4422 J. Am. Chem. Soc., Vol. 119, No. 19, 1997
Nozaki et al.
d8 for NMR spectroscopy of oxygen- and moisture-sensitive materials
were distilled over Na-K alloy. Triethylamine was distilled under
argon after drying over calcium hydride. Vinyl acetate and styrene
were distilled before use. Carbon monoxide (99.9%) and hydrogen
(99.9999%) were obtained from Teisan Co. (S)-(-)-Binaphthol and
its enantiomer came from Mitubishi Gas Chemical Co. Inc.
Preparation of Hydroxyphosphines with Biphenyl Frameworks.
The above triflates were hydrolized by NaOH in dioxane-MeOH-
H2O and then were reduced by trichlorosilane in the same manner as
their binaphthyl analogs.9b Data for (()-6a (90% yield): mp 71-79
°C; 31P NMR (CDCl3) δ -13.37. Anal. Calcd for C28H25Cl2OP: C,
70.15; H, 5.26. Found: C, 70.08; H, 5.27. Data for (()-2-(diphe-
nylphosphino)-2′-hydroxybiphenyl (6b) was prepared in 60% yield by
the same method: mp 122-123 °C; 31P NMR (CDCl3) δ -12.01. Anal.
Calcd for C24H19OP: C, 81.34; H, 5.40. Found: C, 80.88; H, 5.30.
Prepration of (S)-(1,1′-Binaphthalene-2,2′-dioxy)chlorophosphine
[(S)-4]. A mixture of (S)-2,2′-dihydroxy-1,1′-binaphthyl (3.5 g, 12
mmol) and phosphorus trichloride (25 g, 0.18 mol) was heated at reflux
with stirring under an argon overnight. The excess phosphorus
trichloride in the reaction mixture was removed under reduced pressure.
The last trace of phosphorus trichloride in the residue was removed by
azeotropic distillation with toluene (25 mL) under reduced pressure,
and this procedure was repeated three times. A yellow solid (4.4 g,
100%) was obtained after freeze-drying of the benzene solution of the
residue in Vacuo. The crude product (S)-4 was used for the next
reaction without further purification: 31P NMR (CDCl3) δ 174.0 (s).
General Procedure for Preparation of Phosphine-Phosphite
Ligands Consisting of 2-(Diarylphosphino)-1,1′-binaphthyl Groups
[(R,S)-2a, (R,R)-2a, (R,S)-2b, and (R)-2c]. Hydroxyphosphines (R)-
and (S)-3a were prepared according to the literature procedure.9 To a
solution of (R)-3a (3.4 g, 7.5 mmol) and (S)-4 (4.7 g, 13 mmol) in
ether (170 mL) was added triethylamine (1.4 g, 14 mmol) in ether (40
mL) at 0 °C. The mixture was stirred at room temperature for 10 h,
and then quenched with cold brine (200 mL). The phases were
separated, and the aqueous phase was extracted with ether (200 mL).
The combined organic phases were dried over anhydrous magnesium
sulfate and concentrated under reduced pressure. The residue was
purified by silica-gel column chromatography (n-hexane/dichlo-
romethane ) 2/1 f 5/3) to afford (R,S)-BINAPHOS [(R,S)-2a] as a
white solid (5.2 g, 90%). Data for (R,S)-2a: mp 159-175 °C (unclear);
31P NMR (CDCl3) δ -13.3 (phosphine, JP-P ) 29.0 Hz), 146.2
General Procedure for the Preparation of Phosphine-Phosphite
Ligands Consisting of 2-(Diphenylphosphino)biphenyl Groups
[(S,R)-5a, (R,R)-5a, and (R)-5b]. The racemic 6a was allowed to
couple with (R)-4 in the presence of triethylamine as for its binaphthyl
analog 3. The crude reaction mixture was purified by silica-gel
chromatography (hexane/CH2Cl2 ) 20/1 f 3/1) to give (S,R)-5a (32%
yield) and (R,R)-5a (21% yield). The isomeric phosphine-phosphites
(R,S)-5a and (S,S)-5a were also prepared. Data for (S,R)-5a: mp 155-
162 °C; 31P NMR (CDCl3) δ -13.4 (phosphine, JP-P ) 35.1 Hz),
25
146.7 (phosphite); [R]D ) -281° (c 1.0, toluene). Anal. Calcd for
C48H36Cl2O3P2: C, 72.64; H, 4.57. Found: C, 72.71; H, 5.14. Data
for (S,S)-5a: mp 147-151 °C; 31P NMR (CDCl3) δ -12.6 (phosphine,
21
JP-P ) 12.2 Hz), 145.8 (phosphite); [R]D ) +253 (c 1.0, toluene).
Anal. Calcd for C48H36Cl2O3P2: C, 72.64; H, 4.57. Found: C, 71.98;
H, 5.14. (R)-5b was given as a mixture of diastereomers (S,R)-5b and
(R,R)-5b via a method similar to that for 6b. Separation of the
diasteromers by either column chromatgraphy or recrystallization was
unsuccessful. Data for (S,R)- and (R,R)-5b (55:45, 871 mg, 62%
yield): the mixture melted in the range 150-156 °C; 31P NMR (CDCl3)
δ for major, -11.9 (phosphine, JP-P ) 35.1 Hz), 146.8 (phosphite);
for minor, -11.5 (phosphine, JP-P ) 21.4 Hz), 146.8 (phosphite);
22
[R]D (as a mixture) ) +324° (c 1.0, toluene). Anal. Calcd for
C44H30O3P2: C, 79.04; H, 4.52. Found: C, 79.18; H, 4.55.
(phosphite); [R]23 ) +339° (c 1.3, toluene). Anal. Calcd for
Preparation of Rh(acac)(phosphine-phosphite). In a 20-mL
Schlenk tube were dissolved (R,S)-2a (50.0 mg, 0.0651 mmol) and
Rh(CO)2(acac) (16.8 mg, 0.0651 mmol) in CH2Cl2 (5 mL). The
solution was stirred at room temperature for 5 min. The reaction
mixture was concentrated under reduced pressure to give Rh(acac)-
[(R,S)-2a] as a yellow solid. Purification of the complex by recrys-
tallization was unsuccessful: 31P NMR (CDCl3) δ 48.9 (phosphine,
JRh-P ) 174.0 Hz, JP-P ) 83.9 Hz), 161.8 (phosphite, JRh-P ) 331.1
Hz). Rh(acac) complexes of (R,R)-2a, (R,S)-2b, (R)-2c, (S,R)-5a, and
(R,R)-5a were also prepared, and the formations of these complexes
were confirmed by 31P NMR. A mixture of (S,R)-5b and (R,R)-5b
gave a single species by an admixture with Rh(CO)2(acac), which was
assigned to be Rh(acac)[(S,R)-5b] (see the text). 31P NMR (CDCl3) of
Rh(acac)(ligand) complexes are as follows: (R,R)-2a, δ 51.9 (phos-
D
C52H34O3P2: C, 81.24; H, 4.46. Found: C, 81.16; H, 4.66. Other
phosphine-phosphite ligands (R,R)-2a, (R,S)-2b, and (R)-2c, were
similarly prepared. Data for (R,R)-2a: 99% yield, pale yellow solid
(hexane-CH2Cl2), mp 168-173 °C (unclear); 31P NMR (CDCl3) δ
-12.7 (phosphine, JP-P ) 9.2 Hz), 145.8 (phosphite); [R]23D ) -214°
(c 1.2, toluene). Anal. Calcd for C52H34O3P2: C, 81.24; H, 4.46.
Found: C, 80.76; H, 5.53. Data for (R,S)-2b: 98% yield, pale yellow
solid (hexane-CH2Cl2): mp 158-162 °C (unclear); 31P NMR (CDCl3)
δ -12.4 (phosphine, JP-P ) 30.5 Hz), 145.5 (phosphite); [R]23
)
D
+228° (c 1.0, toluene). Anal. Calcd for C56H42O3P2: C, 81.54; H,
5.13. Found: C, 81.33; H, 5.31. (R)-2c: 77% yield, pale yellow solid
(hexane-CH2Cl2): mp 102-109 °C (unclear); 31P NMR (CDCl3) δ
-13.1 (phosphine, JP-P ) 13.7 Hz), 126.8 (phosphite); [R]23D ) +92.4°
(c 1.0, toluene). Anal. Calcd for C44H30O3P2: C, 79.04; H, 4.52.
Found: C, 79.21; H, 4.78.
Preparation of 2,2′-Bis[[(trifluoromethylsulfonyl]oxy]biphenyls.
To a solution of (()-5,5′-dichloro-4,4′,6,6′-tetramethylbiphenyl-2,2′-
diol (6.22 g, 20.0 mmol),12a 2,6-lutidine (4.72 g, 44.0 mmol), and
4-(dimethylamino)pyridine (732 mg, 6.00 mmol) in CH2Cl2 (30 mL)
was added trifluoromethanesulfonic anhydride (12.4 g, 44.0 mmol) at
0 °C under argon. The mixture was stirred at room temperature for 1
h. The reaction mixture was concentrated and chromatographed on
silica gel (hexane/CH2Cl2 ) 1/1) to give (()-5,5′-dichloro-4,4′,6,6′-
tetramethyl-2,2′-bis[[(trifluoromethylsulfonyl]oxy]biphenyl (10.9 g, 18.9
mmol, 95%). mp 90-91 °C. Anal. Calcd for C18H14Cl2F6O6S2: C,
37.58; H, 2.45. Found: C, 37.77; H, 2.39. Similary, 2,2′-bis-
[[(trifluoromethyl)sulfonyl]oxy]biphenyl was prepared from biphenyl-
2,2′-diol (96%): mp 33-34 °C. Anal. Calcd for C14H8F6O6S2: C,
37.34; H, 1.79. Found: C, 33.76; H, 1.59.
Preparation of 2-(Diphenylphosphinyo)-2′-[[(trifluoromethyl)-
sulfonyl]oxy]biphenyls. The title compounds were prepared in the
same manner as their binaphthyl analogs. Data for (()-3,3′-Dichloro-
6-(diphenylphosphino)-2,2′,4,4′-tetramethyl-6′-[[(trifluoromethyl)sulfo-
nyl]oxy]biphenyl (62% yield): mp 159-160 °C; 31P NMR (CDCl3) δ
27.75. Anal. Calcd for C29H24F3O4SPCl2: C, 55.51; H, 3.86. Found:
C, 55.57; H, 3.89. Data for (()-2-(diphenylphosphino)-2′-[[(trifluo-
romethylsulfonyl]oxy]biphenyl (77%): mp 123-124 °C; 31P NMR
(CDCl3) δ 27.78. Anal. Calcd for C25H18F3O4PS: C, 59.76; H, 3.61.
Found: C, 60.48; H, 3.66.
phine, JRh-P ) 178.5 Hz, JP-P ) 80.4 Hz), 152.5 (phosphite, JRh-P
)
325.1 Hz); (R,S)-2b, δ 48.7 (phosphine, JRh-P ) 172.4 Hz, JP-P ) 82.4
Hz), 160.9 (phosphite, JRh-P ) 332.6 Hz); (R)-2c, δ 49.4 (phosphine,
JRh-P ) 175.5 Hz, JP-P ) 82.4 Hz), 136.2 (phosphite, JRh-P ) 328.0
Hz); (S,R)-5a, δ 49.4 (phosphine, JRh-P ) 175.5 Hz, JP-P ) 84.0 Hz),
159.8 (phosphite, JRh-P ) 330.4 Hz); (R,R)-5a, δ 51.2 (phosphine, JRh-P
) 180.0 Hz, JP-P ) 82.4 Hz), 154.7 (phosphite, JRh-P ) 325.0 Hz);
(S,R)-5b (from a mixture of (S,R)-5b and (R,R)-5b), δ 50.4 (phosphine,
JRh-P ) 174.0 Hz, JP-P ) 87.0 Hz), 160.2 (phosphite, JRh-P ) 328.1
Hz).
General Procedure for the Asymmetric Hydroformylation of
Olefins Catalyzed by Rhodium(I) Complexes of Phosphine-
Phosphite Ligands. A solution of styrene (7a) (2.08 g, 20.0 mmol),
dicarbonyl(2,4-pentanedionato)rhodium (2.6 mg, 0.010 mmol), and
(R,S)-2a (31 mg, 0.040 mmol) in benzene (1 mL) was degassed by
freeze-pump-thaw cycles and transferred into a 50-mL stainless-steel
autoclave. Carbon monoxide (50 atm) and dihydrogen (50 atm) were
charged, and the solution was stirred at 60 °C for 43 h. Conversion to
aldehydes (>99%) and the regioselectivity of the reaction (2-phenyl-
propanal (8a)/3-phenylpropanal (9a) ) 88/12) were determined by 1H
NMR spectroscopy of the crude reaction mixture without evaporation
of the solvent. Chromatography on silica gel followed by short pass
distillation of the reaction mixture gave a pure sample of (R)-(+)-2-
phenylpropanal [(R)-8]. Optical rotation was used to determine the
absolute configuration.34 The enantiomeric excess of the product 8a
was determined to be 94% ee by oxidation of 8a to the corresponding