Facile preparation of a new BINAP-based building block, 5,5′-DiiodoBINAP, and its synthetic application

Article abstract of DOI:10.1021/jo0517186

Bis(pyridine)iodonium tetrafluoroborate was successfully used for regioselective iodination of BINAP dioxide to give 5,5′-diiodoBINAP dioxide in an excellent yield of 92%, with no observed formation of 4,4′-diiodoBINAP dioxide. A Sonogashira cross-couplin

Full text of DOI:10.1021/jo0517186

Facile Preparation of a New BINAP-Based
Building Block, 5,5′-DiiodoBINAP, and Its
Synthetic Application
have been prepared in several steps starting from 6- or
6
,6′-substituted 1,1′-bi-2-naphthol.4 However, these de-
,5
rivatizations are inferior to direct functionalization of
BINAP due to their low yields and associated handling
losses. Direct nitration at the 5,5′-positions of BINAP
T
o
y
o
s
h
i
S
h
i
m
a
d
a
,
*
,
†
M
a
s
a
h
i
k
o
S
u
d
a
,
‡
6
†
‡
dioxide, followed by reduction to 5,5′-diamino-BINAP,
Toyohiro Nagano, and Kiyomi Kakiuchi
7
was reported in 1987. The 5,5′-diamino-BINAP was for
Department of Chemical Engineering, Nara National
College of Technology, 22 Yata-cho, Yamatokoriyama, Nara
the first time used by Chan et al. for preparation of
soluble polymer-supported catalysts for asymmetric hy-
drogenation.8 Recently, K o¨ ckritz et al. have reported
regioselective bromination at the 4,4′-positions of BINAP
dioxide and Lemaire et al. have reported bromination at
the 5,5′-positions of BINAP dioxide in the presence of
6
39-1080, Japan, and Graduate School of Materials Science,
Nara Institute of Science and Technology (NAIST), 8916-5,
Takayama, Ikoma, Nara 630-0192, Japan
shimada@chem.nara-k.ac.jp
Received August 13, 2005
9
iron. Although Lemaire et al. transformed bromo atoms
at the 5,5′-positions of BINAP dioxide to perfluoroalkyl
or cyano groups, transition metal-catalyzed cross-cou-
pling reactions at the 5,5′-positions have not been re-
ported. It is well-known that arylbromide is less reactive
than aryliodide toward transition metal-catalyzed cross-
coupling.10 To our knowledge, the preparation of 4,4′-
diphenyl-BINAP by Suzuki coupling is the only cross-
coupling reaction of this type that has been reported in
the literature.11 Here we report a new facile regioselective
iodination at the 5,5′-position of BINAP and subsequent
Sonogashira coupling reaction leading to the ethynyl-
BINAP, which is useful as a chiral ligand for a rhodium-
catalyzed asymmetric 1,4-additon.
First, we attempted to direct iodination of BINAP
6
12
dioxide with iodine monochloride and with N-iodosuc-
Bis(pyridine)iodonium tetrafluoroborate was successfully
used for regioselective iodination of BINAP dioxide to give
1
3
cinimide in the presence of trifluoroacetic acid. How-
ever, in both cases no iodination reaction occurred and
the starting materials were recovered unchanged. More
5
,5′-diiodoBINAP dioxide in an excellent yield of 92%, with
no observed formation of 4,4′-diiodoBINAP dioxide. A So-
nogashira cross-coupling reaction with 5,5′-diiodoBINAP
dioxide gave the desired bis(trimethylsilylethynyl) product
in 86% yield. The resulting 5,5′-disubstituted BINAP di-
oxides were reduced to the corresponding phosphines, which
were used as chiral ligands for rhodium-catalyzed asym-
metric 1,4-addition of phenylboronic acid to 2-cyclohexenone
to give 3-phenylcyclohexanone in excellent yield with high
enantioselectivity.
(
4) (a) Vankelecom, I. F. J.; Tas, D.; Parton, R. F.; Van de Vyver,
V.; Jacobs, P. A. Angew. Chem., Int. Ed. Engl. 1996, 35, 1346-1348.
(b) Bayston, D. J.; Fraser, J. L.; Ashton, M. R.; Baxter, A. D.; Polywka,
M. E. C.; Moses, E. J. Org. Chem. 1998, 63, 3137-3140. (c) Saluzzo,
C.; Lemaire, M. Adv. Synth. Catal. 2002, 344, 915-928. (d) Guerreiro,
P.; Ratovelomanana-Vidal, V.; Genet, J.-P.; Dellis, P. Tetrahedron Lett.
2001, 42, 3423-3426. (e) Yu, H.-B.; Hu, Q.-S.; Pu, L. Tetrahedron Lett.
2000, 41, 1681-1685. (f) Yu, H.-B.; Hu, Q.-S.; Pu, L. J. Am. Chem.
Soc. 2000, 122, 6500-6501.
(
5) (a) Saluzzo, C.; Ter Halle, R.; Touchard, F.; Fache, F.; Schulz,
E.; Lemaire, M. J. Organomet. Chem. 2000, 603, 30-39. (b) Ter Halle,
R.; Colasson, B.; Schulz, E.; Spagnol, M.; Lemaire, M. Tetrahedron Lett.
2000, 41, 643-646. (c) Saluzzo, C.; Lamouille, T.; Herault, D.; Lemaire,
M. Bioorg. Med. Chem. Lett. 2002, 12, 1841-1844. (d) Shimada, T.;
Aoki, K.; Shinoda, Y.; Nakamura, T.; Tokunaga, N.; Inagaki, S.;
Hayashi, T. J. Am. Chem. Soc. 2003, 125, 4688-4689. (e) Otomaru,
Y.; Senda, T.; Hayashi, T. Org. Lett. 2004, 6, 3357-3359.
(6) Shimada, T.; Kurushima, H.; Cho, Y.-H.; Hayashi, T. J. Org.
Chem. 2001, 66, 8854-8858.
One of the most useful chiral phosphine ligands is 2,2′-
bis(diphenylphosphino)-1,1′-binaphthyl (BINAP), which
1
exhibits high enantioselectivity in several types of asym-
metric reactions including ruthenium-catalyzed hydro-
2
genation and rhodium-catalyzed 1,4-addition and its
3
related reactions. Over the past decade, there have been
major efforts to prepare BINAP derivatives for recycling
catalytic systems and achieving higher selectivity in
(
7) Okano, T.; Kumobayashi, H.; Akutagawa, S.; Kiji, J.; Konishi,
H.; Fukuyama, K.; Shimano, Y. U.S. Patent 4 705 895, 1987.
(8) Fan, Q.-H.; Ren, C.-Y.; Yeung, C.-H.; Hu, W.-H.; Chan, A. S. C.
J. Am. Chem. Soc. 1999, 121, 7407-7408.
4
asymmetric synthesis. Most of these BINAP derivatives
(9) (a) Kant, M.; Bischoff, S.; Siefken, R.; Gr u¨ ndemann, E.; K o¨ ckritz,
†
Nara National College of Technology.
A. Eur. J. Org. Chem. 2001, 477-481. (b) Berthod, M.; Saluzzo, C.;
Mignani, G.; Lemaire, M. Tetrahedron: Asymmetry 2004, 15, 639-645.
(c) Berthod, M.; Mignani, G.; Lemaire, M. Tetrahedron: Asymmetry
2004, 15, 1121-1126. (d) Berthod, M.; Mignani, G.; Woodward, G.;
Lemaire, M. Chem. Rev. 2005, 105, 1801-1836.
‡
Nara Institute of Science and Technology.
(1) (a) Miyashita, A.; Yasuda, A.; Takaya, H.; Toriumi, K.; Ito, T.;
Souchi, T.; Noyori, R. J. Am. Chem. Soc. 1980, 102, 7932-7934. (b)
Takaya, H.; Mashima, K.; Koyano, K.; Yagi, M.; Kumobayashi, H.;
Taketomi, T.; Akutagawa, S.; Noyori, R. J. Org. Chem. 1986, 51, 629-
(10) Jutland, A.; Mosleh, A. Organometallics 1995, 14, 1810-1817.
(11) (a) Hu, A.; Ngo, H. L.; Lin, W. J. Am. Chem. Soc. 2003, 125,
11490-11491. (b) Hu, A.; Ngo, H. L.; Lin, W. Angew. Chem., Int. Ed.
2004, 43, 2501-2503. (c) Ogasawara, M.; Nagano, T.; Hayashi, T. J.
Org. Chem. 2005, 70, 5764-5767.
(12) Merkushev, E. B. Synthesis 1988, 923-937.
(13) Castanet, A. S.; Colobert, F.; Broutin, P. E. Tetrahedron Lett.
2002, 43, 5047-5048.
6
35.
(
2) (a) Noyori, R. Asymmetric Catalysis in Organic Synthesis;
Wiley: New York, 1994. (b) Okuma, T.; Noyori, R. In Comprehensive
Asymmetric Catalysis; Jacobsen, E., Pfaltz, A., Yamamoto, H., Eds.;
Springer: Berlin, Germany, 1999; Vol. 1, Chapter 6.1, pp 199-246.
(
c) Noyori, R.; Okuma, T. Angew. Chem., Int. Ed. 2001, 40, 40-73.
(3) Hayashi, T.; Yamasaki, K. Chem. Rev. 2003, 103, 2829-2844.
10.1021/jo0517186 CCC: $30.25 © 2005 American Chemical Society
10178
J. Org. Chem. 2005, 70, 10178-10181
Published on Web 10/22/2005

SCHEME 1a
a
Reaction conditions: (a) trimethylsilylacetylene, PdCl2(PPh3)2, CuI, Et3N, THF, 50 °C, 86%; (b) MeOTf, LiAlH4, cyclopentylmethyl
ether, room temperature, 82%; (c) TBAF, THF, room temperature, 98%; (d) trichlorosilane, toluene, reflux, 92%.
reactive iodination reagents were required to obtain
iodinated BINAP dioxide. We found that the use of bis-
TABLE 1. Direct Iodination of BINAP Dioxide 1
14
(
pyridine)iodonium tetrafluoroborate (IPy
the corresponding diiodoBINAP dioxide in excellent yield.
IPy BF
, which was developed by Barluenga,14 is a
2
BF
4
)
gives
2
4
powerful and highly selective iodination reagent under
mild conditions. Iodination of (R)-2,2′-bis(diphenylphos-
phinyl)-1,1′-binaphthyl (1) with 3 equiv of IPy
2 4
BF in
CH Cl at 25 °C for 20 h gave (R)-2,2′-bis(diphenylphos-
2
2
phinyl)-5,5′-diiodo-1,1′-binaphthyl (2), with high regio-
selectivity, in 92% yield, with no observed formation of
the 4,4′-diiodo product (entry 2).15 The use of 2 equiv of
recovery or yields (%)a
IPy2BF4 temp time
yield
(%)
entry (equiv)
(°C)
(h)
1
2
3
1
2
3
4
5
2.0
3.0
1.0
2.0
2.0
25
25
20
20
20
40
80
1
64
100
5
35
0
46
49
56
IPy
2
BF
4
under the same reaction conditions afforded a
92b
0
49
44
7
reaction mixture consisting of (R)-2,2′-bis(diphenylphos-
phinyl)-5-iodo-1,1′-binaphthyl (3) and 2 in a ratio of 35/
25
-30
-30
7
37
15c
6
4 together with 1 (1%) (entry 1). Although a decrease
to 1 equiv of IPy BF produced 3 preferentially (46%), a
halved amount of starting material was unreactive (entry
). Carrying out the reaction at -30 °C for 40 h in the
presence of 2 equiv of IPy BF increased selectivity,
a
Determined by NMR analysis. b Isolated yield of 2. c Isolated
2
4
yield of 3.
3
2
4
in excellent yield,16 compared to the corresponding bro-
mination procedure, which generates a mixture of mono-
and dibromo products. Furthermore, the higher reactiv-
resulting in a ratio of 49/7 for 3 and 2, and increasing
the reaction time to 80 h afforded 3 and 2 in a ratio of
9
5
6/37 (entry 4 and 5). After purification by silica gel
ity of aryl iodide in transition metal-catalyzed coupling
chromatography, monoiodoBINAP dioxide was isolated,
albeit in 15% yield because of difficulty in separating the
monoiodo product from starting material 1. In this work,
reactions, which is known as the order of PhI . PhOTf
>
PhBr,10 is to expected to facilitate preparation for new
functionalized BINAPs starting from 2.
iodination of BINAP dioxide with use of IPy
2 4
BF is shown
To clarify the availability of diiodoBINAP dioxide as a
building block, we examined the Sonogashira coupling
reaction of 2 with trimethylsilylacetylene. As expected,
the reaction proceeded smoothly under the general So-
nogashira reaction conditions17 to give the corresponding
R)-2,2′-bis(diphenylphosphinyl)-5,5′-bis(trimethylsilyl-
ethynyl)-1,1′-binaphthyl (5) in 86% yield (Scheme 1).
Reduction of diphenylphosphinyl groups in 5 was carried
to be a simple method for obtaining the diiodo product 2
(14) (a) Barluenga, J.; Gonzalez, J. M.; Campos, P. J.; Asensio, G.
Angew. Chem., Int. Ed. 1985, 24, 319-320. (b) Barluenga, J.; Rod-
riguez, M. A.; Campos, P. J. J. Org. Chem. 1990, 55, 3104-3106. (c)
Barluenga, J.; Gonzalez, J. M.; Campos, P. J.; Asensio, G. J. Chem.
Soc., Perkin Trans. 1 1984, 2623-2624. (d) Barluenga, J.; Gonzalez,
J. M.; Martin, M.; Campos, P. J. Tetrahedron Lett. 1993, 24, 3893-
(
3
896. (e) Barluenga, J.; Gonzalez, J. M.; Martin, M.; Campos, P. J.;
Asensio, G. J. Org. Chem. 1993, 58, 2058-2060.
15) The position of the diiodo in BINAP dioxide was determined
(
1
1
by the 2D H NMR spectrum of 2 and previously reported H NMR
data of both BINAP dioxide and brominated BINAP dioxides (see
the Supporting Information).
2 4
(16) Direct iodination of BINAP with 10 equiv of IPy BF at 25 °C
for 20 h gave 5,5′-diiodoBINAP dioxide 2 with several unidentified
6
9
byproducts.
J. Org. Chem, Vol. 70, No. 24, 2005 10179

SCHEME 2
Preparation of (R)-2,2′-Bis(diphenylphosphinyl)-5,5′-
diiodo-1,1′-binaphthyl (2). To a solution of bis(pyridine)-
iodonium tetrafluoroborate (395 mg, 1.06 mmol) and (R)-2,2′-
bis(diphenylphosphinyl)-1,1′-binaphthyl (1) (229 mg, 0.35 mmol)
in dichloromethane (6 mL) was added dropwise trifluoromethane-
sulfonic acid (0.19 mL, 2.12 mmol) and the mixture was stirred
at room temperature for 20 h. The reaction was quenched with
saturated sodium thiosulfate solution and extracted with dichlo-
romethane. The organic phase was washed with brine and then
with water, dried over sodium sulfate, and concentrated. The
residue was chromatographed on silica gel (hexane/EtOAc ) 1/2)
to give 304.0 mg (92%) of (R)-2,2′-bis(diphenylphosphinyl)-5,5′-
out under reduction condition of 2 with trichlorosilane
to (R)-2,2′-bis(diphenylphosphino)-5,5′-diiodo-1,1′-binaph-
thyl (4) in 92% yield. However, the reduction of 5 by
trichlorosilane gave many reduction products, which
displayed a large number of 31P NMR signals ranging
throughout the phosphine region. Instead of trichloro-
silane, the use of lithium aluminum hydride with methyl
trifluoromethanesulfonate, as previously reported by
2
0
diiodo-1,1′-binaphthyl: mp 325-327 °C; [R]
D
+299.6 (c 0.50,
) δ 8.14 (dd, J ) 8.9, 1.9 Hz, 2H), 7.93
dd, J ) 7.3, 0.8 Hz, 2H), 7.68 (ddd, J ) 12.1, 7.0, 1.9 Hz, 4H),
1
benzene); H NMR (CDCl
3
(
7
.51 (dd, J ) 11.3, 8.9 Hz, 2H), 7.21-7.41 (m, 16H), 6.73 (d, J
13
)
8.6 Hz, 2H), 6.46 (dd, J ) 8.6, 7.3, 0.8 Hz, 2H); C NMR
3
1
(CDCl ) δ 99.5 (C-I); P NMR (CDCl ) δ 28.34. HRMS-FAB (m/
3
3
+
z) M calcd for C44
Calcd for C44
30
H I
O P
2 2 2
905.9810, found 905.9797. Anal.
: C, 58.24; H, 3.34. Found: C, 58.24; H,
H
30
I
2
O
2
P
2
1
8
3.20.
Imamoto, successfully reduced the phosphine oxide 5
to give (R)-2,2′-bis(diphenylphosphino)-5,5′-bis(trimeth-
ylsilylethynyl)-1,1′-binaphthyl (6), which was trans-
formed to 7 by deprotection of the trimethylsilyl group
with TBAF (Scheme 1).
(
R)-2,2′-Bis(diphenylphosphinyl)-5-iodo-1,1′-binaphth-
yl (3). To a solution of bis(pyridine)iodonium tetrafluoroborate
151 mg, 0.406 mmol) and (R)-2,2′-bis(diphenylphosphinyl)-1,1′-
(
binaphthyl (1) (133 mg, 0.203 mmol) in dichloromethane (4 mL)
was added dropwise trifluoromethanesulfonic acid (72 µL, 0.812
mmol) at -30 °C and the mixture was stirred for 80 h. The
reaction was quenched with saturated sodium thiosulfate solu-
tion and extracted with dichloromethane. The organic phase was
washed with brine and then with water, dried over sodium
sulfate, and concentrated. The residue was chromatographed on
Next we attempted the rhodium-catalyzed asymmetric
,4-addition of phenyl boronic acid to 2-cyclohexenone
1
1
9
(
Scheme 2). As shown in Scheme 2, both 4 and 6 showed
high enantioselectivities, as did BINAP, although the
reaction with 7 did not proceed, probably due to unfavor-
able interaction between the catalyst and its terminal
alkyne groups. We concluded that derivatization at the
silica gel (hexane/EtOAc ) 1/1) to give 75.3 mg (15%) of (R)-
1
2
(
,2′-bis(diphenylphosphinyl)-5-iodo-1,1′-binaphthyl: H NMR
3
CDCl ) δ 8.11 (dd, J ) 8.9, 1.9 Hz, 1H), 7.93 (d, J ) 7.3 Hz,
1
7
6
H), 7.86 (dd, J ) 8.1, 2.2 Hz, 2H), 7.80 (d, J ) 8.9 Hz, 2H),
.64-7.72 (m, 4H), 7.22-7.52 (m, 17H), 6.85 (d, J ) 8.6 Hz, 1H),
.75 (d, J ) 7.3 Hz, 1H), 6.67 (d, J ) 8.6 Hz, 1H), 6.49 (t, J )
5
,5′-positions of BINAP does not influence enantioselec-
tivities or yields in rhodium-catalyzed asymmetric 1,4-
additions.
In summary, we have achieved facile preparation of a
8.6 Hz, 1H); 13C NMR (CDCl ) δ 99.5 (C-I); 31P NMR (CDCl ) δ
3
3
+
28.88, 28.24. HRMS-FAB (m/z) M calcd for C44
H
31IO
2
P
2
780.0844,
found 780.0819.
new BINAP-based building block, 2,2′-bis(diphenylphos-
(R)-2,2′-Bis(diphenylphosphino)-5,5′-diiodo-1,1′-binaph-
phinyl)-5,5′-diiodo-1,1′-binaphthyl, using IPy
iodination reagent. Efficient iodination of BINAP dioxide
with IPy BF followed by Sonogashira coupling proceeded
2 4
BF as an
thyl (4). To a solution of (R)-2,2′-bis(diphenylphosphinyl)-5,5′-
diiodo-1,1′-binaphthyl (2) (1.93 g, 2.12 mmol) in toluene (120 mL)
was added dropwise trichlorosilane (7.0 mL, 69.4 mmol) and the
mixture was refluxed for 3 h. Excess trichlorosilane and toluene
were removed under reduced pressure and the residue was
chromatographed on silica gel (hexane/EtOAc ) 5/1) to give 1.71
g (92%) of (R)-2,2′-bis(diphenylphosphino)-5,5′-diiodo-1,1′-bi-
2
4
smoothly to afford diethynyl BINAP dioxide in 79%
overall yield. Since functionalization at the 5,5′-positions
of BINAP does not influence enantioselectivity, 5,5′-
substituted BINAP and BINAP dioxide are useful as
BINAP building blocks. Several functionalizations of
BINAP are currently in progress.
2
0
1
naphthyl: mp 259-261 °C; [R]
D
+163.1 (c 0.50, benzene); H
) δ 8.15 (d, J ) 8.1 Hz, 2H), 7.89 (d, J ) 7.3 Hz,
H), 7.50 (d, J ) 8.1 Hz, 2H), 7.19-6.98 (m, 20H), 6.68 (d, J )
NMR (CDCl
3
2
8
(
1
3
3
.6 Hz, 2H), 6.51 (t, J ) 8.6 Hz, 2H); C NMR (CDCl ) δ 99.4
3
1
+
C-I); P NMR (CDCl
for C44 874.9912, found 874.9891
R)-2,2′-Bis(diphenylphosphinyl)-5,5′-bis(trimethylsilyl-
ethynyl)-1,1′-binaphthyl (5). To a mixture of 2 (4.80 g, 5.26
mmol), PdCl (PPh (369 mg, 0.526 mmol), and CuI (100 mg,
3
) δ -14.98. HRMS-FAB (m/z) M calcd
Experimental Section
30 2 2
H I P
(
General. All manipulations were carried out under a nitrogen
2 5
atmosphere. Nitrogen gas was dried by passage through P O .
1
2
3 2
)
NMR spectra were recorded at 270 MHz for H, 67.5 MHz for
1
3
31
0.526 mmol) in THF (120 mL) was added triethylamine (5.8 mL,
41.4 mmol) and the mixture was stirred at room temperature
for 30 min. After the mixture was cooled to 0 °C, trimethyl-
silylacetylene (1.30 g, 13.2 mmol) was added and the solution
was stirred at 50 °C for 48 h. It was then diluted with water
C, and 109 MHz for P. Chemical shifts are reported in δ ppm,
1
referenced to an internal tetramethylsilane standard for
NMR, chloroform-d (δ 77.0) for C NMR, and external 85% H -
3
PO
Materials. IPy
according to the reported procedures.
H
1
3
3
1
4
standard for P NMR.
1
4
2 4 2
and [Rh(acac)(C H )
]20 were prepared
2
BF
4
2
and extracted with Et O. The combined organic phases were
washed with saturated ammonium chloride, brine, and water,
dried over magnesium sulfate, and concentrated. The residue
was chromatographed on silica gel (hexane/EtOAc ) 1/2) to give
3.82 g (86%) of (R)-2,2′-bis(diphenylphosphinyl)-5,5′-bis(tri-
(
17) (a) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
975, 50, 4467-4470. (b) Takahashi, S.; Kuroyama, Y.; Sonogashira,
K.; Hagihara, N. Synthesis 1980, 627-629.
18) Imamoto, T.; Kikuchi, S.; Miura, T.; Wada, Y. Org. Lett. 2001,
1
2
0
methylsilylethynyl)-1,1′-binaphthyl: mp 274-277 °C; [R]
D
(
1
+
377.5 (c 0.50, benzene); H NMR (CDCl
3
) δ 8.40 (dd, J ) 8.6,
3
, 87-90. The isolated yield of the reduction product was improved
2
7
.2 Hz, 2H), 7.74 (dd, J ) 12.2, 7.6 Hz, 4H), 7.55-7.47 (m, 4H),
from 42% to 82% by the use of cyclopentylmethyl ether (CPME),
supplied by ZEON Corporation, in place of dimethoxyethane as solvent.
1
3
.41-7.23 (m, 16H), 6.63 (m, 4H), 0.32 (s, 18H); C NMR
3
1
(
CDCl
3
) δ 102.7, 99.8 (ethynyl C); P NMR (CDCl
3
) δ 28.48.
(
19) Takaya, Y.; Ogasawara, M.; Hayashi, T.; Sakai, M.; Miyaura,
N. J. Am. Chem. Soc. 1998, 120, 5579-5580.
20) Cramer, R. Inorg. Synth. 1974, 15, 16-17.
Anal. Calcd for C54
76.27; H, 5.59.
H O P Si : C, 76.57; H, 5.71. Found: C,
48 2 2 2
(
10180 J. Org. Chem., Vol. 70, No. 24, 2005

(
R)-2,2′-Bis(diphenylphosphino)-5,5′-bis(trimethylsilyl-
mmol) and the mixture was stirred at room temperature for 2
h. It was then diluted with water and extracted with Et O. The
ethynyl)-1,1′-binaphthyl (6). To a solution of 5 (6.34 g, 7.48
mmol) in cyclopentylmethyl ether (90 mL) was added methyl
trifluoromethanesulfonate (2.1 mL, 18.6 mmol) at 0 °C and the
mixture was stirred at room temperature for 2 h. After the
mixture was cooled to 0 °C, lithium aluminum hydride (1.42 g,
2
combined organic phases were washed with brine and water,
dried over magnesium sulfate, and concentrated. The residue
was chromatographed on silica gel (hexane/EtOAc ) 3/1) to give
448.9 mg (98%) of (R)-2,2′-bis(diphenylphosphino)-5,5′-diethynyl-
2
0
3
7.4 mmol) was added and the solution was stirred at room
1,1′-binaphthyl: mp 138-140 °C; [R]
D
+170.7 (c 0.50, benzene);
1
temperature for 5 h. The reaction mixture was treated by
successive dropwise addition of 1.4 mL of water, 1.4 mL of 15%
sodium hydroxide solution, and 4.2 mL of water and was then
extracted with benzene (three times). The combined organic
phases were dried over sodium sulfate and concentrated. The
residue was chromatographed on silica gel (hexane/EtOAc ) 3/1)
to give 4.92 g (82%) of (R)-2,2′-bis(diphenylphosphino)-5,5′-bis-
H NMR (CDCl
7.35-7.00 (m, 20H), 6.81-6.69 (m, 4H), 3.41 (s, 2H); C NMR
3
) δ 8.43 (d, J ) 8.9 Hz, 2H), 7.57-7.51 (m, 4H),
1
3
3
1
(CDCl
3
) δ 82.1, 81.7; P NMR (CDCl
3
) δ -15.04. HRMS-FAB
+
(m/z) [M + H] calcd for C48
H P 671.1979, found 671.2056.
32 2
Acknowledgment. We thank Central Glass Co. for
a generous gift of trifluoromethanesulfonic anhydride,
which is essential for preparing BINAP.
2
0
(
+
trimethylsilylethynyl)-1,1′-binaphthyl: mp 134-136 °C; [R]
D
1
3
199.0 (c 0.50, benzene); H NMR (CDCl ) δ 8.42 (d, J ) 8.6
Hz, 2H), 7.55-7.50 (m, 4H), 7.39-6.99 (m, 20H), 6.77-6.59 (m,
4
H), 0.38 (s, 18H); 13C NMR (CDCl
3
) δ 82.1, 81.7 (ethynyl C);
Supporting Information Available: 1H NMR, 31P NMR,
31
+
P NMR (CDCl
Si 814.2770, found 814.2742.
R)-2,2′-Bis(diphenylphosphino)-5,5′-diethynyl-1,1′-bi-
3
) δ -15.22. HRMS-FAB (m/z) M calcd for
13
1
and C NMR spectra of compounds 2 and 5 and 2D H NMR
spectrum of 2. This material is available free of charge via
the Internet at http://pubs.acs.org.
C
54
(
H
48
P
2
2
naphthyl (7). To a solution of 6 (558.3 mg, 0.685 mmol) in THF
3.4 mL) was added tetrabutylammonium fluoride (4.1 mL, 4.11
(
JO0517186
J. Org. Chem, Vol. 70, No. 24, 2005 10181