S. Gladiali, A. Dore, D. Fabbri, S. Medici, G. Pirri, S. Pulacchini
FULL PAPER
point apparatus and are not corrected. Ϫ Elemental analyses were
performed with a PerkinϪElmer Analyzer 240B by Mr. A. Canu
Ar, 2 H, Ar). Ϫ 31P NMR (CDCl3): δ ϭ Ϫ16.52, Ϫ15.05. Ϫ
C46H36P2 (650.73): calcd. C 84.9, H 5.58; found C 85.18; H 5.36.
`
(Dipartimento di Chimica, Universita di Sassari). Solvents were Ϫ Method B: Direct Coupling of 7 with Disubstituted Phosphanes:
dried and distilled under nitrogen before use. Commercial reagents
A solution of (dppe)NiCl2 (0.1 g, 0.2 mmol) in DMF (5 mL) con-
(Aldrich) were used as received. Compounds 5, 6a, 7 and 8a [(S)-
taining di-o-tolylphosphane (0.5 g, 2.33 mmol) was stirred at 100
configuration] were prepared from (S)-BINOL as reported in ref.[12] °C for 10 min. To this mixture was added a solution of 2-di-
Compound 2 was prepared from racemic BINOL as reported in
phenylphosphanyl-1,1Ј-binaphthalene-2Ј-yl triflate (7) (1.17 g,
2.0 mmol) and Et3N (1.5 mL) in DMF (8 mL) and the mixture was
heated at 100 °C for 4 h. After being cooled to room temperature,
the mixture was poured into H2O and the resulting brown solid
was filtered off, dissolved in CH2Cl2 and dried (Na2SO4). Evapora-
tion of the solvent under reduced pressure gave a brown solid,
which was purified by flash chromatography on silica gel using
CH2Cl2 as eluent.
ref.[18]
Preparation of Monophosphinyl Monotriflates 6: These compounds
were prepared from (S)-BINOL ditriflate 5 according to the pro-
[12]
cedure reported in ref.
(S)-6b: 73% yield. Ϫ 1H NMR (CDCl3): δ ϭ 2.12 (s, 3 H, CH3),
2.44 (s, 3 H, CH3), 6.86Ϫ7.09 (series of m, 6 H, Ar), 7.21Ϫ7.42
(series of m, 9 H, Ar), 7.58 (t, J ϭ 7.2 Hz, 1 H, Ar), 7.85 (d, J ϭ
8.1 Hz, 2 H, Ar), 7.96 (dd, J ϭ 5.4, 9.3 Hz, 2 H, Ar). Ϫ 31P NMR
(CDCl3): δ ϭ 35.00. Ϫ C35H26F3O4PS (630.62): calcd. C 66.66, H
4.16; found C 66.38, H 4.24.
4c: 0.55 g (42%); m.p. 230Ϫ236 °C. Ϫ [α]2D5 ϭ Ϫ57.3 (c ϭ 1,
CHCl3). Ϫ 1H NMR (CDCl3): δ ϭ 1.73 (s, 3 H, CH3), 2.23 (d, J ϭ
1.5 Hz, 3 H, CH3), 6.46 (d, J ϭ 7.8 Hz, 1 H, Ar), 6.6Ϫ7.9 (series
of m, 29 H, Ar). Ϫ 31P NMR (CDCl3): δ ϭ Ϫ14.12 (d, J ϭ 15.2 Hz,
1 P), Ϫ30.27 (s, broad, 1 P). Ϫ 13C NMR (CDCl3) aliphatic only:
δ ϭ 18.16 (d, J ϭ 25.1 Hz, 1 C, CH3), 18.9 (dd, J ϭ 18.9, J ϭ
7.7 Hz, 1 C, CH3). Ϫ C46H36P2 (650.73): calcd. C 84.9, H 5.58;
found C 84.72, H 5.82.
(S)-6c: 14% yield; m.p. 210Ϫ212 °C. Ϫ 1H NMR (CDCl3): δ ϭ
1.5Ϫ2.15 (series of m, 22 H), 7.13 (d, J ϭ 8.4 Hz, 1 H, Ar),
7.22Ϫ7.80 (series of m, 9 H, Ar), 7.96 (d, J ϭ 8.1 Hz, 1 H, Ar),
8.04 (t, J ϭ 9.0 Hz, 1 H, Ar). Ϫ 31P NMR (CDCl3): δ ϭ 46.90. Ϫ
C33H34F3O4PS (614.66): calcd. C 64.48, H 5.57; found C 64.35,
H 5.44.
Preparation of Diphosphane Rhodium(I) Diolefin Complexes 13. ؊
Method A, [(4c)Rh(cod)]؉BF4 (13a): AgBF4 (56 mg, 0.15 mmol)
؊
Preparation of Phosphanyl؊Phosphanes 8: A solution of the appro-
priate diarylphosphane oxide (5.0 mmol) and (dppe)NiCl2 [dppe ϭ
was added to a solution of [Rh(cod)Cl]2 (37 mg, 0.075 mmol) in
THF (10 mL) with vigorous stirring for 30 min. The suspension
1,2-bis(diphenylphosphanyl)ethane] (0.22 g, 0.43 mmol) in DMF was filtered through Celite to remove the silver salts and ligand 4c
(10 mL) was stirred at 100 °C for 10 min. A solution of 2-di- (100 mg, 0.15 mmol) was added to the yellow solution. After stir-
phenylphosphanyl-1,1Ј-binaphthalene-2Ј-yl triflate (7) (2.5 g, ring 10 min at room temperature, the solution was concentrated
4.26 mmol) and Et3N (3 mL) in DMF (15 mL) was added and the and ether was added causing the precipitation of 13a as a dark-
mixture was stirred at 100 °C for 10Ϫ14 h. After cooling, the mix-
yellow solid, which was filtered off and washed several times with
ture was diluted with aqueous NH4Cl and extracted with CH2Cl2 anhydrous ether; 100 mg (70%). Ϫ M.p. decomposition at 120 °C.
1
(100 mL). The organic phase was washed with H2O, dried and
evaporated to give a brown solid, which was purified by flash chro-
Ϫ H NMR: Very broad signals in both the aromatic and the ali-
phatic regions.
Ϫ
31P NMR: no detectable signal.
Ϫ
matography on silica gel using EtOAc as eluent. Slightly lower C54H48P2RhBF4 (948.64)
yields were obtained using Pd(OAc)2/dppe as the catalyst.
Method B, [(4c)Rh(nbd)]؉PF6 (13b): To a solution of ligand 4c
(100 mg, 0.15 mmol) in benzene (4 mL) and THF (1 mL) was ad-
ded [Rh(nbd)Cl]2 (35.5 mg, 0.075 mmol). The colour of the solu-
tion immediately turned to deep red. After 5 min, KPF6 (28 mg,
0.15 mmol) in acetone (2 mL) was added, followed by diethyl ether
(5 mL). The reaction mixture was stirred for 3 h, during which time
an orange solid separated. The solid was filtered off, washed with
benzene and diethyl ether and air-dried. The orange crystalline
powder was dissolved in the minimal amount of dichloromethane
and crystallized by addition of ethanol and diethyl ether; 104 mg
(70%); m.p. decomposition at 230 °C Ϫ 1H NMR (CDCl3): δ ϭ
1.47 (d, J ϭ 9 Hz, 1 H, CH2), 1.56 (s, 3 H, CH3), 1.65 (d, J ϭ
9 Hz, 1 H, CH2), 3.26 (s, broad, 3 H, CH3), 3.65 (s, broad, 1 H,
allylic), 4.00 (s, broad, allylic), 4.18 (s, broad, 1 H, vinylic), 4.69 (s,
broad, 1 H, vinylic), 5.01 (s, broad, 1 H, vinylic), 5.43 (s, broad, 1
H, vinylic), 6.20Ϫ8.48 (series of m, 30 H, Ar). Ϫ 13C NMR: δ ϭ
Ϫ
8a: 1.90 g (70%); m.p. 172Ϫ173 °C. Ϫ IR (KBr): ν˜ ϭ 1208 cmϪ1
.
1
Ϫ H NMR (CDCl3): δ ϭ 6.63 (d, J ϭ 8.1 Hz, 1 H, Ar), 6.72 (dt,
J ϭ 1.2, 6.6 Hz, 1 H, Ar) 6.81Ϫ7.43 (series of m, 23 H, Ar), 7.60
(m, 3 H, Ar), 7.79 (d, J ϭ 8.1 Hz, 1 H, Ar), 7.81 (d, J ϭ 8.4 Hz, 1
H, Ar), 7.82 (d, J ϭ 7.8 Hz, 1 H, Ar), 7.93 (dd, J ϭ 2.4, 8.4 Hz, 1
H, Ar). Ϫ 31P NMR (CDCl3): δ ϭ Ϫ14.70, 27.69. Ϫ C44H32OP2
(638.67): calcd. C 82.74, H 5.05; found C 82.68, H 5.16.
8b: 1.47 g (52%); m.p. 156Ϫ158 °C. Ϫ 1H NMR (CDCl3): δ ϭ 2.23
(s, 3 H, CH3), 2.29 (s, 3 H, CH3), 6.60 (m, 2 H, Ar), 6.70 (m, 2 H,
Ar), 6.80Ϫ7.91 (series of m, 26 H, Ar). Ϫ 31P NMR (CDCl3): δ ϭ
Ϫ14.79, 27.91. Ϫ C46H36OP2 (666.73): calcd. C 82.87, H 5.44;
found C 83.13, H 5.31.
Preparation of Diphosphanes 4. ؊ Method A: Reduction of Phosphi-
nyl-phosphanes 8: To a mixture of 2-(diphenylphosphanyl)-2Ј-(di-p-
tolylphosphinyl)-1,1Ј-binaphthalene (8b) (1.0 g, 1.5 mmol) and
Et3N (5 mL) in xylene (35 mL) was added HSiCl3 (0.74 mL) at 0
°C. The mixture was stirred at 120 °C for 12 h. After cooling, the
mixture was diluted with Et2O and quenched with saturated
NaHCO3. The organic phase was separated, dried over Na2SO4
and evaporated. The product was purified by flash chromatography
using CH2Cl2/petroleum ether (1:1) as eluent.
3
3
22.8 (d, JC,P ϭ 3.5 Hz, 1 C, CH3), 26.2 (d, JC,P ϭ 10.1 Hz, 1 C,
CH3), 52.6 (s, 1 C, CH, allylic), 53.6 (s, 1 C, CH, allylic), 69.6 (s, 1
C, CH2), 77.2 (m, 1 C, CH, vinylic), 85.0 (m, 1 C, CH, vinylic),
86.0 (m, 1 C, CH, vinylic), 89.0 (m, 1 C, CH, vinylic), 124.4Ϫ141.7
(series of m, 44 C, Ar). Ϫ 31P NMR (CDCl3): δ ϭ Ϫ144.9 (m,
1
2
PF6Ϫ), 22.14 (dd, JP,Rh ϭ 154.4, JP,PЈ ϭ 33 Hz, 1 P), 26.75 (dd,
1JP,Rh ϭ 156.3, JP,PЈ ϭ 33 Hz, 1 P). Ϫ C53H44P2RhPF6 (990.76):
2
calcd. C 64.25, H 4.48; found C 64.42, H 4.62.
4b: 0.44 g (45%); m.p. 188Ϫ189 °C. Ϫ [α]2D5 ϭ Ϫ220 (c ϭ 0.4, ben-
zene). Ϫ H NMR (CDCl3): δ ϭ 2.24 (s, 3 H, CH3), 2.26 (s, 3 H,
1
Asymmetric Hydrogenation of Methyl Acetamidoacrylate: Methyl
CH3), 6.81Ϫ7.48 (series of m, 28 H, Ar), 7.81Ϫ7.91 (series of m, acetamidoacrylate 11 (143 mg, 1 mmol) and complex 13b (9.5 mg,
2864 Eur. J. Org. Chem. 2000, 2861Ϫ2865