N. Thasana et al. / Tetrahedron Letters 44 (2003) 1019–1021
1021
Acknowledgements
2000, 41, 21–24; (b) Au, A. T. Synth. Commun. 1984, 14,
749–753.
We acknowledge the financial contribution from the
Thailand Research Fund (TRF) for the generous sup-
port of the research program and the award of Senior
Research Scholar to S.R. as well as the award of the
Royal Golden Jubilee Scholarship to N.T. We also
acknowledge the facilities in the Department of Chem-
istry provided by the PERCH program.
10. A typical procedure for the preparation of aromatic
cyanohydrin carbonate ester: To a stirred solution of
2-benzyloxy benzaldehyde 1h (5.3 g, 25.0 mmol), ethyl
chloroformate (3.0 g, 27.5 mmol), and benzyltrimethyl
ammonium chloride (0.3 g, 1.6 mmol), in
dichloromethane (40 mL) cooled in an ice-bath were
slowly added a solution of potassium cyanide (2.45 g,
50.0 mmol), in distilled water (40 mL). The mixture was
stirred overnight at room temperature. The organic layer
was washed with water, saturated sodium hydrogen car-
bonate solution, dried (Na2SO4), and evaporated to give
a yellow oil. Purification by distillation under reduced
pressure yielded 2-benzyloxyphenyl cyanohydrin carbon-
ate ester 2h (6.03 g, 78%).
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11. Compound 2h: oil; IR (neat): wmax 1757 (CꢀO), 1603,
1
1494, 1455, 1372, 1251, 1008 cm−1; H NMR (200 MHz,
CDCl3) l 1.28 (t, 3H, J=7.0 Hz, CH3), 4.21 (dq, 2H,
J=7.0 Hz, CH2), 5.12 (s, 2H, CH2), 6.65 (s, 1H, CH),
6.97 (dd, 1H, J=1.0, 8.0 Hz, ArH), 7.02 (t, 1H, J=7.4
Hz, ArH), 7.37 (m, 6H, ArH), 7.59 (dd, 1H, J=1.8, 7.6
Hz, ArH); 13C NMR (50 MHz, CDCl3) ppm 14.0, 61.8,
65.3, 70.3, 112.2, 115.8, 119.7, 121.1, 127.1, 128.0, 128.5,
128.7, 131.9, 135.9, 155.3, 155.7; MS (EI) m/z 311 (M+,
14), 310 (37), 245 (16), 220 (16), 91 (100). HRMS calcd
for C18H17NO4: 311.1158. Found: 311.1159.
12. A typical procedure for the aromatic cyanohydrin carbon-
ate ester rearrangement: A solution of lithium diisopropyl
amide (LDA) (1.2 mmol) was prepared at 0°C from
diisopropyl amine (0.2 mL, 1.2 mmol) in dry THF (3 mL)
and 1.3 M n-butyllithium (1 mL, 1.2 mmol). After 30
min, the solution was cooled to −78°C and a solution of
2-benzyloxyphenyl cyanohydrin carbonate ester 2h (0.17
g, 0.5 mmol) in dry THF (2 mL) was added dropwise.
The solution was stirred at −78°C for an hour and
allowed to reach room temperature overnight. The mix-
ture was quenched with saturated aq. ammonium chlo-
ride and extracted with dichloromethane. The organic
layer was washed with water, brine, dried (Na2SO4), and
evaporated to give a yellow solid. Recrystallization using
ethyl acetate and hexane yielded 2-phenylbenzofuran-3-
carboxylic acid 11 (0.077 g, 65%) as yellowish crystals.
13. Compound 11: mp 167–168°C; IR (KBr): wmax 3216
(OH), 1607 (CꢀO), 1562, 1482, 1418, 1288, 1213, 1131
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1
cm−1; H NMR (400 MHz, CDCl3) l 7.06 (bs, 1H, OH),
7.51 (m, 5H, ArH), 7.72 (dt, 1H, J=1.4, 8.6 Hz, ArH),
8.27 (m, 3H, ArH); 13C NMR (100 MHz, CDCl3) ppm
118.3, 120.7, 124.5, 125.5, 127.8, 128.6, 130.2, 131.1,
133.6, 138.5, 144.9, 155.5, 173.5; MS (EI) m/z 238 (M+,
100). HRMS calcd for C15H10O3: 238.0629. Found:
238.0625.
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9. (a) Kraus, G. A.; Dneprovskaia, E. Tetrahedron Lett.