Catalytic asymmetric hydrogenation of α-ketoesters and quinoline using electronically enriched BINAP

Article abstract of DOI:10.1016/j.tetasy.2007.09.022

Electronically enriched chiral BINAP derivatives were synthesized incorporating electron-donating substituents at the para-phenyl position and evaluated for the Ru-catalyzed homogeneous asymmetric hydrogenation of α-ketoesters with up to 92% ee. These diphophosphines were also excellent ligands for the iridium-catalyzed asymmetric hydrogenation of quinolines.

Full text of DOI:10.1016/j.tetasy.2007.09.022

Available online at www.sciencedirect.com
Tetrahedron: Asymmetry 18 (2007) 2305–2312
Catalytic asymmetric hydrogenation of a-ketoesters
and quinoline using electronically enriched BINAP
*
*
´
Mohamad Jahjah, Mohamad Alame, Stephane Pellet-Rostaing and Marc Lemaire
ICBMS, Institut de Chimie et Biochimie Mole´culaires et Supramole´culaires, UMR-CNRS 5246,
`
Universite´ de Lyon, Universite´ Claude Bernard Lyon 1, CPE Lyon, Laboratoire de Catalyse et Synthese Organique,
43 boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France
Received 1 June 2007; revised 14 September 2007; accepted 19 September 2007
Abstract—Electronically enriched chiral BINAP derivatives were synthesized incorporating electron-donating substituents at the para-
phenyl position and evaluated for the Ru-catalyzed homogeneous asymmetric hydrogenation of a-ketoesters with up to 92% ee. These
diphophosphines were also excellent ligands for the iridium-catalyzed asymmetric hydrogenation of quinolines.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
metric hydrogenation of a and b-ketoesters. This ligand
was compared with other atropoisomer diphosphines
(BINAP and MeO–BIPHEP) with respect to their calcu-
lated dihedral angle.4 However, less is known regarding
the asymmetric catalytic hydrogenation of a-ketoesters
with chiral ruthenium(II)-modified BINAP catalysts.5
The continually increasing need for enantiomerically pure
chemicals has driven numerous major advances in the area
of homogeneous asymmetric catalysis.1 The search for eas-
ily accessible and versatile chiral ligands for transition met-
als, showing high enantioselection ability in homogeneous
catalysis, is still an ongoing challenge in chemical research,
especially in the asymmetric hydrogenation of a-ketoesters
and nitrogen-containing heteroaromatic compounds.
Asymmetric hydrogenation of nitrogen-containing
heteroaromatic compounds also provides an attractive
and convenient approach to enantiomerically pure hetero-
cycloalkanes as structural units of a number of alkaloids.6
However, a variety of chiral Rh, Ru and Ir complexes,
which have been demonstrated to be highly efficient and
enantioselective in the hydrogenation of prochiral olefins,
ketones and imines, often failed to give good results in this
particular case.7 So far only limited examples of the homo-
geneous asymmetric hydrogenation of heteroaromatic
compounds have been reported.3j,7–9 Zhou et al. found that
the iridium complex generated in situ from [Ir(COD)Cl]2
and (R)-MeO–BIPHEP, (R)-BINAP or ferrocenyloxazol-
inc-derived P,N ligands worked efficiently in the enantio-
selective hydrogenation of quinoline derivatives at room
temperature, providing optically active tetrahydroquino-
lines bearing a stereogenic carbon at the 2-position with
high enantioselectivities and yields.9a–c More recently,
Fan and Chan proposed the use of chiral diphosphinite
ligand derived from (R)-1,10-spiro-biindane-7,70-diol as a
highly effective ligand in the Ir-catalyzed asymmetric
hydrogenation of quinolines with high enantioselectivity
up to 94%.9e
The reduction of a-ketoesters and a-ketoamides has
attracted considerable attention over the last few years,
because optically active a-hydroxy esters represent an
important class of building blocks for the synthesis of nat-
ural products.2 Amongst the many methods available for
the reduction of a-ketoesters, homogeneous hydrogenation
with Ru-catalysts is one of the more technically feasible
catalytic methods, which allow the preparation of the cor-
responding hydroxy ester derivatives with enantioselecti-
vities up to 90%.3 Amongst the best catalysts, Chan’s
PQ-Phos ligands are very effective for hydrogenation of a
and b-ketoesters with ee’s of 96–98%.3j Another notable
example is the asymmetric hydrogenation of methyl ben-
zoylformate BICHEP–Ru complexes with an ee of 99%.3i
Recently, an optically active atropoisomer diphosphine
ligand, Synphos, was studied in ruthenium-catalyzed asym-
*
Corresponding authors. Fax: +33 (0)4 72 43 14 08 (S.P.-R.); e-mail:
pellet@univ-lyon1.fr
0957-4166/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2007.09.022

2306
M. Jahjah et al. / Tetrahedron: Asymmetry 18 (2007) 2305–2312
Knowing that the electronic tuning of a ligand such as
BINAP could be connected to the enantioselectivity,10–14
we herein report a comparative study of the asymmetric
hydrogenation of a-ketoesters and 2-methylquinoline with
commercially available BINAP and electronically enriched
BINAP derivatives containing MeO- or HO-phenyl
substituted.
Asymmetric reduction of a-ketoesters and hydrogenation
of 2-methylquinoline was performed in appropriate sol-
vents, respectively, EtOH or MeOH and toluene. Unfortu-
nately, the low solubility of tetrahydroxy-BINAP (R)-3 in
aprotic apolar solvents prevented us to evaluate the effi-
ciency of the ligand for the hydrogenation of the 2-methyl-
quinoline. In order to improve the solubility, we focused
our effort on the synthesis of the lipophilic analogue 6,60-
didodecyl tetrahydroxy-BINAP (R)-9, which was prepared
in a seven step strategy starting from enantiomerically pure
BINOL. As depicted in Scheme 1, the 6,60-positions were
brominated with Br2 in 75% yield according to Cram
et al.19 Benzylation of the (R)-6,60-dibromo-1,10-bis-2-
naphtol (R)-4 afforded (R)-5 in 78% yield.20 The protected
BINOL was cross coupled21 with commercially available
dodecylmagnesium bromide (89%). Deprotection of the
resulting (R)-6 using TMSI22 gave the bis-dodecylbinol
(R)-7 in 91% yield. The (R)-6,60-didodecyl-2,20-ditrifluo-
romethanesulfonate-1,10-binaphthyl (R)-8 was then ob-
tained using trifluoromethanesulfonic anhydride and
pyridine.23 The preparation of the enantiopure 6,60-didode-
2. Results and discussion
2.1. Synthesis of BINAP derivatives
The di-p-anisylphosphine–borane 1 was obtained in 39%
yield via the preparation of the bis(4-methoxyphenyl)phos-
phine oxide intermediate as reported in the literature.15
The preparation of enantiopure BINAP derivatives in-
volved a coupling reaction of the di-p-anisylphosphine–
borane 1 with (R)-2,20-ditrifluoromethanesulfonate-1,10-
binaphthyl16 in the presence of DABCO and NiCl2dppe
in DMF (Scheme 1). Tetramethoxy-BINAP (R)-2 was
obtained in 66% yield.14,17 This synthetic method was
proved to be more efficient than those previously described
by Takaya et al.18 The tetrahydroxy (R)-3 was obtained by
a deprotection of hydroxyl substituents of (R)-2 with BBr3
in quantitative yield.
cyl-tetramethoxy-BINAP (R)-9 involved
a
coupling
reaction between the di-p-anisylphosphine–borane 1 and
(R)-8 in the presence of DABCO and NiCl2dppe in
DMF. 6,60-Didodecyl-tetramethoxy-BINAP (R)-9 was
obtained in 68% yield. 6,60-Didodecyl-tetrahydroxy-
BINAP (R)-10 was finally obtained by deprotection of
the hydroxyl substituents with BBr3 in 95% yield.
BH3
H P
OMe
P
OMe
OTf
OTf
P
P
OH
OH
2
BBr3, CH2Cl2
98%
1
2
2
NiCl2dppe,
P
OMe
DABCO, DMF
66%
2
2
(R)-2
(R)-3
C12H25
Br
Br
n-C12H25MgBr
OR
OR
OR
OR
NiCl2(dppp)
Br2, CH2Cl2
82%
OH
OH
45%
C12H25
(CF3SO2)2O
pyridine
(R)-4 (R = H)
(R)-BINOL
(R)-6 (R = Bn)
(R)-7 (R = H)
TMSI
91%
BnBr, K2CO3
78%
quantitative
(R)-5 (R = Bn)
C12H25
C12H25
C12H25
BBr3
1, NiCl2dppe
P
P
OMe
P
P
OH
2
CH2Cl2
2
DABCO, DMF
OTf
OTf
98%
68%
OMe
OH
2
2
C12H25
C12H25
C12H25
(R)-9
(R)-8
(R)-10
Scheme 1. Synthesis of ligands (R)-2, (R)-3 and (R)-10.

M. Jahjah et al. / Tetrahedron: Asymmetry 18 (2007) 2305–2312
2307
2.2. Hydrogenation of a-ketoesters
With ees of 87% and 79% (Table 1, entries 3 and 6), the
electron enriched tetrahydroxy-BINAP (R)-3 was slightly
more efficient for the reduction of the methyl and ethyl
pyruvate than tetramethoxy-BINAP (R)-2 with ees of
84% and 75%, respectively, (Table 1, entries 2 and 5).
These results compare favourably to those obtained in
the reduction of the methyl pyruvate 12a and ethyl pyru-
vate 12b using BINAP as ligand in the same solvent
(78% and 65% ee) (Table 1, entries 1 and 4). Moreover
this phenomenon is particularly observed with methyl
benzoylformate 14c, which is hydrogenated with a higher
enantioselectivity (92% ee) with the electronically
enriched BINAP tetramethoxy-BINAP (R)- 2 or tetra-
hydroxy-BINAP (R)-3, whereas it is reduced with only
77% ee with the (R)-BINAP. Finally, when 11d was used
as catalyst for the hydrogenation of 12c, an ee of 91%
was obtained, similar to the ee obtained with 11, demon-
strating that the efficiency of the catalyst was not influ-
enced by the alkyl chain grafted on the naphthyl
moiety of (R)-10.
The hydrogenation of various a-ketoesters was carried out
with catalyst, ligands (R)-2, (R)-3 and (R)-10 and com-
pared with the (R)-BINAP in order to evaluate the effect
of the methoxy groups at the para-position of the phenyl
of the BINAP. Ru(I)-catalysts 11a–d were prepared
in situ by stirring a solution of [Ru(C6H6)Cl2]2 precursor
and the diphosphine ligands (Scheme 2) prior to the intro-
duction of the a-ketoesters and being pressurized under H2.
The asymmetric hydrogenation reaction was carried out
under hydrogen pressure (40 bar) at 50 ꢁC in the presence
of the chiral catalyst.
The catalytic hydrogenation of substrates 12a–c using
BINAP and BINAP derivatives (R)-2 and (R)-3 as the
ligand was also performed. Whatever the substrate, a total
conversion was observed with moderate to good enantio-
meric excesses (Table 1).
R
+
R
R
Ar2
P
[RuC6H6Cl2]2
Solvent
PAr2
PAr2
Ru
Cl-
Cl
P
Ar2
R
(R)-BINAP: R = H; Ar = Ph
11a-d
(R)-2:
(R)-3:
(R)-10:
R = H; Ar = p-MeOC6H4
R = H; Ar = p-HOC6H4
R = C12H25; Ar = p-HOC6H4
Scheme 2. General procedure for BINAP complex synthesis.
Table 1. Ruthenium-catalyzed reduction of ketoesters with (R)-BINAP, tetramethoxy-BINAP (R)-2 and tetrahydroxy-BINAP (R)-3
O
OH
[RuBnCl2]2
O
O
R
R'
R
R'
Solvent, H2 (40 bars), 50 °C, 24 h
O
O
Substratea
Entry
Ligand
Solvent
Conv.b (%)
eeb (%)
O
1
2
3
(R)-BINAP
(R)-2
(R)-3
MeOH
MeOH
MeOH
100
100
97
78 (R)
84 (R)
87 (R)
OMe
O
12a
12b
O
OEt
4
5
6
(R)-BINAP
(R)-2
(R)-3
EtOH
EtOH
EtOH
100
100
95
65 (R)
75 (R)
79 (R)
O
O
OMe
7
8
9
(R)-BINAP
(R)-2
(R)-3
MeOH
MeOH
MeOH
MeOH
100
100
100
100
77 (R)
91 (R)
92 (R)
91 (R)
Ph
12c
O
10
(R)-10
a Hydrogenation was performed in homogeneous conditions, [S] = 0.8 M; L/M = 1; S/metal = 100; 40 bars H2; 50 ꢁC; 24 h; [M] + L* + solvent, stirring
16 h at rt + substrate.
b Conversion and enantioselectivity were determined by GC on a lipodex A (25 m · 0.25 mm) column.

2308
M. Jahjah et al. / Tetrahedron: Asymmetry 18 (2007) 2305–2312
0
´
´
Table 2. Iridium-catalyzed reduction of 2-methylquinoline with (R)-BINAP, tetramethoxy-BINAP (R)-2 and 6,6 -didodecyl tetrahydroxy-BINAP (R)-10
[Ir(COD)Cl]2/ L*
Solvent, 40 bars, I2, t. a., 24 h
N
N
H
Substratea
Entry
Ligand
Solvent
Conv.b (%)
eeb (%)
1
2
3
4
(R)-BINAP
(R)-2
(R)-3
Toluene
Toluene
Toluene
Toluene
30–70
70–75
10
33–55 (R)
63 (R)
—
N
(R)-10
89
70 (R)
13
a Hydrogenation was performed in homogeneous conditions, [S] = 0.2 M; L/M = 1.1; S/M = 100; 40 bars H2; I2/M = 5; 24 h at rt.
b Conversion and enantioselectivity were determined by HPLC: Chiralcel OJ-H column.
With a higher Hammett r-coefficient for the p-OH-BINAP
derivative (ꢀ0.38) than that of p-OMe–BINAP derivative
(ꢀ0.28), enantioselectivities of the hydrogenation of a-
ketoesters appeared to be better with the p-OH–BINAP
(Table 1, entries 8 and 9).
BINAP (R)-3 and (R)-6,60-didodecyl-tetrahydroxy-BINAP
(R)-10.
The nature of the groups at the para-phenyl position
clearly influences the enantiomeric excess. More impor-
tantly, we have shown that the introduction of electron-
donating groups on the para-phenyl position of the BINAP
could have a direct influence on the enantiomeric excess
and on the activity of catalyst (under identical operating
conditions).
2.3. Hydrogenation of 2-methylquinoline
2-Methylquinoline 13 was reduced in toluene to compare
(R)-BINAP with tetramethoxy-BINAP (R)-2 and 6,60-dido-
decyl tetrahydroxy-BINAP (R)-10, which was more solu-
ble in the solvent than the nonalkylated tetrahydroxy-
BINAP (R)-3. The asymmetric hydrogenation reaction
was carried out under hydrogen pressure (40 bar) at room
temperature, in the presence of the chiral catalyst prepared
in situ. The catalysts were obtained by the addition of the
chiral ligand to the metal precursor in toluene. Iodine and
the 2-methylquinoline were added successively to the reac-
tion mixture before setting under hydrogen pressure. The
results obtained are shown in Table 2.
4. Experimental
4.1. General methods
All organic and organometallic reagents used were pure
1
commercial products. H, 13C and 31P NMR spectra were
recorded with a Bruker AM300 (1H, 300 MHz, 13C,
75 MHz) in CDCl3 as solvent. Polarimetric measurements
were performed on a Perkin–Elmer 241 apparatus, at ambi-
ent temperature. Conversions and enantiomeric excesses
were determined by GC analysis on a chiral CHIRASIL-
VAL column. Hydrogenation experiments were performed
in a mini-autoclave of stainless steel of 15 mL from Amtec
(www.amtec-chemnitz.de).
In the presence of BINAP, the reduction of 2-methylquino-
line is difficult to reproduce under our conditions. Indeed,
under identical conditions, the conversion rate varied be-
tween 30% and 70%. As for enantiomeric excess, it varies
between 33% and 53%. It should be noted that the enantio-
meric excess reported by Zhou et al.9a for this reduction, in
the presence of the BINAP, is 87% while working in a
gloves box. On the other hand, in the presence of tetra-
methoxy-BINAP (R)-2, the reduction is reproducible
(63% ee, 75% yield). Very low conversion was observed
in the presence of tetrahydroxy-BINAP (R)-3 probably
due to the poor solubility of this ligand in toluene (Table
2, entry 3). Conversely, when we used the more soluble
6,60-didodecyl tetrahydroxy-BINAP (R)-10, an increase in
enantiomeric excess was observed (70% ee, 89% yield)
(Table 2, entry 4).
(R)-BINAP was purchased from Stem Chemicals. All
yields are isolated yields.
4.2. Synthesis of ligands
4.2.1. Bis(4-methoxyphenyl)phosphine oxide. A solution of
magnesium (4.125 g, 0.171 mol) in THF (10 mL) was stir-
red under Ar at room temperature for 1 h. A solution of
4-bromoanisole (19.53 mL, 0.156 mol) in THF (30 mL)
was slowly added at 45 ꢁC and the mixture was stirred at
5 ꢁC for 1 h. Next, diethyl phosphite (10 mL, 0.78 mol)
was added and the mixture was stirred at 45 ꢁC for 2 h.
After cooling (0 ꢁC), water (50 mL), ethyl acetate
(100 mL) and HCl 10% (50 mL) were added successively.
The mixture was stirred at room temperature for 30 min.
The reaction mixture was portioned, and the aqueous layer
extracted three times with ethyl acetate (60 mL). The com-
bined organic layers were washed with HCl 2% (200 mL)
and brine (100 mL), and dried over anhydrous magnesium
sulfate. The solution was then filtered and the filtrate con-
3. Conclusion
In conclusion we have devised an effective approach to the
synthesis and tested new BINAP derivatives for the Ru-cat-
alyzed homogeneous asymmetric hydrogenation of a-keto-
esters and quinoline. We have shown that in both cases,
electronically enriched BINAP derivatives lead to higher
ees than (R)-BINAP the best ligand being tetrahydroxy-

M. Jahjah et al. / Tetrahedron: Asymmetry 18 (2007) 2305–2312
2309
centrated under reduced pressure. The residue obtained
was purified by column chromatography on silica gel using
ethyl acetate as the eluent to give the product (13.2 g, white
crystal, 65%). Mp = 124–125 ꢁC; 1H NMR (300 MHz,
CDCl3): d 3.71 (s, 6H, OCH3), 6.92 (d, J = 7 Hz, 4H,
Harom.), 7.55 (dd, J = 14.2, 7 Hz, 4H, Harom.), 7.94 (d,
J = 480 Hz, 1H, HP); 13C NMR (300 MHz, CDCl3):
55.8, 114.7 (d, J = 20), 123.5 (d, J = 110), 133.0 (d,
J = 20), 163.2 (d, J = 10); 31P{1H} NMR (81 MHz,
CDCl3): d 20.9 (s).
and the reaction mixture was stirred at 0 ꢁC for 1 h, and
then at room temperature for 24 h. The solution was
cooled to 5 ꢁC and CH3OH (10 mL) was carefully added.
After removal of the organic solvents, the residue was
recrystallized from hot CH3OH (10 mL) by adding cold
water (5 mL) to give (R)-3 (392 mg, 98%). White solid;
25
mp >220 ꢁC; ½aꢁD ¼ þ29 (c 0.9, MeOH); 1H NMR
(300 MHz, DMSO-d6): d 6.55 (d, J = 8.6 Hz, 2H, Harom.),
6.65–6.69 (m, 6H, Harom.), 6.82 (br t, J = 7.5 Hz, 2H,
Harom.), 7.13 (dd, J = 11.5, 8.6 Hz, 4H, Harom.), 7.31 (dd,
J = 11.5, 8.6 Hz, 2H, Harom.), 7.38 (br t, J = 7.5 Hz, 2H,
Harom.), 7.44 (dd, J = 11.5, 8.6 Hz, 2H, Harom.), 7.86–7.92
(m, 4H, Harom.), 9.95 (s, 4H, OH); 31P {1H}NMR
(81 MHz, DMSO-d6): ꢀ18.42 (s).
4.2.2. Bis(4-methoxyphenyl)phosphine–borane complex 1.
A solution of cerium chloride (11.27 g, 45.75 mmol) in
THF (35 mL) was stirred under Ar at room tempera-
ture (25 ꢁC) for 30 min. Sodium borohydride (1.8 g,
47.28 mmol) was added and the mixture stirred at room
temperature for 1 h. Next bis(4-methoxyphenyl)phosphine
oxide (4 g, 15.25 mmol) and lithium aluminium hydride
(0.7 g, 18.3 mmol) were added successively at 5 ꢁC and
the mixture stirred at room temperature for 3 h. 3 M-
NaOH (50 mL) was added at 3 ꢁC, followed by ethyl ace-
tate (50 mL), water (20 mL) and filtered on Celite. The
mixture was stirred at room temperature for 30 min and
then filtered. The filtrate was partitioned, and the aqueous
layer was extracted three times with ethyl acetate (90 mL).
The combined organic layers were washed with water
(2 · 100 mL), brine (100 mL), dried over anhydrous mag-
nesium sulfate, filtered and concentrated under reduced
pressure. The residue was purified by column chromatogra-
phy on silica gel (eluent n-hexane/ethyl acetate 5:1!2:1) to
4.2.5. (R)-6,60-Dibromo-2,20-dihydroxy-1,10-binaphthyl (R)-
4. (2.10 g, 7.34 mmol) of enantiomerically pure (R)-2,20-
dihydroxy-1,10-dinaphthyl [(R)-BINOL] was dissolved in
CH2Cl2 (40 mL), and the system was cooled to ꢀ75 ꢁC.
Bromine (1 mL, 19.6 mmol) was added dropwise over 20–
30 min with constant stirring at ꢀ75 ꢁC. After stirring an
additional 2.5 h while warming to 25 ꢁC, the reaction mix-
ture was stirred further for 30 min and the excess Br2 was
destroyed by the addition of 50 mL of 10% aqueous solu-
tion of sodium bisulfite. The layers were separated, and
the organic layer was washed with brine, dried over
MgSO4, filtered and concentrated under reduced pressure
to give 3.6 g of solid, which was recrystallized from tolu-
ene–cyclohexane to afford (R)-4 (2.73 g, 84%) as a white
1
solid. H NMR (300 MHz, CDCl3): d 4.69 (s, 2H, OH),
1
give 1 (2.4 g, white crystals, 60%). H NMR (300 MHz,
6.90 (d, J = 8.8 Hz, 2H, Harom.), 7.30 (d, J = 9.2 Hz, 2H,
CDCl3): 0.43–1.57 (m, 3H, BH3): d 3.82 (s, 6H, OCH3),
6.24 (dq, J = 377.9, 6.78 Hz, 1H, HP), 6.95 (dd, J = 8.71,
1.72 Hz, 4H, Harom.), 7.53–7.60 (m, 4H, Harom.); 31P{1H}
NMR (81 MHz, CDCl3): d ꢀ4.53 to ꢀ2.73 (m), ꢀ1.26 to
0.40 (m), ꢀ4.15 (m).
Harom.), 7.31 (dd, J = 8.8, 2.2 Hz, 2H, Harom.), 7.80 (d,
J = 8.8 Hz, 2H, Harom.), 7.98 (d, J = 2.2 Hz, 2H, Harom.);
25
mp 210 ꢁC; ½aꢁD ¼ ꢀ129 (c 1, CH2Cl2).
4.2.6. (R)-6,60-Dibromo-2,20-dibenzoxy-1,10-binaphthyl (R)-
5. (R)-6,60-Dibromo-1,10-bis-2-naphtol (R)-4 (0.50 g,
1.13 mmol), benzyl bromide (0.40 mL, 3.38 mmol) and
potassium carbonate (0.78 g, 5.65 mol) were stirred in
refluxing acetone (10 mL) under an argon atmosphere for
18 h. After cooling to room temperature, the reaction mix-
ture was poured into dichloromethane (25 mL) and water
(25 mL). The layers were separated and the aqueous layer
extracted with dichloromethane (2 · 25 mL). The com-
bined organic layers were dried over MgSO4, filtered and
solvents removed in vacuo. The residue was purified by trit-
uration with hexane to afford (R)-5 (0.55 g, 78%) as a white
solid.
4.2.3.
(R)-2,20-Bis[bis(4-methoxyphenyl)phosphino]-1,10-
binaphthyl (R)-2. Under an argon atmosphere, to a solu-
tion (5 mL) of [1,2-bis(diphenylphosphino)-ethane]dichloro-
nickel (53 mg, 0.1 equiv), (R)-2,20-bis(trifluoromethane-
sulfonyloxy)-1,10binaphtyl (500 mg, 0.91 mmol) and 1,4-
diazabicyclo[2,2,2]octane (613 mg, 6.0 equiv) in DMF was
added at room temperature bis(4-methoxyphenyl)phos-
phine-borane complex 1 (543 mg, 2.3 equiv) and the mix-
ture stirred at room temperature for 30 min and then at
110 ꢁC for 48 h. DMF was evaporated under reduced pres-
sure and methanol was added to the residue to give the title
25
compound (R)-2 (444 mg, white crystals, 66%). ½aꢁD
¼
1
þ107:6 (c 0.4, CHCl3); H NMR (300 MHz, CDCl3): d
3.73 (s, 12H, CH3), 6.64 (d, J = 8.35 Hz, 4H, Harom.),
6.69 (d, J = 8.19 Hz, 4H, Harom.), 6.80 (d, J = 8.49 Hz,
2H, Harom.), 6.92–7.03 (m, 10H, Harom.), 7.30–7.38 (m,
2H, Harom.), 7.40–7.45 (m, 2H, Harom.), 7.82 (d, J =
8.13 Hz, 2H, Harom.), 7.87 (d, J = 8.52 Hz, 2H, Harom.);
31P{1H} NMR (81 MHz, CDCl3): d ꢀ16.86 (s).
1H NMR (300 MHz, CDCl3): d 5.0 (s, 4H, 2OCH2), 6.88
(m, 4H, Harom.), 7.05 (m, 6H, Harom.), 7.25–7.29 (m, 4H,
Harom.), 7.34 (d, J = 9.03 Hz, 2H, Harom.), 7.75 (d,
J = 9.03 Hz, 2H, Harom.), 7.95 (d, J = 3.18 Hz, 2H, Harom.);
25
½aꢁD ¼ þ188 (c 1, CH2Cl2).
4.2.7.
(R)-6,60-Didodecyl-2,20-dibenzoxy-1,10-binaphthyl
(R)-6. [1,3-Bis(diphenylphosphino)propane]NiCl2 (65 mg,
0.12 mmol) and n-dodecyl magnesium bromide (14.4 mL
of a 1.0 M solution in diethyl ether, 0.48 mmol, Acros) were
added to a stirred solution of (R)-2,20-dibenzyloxy-6,60-di-
bromo-1,10-binaphthyl (R)-5 (3 g, 4.8 mmol) in diethyl ether
(150 mL). After heating at reflux for 16 h, the solution was
4.2.4.
binaphthyl (R)-3.
(R)-2,20-Bis[bis(4-hydroxyphenyl)phosphino]-1,10-
A
solution of (R)-2,20-bis[bis(4-
methoxyphenyl)phosphino]-1,10-binaphthyl (433 mg, 0.56
mmol) in dry CH2Cl2 (20 mL) was cooled at 0 ꢁC. A 1 M
solution of BBr3 in CH2Cl2 (5.6 mL, 5.6 mmol) was added,

2310
M. Jahjah et al. / Tetrahedron: Asymmetry 18 (2007) 2305–2312
cooled to room temperature. Water (100 mL) was carefully
added followed by HCl (2 M, 100 mL). The aqueous phase
was then separated and extracted with ethyl acetate
(3 · 50 mL). The combined organic layers were washed with
brine (2 · 50 mL), dried over MgSO4 filtered and concen-
trated under reduced pressure. The crude product was puri-
fied by flash chromatography on silica gel using (heptane/
diethyl ether 98.5:1.5) as the eluent to afford (R)-(R)-6
(3.39 g, 89%) as a colourless viscous oil. 1H NMR
trated under reduced pressure to afford (R)-8 (8.96 g,
99%) as a grey oil. H NMR (300 MHz, CDCl3): d 0.85–
1
0.95 (t, J = 6.8 Hz, 6H, 2CH3), 1.22–1.41 (m, 36H,
2(CH2)9CH3), 1.58–1.71 (m, 4H, 2ArCH2CH2) 2.78 (t,
J = 7.7 Hz, 4H, 2 ArCH2), 7.15 (d, J = 8.7 Hz, 2H, Harom.),
7.20 (d, J = 8.25 Hz, 2H, Harom.), 7.35 (d, J = 8.6 Hz, 2H,
Harom.), 7.75 (s, 2H, Harom.), 8.03 (d, J = 9.03 Hz, 2H,
Harom.); 19F NMR (122 MHz, CDCl3): d ꢀ75.2 (s).
(300 MHz, CDCl3):
d
0.85–0.95 (t, J = 6.8 Hz, 6H,
4.2.10.
phosphino]-1,10-binaphthyl (R)-9. To
[1,2-bis(diphenylphosphino)-ethane]dichloronickel (30 mg,
0.05 mmol),
(R)-2,20-bis(trifluoromethanesulfonyloxy)-
(R)-6,60-Didodecyl-2,20-bis[bis(4-methoxyphenyl)-
solution of
2 · CH3), 1.22–1.41 (m, 36H, 2 (CH2)9CH3), 1.65–1.72 (m,
4H, 2 ArCH2CH2) 2.73 (t, J = 7.7 Hz, 4H, 2 ArCH2),
5.04 (s, 4H, 2OCH2), 6.96–6.98 (m, 4H, Harom.), 7.08–7.18
(m, 10H, Harom.), 7.39 (d, J = 9 Hz, 2H, Harom.), 7.66 (br
s, 2H, Harom.), 7.87 (d, J = 9 Hz, 2H, Harom.); 13C NMR
(75 MHz, CDCl3): d 14.1, 20.4, 22.7, 22.4, 29.5, 29.6, 29.7,
29.7, 29.78, 31.4, 31.9, 35.9, 71.3, 116.2, 120.9, 125.5,
126.2, 126.8, 127.2, 127.9, 128.1, 128.6, 129.6, 132.6,
137.7, 138.2, 153.5; MS (ESI): m/z: 803.5 [M+H]+; Elemen-
tal Anal. Calcd for C58H74O2(803.24): C, 86.73; H, 9.29.
a
1,10binaphthyl (R)-8 (450 mg, 0.5 mmol) and 1,4-diaza-
bicyclo[2,2,2]octane (340 mg, 3 mmol) in anhydrous
DMF (5 mL) under an argon atmosphere was added at
room temperature bis(4-methoxyphenyl)phosphine–borane
complex 1 (330 mg, 1.2 mmol) and the mixture stirred at
room temperature for 30 min and then at 110 ꢁC for
48 h. DMF was evaporated under reduced pressure and
methanol was added to the residue to afford (R)-9 (380
mg, 68%) as a white solid.
Found: C, 86.60; H, 9.30; Rf = 0.63 (light petroleum/diethyl
25
ether, 2:1); ½aꢁD ¼ þ205:7 (c 1, CHCl3).
4.2.8.
(R)-6,60-Didodecyl-2,20-dihydroxy-1,10-binaphthyl
1H NMR (300 MHz, CDCl3): d 0.80 (t, J = 6.55 Hz, 6H,
2CH3), 1.20–1.30 (m, 36H, 2(CH2)9CH3), 1.47–1.58 (m,
4H, 2ArCH2CH2), 2.60–2.70 (m, 4H, 2 ArCH2), 6.40 (d,
J = 8.67 Hz, 6H, Harom.), 6.75 (m, 6H, Harom.), 6.80 (dd,
J = 9.63, 1.5, 2H, Harom.), 7.09 (t, J = 6.78 Hz, 2H, Harom.),
7.26 (m, 6H, Harom.), 7.56 (m, 3H, Harom.), 7.76 (d,
J = 8.85 Hz, 1H, Harom.), 31P NMR (81 MHz, CDCl3): d
ꢀ17.5 (s); Elemental Anal. Calcd for C72H88O4P2
(R)-7. NaI (2.13 g, 14.21 mmol) and TMSCl (1.80 mL,
14.21 mmol) were added to a stirred solution of dido-
decylbisether (R)-6 (1.14 g, 1.42 mmol) in toluene (20 mL)
and acetonitrile (40 mL). The reaction mixture was heated
at 40 ꢁC for 2 h. After cooling to room temperature, water
(40 mL) was added, the aqueous phase was then separated
and extracted with diethyl ether (3 · 40 mL). The combined
organic components were washed with a 1 M aqueous
Na2S2O3 solution (60 mL) and brine (60 mL), dried over
MgSO4, filtered and concentrated under a reduced pres-
sure. The crude product was purified by flash chromatogra-
phy on silica gel using (heptane/diethyl ether 10:1) as the
(1078.41): C, 80.11; H, 8.22; P, 5.74. Found: C, 80.39; H,
25
8.37; P, 5.69; ½aꢁD ¼ ꢀ25:65 (c 0.635, CHCl3).
4.2.11.
(R)-6,60-Didodecyl-2-20-bis[bis(4-hydroxyphenyl)-
phosphino]-binaphthyl (R)-10. A solution of (R)-6,60-
didodecyl-2,20-bis[bis(4-methoxyphenyl)phosphino]-1,10-bi-
naphthyl (R)-9 (1.055 g, 1 mmol) in dry dichloromethane
(20 mL) was cooled at 0 ꢁC. A 1 M solution of BBr3 in
dichloromethane (10 mL, 10 mmol) was added and the
reaction mixture was stirred at 0 ꢁC for 1 h, and then at
room temperature for 24 h. The solution was cooled to
5 ꢁC and methanol (20 mL) was added carefully. After re-
moval of the organic solvents, the crude product was
recrystallized from hot methanol (20 mL) by adding cold
water (10 mL) to afford hydroxyphosphine (R)-10
(970 mg, 95%) as a white solid. 1H NMR (300 MHz,
CDCl3): d 0.87 (t, J = 6.50 Hz, 6H, 2CH3), 1.20–1.35 (m,
36H, 2 (CH2)9CH3), 1.40–1.60 (m, 4H, 2ArCH2CH2),
2.65–2.78 (m, 4H, 2ArCH2), 6.58 (br t, J = 8.88 Hz, 8H,
Harom.), 6.73 (d, J = 8.67 Hz, 2H, Harom.), 6.75 (dd,
J = 9.60, 1.49 Hz, 2H, Harom.), 6.81–6.89 (m, 8H, Harom.),
7.35 (dd, J = 8.20, 2.41 Hz, 2H, Harom.), 7.60 (s, 2H,
Harom.), 7.80 (d, J = 8.50 Hz, 2H, Harom.), 9.95 (s, 4H, 4
OH) 31P NMR (81 MHz, CDCl3): d ꢀ17.2 (s); 13C NMR
(75 MHz, CDCl3, 25 ꢁC): d 14.6, 21.5, 23.1, 27.3, 29.8,
29.9, 30.0, 30.1, 30.2, 31.8, 32.3, 36.5, 115.8, 128.0, 128.1,
128.5, 131.4, 131.9, 132.3, 133.9, 134.4, 134.9, 135.6,
135.9, 141.8, 156.4, 172.5; Elemental Anal. Calcd for
C68H80O4P2 (1022.55): C, 79.81; H, 7.88; P, 6.05. Found:
1
eluent to afford (R)-7 (0.82 g, 91%) as a colourless oil; H
NMR (300 MHz, CDCl3): d 0.84–0.95 (t, J = 6.8 Hz, 6H,
2CH3), 1.22–1.41 (m, 36H, 2(CH2)9CH3), 1.64–1.71 (m,
4H, 2ArCH2CH2), 2.73 (t, J = 7.7 Hz, 4H, 2 ArCH2),
5.00 (s, 2H, 2OH), 7.10 (d, J = 8.6 Hz, 2H, Harom.), 7.17
(dd, J = 8.6, 1.5 Hz, 2H, Harom.), 7.35 (d, J = 8.9 Hz, 2H,
Harom.), 7.67 (br s, 2H, Harom.), 7.91 (d, J = 8.6 Hz, 2H,
Harom.); 13C NMR (75 MHz, CDCl3, 25 ꢁC): d 14.1, 22.7,
29.2, 29.3, 29.4, 29.6, 29.7, 29.8, 31.4, 31.9, 35.8, 110.8,
117.6, 124.1, 126.8, 129.0, 129.5, 130.8, 131.7, 138.6,
152.0; MS (ESI): m/z: 623.5 [M+H]+; Elemental Anal.
Calcd for C44H62O2 (622.98): C, 84.83; H, 10.03. Found:
C, 84.60; H, 10.27; Rf = 0.16 (light petroleum/diethyl ether,
3:1); ½aꢁD ¼ ꢀ51:4 (c 1, CHCl3).
25
4.2.9. (R)-6,60-Didodecyl-2,20-ditrifluoromethanesulfonate-
1,10-binaphthyl (R)-8. To
a
solution of (R)-6,60-di-
dodecyl-2,20-dihydroxy-1,10-binaphthyl
(R)-7
(6.23 g,
10.2 mmol) in dichloromethane (15 mL) was added pyri-
dine (2.5 mL, 30.6 mmol) at room temperature. Trifluo-
romethanesulfonic anhydride (4 mL, 23.8 mmol) was
added at 5 ꢁC and the mixture was stirred at 5–10 ꢁC for
8 h. Hexane (15 mL) was then added and the mixture stir-
red at room temperature for 30 min. The reaction mixture
was filtered and purified on silica gel using (dichlorometh-
ane/hexane 1:1) as the eluent and the filtrate was concen-
C, 79.59; H, 7.67; P, 6.02; mp 127–129 ꢁC; Rf = 0.32 (cyclo-
25
hexane/ethylacetate 95:5); ½aꢁD ¼ þ42:0 (c 0.83, CH2Cl2).

M. Jahjah et al. / Tetrahedron: Asymmetry 18 (2007) 2305–2312
2311
Wang, G.-Z.; Mallat, T.; Baiker, A. Tetrahedron: Asymmetry
1997, 8, 2133; (g) Carpentier, J. F.; Mortreux, A. Tetra-
hedron: Asymmetry 1997, 8, 1083; (h) Blaser, H.-U.; Jalett,
H.-P.; Spindler, F. J. Mol. Catal. 1996, 107, 85; (i) Chiba, T.;
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1993, 34, 2351; (j) Qiu, L.; Kwong, F. Y.; Wu, J.; Lam,
W. H.; Chan, S.; Yu, W.-Y.; Li, Y.-M.; Guo, R.; Zhou, Z.;
Chan, A. S. C. J. Am.Chem. Soc. 2006, 128, 5955.
4.2.12. General procedure for hydrogenation of a-ketoesters
12a–c with the system [Ru(C6H6)Cl2]2/chiral ligand. In a
Schlenk tube, [Ru(C6H6)Cl2]2 (2 mg, 8 lmol) and ligand
(8 lmol) were mixed in 1 mL of solvent. After 16 h of stir-
ring at room temperature under an argon atmosphere, the
substrate (0.8 mmol) was introduced and the resulting solu-
tion was stirred under a hydrogen pressure (40 bars) in a
stainless-steal reactor (previously degased three times with
argon and twice with hydrogen) for 24 h, at 50 ꢁC. The
reaction mixture was filtered on Celite and analyzed by chi-
ral GC (Lipodex A, 25 m) to determine both conversion
and enantiomeric excess.
4. Dupart de Paule, S.; Severine, J.; Ratovelomanana-Vidal, V.;
Genet, J. P.; Champion, N.; Dellis, P. Eur. J. Org. Chem.
2003, 10, 1931.
5. (a) Genet, J. P.; Pinel, C.; Mallart, S.; Juge, S.; Cailhol, N.;
Laffitte, J. A. Tetrahedron Lett. 1992, 33, 5343; (b) Geneˆt, J. P.;
GC conditions
Substrate
Conditions
Lipodex A
Retention time
Methyl pyruvate 12a
Starting material: 3.30 min
50 ꢁC (1 min)–1 ꢁC/min–70 ꢁC (1 min)
Enantiomers: 3.75; 4.62 min
Starting material: 4.42 min
Enantiomers: 8.01; 9.45 min
Starting material: 23.31 min
Enantiomers: 25.98; 27.24 min
Ethyl pyruvate 12b
Lipodex A
40 ꢁC (15 min)–1 ꢁC/min–60 ꢁC (5 min)
Lipodex A
80 ꢁC (1 min)–1 ꢁC/min–150 ꢁC (1 min)
Methyl benzoylformate 12c
Pinel, C.; Ratovelomanana-Vidal, V.; Mallart, S.; Pfister, X.;
Bischoff, L.; Cano De Andrade, M. C.; Darses, S.; Galopin, C.;
Laffitte, J. A. Tetrahedron: Asymmetry 1994, 5, 675.
6. (a) Barton, D. H.; Nakanishi, K.; Meth-Cohn, O. In
Comprehensive Natural Products Chemistry; Elsevier: Oxford,
1999; Vols. 1–9; (b) Katritzky, A. R.; Rachwal, S.; Rachwal,
B. Tetrahedron 1996, 52, 15031; (c) Rylander, P. N. Catalytic
Hydrogenation in Organic Synthesis; Academic Press: New
York, 1979; p 175.
7. (a) Blaser, H.-U.; Malan, C.; Pugin, B.; Splindler, F.; Steiner,
H.; Studer, M. Adv. Synth. Catal. 2003, 345, 103; (b) Tang,
W.; Zhang, X. Chem. Rev. 2003, 103, 3029; (c) Lin, G. O.; Li,
Y. M.; Chan, A. S. C. Principles and Applications of
Asymmetric Synthesis; Wiley-Interscience: New York, 2001.
8. (a) Henschke, J. P.; Burk, M. J.; Malan, C. G.; Herzberg, D.;
Peterson, J. A.; Wildsmith, A. J.; Cobley, C. J.; Casy, G. Adv.
Synth. Catal. 2003, 345, 300; (b) Kuwano, R.; Kaneda, K.;
Ito, T.; Sato, K.; Kurokawa, T.; Karube, D.; Ito, Y. Org.
Lett. 2004, 6, 2213; (c) Reetz, M. T.; Li, X. Chem. Commun.
2006, 2159; (d) Lam, K. H.; Xu, L.; Feng, L.; Fan, Q.-H.;
Lam, F. L.; Lo, W.-H.; Chan, A. S. C. Adv. Synth. Catal.
2005, 347, 1755.
4.2.13. Procedure for Ir-catalyzed asymmetric hydrogena-
tion of 2-methylquinoline 13. A mixture of [Ir(COD)Cl]2
(3.4 mg, 5 lmol) and the desired ligand (11 lmol) in dry
toluene (5 mL) was stirred at room temperature for
30 min under an argon atmosphere at room temperature.
The mixture was transferred by syringe to a stainless steel
autoclave, in which I2 (12.7 mg, 0.05 mmol) and 2-methyl-
quinoline 15 (1.0 mmol) were placed beforehand. The
hydrogenation was performed at room temperature under
hydrogen (40 bars) for 12–15 h. The conversion and enan-
tiomeric excess were determined by chiral HPLC with
chiral columns (OJ-H).
4.2.14. HPLC conditions for the 2-methylquinoline. Chi-
ralcelꢂ OJ-H column, heptane/isopropanol (90:10),
0.5 mL/min, starting material 12.12 min, enantiomers
17.49 and 19.40 min, wavelength: 260 nm.
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