Palladium and Copper Bimetallic Catalyst
1H), 2.93 (ddddd, J ) 16.4, 5.2, 2.8, 2.8, 2.8 Hz, 1H), 3.45 (dt, J )
9.6, 6.8 Hz, 1H), 3.72 (dt, J ) 9.6, 6.8 Hz, 1H), 4.70 (ddd, J ) 2.0,
2.0, 2.0 Hz, 2H), 5.22 (d, J ) 5.2 Hz, 1H), 6.43 (br s, 1H), 7.14 (d,
J ) 7.2 Hz, 2H), 7.21 (t, J ) 7.2 Hz, 1H), 7.34 (t, J ) 7.2 Hz, 2 H).
13C NMR (101 MHz, CDCl3): δ 13.8, 19.3, 31.7, 41.1, 67.0, 67.9,
102.2, 121.5, 126.4, 127.8, 128.4, 137.4, 139.1. Anal. Calcd for
C15H20O2: C, 77.55; H, 8.68. Found: C, 77.53; H, 8.62.
(R,2R)- and (R,2S)-8 in 72% NMR yield (0.72 mmol, terephthalalde-
hyde as an internal standard). Further purification was made by column
chromatography on silica gel (EtOAc/n-hexane ) 1/1) to give a
mixture of (R,2R)- and (R,2S)-8 in 66% yield (56.3 mg, 0.66 mmol)
as a powder. The diastereomer excess was determined by HPLC
analysis (i-PrOH/n-hexane ) 1/9, 3.0 mL/min, 300 nm) to be 30% de
(65/35). FTIR (KBr, cm-1): 3735, 3324, 3048, 2974, 2926, 2369, 1637,
1588, 1545, 1454, 1415, 1373, 1341, 1316, 1231, 1184, 1097, 1051,
1031, 998, 926, 780, 655, 614, 527, 444. 1H NMR (400 MHz, CDCl3):
δ 1.19 (t, J ) 7.2 Hz, 3.9H), 1.20 (t, J ) 7.2 Hz, 2.1H), 1.71 (d, J )
6.8 Hz, 6H), 2.66 (dm, J ) 16.4 Hz, 0.7 H), 2.68 (dm, J ) 16.4 Hz,
1.3H), 2.91 (dm, J ) 16.4 Hz, 2H), 3.45 (dq, J ) 9.6, 7.2 Hz, 2H),
3.76 (dq, J ) 9.6, 7.2 Hz, 2H), 4.60-4.68 (m, 4H), 4.87 (d, J ) 7.2
Hz, 2H), 5.21 (d, J ) 5.2 Hz, 0.7H), 5.22 (d, J ) 5.2 Hz, 1.3H),
5.76-5.86 (m, 2H), 6.08 (s, 2H), 6.35 (br s, 2H), 7.02 (dm, J ) 8.8
Hz, 2H), 7.19 (dm, J ) 8.4 Hz, 2H), 7.44-7.61 (m, 4H), 7.82 (d, J )
(c) (Z)-4-(4-Nitrobenzylidene)-2-ethoxytetrahydrofuran (3g).
Pd(OAc)2 (22.5 mg, 0.1 mmol), Cu(OAc)2 (18.2 mg, 0.1 mmol),
catechol (4) (22.0 mg, 0.2 mmol), and (S,S)-4,4′-bisbenzyl-2,2′-
bioxazoline (5a) (64.0 mg, 0.2 mmol) were dissolved in toluene (4.0
mL) in a 25 mL side-armed round-bottomed flask under O2 (balloon),
and the mixture was stirred for 30 min at room temperature. Ethyl
vinyl ether (2a) (577 mg, 8.0 mmol) was added to the flask, and a
solution of (E)-3-(4-nitrophenyl)-2-propen-1-ol (1b) (358 mg, 2.0
mmol) in toluene (1.0 mL) was then added. After the reaction mixture
was stirred for 24 h at room temperature, the mixture was filtered
through a Florisil column (15 mm × 60 mm, 5 g, EtOAc). Evaporation
of the solvent under reduced pressure gave 3g in a solid state. The
pure product 3g was obtained by column chromatography (100-200
mesh silica gel, EtOAc/n-hexane ) 1/4) in 74% yield (367 mg, 0.74
mmol) as a brown solid. The enantiomer excess (34% ee) was
determined by HPLC analysis (i-PrOH/n-hexane ) 1/9, 2.0 mL/min,
258 nm). Mp: 75-76 °C. FTIR (Nujol, cm-1): 2927, 1652, 1592, 1513,
1099, 1049, 996. GCMS: m/e 249 (M+). 1H NMR (400 MHz, CDCl3):
δ 1.21 (t, J ) 7.2 Hz, 3H), 2.77 (d, J ) 16.8 Hz, 1H), 2.98 (ddddd,
J ) 16.9, 5.2, 2.4, 2.4, 2.4 Hz, 1H), 3.52 (dq, J ) 9.7, 7.2 Hz, 1H),
3.78 (dq, J ) 9.7, 7.2 Hz, 1H), 4.71 (ddd, J ) 2.4, 2.4, 1.6 Hz, 2H),
5.26 (d, J ) 5.2 Hz, 1H), 6.51 (br s, 1H), 7.20 (d, J ) 8.9 Hz, 2H),
8.19 (d, J ) 8.9 Hz, 2H). 13C NMR (101 MHz, CDCl3): δ 15.1, 41.6,
62.8, 67.8, 101.9, 120.0, 123.9, 128.2, 143.4, 143.7, 145.0. Anal. Calcd
for C13H15NO4: C, 62.64; H, 6.07; N, 5.62. Found: C, 62.38; H, 6.05;
N, 5.50.
8.4 Hz, 1H), 7.89 (dm, J ) 7.6 Hz, 1H), 8.19 (d, J ) 8 Hz, 1H). 13
C
NMR (101 MHz, CDCl3): δ 15.2, 21.7, 35.8, 41.0, 41.1, 46.0, 62.6,
67.9, 102.0, 106.1, 120.4, 120.5, 120.9, 122.5, 123.2, 125.3, 125.9,
126.6, 128.3, 128.6, 128.8, 130.9, 133.0, 134.0, 136.7, 137.9, 138.6,
154.5. HRMS (EI): calcd for C26H28N2O3, 416.2100 (M+); found,
416.2107. When the resulting powder was treated with ethyl acetate,
yellow-orange material was dissolved into the ethyl acetate solution.
The remaining powder was white. A portion of the white powder (10.3
mg) was dissolved into 1,2-dimethoxyethane in a sample tube. The
tube was placed in a bottle containing diisopropyl ether overnight in
the refrigerator, and then the mixture stood at room temperature. As
the result, colorless single crystals (mp: 189-192 °C) were obtained,
1
which was found to be (R,2S)-8 by X-ray analysis. H NMR (400
MHz, CDCl3): δ 1.19 (t, J ) 7.2 Hz, 3H), 1.70 (d, J ) 7.2 Hz, 3H),
2.68 (dm, J ) 16.8 Hz, 1H), 2.90 (dm, J ) 16.8 Hz, 1H), 3.49 (dq,
J ) 9.6, 7.2 Hz, 1H), 3.76 (dq, J ) 10.0, 7.2 Hz, 1H), 4.62-4.65 (m,
2H), 4.86 (d, J ) 7.6 Hz, 1H), 5.21 (d, J ) 4.8 Hz, 1H), 5.76-5.84
(m, 1H), 6.07 (s, 1H), 6.34 (br s, 1H), 7.01 (dm, J ) 8.4 Hz, 2H),
7.18 (dm, J ) 8.8 Hz, 2H), 7.44-7.59 (m, 4H), 7.81 (d, J ) 8.0 Hz,
1H), 7.88 (d, J ) 8.4 Hz, 1H), 8.19 (d, J ) 8.8 Hz, 1H).
Synthesis of (Z)-4-(4-Aminobenzylidene)-2-ethoxytetrahydro-
furan (6). 3g (125 mg, 0.5 mmol), FeCl3 (40.6 mg, 0.25 mmol), and
active-C (284 mg, 7 equiv per FeCl3) were dissolved in THF (2.5 mL)
and EtOH (2.5 mL) in a 25 mL side-armed round-bottomed flask.
Hydrazine monohydrate (0.1 mL, 2 mmol) was added to the mixture
at 70 °C with stirring. After stirring for 2 h at 70 °C, the reaction
mixture was filtered through filter paper, and the solvent was
evaporated under reduced pressure. The resulting mixture was diluted
by adding ethyl acetate (30 mL), washed with water (2 × 20 mL) and
brine (30 mL), and dried (MgSO4). Removal of the solvent gave pure
6 in 62% NMR yield (68.2 mg, 0.62 mmol, terephthalaldehyde as an
internal standard) as a brown solid. Mp: 44-45 °C. FTIR (KBr, cm-1):
3449, 3356, 3218, 2979, 2933, 1627, 1606, 1516, 1459, 1422, 1374,
1348, 1291, 1182, 1114, 1091, 1052, 1035, 995, 912, 865, 851, 570,
Isolation of PdCl2-(S,S)-5a Complex from a Catalyst Solu-
tion. Pd(OAc)2 (67.4 mg, 0.3 mmol), Cu(OAc)2 (54.5 mg, 0.3 mmol),
catechol (4) (33.0 mg, 0.3 mmol), and (S,S)-4,4′-bisbenzyl-2,2′-
bioxazoline (5a) (96.1 mg, 0.3 mmol) were dissolved in toluene (9.0
mL) in a 25 mL side-armed round-bottomed flask under O2 (balloon),
and the reaction mixture was stirred for 1 h at room temperature. The
solution was diluted with CH2Cl2 and washed with a saturated NaCl
solution (50 mL). The organic layer was collected, dried over MS3Å
powder, filtered, and concentrated under reduced pressure. The resulting
black powder was dissolved into the least amount of CH2Cl2. The
solution was passed through a Florisil column (10 mm × 40 mm,
1.5 g, CH2Cl2), and evaporation of the solvent gave a PdCl2-(S,S)-5a
complex as a nearly pure form in 74% NMR yield (terephthalaldehyde
as an internal standard) (109.8 mg, 0.22 mmol) as a brown solid. Mp:
257-258 °C. 1H NMR (400 MHz, CDCl3): δ 3.01 (dm, J ) 13.6 Hz,
2H), 3.63 (dm, J ) 13.6 Hz, 2H), 4.69-4.82 (m, 6H), 7.24-7.40 (m,
10H). 13C NMR (101 MHz, CDCl3): δ 29.7, 39.4, 64.1, 127.5, 129.0,
129.7, 134.5, 159.8. Anal. Calcd for C20H20N2O2PdCl2: C, 48.26; H,
4.05; N, 5.62. Found: C, 48.58; H, 4.08; N, 5.66. In the absence of
catechol, the same complex was obtained only in 31% NMR yield.
1
528, 419. H NMR (400 MHz, CDCl3): δ 1.20 (t, J ) 7.2 Hz, 3H),
2.67 (dm, J ) 16.4 Hz, 1H), 2.90 (ddddd, J ) 16.0, 5.2, 2.4, 2.4, 2.4
Hz, 1H), 3.50 (dq, J ) 9.6, 7.2 Hz, 1H), 3.76 (dq, J ) 9.6, 7.2 Hz,
1H), 4.64-4.66 (m, 2H), 5.21 (d, J ) 4.4 Hz, 1H), 6.31 (br s, 1H),
6.65 (dm, J ) 8.4 Hz, 2H), 6.94 (dm, J ) 8.4 Hz, 2H). 13C NMR
(101 MHz, CDCl3): δ 15.2, 41.0, 62.6, 68.0, 102.0, 115.0, 121.3, 128.3,
129.0, 135.0, 144.9. HRMS (EI): calcd for M+ - C2H5O (C13H17NO2),
174.0913; found, 174.0900.
Synthesis of (Z)-4-(4-N-(R)-(1-Naphthylethyl)ureylene)ben-
zylidene-2-ethoxytetrahydrofuran (8). The amine 6 (50 mg, 0.23
mmol) was dissolved in THF (0.9 mL) in a 25 mL side-armed round-
bottomed flask, and the reaction mixture was stirred at room temper-
ature. Isocyanic acid (R)-(-)-(1-isocyanatoethyl)naphthalene (7) (0.04
mL, 0.23 mmol) was added to the flask, and the reaction mixture was
stirred for 21 h at room temperature. N,N-Dimethyl-1,3-propanediamine
(0.01 mL, 0.08 mmol) was then added to the flask, and the mixture
was stirred for 30 min. After the reaction mixture was evaporated under
reduced pressure, the resulting mixture was diluted by adding 30 mL
of chloroform, washed with 3% citric acid (2 × 20 mL) and brine (30
mL), and dried (MgSO4). Removal of the solvent gave a mixture of
Supporting Information Available: Detailed experimental
procedures and characterization data for all reported new com-
pounds and X-ray crystallographic data for single diastereomer
(R,2S)-8. 1H and 13C NMR spectra for all reported new compounds.
This material is available free of charge via the Internet at
JO802807W
J. Org. Chem. Vol. 74, No. 8, 2009 3053