Xie et al.
2-Dicyclohexylphosphino-2′-alkoxy-1,1′-binaphthyl (6a-c). A
typical procedure was given for the preparation of 2-dicyclohexy-
lphosphino-2′-methoxy-1,1′-binaphthyl (6a).28 To a mixture of 5a
(4.30 g, 8.60 mmol) and Et3N (40.4 g, 40.0 mmol) in toluene (200
mL) was added Cl3SiH (13.7 g, 100 mmol) at 0 °C. The reaction
mixture was stirred at 120 °C for 5 h. After cooling to room
temperature, the mixture was diluted with Et2O and quenched with
saturated NaHCO3. The resulting suspension was filtered through
Celite, and the solid was washed with Et2O. The combined organic
layer was dried over MgSO4 and concentrated under reduced
pressure to give 6a as a white solid (4.30 g, 76%): mp 196-200
by tuning the substituents on the phosphino group. Furthermore,
the catalytic activity of the synthesized ligands matches or
exceeds that of some of the best phosphine ligands (9 and 10)
reported previously. Combined with the expedient synthesis and
stability, these MOP-type ligands may facilitate the practical
usefulness and expand the scope of the C-N bond forming
reactions.
Experiment Section
1
2-Dicyclohexylphosphino-2′-hydroxybinaphthyl (3). To a solu-
tion of 1,1′-bi-2-naphthol (80.0 g, 280 mmol) in 1,2-dichlorobenzene
(500 mL) was added HY zeolite (45.0 g, SiO2/Al2O3 ) 16), and
the mixture was heated to 180 °C for 4 h with stirring. After cooling
to 80 °C, the reaction mixture was filtered and concentrated under
reduced pressure. Methanol (100 mL) was added to the residue to
obtain a yellowish crystal, which was washed with methanol and
dried in vacuo to give pure binaphthofuran (2) (70.5 g, 94%). To
a suspension of lithium chip (6.10 g, 870 mmol) in Et2O (200 mL)
was added dropwise a solution of 2 (15.7 g, 58.0 mmol) in toluene
(250 mL), and the mixture was stirred at room temperature for 4 h
to achieve the complete conversion of the starting material. After
the removal of excess lithium by filtration, Cy2PCl (16.4 g, 70.0
mmol) was added by a syringe to the solution cooled to 0 °C, and
the mixture was stirred for 2 h at room temperature to give a white
precipitate, which was filtered, washed with Et2O (50 mL × 2),
dried in vacuo, and dissolved in CH2Cl2 (200 mL). The solution
was neutralized with 3 N HCl, washed with H2O (50 mL × 2),
and concentrated under reduced pressure. To the residue was added
MeOH (50 mL), and the mixture was stirred for 4 h to give a white
solid. Filtration, washing with MeOH, and drying in vacuo gave
22.4 g (83%) of 3: 1H NMR (400 MHz, DMSO) δ 0.86-1.91 (m,
22 H), 6.67 (d, J ) 8.4 Hz, 1 H), 7.29-6.98 (m, 5 H), 7.44-7.47
(m, 1 H), 7.74-7.96 (m, 5 H), 9.40 (s, 1 H); 31P NMR (162 MHz,
DMSO) δ -9.0.
°C; H NMR (400 MHz, CDCl3) δ 0.90-1.80 (m, 22 H), 3.75 (s,
3 H), 6.90 (d, J ) 8.8 Hz, 1 H), 7.12-7.28 (m, 4 H), 7.39-7.46
(m, 2 H), 7.76-8.01 (m, 5 H); 13C NMR (100 MHz, CDCl3) δ
26.4, 26.5, 27.2, 27.3, 27.5, 27.6, 29.8, 29.9, 30.4, 30.5, 30.55, 30.6,
34.3, 34.5, 35.2, 35.4, 55.5, 112.2, 123.1, 125.7, 125.9, 126.2, 126.7,
126.9, 127.8, 127.82, 128.5, 129.1, 129.6, 133.3, 133.5, 134.3,
143.2, 154.3; 31P NMR (162 MHz, CDCl3) δ -7.9; IR (KBr, cm-1
)
ν 3051 (w), 2923 (s), 2846 (s), 1593 (m), 1508 (m), 1460 (w),
1269 (s), 1249 (s), 1081 (m), 815 (m), 806 (s), 747 (m); EIMS m/z
481 (M+, 1). Anal. Calcd for C33H37OP: C, 82.47; H, 7.76.
Found: C, 81.60; H, 7.62. 2-Dicyclohexylphosphino-2′-isopro-
poxy-1,1′-binaphthyl (6b): a white solid (87% yield); mp 150-
154 °C; 1H NMR (400 MHz, CDCl3) δ 0.82 (d, J ) 5.6 Hz, 3 H),
0.88-1.85 (m, 25 H), 4.50-4.56 (m, 1 H), 6.92 (d, J ) 8.8 Hz, 1
H), 7.12-7.27 (m, 4 H), 7.36-7.44 (m, 2 H), 7.75-7.94 (m, 5 H);
13C NMR (100 MHz, CDCl3) δ 22.1, 22.6, 26.4, 26.5, 27.2, 27.3,
27.5, 29.98, 30.01, 30.1, 30.5, 30.61, 30.64, 34.6, 35.3, 35.4, 70.4,
115.4, 123.2, 125.49, 125.55, 126.0, 126.3, 126.4, 127.1, 127.5,
127.7, 128.5, 129.1, 129.2, 133.4, 153.1; 31P NMR (162 MHz,
CDCl3) δ -8.0; IR (KBr, cm-1) ν 3055 (w), 2976 (w), 2923 (s),
2848 (s), 1593 (w), 1508 (m), 1445 (w), 1239 (s), 1116 (m), 1000
(m), 814 (m), 745 (s), 685 (w); EIMS m/z 509 (M+, 1), 451 (base
peak). Anal. Calcd for C35H41OP: C, 82.64; H, 8.13. Found: C,
82.22; H, 8.24. 2-Dicyclohexylphosphino-2′-benzyloxy-1,1′-bi-
1
naphthyl (6c): a white solid (73% yield); mp 160-163 °C; H
2-Dicyclohexylphosphinyl-2′-methoxy-1,1′-binaphthyl (5a-c).
A typical procedure was given for the preparation of 2-dicyclo-
hexylphosphinyl-2′-isopropoxy-1,1′-binaphthyl (5b).40 H2O2 (20
mL, 30%) was added dropwise to the solution of 3 (22.4 g, 48.0
mmol) in CH2Cl2 (200 mL) at 0 °C to give a white solid. The white
solid was filtered, washed with CH2Cl2 and MeOH, and dried in
vacuo to give 4 (20.9 g, 90%). To a suspension of 4 (8.00 g, 19.0
mmol) in 100 mL of THF was added NaH (1.50 g, 37.0 mmol) in
three portions, and the mixture was stirred for 30 min at room
temperature, during which time the white solid was dissolved. After
the removal of the solvent, the residue was dissolved in acetone
(200 mL), and K2CO3 (13.1 g, 95.0 mmol) and iPrBr (9.30 g, 76.0
mmol) were added. The reaction mixture was refluxed for 24 h
and filtered, and the solid was washed with CH2Cl2. The combined
organic layer was concentrated under reduced pressure to give a
thick oil, which was chromatographed on silica gel (hexane/CH2-
Cl2/EtOAc, 1:1:2) to give 5b (5.70 g, 63%) as a white solid: 1H
NMR (400 MHz, CDCl3) δ 0.72 (d, J ) 5.6 Hz, 3 H), 0.94-1.83
(m, 25 H), 4.47-4.50 (m, 1 H), 6.88 (d, J ) 8.0 Hz, 1 H), 7.10-
7.30 (m, 4 H), 7.37-7.50 (m, 2 H), 7.83 (d, J ) 8.0 Hz, 1 H),
7.90-8.04 (m, 4 H); 31P NMR (162 MHz, CDCl3) δ 48.0.
2-Dicyclohexylphosphinyl-2′-methoxy-1,1′-binaphthyl (5a):28, 40
NMR (400 MHz, CDCl3) δ 0.83-1.85 (m, 22 H), 5.04 (s, 2 H),
6.91-7.94 (m, 17 H); 13C NMR (100 MHz, CDCl3) δ 26.3, 26.4,
27.2, 27.3, 27.4, 29.8, 29.96, 29.99, 30.00, 30.1, 30.3, 30.4, 30.57,
30.59, 34.4, 34.5, 34.57, 34.58, 35.2, 35.4, 70.0, 114.3, 123.4, 125.8,
125.9, 126.0, 126.3, 126.7, 127.0, 127.2, 127.7, 127.9, 128.1, 128.7,
129.2, 129.5, 133.4, 133.5, 133.6, 134.4, 137.6, 153.6; 31P NMR
(162 MHz, CDCl3) δ -7.9; IR (KBr, cm-1) ν 3051 (w), 2918 (s),
2846 (s), 1620 (w), 1592 (m), 1508 (m), 1446 (m), 1288 (w), 1224
(s), 1088 (m), 815 (m), 744 (m), 736 (s), 696 (w); EIMS m/z 557
(M+, 1), 451 (base peak). Anal. Calcd for C39H41OP: C, 84.14; H,
7.42. Found: C, 84.13; H, 7.56.
2-Di-tert-butylphosphino-2′-hydroxybinaphthyl (7). To a sus-
pension of lithium chip (4.20 g, 600 mmol) in Et2O (200 mL) was
added dropwise a solution of 2 (16.1 g, 60.0 mmol) in toluene (250
mL), and the mixture was stirred at room temperature for 4 h. After
t
the removal of excess lithium, Bu2PCl (13.0 g, 72.0 mmol) and
CuI (900 mg, 4.80 mmol) were added to the solution at 0 °C, and
the mixture was stirred overnight at 45 °C to give a white
precipitate. The white precipitate was filtered, washed with Et2O
(50 mL × 2), dried in vacuo, and dissolved in CH2Cl2 (200 mL).
The solution was neutralized with 3 N HCl, washed with H2O (50
mL × 2), and concentrated under reduced pressure. The residue
was triturated MeOH (50 mL), and the mixture was stirred for 2 h
to give a white solid. Filtration, washing with MeOH, and drying
in vacuo gave 7 (16.6 g, 67%): 1H NMR (400 MHz, CDCl3) δ
1.01 (d, J ) 11.2 Hz, 9 H), 1.20 (d, J ) 11.2 Hz, 9 H), 4.70 (s, 1
H), 6.90 (d, J ) 8.4 Hz, 1 H), 7.11-7.30 (m, 5 H), 7.50-7.53 (m,
1 H), 7.82-7.98 (m, 4 H), 8.11 (d, J ) 8.4 Hz, 1 H); 31P NMR
(162 MHz, CDCl3) δ 25.2.
1
72% yield; H NMR (400 MHz, CDCl3) δ 0.84-1.72 (m, 22 H),
3.76 (s, 3 H), 6.84 (d, J ) 8.4 Hz, 1 H), 7.12-7.31 (m, 4 H),
7.41-7.64 (m, 2 H), 7.86 (d, J ) 8.4 Hz, 1 H), 7.94 (d, J ) 8.4
Hz, 1 H), 8.01-8.05 (m, 3 H); 31P NMR (162 MHz, CDCl3) δ
48.0. 2-Dicyclohexylphosphinyl-2′-benzyloxy-1,1′-binaphthyl (5c):
38
1
58% yield; H NMR (400 MHz, CDCl3) δ 0.52-1.76 (m, 22
H), 5.04 (q, J ) 12.4 Hz, 2 H), 6.81-8.04 (m,17 H); 31P NMR
(162 MHz, CDCl3) δ 48.3.
2-Di-tert-butylphosphino-2′-methoxy-1,1′-binaphthyl (8a-c).
A typical procedure was given for the preparation of 2-di-tert-
butylphosphino-2′-isopropoxy-1,1′-binaphthyl (8b). To a suspension
of 7 (4.20 g, 10.0 mmol) in THF (100 mL) was added NaH (800
(40) Kawashima, Y.; Okana, K.; Nozaki, K.; Hiyama, T. Bull. Chem.
Soc. Jpn. 2004, 77, 347.
6528 J. Org. Chem., Vol. 71, No. 17, 2006