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Typical Procedure
for Preparing Compound 3
A mixture of 1a (152
mg, 1.0 mmol), 2a (261 mg, 1.0 mmol), SeO2 (4.4
mg, 0.04 mmol), and Na2CO3 (10.6 mg, 0.1 mmol)
in MeCN (10 mL) was stirred for 4.5 h at r.t. After complete consumption
of starting material (TLC), MeCN was removed in vacuum to give yellow
syrup. The residue was extracted with CH2Cl2 (2 × 30
mL). The combined organic layers were washed with brine (10 mL)
and dried over anhyd Na2SO4. The extracts
were then concentrated under reduced pressure, and the residue was
purified by column chromatography (eluent: PE-EtOAc) on
SiO2 to give an 81% yield of 3a [(Z)-3a, 129 mg;
(E)-3a, 100
mg].
Compound (Z)-3a: ¹H NMR (400 MHz,
CDCl3): δ = 8.08 (d, J = 8.5
Hz, 2 H), 7.95 (d, J = 8.5
Hz, 2 H), 7.69-7.44 (m, 6 H), 7.10 (s, 1 H), 2.17 (s, 3
H). ¹³C NMR (100 MHz, CDCl3): δ = 191.9,
188.2, 160.6, 137.8, 134.9, 134.8, 132.7, 130.0, 129.1, 128.6, 128.1,
116.0, 15.4. IR (KBr): ν = 2926, 1670, 1635, 1596,
1537, 1246, 1023, 699 cm-¹.
Compound
(E)-3a: ¹H
NMR (400 MHz, CDCl3): δ = 8.00 (d, J = 8.0 Hz,
2 H), 7.89 (d, J = 8.0
Hz, 2 H), 7.57-7.43 (m, 6 H), 7.04 (s, 1 H), 2.45 (s, 3
H). ¹³C NMR (100 MHz, CDCl3): δ = 193.7,
185.1, 160.8, 137.2, 134.9, 133.6, 133.0, 128.8, 128.7, 128.6, 128.4,
115.8, 14.9. IR (KBr): ν = 3413, 1674, 1637, 1540,
1220, 781, 703, 632 cm-¹. Spectral
data were in agreement with those previously reported.³