (1H, d, J ppm; HRMS (ESI, 70 eV): m/z = 271.0372 [M++Na] (calcu-
= 9.3 Hz), 8.01 (1H, d, J = 8.4 Hz), ppm.
lated mass for C16H8O3Na: 271.0371 [M++Na]).
[2-(Furan-2-yl)-naphthalen-1-yl]acetic acid (9) Naphtho[1,2-b]furan-4,5-dione (18)
A mixture of compound 8 (100 mg, 0.38 mmol), KOH (43 mg, To a stirred solution of potassium nitrosodisulfonate (Fremy’s
0.76 mmol), 2 mL water and 2 mL ethanol was refluxed on a salt) (170 mg, 0.63 mmol) in 5 mL 1/6 (M) Na2HPO4 solution
water bath for 15 h. Excess EtOH was distilled out as much as taken in a 25 mL round bottomed flask, a solution of the
possible and then the residue was diluted with 2–3 mL of water. furonaphthol 17 (50 mg, 0.27 mmol) in 2 mL methanol was
Neutral part was extracted with ether. Aqueous alkaline part added drop wise. Stirring was continued at 0–5 °C for 2 h and
was cooled in ice and acidified with HCl. Separated solid was then left overnight in freeze. The brick red solid separated was
thoroughly extracted with ethyl acetate. After usual work up, 80 filtered to obtain 35 mg of crude product which on purification
mg (85%) of the acid 9 was obtained as white solid, m.p., by column chromatography (silica gel/pet. ether–ethyl acetate,
197–199 °C. IR (KBr) νmax 1692.2 cm−1. (Treatment of the acid 5:1) afforded 30 mg (56%) of the title compound (18). An
9 with diazomethane in ether produced the methyl ester deriv- analytical sample was prepared by further recrystallisation from
ative identical with compound 8.)
pet. ether–EtOAc mixture; m.p., 205–206 °C (lit. [30] m.p
213–215 °C ). IR(KBr) νmax 1674.9 cm−1 (br, strong); 1H NMR
(500 MHz, CDCl3) δ: 6.88 (1H, d, J = 1.8 Hz), 7.48 (1H, t, J =
Phenanthro[1,2-b]furan-11-ol (12)
A mixture of compound 9 (100 mg, 0.39 mmol), 3 mL trifluoro- 7.5 Hz), 7.51 (1H, d, J = 1.8 Hz), 7.67 (1H, t, J = 7.5 Hz), 7.74
acetic anhydride, 0.9 mL trifluoroacetic acid was stirred at room (1H, d, J = 7.5 Hz), 8.1 (1H, d, J = 7.7 Hz) ppm; 13C NMR (125
temperature overnight protecting from moisture. The mixture MHz, CDCl3) δ: 108.94, 121.56, 122.41, 128.49, 128.81,
was then poured in ice cold saturated NaHCO3 solution and 130.36, 130.64, 135.48, 145.13, 160.64, 174.54, 180.56 ppm.
stirred well and extracted thoroughly with CH2Cl2. The organic HRMS (ESI, 70 eV): m/z = 199.0399 [M++H] (calculated mass
layer was washed with aq. NaHCO3 solution and finally with for C12H7O3: 199.0391 [M++H]).[lit. [30]: 1H NMR (300 MHz,
H2O and dried (Na2SO4). Removal of solvent afforded the CDCl3) δ: 8.09 (1H, d, J = 7.9 Hz), 7.73–7.62 (2H, m), 7.49
crude product which was purified by column chromatography (1H, d, J = 2.0 Hz), 7.45 (1H, m), 6.86 (1H, d, J = 2.0 Hz)].
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