K. Aikawa et al.
Bull. Chem. Soc. Jpn. Vol. 85, No. 2 (2012)
207
mmol) and silver hexafluoroantimonate (7.6 mg, 0.022 mmol).
Kinetic constants were calculated at the four temperatures,
and ¦Gº values were calculated by Arrhenius and Eyring
equations (see, Supporting Information).
ature. The reaction mixture was extracted with ether. Purifica-
tion by silica gel chromatography (hexane/ethyl acetate =
5/1) gave the alcohol product (16.8 mg, yield 81%). The
enantiomeric excess (% ee) was determined by chiral HPLC
analysis (99% ee). 1H NMR (300 MHz, CDCl3): ¤ 1.32 (t,
J = 7.2 Hz, 3H), 3.11 (d, J = 5.7 Hz, 1H), 4.31 (q, J = 7.2 Hz,
2H), 4.82 (br s, 1H), 6.25 (dd, J = 15.9, 5.7 Hz, 1H), 6.82 (d,
J = 15.9 Hz, 1H), 7.26-7.42 (m, 5H); 13C NMR (75 MHz,
CDCl3): ¤ 14.2, 62.3, 71.3, 125.5, 126.7, 128.0, 128.6, 132.2,
136.2, 173.3; FT-IR (neat, cm¹1): 3430, 3069, 3035, 2927,
1739, 1596, 1494, 1364, 1453, 1232, 1082, 923, 863, 699;
HRMS (ESI-TOF): Calcd for C12H15O3 [M + H]+: 207.1021,
Typical Procedure for Determination of Half-Life of
BIPHEPs-Ligand (Scheme 2). To a solution of enantiopure
(R)-BIPHEP-PdCl2 (R-2a) (2.8 mg, 0.004 mmol) (or (R)-
BIPHEP-PtCl2 (R-3a)) in dichloromethane (0.7 mL) was added
a solution of DPPE (2.0 mg, 0.005 mmol) (or DPPP) in
dichloromethane (0.3 mL) at 0 °C (or 25 °C). After the mixture
was stirred for a certain time at 0 °C (or 25 °C), a solution of
[PdCl2(cod)] (1.4 mg, 0.005 mmol) in dichloromethane (0.2
mL) was added to the mixture. The solvent was evaporated
under reduced pressure. To a solution of the residue and (S,S)-
DPEN (2.5 mg, 0.012 mmol) in CDCl3 (or CD2Cl2) (0.8 mL)
was added silver hexafluoroantimonate (6.9 mg, 0.02 mmol) at
0 °C, and the mixture was stirred at room temperature for
30 min. Enantiomeric excess of the complex was determined by
31P NMR analyses. Kinetic constant and half-life were calcu-
lated with four measurements at different times (see, Support-
ing Information).
25
found: 207.1025; ½¡ꢀD +67.8 (c 1.59, CHCl3); 99% ee; HPLC
analysis (DAICEL CHIRALPAK AD-H, eluent, hexane/
2-propanol = 97:3, flow rate, 0.6 mL min¹1, 20 °C, detection
254 nm light): tR of major isomer 33.5 min and minor isomer
39.7 min.
(S)-Furan-2-ylhydroxyacetic Acid Ethyl Ester (14)
(Table 6).
To a solution of (R)-4,4¤-Me-BIPHEP-PdCl2
(R-2f ) (1.8 mg, 0.0025 mmol) in toluene (0.5 mL) was added
silver hexafluoroantimonate (2.1 mg, 0.006 mmol) at 0 °C under
argon atmosphere. After the solution was stirred for 30 min
at 0 °C, ethyl glyoxylate (11) (1020.9 mg, 10.0 mmol) and
2-trimethylsilylfuran (13) (762.3 mg, 5.0 mmol) were added at
¹40 °C. After stirring for 24 h at ¹20 °C, the reaction mixture
was directly loaded on to a silica gel column and eluted
with hexane/ethyl acetate = 1/1 to remove the catalyst. To a
solution of the crude product in THF (5.0 mL) was added 1 M
HCl (3.0 mL). After stirring for 30 min at room temperature,
the mixture was extracted with ether. The organic layer was
washed with water, brine, dried over Na2SO4, and evaporated
under reduced pressure. Purification by silica gel chromatog-
raphy (hexane/ethyl acetate = 1/1) gave the alcohol product
(663.6 mg, yield 78%). The enantiomeric excess (% ee)
(S)-Ethyl
2-Hydroxy-4-methyl-2-trifluoromethyl-4-
pentenoate (9) (Table 4). To a solution of (R)-4,4¤-t-Bu-
BIPHEP-PdCl2 (R-2b) (3.2 mg, 0.004 mmol) in ethyl trifluoro-
pyruvate (8) (5.3 mL, 40 mmol) was added silver hexafluoro-
antimonate (3.1 mg, 0.0088 mmol) at 0 °C under argon at-
mosphere. After the solution was stirred for 30 min at 0 °C,
isobutene (7) (ca. 9.0 g, ca. 160 mmol) was added at ¹30 °C.
After stirring for 10 min at ¹20 °C, the reaction mixture was
directly loaded on to a silica gel column and eluted with
hexane/ethyl acetate = 1/1 to remove the catalyst. Conversion
was determined by 19F NMR using BTF as an internal standard
(conv. 97%, and isolated yield 97%). The enantiomeric excess
(% ee) was determined by chiral GC analysis (98% ee).
1H NMR (300 MHz, CDCl3): ¤ 1.37 (t, J = 6.0 Hz, 3H), 1.78
(s, 3H), 2.59 (d, J = 14.1 Hz, 1H), 2.76 (d, J = 14.1 Hz, 1H),
3.83 (s, 1H), 4.28-4.44 (m, 2H), 4.82 (s, 1H), 4.92 (s, 1H);
13C NMR (75 MHz, CDCl3): ¤ 13.9, 24.0, 38.75, 38.76, 63.73,
116.1, 119.5 (q, JC-F = 285.0 Hz), 138.72, 169.53; 19F NMR
(282 MHz, CDCl3): ¤ ¹78.82 (s, 3F); FT-IR (neat, cm¹1):
3492, 2986, 2359, 1741, 1448, 1372, 1312, 1223, 1184, 1130,
1065, 1018, 903, 697; HRMS (ESI-TOF): Calcd for C9H14F3O3
1
was determined by chiral HPLC analysis (98% ee). H NMR
(300 MHz, CDCl3): ¤ 1.27 (t, J = 7.2 Hz, 3H), 3.38 (d, J =
6.9 Hz, 1H), 4.21-4.36 (m, 2H), 5.17 (d, J = 6.9 Hz, 1H), 6.35-
6.38 (m, 2H), 7.39 (dd, J = 1.8, 0.9 Hz, 1H); 13C NMR
(75 MHz, CDCl3): ¤ 14.0, 62.4, 66.9, 108.5, 110.5, 142.9,
151.0, 171.5; FT-IR (KBr pellet, cm¹1): 3422, 2976, 2954,
2359, 1737, 1589, 1495, 1456, 1363, 1292, 1133, 1001, 892,
831; HRMS (ESI-TOF): Calcd for C8H11O4 [M + H]+:
21
25
[M + H]+: 227.0895, found: 227.0886; ½¡ꢀD +6.3 (c 3.11,
171.0657, found: 171.0651; ½¡ꢀD +108.3 (c 0.80, CHCl3);
CHCl3); 98% ee; GC (column, CP-Chirasil-Dex CB, i.d.
0.25 mm © 25 m, CHROMPACK; carrier gas, nitrogen 75 kPa;
column temp. 70 °C; injection temp. 100 °C): tR of minor
isomer 14.9 min, tR of major isomer 16.2 min.
98% ee; HPLC analysis (DAICEL CHIRALCEL OD-H,
¹1
eluent, hexane/2-propanol = 96:4, flow rate, 1.0 mL min
,
20 °C, detection 210 nm light): tR of major isomer 11.7 min and
minor isomer 14.4 min.
(S)-Ethyl 2-Hydroxy-4-phenyl-3-butenoate (12) (Table 5).
To a solution of (R)-4,4¤-Me-BIPHEP-PdCl2 (R-2f ) (3.6 mg,
0.005 mmol) in dichloromethane (1.0 mL) was added silver
hexafluoroantimonate (3.8 mg, 0.011 mmol) at 0 °C under
argon atmosphere. After the solution was stirred for 30 min
at 0 °C, ethyl glyoxylate (11) (30.6 mg, 0.3 mmol) and tri-
methyl(2-phenylethenyl)silane (10) (17.6 mg, 0.1 mmol) was
added at 0 °C. After stirring for 24 h at 0 °C, the reaction mixture
was directly loaded on to a silica gel column and eluted with
hexane/ethyl acetate = 1/1. After the solvent was removed
under reduced pressure, to the residue was added 1 M HCl/THF
(1 mL/1 mL) followed by stirring for 15 min at room temper-
(S)-4-Hydroxy-4-methyl-6-triisopropylsilanyloxyhept-6-
en-3-one (17) (Scheme 4). To a solution of (R)-4,4¤-Me-
BIPHEP-PdCl2 (R-2f ) (7.3 mg, 0.01 mmol) in dichloromethane
(2.0 mL) was added silver hexafluoroantimonate (7.6 mg,
0.022 mmol) at 0 °C under argon atmosphere. After the solution
was stirred for 30 min at 0 °C, 2,3-pentanedione (16) (47.4 ¯L,
0.44 mmol) and triisopropyl 2-propenyl ether (15) (42.9 mg,
0.2 mmol) were added to the mixture at ¹78 °C. After stirred
for 24 h at ¹78 °C, triethylamine (30 ¯L) was added at that
temperature. Et2O (10 mL) was poured into the reaction
mixture. The solution was washed with sat. NaHCO3 and
brine, dried over anhydrous magnesium sulfate, and evaporated