SCHEME 1. Proposed Mechanism of Palladium-Catalyzed
Isomerization of (Z)-Alkenes in the Presence of Tributyltin
Hydride
(E)-Stilbene (4b). Rf ) 0.32 (hexane/EtOAc 50:1); mp 112∼
1
113 °C; H NMR (300 MHz, CDCl3) δ 7.29-7.60 (m, 12H); 13C
NMR (125 MHz, CDCl3) δ 126.78, 127.87, 128.94, 128.99, 137.62.
1H NMR and 13C NMR spectra were identical to an authentic
sample.
(E)-4-Bromo-1-phenylbut-1-ene (5b). Rf ) 0.24 (hexane/EtOAc
1
20:1); H NMR (300 MHz, CDCl3) δ 3.84 (s, 3H), 6.48 (d, 1H,
J ) 15.9 Hz), 7.39-7.45 (m, 3H), 7.53-7.58 (m, 2H), 7.74 (d,
1H, J ) 15.9 Hz); 13C NMR (125 MHz, CDCl3) δ 51.85, 118.08,
128.30, 129.11, 130.50, 134.65, 145.06, 167.58. 1H NMR and 13
NMR spectra were identical to an authentic sample.
C
(E)-4-Benzyloxy-1-phenylbut-1-ene (6b). Rf ) 0.27 (hexane/
1
EtOAc 30:1); H NMR (300 MHz, CDCl3) δ 2.59 (dt, 2H, J )
6.9, 6.6 Hz), 3.65 (t, 2H, J ) 6.6 Hz), 4.60 (s, 2H), 6.30 (dt, 1H,
J ) 15.9, 6.9 Hz), 6.52 (d, 1H, J ) 15.9 Hz), 7.22-7.43 (m, 10H);
13C NMR (125 MHz, CDCl3) δ 33.78, 70.10, 73.24, 126.29, 127.28,
127.29, 127.83, 127.94, 128.03, 128.64, 128.72, 131.88, 137.87,
138.73.
(E)-5-Decene (7b). bp 170∼173 °C (13 Torr, 61 °C); 1H NMR
(300 MHz, CDCl3) δ 0.88-0.98 (m, 6H), 1.28-1.44 (m, 8H),
1.97-2.12 (m, 4H), 5.40-5.46 (m, 2H); 13C NMR (125 MHz,
Summarizing, it was found that isomerization of (Z)-olefin
compounds proceeded smoothly in the presence of palladium(II)
acetate and tributyltin hydride to give (E)-olefin compounds in
good yields. The described isomerization reaction provides a
powerful method of preparing pure (E)-olefin compounds.
1
CDCl3) δ 14.16, 22.42, 32.08, 32.50, 130.54. H NMR and 13C
NMR spectra were identical to an authentic sample.
(E)-1-Benzyloxy-5-phenylpent-2-ene (8b). Rf ) 0.25 (hexane/
EtOAc 3:1); 1H NMR (300 MHz, CDCl3) δ 2.44 (dt, 2H, J ) 7.5,
6.3 Hz), 2.78 (t, 2H, J ) 7.5 Hz), 4.03 (d, 2H, J ) 6.0 Hz), 4.52
(s, 2H), 5.69-5.81 (m, 2H), 7.23-7.44 (m, 10H); 13C NMR
(125 MHz, CDCl3) δ 34.32, 35.76, 71.05, 72.11, 126.10, 127.26,
127.78, 128.03, 128.58, 128.60, 128.66, 128.68, 134.00, 138.72,
142.01.
(E)-Dimethyl fumarate (9b). Rf ) 0.34 (hexane/EtOAc 6:1);
1H NMR (300 MHz, CDCl3) δ 3.82 (s, 6H), 6.87 (s, 2H); 13C NMR
(125 MHz, CDCl3) δ 52.42, 133.56, 165.50. 1H NMR and 13C NMR
spectra were identical to an authentic sample.
(E)-5-Phenylpent-2-en-1-ol (10b). Rf ) 0.27 (hexane/EtOAc
3:1); 1H NMR (300 MHz, CDCl3) δ 1.34-1.38 (br, 1H), 2.42 (dt,
2H, J ) 7.5, 6.0 Hz), 2.75 (t, 2H, J ) 7.5 Hz), 4.13 (d, 2H, J )
6.6 Hz), 5.66-5.84 (m, 2H), 7.20-7.37 (m, 5H); 13C NMR
(125 MHz, CDCl3) δ 34.18, 35.78, 63.91, 126.12, 128.56, 128.66,
129.87, 132.47, 141.93.
Experimental Section
General Methods. Commercially available reagents were used
without additional purification, unless otherwise stated. All anhy-
drous solvents were distilled over CaH2 or P2O5 or Na/benzophe-
none prior to reaction. All reactions were performed under an inert
atmosphere of nitrogen or argon. Nuclear magnetic resonance
spectra (1H and 13C NMR) were recorded on 300 and 500 MHz
spectrometers for CDCl3 solutions, and chemical shifts are reported
as parts per million (ppm) relative to, respectively, residual CHCl3
δH (7.26 ppm) and CDCl3 δC (77.0 ppm) as internal standards.
Resonance patterns are reported with the notations s (singlet), d
(doublet), t (triplet), q (quartet), and m (multiplet). In addition, the
notation br is used to indicate a broad signal. Coupling constants
(J) are reported in hertz (Hz).
(E)-3-Phenylprop-2-enyl acetate (11b). Rf ) 0.26 (hexane/
General Procedure for the Isomerization of (Z)-Alkenes to
(E)-Alkenes. To a stirred solution of (Z)-alkene (1 mmol) in
anhydrous CH2Cl2 (3.3 mL) was added Bu3SnH (2.2 mmol),
Pd(OAc)2 (0.05 mmol), and triethylamine (0.16 mmol) at room
temperature under N2, and the reaction mixture was heated at reflux
for the reaction time. The mixture was cooled in an ice bath and
then was filtered through a Celite pad and was carefully concen-
trated in vacuo. The residue was purified by silica gel column
chromatography or distillation to afford corresponding (E)-alkene.
(E)-3-Benzyloxy-1-phenylprop-1-ene (2). Rf ) 0.27 (hexane/
1
EtOAc 20:1); H NMR (300 MHz, CDCl3) δ 2.15 (s, 3H), 4.78
(dd, 2H, J ) 6.3, 1.2 Hz), 6.34 (dt, 1H, J ) 15.9, 6.3 Hz), 6.70 (d,
1H, J ) 15.9 Hz), 7.30-7.47 (m, 5H); 13C NMR (125 MHz, CDCl3)
δ 21.22, 65.29, 123.45, 126.85, 128.31, 128.84, 134.45, 136.48,
171.03.
Acknowledgment. This work was supported by the Korea
Research Foundation Grant funded by the Korean Government
(MOEHRD) (KRF-2006-311-E00613) and by the Brain Korea
21 program.
1
EtOAc 30:1); H NMR (300 MHz, CDCl3) δ 4.26 (d, 2H, J )
6.3 Hz), 4.64 (s, 2H), 6.39 (dt, 1H, J ) 15.9, 6.3 Hz), 6.70 (d, 1H,
J ) 15.9 Hz), 7.30-7.48 (m, 10H); 13C NMR (125 MHz, CDCl3)
δ 71.58, 72.97, 126.91, 127.33, 128.48, 128.51, 128.63, 129.39,
133.29, 137.54, 139.12. 1H NMR and 13C NMR spectra were
consistent with literature values reported in Arch. Pharm. Res. 2001,
24, 371.
Supporting Information Available: Experimental procedures
and characterization data for all compounds are provided. This
materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.
JO0705263
5426 J. Org. Chem., Vol. 72, No. 14, 2007