Synthesis of novel diphosphite ligands derived from d-mannitol and their application in Cu-catalyzed enantioselective conjugate addition of organozinc to enones

Article abstract of DOI:10.1016/j.tetasy.2010.12.009

A series of novel chiral diphosphite ligands have been synthesized from d-mannitol derivatives and chlorophosphoric acid diary ester, and were successfully employed in the copper catalyzed enantioselective conjugate addition of organozinc reagents diethyl

Full text of DOI:10.1016/j.tetasy.2010.12.009

Tetrahedron: Asymmetry 21 (2010) 2993–2998
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Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Synthesis of novel diphosphite ligands derived from D-mannitol
and their application in Cu-catalyzed enantioselective conjugate addition
of organozinc to enones
Qing-Lu Zhao a,b, Lai-Lai Wang a, , Ai-Ping Xing a,b
⇑
a
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
Graduate University of Chinese Academy of Sciences, Beijing 100039, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel chiral diphosphite ligands have been synthesized from D-mannitol derivatives and
chlorophosphoric acid diary ester, and were successfully employed in the copper catalyzed enantioselec-
tive conjugate addition of organozinc reagents diethylzinc and dimethylzinc to cyclic and acyclic enones.
Received 5 November 2010
Accepted 8 December 2010
Available online 14 January 2011
The stereochemically matched combination of
D
-mannitol and (R)-H
8
-binaphthyl in ligand 1,2:5,6-di-O-
-mannitol was essential to afford
0
0
8
isopropylidene-3,4-bis[(R)-1,1 -H -binaphthyl-2,2 -diyl] phosphite-
D
93% ee for 3-ethylcyclohexanone, 92% ee for 3-ethylcyclopentanone, and 90% ee for 3-ethylcyclohepta-
2
none in toluene, using Cu(OTf) as a catalytic precursor. The results clearly indicated that the chiral orga-
nocopper reagent exhibited high enantioselectivies for cyclic enones bearing different ring sizes. As for
the backbone of this type of ligand, it has been demonstrated that 1,2:5,6-di-O-isopropylidene- -manni-
tol was more efficient than 1,2:5,6-di-O-cyclohexylidene- -mannitol. The sense of the enantiodiscrimina-
D
D
tion was mainly determined by the configuration of the diaryl phosphite moieties in the 1,4-addition of
cyclic enones.
Ó 2010 Elsevier Ltd. All rights reserved.
1
. Introduction
alcohols, derived from easily accessible and commercially available
carbohydrates, have been used as starting materials for the synthe-
1
0
Asymmetric conjugate addition of organometallic reagents to
,b-unsaturated carbonyl compounds, including organozinc, -lith-
sis of chiral phosphite ligands.
-Mannitol is one of the most important carbohydrates and is ex-
a
D
ium, -aluminum, -boron, and Grignards is one of the most powerful
tremely useful for the synthesis of chiral ligands, since they are of
high enantiomeric purity and are readily available. In addition, their
highly functionalized property makes it straightforward to design
novel ligands bearing specific structures through modifications.
tools for the stereoselective construction of carbon–carbon bonds
1
in the synthesis of biologically active compounds, such as erogor-
2
3
giaene, (ꢀ)-pumiliotoxin C, and b-
D-mannosyl phosphomycoke-
4
tide. During the past decades, much effort has been focused on
the development of Cu-catalyzed enantioselective 1,4-conjugate
Some examples of this are classified according to
tons and are schematically presented in Figure 1. As exhibited in Fig-
ure 1, versatile phosphorus ligands using -mannitol as a backbone
D-mannitol skele-
additions of organozincs to
a
,b-unsaturated carbonyl compounds
D
due to the low cost and a wide range of catalytic activities of
copper salts in various reactions, such as oxidation, reduction,
addition reactions to multiple bonds and cross coupling reactions.
Since the pioneering discovery of Alexakis in 1993,5 dramatic
breakthroughs have been achieved using numerous chiral phos-
were synthesized, and applied in asymmetric catalytic reactions,
such as the mono- and diphosphite ligands based on 1,4:3,6-di-O-
dianhydro-
D-mannitol, which gave excellent enantioselectivities
in the Rh-catalyzed asymmetric hydrogenation of dimethyl itaco-
1
1
nate and methyl N-acetamidoacrylate, and diphosphite ligands
based on 1,2:5,6-di-O-cyclohexylidene- -mannitol afforded moder-
ate enantioselectivities in Rh-catalyzed asymmetric hydroformyla-
6
7
phorous ligands, such as phosphoramidites, phosphites, P, N li-
gands and other types9 in this reaction. Of the various ligands
mentioned above, phosphite ligands have been paid much atten-
tion recently, owing to their efficiency for 1,4-addition, facile prep-
aration from a plethora of alcohols and chlorophosphites, and
lower sensitivity to air and moisture. In this context, a great many
D
8
1
2
tion. A cooperative effect has been demonstrated between the
stereogenic centers of the ligand backbone and the stereogenic
binaphthyl phosphite moieties.
In our previous work, chiral diphosphite ligands 1a and 1b
(
Fig. 2) and P, N-ligands, based on 1,2:5,6-di-O-cyclohexylidene-
-mannitol, were synthesized and applied in the Cu-catalyzed
conjugate addition of Et Zn to cyclic enones with moderate
D
⇑
Corresponding author. Tel.: +86 (0) 931 4968161; fax: +86 (0) 931 4968129.
E-mail address: wll@licp.cas.cn (L.-L. Wang).
2
0
957-4166/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2010.12.009

2
994
) 1,4:3,6-di-O-dianhydro-D-Mannitol as a backbone
Q.-L. Zhao et al. / Tetrahedron: Asymmetry 21 (2010) 2993–2998
1
cyclohexylidene-D-mannitol 1 or 1,2:5,6-di-O-isopropylidene-D-
mannitol 2, and chlorophosphoric acid diary ester 5 derived
O
O
0
0
0
0
0
0
PPh2
O
P
O
P
from 2,2 -dihydroxy-5,5 ,6,6 ,7,7 , 8,8 -octahydro-1,1 -binaphthol
-binaphthol) or binaphthol. Compound 5 was conveniently
O
O
*
O
*
O
O
(H
8
H
H
H
H
H
H
O
13
O
O
O
prepared according to the literature procedures. In contrast with
Ph2P
P
O
RO
*
O
ligands 1c, 1d, 2c, and 2d, the binaphthyl moieties of ligands 1a,
1
8
b, 2a, and 2b were replaced by H -binaphthyl (Fig. 2). All ligands
Rh-hydrogenation, 58% ee
Rh-hydrogenation, 98.2% ee Rh-hydrogenation, 99% ee
were purified on a silica gel column under a nitrogen atmosphere
with moderate to good yields. The white solid ligands 1c–1d and
2
) 1,4:3,6-di-O-benzylidene-D-Mannitol
3) 1:3,4:6-derivatived-D-Mannitol
as a backbone
2a–2d were air-stable at room temperature. The P NMR, 1
3
1
H
as a backbone
1
3
NMR and C NMR were consistent with the expectation for these
ligands.
Ph
O
R
O
O
OR
O
O
P
N
O
O
O
P
O
O
O
O
O
Ph
O
R
*
*
P
P
OH
OH
O
DMAP, NEt3
O
O
O
O
O
O
O
Rh-hydrogenation, 98.5% ee
Rh-hydrogenation, 94% ee
+
*
P
Cl
Cl
O
2
CH Cl
O
2
4
) 1,2:5,6-di-O-isopropylidene-D-Mannitol or 1,2:5,6-di-O-cyclohexylidene-D-Mannitol
as a backbone
5
O
O
1
O
O
O
O
O
1c, 1d
Ph2P
P
P
P
*
OPPh2
OPPh2
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
P
P
*
OH
OH
O
DMAP, NEt3
O
O
O
O
O
O
+
*
P
O
O
O
O
O
O
2
CH Cl
2
O
5
*
Rh-hydrogenation
0% ee
Rh-hydrogenation
96.7% ee
Rh-hydroformylation, 75% ee
Cu-1,4-addition, 71% ee
O
O
O
6
2
2a, 2b, 2c, 2d
Figure 1. Selected phosphorus ligands based on D-mannitol derivatives.
O
ax
ax
O
O
a: (R)
b: (S)
O
O
c: (R)
d: (S)
=
or
*
ax
ax
enantioselectivity (71% ee). Two notable cooperative effects of the
stereochemistry of the ligands on enantioselectivity were ob-
served in this reaction, one between the phenylcarbamate substi-
tuent and the axially chiral binaphthyl moiety, another between
the stereogenic centers of the mannitol and the chiral binaphthyl
substituents. However, the reaction did have a major problem, in
that the chiral cuprate-mediated reagent exhibited high substrate
specificity. As an effort to overcome the problem and enhance
the enantioselectivity of the reaction, we considered modifying
this type of ligand by introducing new substituents in to the D-
O
Scheme 1. The synthesis of chiral diphosphite ligands derived from D-manntiol.
2
2
.2. Asymmetric 1,4-conjugate addition of ZnR to cyclic enones
7
a
With novel ligands 1c–d and 2a–d in hand, we evaluated their
asymmetric induction abilities in the Cu-catalyzed asymmetric
,4-addition of ZnEt to 2-cyclohexenone 3a, and the results are
summarized in Table 1. In the first set of experiments, we tested,
separately, the new ligands in toluene using Cu(OTf) as a catalytic
precursor (Table 1, entries 1–6). Ligand 1c gave 77% yield and 75%
ee (Table 1, entry 1). In contrast, the use of ligand 1d, in which the
carbohydrate skeleton was the same as in ligand 1c, but the config-
1
2
mannitol skeleton and various diaryl phosphite moieties. Herein,
we report the design and synthesis of novel ligands 1c–1d and
2
2
a–2d (Fig. 2) based on D-mannitol, and their application in the
Cu-catalyzed asymmetric 1,4-conjugate addition of dialkylzincs
to cyclic and acyclic enones.
8
uration of the H -binaphthyl moiety was opposite to that of 1c,
afforded similar yield (73%) but much lower enantioselectivity
(47% ee) (Table 1, entry 2). Ligand 2a, bearing 1,2:5,6-di-O-isopro-
O
O
O
O
*
*
*
*
P
P
P
P
O
O
O
O
O
O
O
O
O
O
pylidene-
D-mannitol as a backbone, produced 85% yield and 74% ee
O
O
(Table 1, entry 3). Ligand 2b, containing the same carbon skeleton
O
O
O
O
as ligand 2a, and opposite axially chirality of the binaphthyl moiety
to 2a, gave much lower yield and enantioselectivity (67% yield and
1
a, 1b, 1c, 1d
2a, 2b, 2c, 2d
5
3% ee) (Table 1, entry 4). Using ligand 2c, the enantioselectivity of
the reaction was enhanced to 83% (Table 1, entries 3 and 5). How-
ever, employing 2d in the reaction, the enantioselectivity of the
reaction decreased to 45% (Table 1, entries 4 and 6). The compari-
son of these results clearly indicated that enantioselectivities de-
pended strongly on the steric and electronic properties of the C-
O
O
ax
ax
ax
ax
O
O
a: (R)
b: (S)
O
O
c: (R)
d: (S)
=
or
*
1
, C-2, C-5, and C-6 stereocenter, and the mannitol skeleton and
Figure 2. Chiral diphosphite ligands derived from D-manntiol.
that the axially chiral binaphthyl or H -binaphthyl moiety had a
8
2
2
. Results and discussion
synergic effect on the enantioselectivity of the reaction. Thus, for
the chiral skeleton of this type of ligands, 1,2:5,6-di-O-isopropyli-
.1. Synthesis of phosphite ligands 1c–1d and 2a–2d
dene-D-mannitol was more efficient than 1,2:5,6-di-O-cyclohexy-
lidene-D-mannitol to afford higher enantioselectivity in toluene
As shown in Scheme 1, diphosphite ligands 1c–1d and 2a–2d
2
using Cu(OTf) as a catalytic precursor (Table 1, entries 1, 2, 5,
were synthesized stereospecifically in one step from 1,2:5,6-di-O-
and 6).

Q.-L. Zhao et al. / Tetrahedron: Asymmetry 21 (2010) 2993–2998
2995
Table 1
With ligand 2c being identified as the most effective ligand,
using Cu(OTf) as a catalyst precursor, the conjugate addition of
ZnEt to 3a in different solvents and at various temperatures was
Cu-catalyzed enantioselective 1,4-addition of ZnEt
2
to 2-cyclohexenonea
2
O
O
2
.
carried out separately. A profound solvent effect on this reaction
was observed (Table 2, entries 1–3). The reactions in solvents
CH Cl and Et O, respectively, gave lower enantioselectivities (Ta-
2 2 2
Cu(OTf)2 or (CuOTf) C6H6, ligand
+
Et2Zn
toluene, 0 o
*
C
3
a
4a
ble 2, entries 1 and 2). When the reaction was carried out in THF,
low catalytic activity and moderate enantioselectivity was ob-
tained (Table 2, entry 3). Toluene was proven to be an appropriate
solvent in our cases (Table 1, entry 5 vs Table 2, entries 1–3). Per-
forming the reaction in toluene at ꢀ20 °C allowed the highest
enantioselectivity with up to 93% ee (Table 2, entry 6). In contrast,
at ꢀ10 °C, ꢀ30 °C, and ꢀ40 °C, respectively, no significant improve-
ment of the enantioselectivites was observed (Table 2, entries 4–8).
Under the optimal reaction conditions, a survey of the reaction
Conv.b (%)
Y.b (%)
%ee (Conf.) c
Entry
Cu salts
L.
L/Cu
1
2
3
4
5
6
7
8
9
0
1
Cu(OTf)
Cu(OTf)
Cu(OTf)
Cu(OTf)
Cu(OTf)
Cu(OTf)
(CuOTf)
Cu(OTf)
Cu(OTf)
Cu(OTf)
Cu(OTf)
2
1c
1d
2a
2b
2c
2d
2c
2c
2c
2c
2c
2
2
2
2
2
2
2
0.5
1.0
1.1
3.0
>99
99
>99
99
>99
98
>99
99
77
73
85
67
90
83
77
85
92
98
87
75 (R)
47 (S)
74 (R)
53 (S)
83 (R)
45 (S)
77 (R)
65 (R)
68 (R)
80 (R)
79 (R)
2
2
2
2
2
2
2
2
2
2
ꢁC
6
H
6
99
>99
>99
scope was then undertaken. When ZnMe
instead of ZnEt , the enantioselectivity of the corresponding 1,4-
adduct decreased to 69% ee (Table 2, entry 9). A similar result in
that ZnMe gave lower enantioselectivity than ZnEt was also ob-
served by Mauduit et al. They found that 90% ee and 45% ee were
obtained in the 1,4-addition of ZnEt or ZnMe to 2-cyclohexenone,
2
was used in the reaction
1
1
2
a
Reaction conditions: Cu(OTf)
2
(0.005 mmol) or (CuOTf)
ligand (0.01 mmol), ZnEt (1.0 M in hexane, 0.6 mmol), 3a (0.25 mmol), toluene
2
2
ꢁC
6
H
6
(0.0025 mmol),
2
2
(
4 mL), 0 °C, 4 h.
2
2
b
The data on conversion and yield were determined by GC using dodecane as an
14
respectively. A possible pathway for the 1,4-addition had been
proposed by Feringa et al. The alkyl transfer to the b-position of
the enone in complex I could produce alkylzinc enolate II, which
upon protonation generated 1,4-adduct III (Scheme 2).6 Based on
the mechanism, we presumed that the ethyl group performed a
more suitable steric and electronic effect than a methyl when the
alkyl transferred to the enone. Thus, we still select ZnEt2 as an
organozinc reagent in the next entries. The asymmetric conjugate
addition reactions of ZnEt2 to 2-cyclopentenone 3b and 2-cyclo-
heptenone 3c as the substrate proceeded successfully to afford
92% ee and 90% ee of the products, respectively (Table 2, entries
10 and 11). It was demonstrated that ligand 2c was efficient for
internal standard with a SE-30 column (30 m ꢂ 0.32 mm I.D.).
c
The enantiomeric excess of 4a was determined by GC equipped with a Chiral-
dex A-TA column (50 m ꢂ 0.25 mm I.D.). The absolute configuration of 4a was
f
determined by comparison with an authentic sample.
We next examined the influence of the copper precursor as well
as copper/ligand ratio on the reactive activity and enantioselectiv-
ity (Table 1, entries 6–9). In comparison to Cu(OTf)
2
, (CuOTf)
2
ꢁC H
6 6
as a catalytic precursor could enhance the enantioselectivity in the
presence of ligand 1a.7
a,7b
However, the catalyst formed in situ by
(
(
CuOTf)
2
ꢁC
6
H
6
and ligand 2c gave slightly lower enantioselectivity
77% ee) (Table 1, entry 7). Thus, Cu(OTf) , owing to its lower sen-
2
the Cu-catalyzed asymmetric conjugate addition of ZnEt to cyclic
2
sitivity to air and moisture, was chosen as a catalytic precursor for
the next experiments. An enhancement in enantioselectivity was
enones bearing different ring sizes. The results were consistent
0
with Chan et al.
s observation that three cyclic enones 3a–3c were
observed with a ratio of Cu(OTf)
2
/ligand ranging from 1/0.5 to 1/
all converted smoothly to the 1,4-adducts with high enantiomeric
7
c
2
(Table 1, entries 5, 8–10). A further increase of the ratio of ligand
excesses. In addition, the asymmetric 1,4-additions of ZnEt2 to
acyclic enones were tested. Unfortunately, low enantioselectivities
were observed: 18% ee for 1,3-diphenyl-2-propenone 3e, 45% ee
2
to Cu(OTf) brought no obvious change of the catalytic activity or
enantioselectivity (Table 1, entry 11).
Table 2
a
Cu-catalyzed enantioselective 1,4-addition of organozinc to cyclic enones
O
O
Cu(OTf)2, ligand 2c
+
ZnR2
solvent, -40 - 20 o
C
*
n
n
R
3
3
3
3
a
n = 1
n = 0
n = 2
n = 1
4a n = 1, R = Et
4b n = 0, R = Et
4c n = 2, R = Et
4d n = 1, R = Me
b
c
d
Entry
Sub.
Prod.
Soln
CH Cl
Et
THF
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
T (°C)
t (h)
Conv.b (%)
Y.b (%)
%ee. (Conf.)b
1
2
3
4
5
3a
3a
3a
3a
3a
3a
3a
3a
3d
3b
3c
4a
4a
4a
4a
4a
4a
4a
4a
4d
4b
4c
2
2
0
0
0
4
4
4
78
99
45
>99
>99
>99
>99
>99
>99
97
40
77
43
2 (R)
2
O
16 (R)
66 (R)
64 (R)
89 (R)
93 (R)
92 (R)
88 (R)
69 (R)
92 (R)
90 (R)
20
4
99
ꢀ10
ꢀ20
ꢀ30
ꢀ40
ꢀ20
ꢀ20
ꢀ20
12
12
12
12
20
12
12
>99
>99
98
>99
55
6
7
8
9c,d
1
0
59
97
c
1
1
99
a
b
c
2 2
Reaction conditions: Cu(OTf) (0.005 mmol), ligand 2c (0.01 mmol), ZnEt (1.0 M in hexane, 0.6 mmol), enone (0.25 mmol), solvent (4 mL).
The date on conversion, yield, enantiomeric excess, and the absolute configuration of the products were determined using the same conditions as noted in Table 1.
The enantiomeric excess was determined by GC equipped with a CP-Chirasil-Dex CB (25 m ꢂ 0.25 mm I.D.).
d
2
ZnMe (1.1 M in toluene, 0.6 mmol), 24 h.

2
996
Q.-L. Zhao et al. / Tetrahedron: Asymmetry 21 (2010) 2993–2998
R2Zn
given as s (singlet), d (doublet), t (triplet) and m (multiplet). HRMS
OZnR
were recorded on a Bulker micrOTOF-QII mass instrument.
All non-aqueous reactions and manipulations were performed
under an N atmosphere with standard Schlenk techniques. Reac-
2
tions were monitored by thin layer chromatography (TLC, silica
gel GF254 plates). Column chromatography separations were con-
L2CuR
+
O
L2CuX
*
or
R
R
RZnX
L2CuX2
II
H+
ducted on silica gel (200–300 mesh). NEt
were distilled with Na and benzophenone as an indicator, and
CH Cl was dried over CaH before use. H -binaphthol was pre-
pared according to a literature procedure.
3 2
, THF, Et O, and toluene
O
R
2
2
2
8
13a
XZn
All the other chemi-
O
*
cals were obtained commercially and used without further
purification.
L
III
Cu
L
I
R
4
.2. Synthesis of ligands 1c–1d and 2a–2d
Scheme 2. Postulated mechanism of the Cu-catalyzed asymmetric addition
reaction.6f
0
4.2.1. 1,2:5,6-Di-O-cyclohexylidene-3,4-bis[(R)-1,1 -H
8
-binaphthyl-
0
2
,2 -diyl]phosphite-
To a 100 mL Schlenk flask equipped with a condenser were
added 1.77 g of (R)-H -binaphthol, 20 mL of toluene, and 10 mL
of PCl . Then the mixture was refluxed for 22 h under a nitrogen
atmosphere. After removal of the excessive PCl and toluene, the
residue was dissolved using 20 mL of toluene, and then was trans-
ferred to another Schlenk flask, and toluene was removed in vacuo
8
to obtain the compound (R)-1,1 -H -binaphthyl-2,2 -diyl-chloro-
D-mannitol 1c
for 3-(4-methoxyphenyl)-1-phenyl-2-propenone 3f, and 53% ee for
8
3
-(4-chlorophenyl)-1-phenyl-2-propenone 3g (Scheme 3). The re-
3
sults indicated that the newly developed diphosphite ligand 2c
was inferior for these acyclic enones. In the 1,4-addition of cyclic
enones, the sense of the enantiodiscrimination was mainly deter-
mined by the configuration of the binaphthyl moieties of the
ligand.
3
0
0
phosphite 5c as a white powder, which was used directly in the fol-
lowing step without further purification. To a stirred solution of
1
,2:5,6-di-O-cyclohexylidene-
5c (646 mg, 1.8 mmol), and DMAP (14.6 mg, 0.12 mmol) in CH
(20 mL) at ꢀ10 °C, NEt (0.34 mL) was slowly added using a syringe
over 2 min, and the solution was stirred for 0.5 h at ꢀ10 °C. The
mixture was then stirred at rt for 1 h. CH Cl was distilled off in va-
D
-mannitol 1 (206 mg, 0.6 mmol),
O
2
Cl
Cu(OTf)2, 2c
O
2
+
ZnEt2
*
3
R'
R''
toluene, -20 oC, 24 h
R'
R''
3
e, 3f, 3g
4e, 4f, 4g
2
2
4
4
4
e: R' = Ph, R'' = Ph, 61% yield, 18% ee (S)
f: R' = 4-MeOPh, R'' = Ph, 50% yield, 45% ee (S)
g: R' = 4-ClPh, R'' = Ph, 53% yield, 53% ee (S)
cuo, and then toluene (20 mL) was added. The solid was removed
by filtration through a pad of silica gel, and the solvent was
removed under reduced pressure. The residue was purified by
Scheme 3. Cu-catalyzed 1,4-conjugate addition of ZnEt
2
to acyclic enones.
f
flash chromatography (toluene, R = 0.56), and furnished ligand 1c
as a white foamy solid (266 mg, 45% yield), mp 128–130 °C.
2
D
0
31
½
a
1
ꢃ
¼ ꢀ165 (c 0.2, CH
2
Cl
46.83 ppm. H NMR (400 MHz, DMSO-d
H), 7.05 (d, J = 8.0 Hz, 2H), 6.94 (d, J = 8.0 Hz, 2H), 6.85 (d,
2
). P NMR (162 MHz, DMSO-d
6
): d
1
3
. Conclusion
6
): d 7.24 (d, J = 7.6 Hz,
2
In conclusion, we have synthesized a novel series of diphosphite
ligands, which are derived from 1,2:5,6-di-O-isopropylidene-
mannitol and 1,2:5,6-di-O-cyclohexylidene- -mannitol. The ligands
were successfully applied in the copper-catalyzed asymmetric con-
jugate addition of dialkylzincs to cyclic enones bearing different
ring sizes with high enantioselectivities. The stereogenic centers
J = 8.0 Hz, 2H), 4.53 (t, J = 6.4 Hz, 2H), 4.16 (d, J = 5.2 Hz, 2H), 4.01
D
-
(
4
t, J = 7.2 Hz, 2H), 3.77 (t, J = 6.8 Hz, 2H), 2.76 (m, 8H), 2.591 (m,
1
3
D
H), 2.12 (m, 4H), 1.34–1.71 (m, 36H) ppm. C NMR (100 MHz,
): d 145.40, 137.98, 137.01, 134.65, 133.76, 129.45,
29.18, 128.77, 127.03, 118.63, 118.39, 109.06, 75.69, 73.58,
4.97, 35.57, 33.75, 28.40, 27.25, 25.17, 24.63, 23.59, 23.41,
DMSO-d
6
1
6
2
1
1.94, 21.84 ppm. HRMS (ESI) calcd for: C58
009.4180, found: 1009.4176, 0.4 ppm.
H
68NaO10P
2
(M+Na)+
of the D-mannitol skeleton and the axially chiral diaryl moieties
of ligands had a synergic effect on the reactive activity and enanti-
oselectivity of the reaction. The sense of the enantiodiscrimination
was predominantly controlled by the configuration of the biaryl
moieties of the ligand in the 1,4-addition of cyclic enones. The
application of these types of ligands to other transition metal-
catalyzed asymmetric reactions is ongoing in our laboratory.
0
4
.2.2. 1,2:5,6-Di-O-cyclohexylidene-3,4-bis[(S)-1,1 -H
8
-binaph-
0
thyl-2,2 -diyl]phosphite-
D
-mannitol 1d
0
0
(
S)-1,1 -H
8
-Binaphthyl-2,2 -diyl-chlorophosphite 5d was syn-
thesized by the same procedure as that of 5c, and was used directly
without further purification. Treatment of compound 1 (206 mg,
0.6 mmol), 5d, (646 mg, 1.8 mmol) and DMAP (14.6 mg,
4
4
. Experimental
0
.12 mmol) as described for the synthesis of ligand 1c afforded li-
gand 1d, which was purified by flash chromatography (toluene,
= 0.65) to produce a white solid (252 mg, 43% yield), mp 111–
.1. General
R
f
2
0
31
Melting points were determined using an X-4 melting point
apparatus and were uncorrected. Optical rotations were measured
112 °C. ½
aꢃ
¼ þ184 (c 0.2, CH
2
Cl
2
). P NMR (162 MHz, DMSO-
): d 7.15 (d,
D
1
d
6
): d 144.91 ppm. HNMR (400 MHz, DMSO-d
6
on a Perkin–Elmer 241 MC polarimeter at 20 °C. NMR spectra were
J = 8.4 Hz, 2H), 7.08 (d, J = 8.0 Hz, 2H), 7.01 (d, J = 8.4 Hz, 2H),
6.86 (d, J = 8.4 Hz, 2H), 4.44 (t, J = 8.8 Hz, 2H), 4.21 (dd, J = 12.8,
5.6 Hz, 2H), 3.87 (dd, J = 8.8, 6.4 Hz, 2H), 3.76 (dd, J = 8.4, 4.8 Hz,
2H), 2.78 (m, 8H), 2.60 (m, 4H), 2.13 (m, 4H), 1.73 (m, 12H),
1
recorded on Bulker 300 MHz or Bulker 400 MHz spectrometers. H
1
3
NMR and C NMR spectra were reported in parts per million with
31
TMS (d = 0.00 ppm) as an internal standard. P NMR spectra was
reported in parts per million with 85% H PO as an external refer-
1
3
3
4
1.56–1.28 (m, 24H) ppm.
6
C NMR (100 MHz, DMSO-d ): d
ence. Proton chemical shifts (d) and coupling constants (J) were re-
ported in ppm and in Hertz, respectively. Spin multiplicities were
145.28, 137.90, 134.67, 133.67, 131.48, 129.47, 129.00, 128.63,
128.59, 127.06, 118.75, 118.58, 109.34, 75.06, 73.13, 67.30, 65.48,

Q.-L. Zhao et al. / Tetrahedron: Asymmetry 21 (2010) 2993–2998
2997
3
2
5.94, 34.17, 29.70, 28.35, 27.18, 27.11, 24.45, 23.55, 23.15, 22.30,
1.89, 21.83, 21.78 ppm. HRMS (ESI) calcd for: C58
25.98, 24.47, 21.96, 21.84 ppm. HRMS (ESI) calcd for:
+
H68NaO10
P
2
C
52
H60NaO10
P
2
(M+Na) 929.3554, found: 929.3559, 0.5 ppm.
+
(
M+Na) 1009.4180, found: 1009.4167, 1.3 ppm.
0
4
2,2
.2.6. 1,2:5,6-Di-O-isopropylidene-3,4-bis[(S)-1,1 -H
8
-binaphthyl-
0
0
-diyl]phosphite-
D
-mannitol 2d
4
2
.2.3. 1,2:5,6-Di-O-isopropylidene-3,4-bis[(R)-1,1 -binaphthyl-
0
Treatment of
1,2:5,6-di-O-isopropylidene-
D
-mannitol 2
,2 -diyl]phosphite-
R)-1,1 -Binaphthyl-2,2 -diyl-chlorophosphite 5a was synthe-
D
-mannitol 2a
0
0
(157 mg, 0.6 mmol), 5d (517 mg, 1.44 mmol) and DMAP
(14.6 mg, 0.12 mmol) as described for the synthesis of ligand 1c
afforded ligand 2d, which was purified by flash chromatography
(
sized by the same procedure as that of 5c, and was used directly
without further purification. Treatment of 1,2:5,6-di-O-isopropyli-
dene-
DMAP (7.3 mg, 0.06 mmol) as described for the synthesis of ligand
c afforded ligand 2a, which was purified by flash chromatography
D
-mannitol 2 (79 mg, 0.3 mmol), 5a (421 mg, 1.2 mmol) and
(toluene, R
mp 118–120 °C. ½
DMSO-d ): d 144.38 ppm. HNMR (400 MHz, DMSO-d
6
f
= 0.26) to obtain a white solid (229 mg, 42% yield),
2
D
0
31
aꢃ
¼ þ213 (c 0.2, CH
2
Cl
2
). P NMR (162 MHz,
): d 7.15
1
1
6
(
1
toluene, R
19–121 °C. ½
f
= 0.36) to afford a white solid (200 mg, 75% yield), mp
(d, J = 8.8 Hz, 2H), 7.07 (d, J = 8.0 Hz, 2H), 7.02 (d, J = 8.0 Hz, 2H),
6.87 (d, J = 8.4 Hz, 2H), 4.44 (t, J = 8.4 Hz, 2H), 4.22 (dd, J = 12.8,
5.6 Hz, 2H), 3.89 (dd, J = 8.4, 6.0 Hz, 2H), 3.77 (dd, J = 8.8, 5.2 Hz,
2H), 2.78 (m, 8H), 2.61 (m, 4H), 2.08–2.17 (m, 4H), 1.73 (m,
12H), 1.47 (m, 4H), 1.37 (s, 6H), 1.28 (s, 6H) ppm. 13C NMR
2
0
31
a
ꢃ
¼ ꢀ309 (c 0.2, CH
2
Cl
2
).
P NMR (162 MHz,
): d 8.15 (d,
D
1
DMSO-d
6
): d 153.30 ppm. HNMR (300 MHz, DMSO-d
6
J = 8.7 Hz, 2H), 8.10 (d, J = 8.1 Hz, 2H), 8.07 (d, J = 8.1 Hz, 2H), 7.96
d, J = 9.0 Hz, 2H), 7.56 (d, J = 9.0 Hz, 2H), 7.52 (t, J = 7.8 Hz, 4H),
.43 (d, J = 9.0 Hz, 2H), 7.36 (t, J = 8.1 Hz, 4H), 7.23 (m, 4H), 4.83
(
7
6
(100 MHz, DMSO-d ): d 145.36, 145.31, 137.95, 137.07, 134.74,
(
(
d
1
1
7
C
m, 2H), 4.42 (dd, J = 10.5, 5.7 Hz, 2H), 4.00 (t, J = 7.8 Hz, 2H), 3.77
133.69, 129.50, 129.02, 128.71, 128.67, 127.11, 118.86, 118.65,
108.93, 74.87, 74.76, 73.49, 65.76, 28.40, 27.25, 27.18, 26.48,
m, 2H), 1.49 (s, 6H), 1.35 (s, 6H) ppm. 13C NMR (75 MHz, DMSO-
): d 147.45, 147.39, 146.53, 131.97, 131.56, 131.15, 130.76,
30.57, 130.03, 128.58, 126.68, 126.50, 126.00, 125.89, 125.32,
25.00, 21.96, 21.90, 21.84 ppm. HRMS (ESI) calcd for:
6
+
C
52
H60NaO10
P
2
(M+Na) 929.3554, found: 929.3552, 0.2 ppm.
25.09, 123.57, 123.50, 121.76, 121.56, 121.37, 108.28, 76.06,
4
.3. Representative procedure for the asymmetric 1,4-addition
5.72, 74.28, 64.44, 25.71, 24.28 ppm. HRMS (ESI) calcd for:
+
of organozincs to 2-cyclohexenone 3a
52
H44NaO10
P
2
(M+Na) 913.2302, found: 913.2300, 0.2 ppm.
0
A solution of Cu(OTf) (0.005 mmol, 1.8 mg) and ligand 2c
2
4
2
.2.4. 1,2:5,6-Di-O-isopropylidene-3,4-bis[(S)-1,1 -binaphthyl-
0
(0.01 mmol, 9.1 mg) in toluene (4 mL) was stirred for 1 h at rt un-
der nitrogen. After the solution was cooled down to 0 °C, 2-cyclo-
hexenone (0.25 mmol, 0.024 mL) was added and the solution was
,2 -diyl]phosphite-
(
D
-mannitol 2b
0
0
S)-1,1 -Binaphthyl-2,2 -diyl-chlorophosphite 5b was prepared
using the same procedure as 5c, and was used directly without fur-
ther purification. Treatment of 1,2:5,6-di-O-isopropylidene- -man-
nitol 2 (157 mg, 0.6 mmol), 5b (505 mg, 1.44 mmol) and DMAP
14.6 mg, 0.12 mmol) as described for the synthesis of ligand 1c
afforded ligand 2b, which was purified by flash chromatography
toluene, R = 0.21) to obtain a white solid (221 mg, 40% yield),
mp 115–117 °C. ½
DMSO-d ): d 150.41 ppm. HNMR (400 MHz, DMSO-d
J = 8.8 Hz, 4H), 8.03 (d, J = 8.0 Hz, 2H), 7.90 (d, J = 8.8 Hz, 2H),
.55 (m, 6H), 7.45 (d, J = 8.8 Hz, 2H), 7.40 (d, J = 8.0 Hz, 2H), 7.36
d, J = 7.6 Hz, 2H), 7.27 (d, J = 8.0 Hz, 2H), 7.20 (d, J = 7.2 Hz, 2H),
.63 (t, J = 8.8 Hz, 2H), 4.42 (dd, J = 12.8, 5.6 Hz, 2H), 4.06 (dd,
J = 8.8, 6.4 Hz, 2H), 3.99 (dd, J = 8.8, 4.8 Hz, 2H), 1.40 (s, 6H), 1.26
2
stirred for 10 min at 0 °C, then ZnEt (0.6 mmol, 0.6 mL of 1.0 M
D
solution in hexane) was added dropwise using a syringe over
2
2
min. After 4 h, the reaction was quenched by H
M HCl (2 mL), and extracted with ethyl acetate (5 mL ꢂ 3). The
solution,
brine, and then dried over anhydrous Na SO , filtered, and concen-
2
O (2 mL) and
(
combined extracts were washed using saturated NaHCO
3
(
f
2
D
0
31
2
4
aꢃ
¼ þ496 (c 0.2, CH
2
Cl
2
). P NMR (162 MHz,
): d 8.11 (t,
1
trated to afford the crude product. The conversion and the yield
were determined by GC equipped with SE-30 column
6
6
a
a
(
30 m ꢂ 0.32 mm I.D.) using dodecane as an internal standard.
7
(
4
The enantiomeric excess was determined by GC with a Chiraldex
A-TA column (50 m ꢂ 0.25 mm I.D.). The absolute configuration
was determined by comparison with authentic samples. The ana-
lytic conditions for the 1,4-adducts are as follows.
1
3
(
s, 6H) ppm. C NMR (100 MHz, DMSO-d
6
): d 147.39, 147.34,
1
1
1
2
9
46.42, 131.98, 131.70, 131.22, 130.86, 130.65, 130.02, 128.67,
28.60, 126.74, 126.60, 126.01, 125.39, 125.18, 123.54, 123.49,
4
.3.1. 3-Ethylcyclohexanone 4a
Chiraldex A-TA column (50 m ꢂ 0.25 mm I.D.) at 120 °C con-
21.75, 121.66, 121.59, 109.12, 75.17, 75.07, 73.42, 65.85, 26.50,
+
stant. t
enantiomer (S).
R R
= 11.52 min for enantiomer (R), and t = 11.79 min for
4.89 ppm. HRMS (ESI) calcd for:
13.2302, found: 913.2280, 1.5 ppm.
C
52
H44NaO10P
2
(M+Na)
4
.3.2. 3-Ethylcyclopentanone 4b
Chiraldex A-TA column (50 m ꢂ 0.25 mm I.D.) at 110 °C con-
stant. t = 12.76 min for enantiomer (R), and t = 12.46 min for
enantiomer (S).
0
4
2
.2.5. 1,2:5,6-Di-O-isopropylidene-3,4-bis[(R)-1,1 -H
8
-binaphthyl-
0
,2 -diyl]phosphite-
Treatment of
D-mannitol 2c
R
R
1,2:5,6-di-O-isopropylidene-
D
-mannitol
2
(
0
157 mg, 0.6 mmol), 5c (860 mg, 2.4 mmol) and DMAP (14.6 mg,
.12 mmol) as described for the synthesis of ligand 1c afforded li-
gand 2c, which was purified by flash chromatography (toluene,
4
.3.3. 3-Ethylcycloheptanone 4c
CP-Chirasil-Dex CB(25 m ꢂ 0.25 mm I.D.) at120 °C constant. t
3.70 min for enantiomer (R), and t = 13.31 min for enantiomer (S).
R
=
R
1
d
f
= 0.32) to obtain a white solid (273 mg, 50% yield), mp 132–
1
R
2
0
31
33 °C. ½
a
ꢃ
¼ ꢀ205 (c 0.2, CH
2
Cl
2
). P NMR (162 MHz, DMSO-
): d 7.13 (d,
D
1
6
): d 146.52 ppm. HNMR (400 MHz, DMSO-d
6
4
.3.4. 3-Methylcyclohexanone 4d
CP-Chirasil-Dex CB (25 m ꢂ 0.25 mm I.D.) at 70 °C constant.
= 37.84 min for enantiomer (R), and t = 38.69 min for enantio-
J = 8.4 Hz, 2H), 7.05 (d, J = 8.4 Hz, 2H), 6.96 (d, J = 8.0 Hz, 2H),
.88 (d, J = 8.0 Hz, 2H), 4.55 (dd, J = 8.8, 5.6 Hz, 2H), 4.19 (dd,
J = 11.6, 5.6 Hz, 2H), 3.95 (t, J = 8.0 Hz, 2H), 3.73 (dd, J = 8.8,
6
t
R
R
mer (S).
5
1
.6 Hz, 2H), 2.77 (m, 8H), 2.58–2.63 (m, 4H), 2.08–2.16 (m, 4H),
1
3
.72 (m, 12H), 1.47 (m, 4H), 1.42 (s, 6H), 1.31 (s, 6H) ppm.
): d 145.48, 145.40, 137.95, 136.99,
34.63, 133.74, 129.43, 129.13, 128.76, 128.71, 127.03, 118.73,
18.44, 108.41, 75.55, 75.30, 74.02, 64.96, 28.40, 27.25, 27.17,
C
4.3.5. 1, 3-Diphenyl-1-pentanone 4e
NMR (100 MHz, DMSO-d
1
1
6
Daicel Chiralcel AD-H 25 cm ꢂ 4.6 mm I.D., hexane/i-PrOH = 95/
5, flow rate = 0.5 mL/min at 25 °C, detected at 254 nm. t = 15.99 min
for enantiomer (R), and t = 13.40 min for enantiomer (S).
R
R

2
998
Q.-L. Zhao et al. / Tetrahedron: Asymmetry 21 (2010) 2993–2998
4
.3.6. 3-(4-Methoxyphenyl)-1-phenylpentanone 4f
7. (a) Zhao, Q. L.; Wang, L. L.; Kwong, F. Y.; Chan, A. S. C. Tetrahedron: Asymmetry
007, 17, 1899–1905; (b) Wang, L. L.; Li, Y. M.; Yip, C. W.; Qiu, L. Q.; Zhou, Z. Y.;
2
Daicel Chiralcel AD-H 25 cm ꢂ 4.6 mm I.D., hexane/i-PrOH = 95/
Chan, A. S. C. Adv. Synth. Catal. 2004, 346, 947–953; (c) Liang, L.; Au-Yeung, T. T.-
L.; Chan, A. S. C. Org. Lett. 2002, 4, 3799–3801; (d) Yan, M.; Zhou, Z.-Y.; Chan, A.
S. C. Chem. Commun. 2000, 115–116; (e) Yan, M.; Yang, L. W.; Wong, K. Y.; Chan,
A. S. C. Chem. Commun. 1999, 11–12; (f) Alexakis, A.; Vastra, J.; Burton, J.;
Benhaim, C.; Mangeney, P. Tetrahedron Lett. 1998, 39, 7869–7872.
5
, flow rate = 0.5 mL/min at 25 °C, detected at 254 nm.
t
R
R
= 25.22 min for enantiomer (R), and t = 17.80 min for enantio-
mer (S).
8.
(a) Xie, Y.; Huang, H.; Mo, W.; Fan, X.; Shen, Z.; Shen, Z.; Sun, N.; Hu, B.; Hu, X.
Tetrahedron: Asymmetry 2009, 20, 1125–1432; (b) Mata, Y.; Diéguez, M.;
Pàmies, O.; Biswas, K.; Woodward, S. Tetrahedron: Asymmetry 2007, 18, 1613–
4
.3.7. 3-(4-Chlorophenyl)-1-phenylpentanone 4g
Daicel Chiralcel AD-H 25 cm ꢂ 4.6 mm I.D., hexane/i-PrOH = 95/
1
617; (c) Liu, L.-T.; Wang, M.-C.; Zhao, W.-X.; Zhou, Y.-L.; Wang, X.-D.
5
,
flow rate = 0.5 mL/min at 25 °C, detected at 254 nm.
Tetrahedron: Asymmetry 2006, 17, 136–141; (d) Morimoto, T.; Mochizuki, N.;
Suzuki, M. Tetrahedron Lett. 2004, 45, 5717–5722; (e) Alexakis, A.; Benhaim, C.;
Rosset, S.; Humam, M. J. Am. Chem. Soc. 2002, 124, 5262–5263; (f) Shintani, R.;
Fu, G. C. Org. Lett. 2002, 4, 3699–3702; (g) Escher, I. H.; Pfaltz, A. Tetrahedron
R R
t = 18.90 min for enantiomer (R), and t = 14.95 min for enantio-
mer (S).
2
000, 56, 2879–2888.
9. (a) Kawamura, K.; Fukuzawa, H.; Hayashi, M. Org. Lett. 2008, 10, 3509–3512;
b) Biradar, D. B.; Gau, H.-M. Tetrahedron: Asymmetry 2008, 19, 733–738; (c)
Acknowledgments
(
Duncan, A. P.; Leighton, J. L. Org. Lett. 2004, 6, 4117–4119; (d) Shi, M.; Wang, C.;
Zhang, W. Chem. Eur. J. 2004, 10, 5507–5516; (e) Hird, A. W.; Hoveyda, A. H.
Angew. Chem., Int. Ed. 2003, 42, 1276–1279; (f) Degrado, S. J.; Mizutani, H.;
Hoveyda, A. H. J. Am. Chem. Soc. 2002, 124, 13362–13363; (g) Mizutani, H.;
Degrado, S. J.; Hoveyda, A. H. J. Am. Chem. Soc. 2002, 124, 779–781; (h) Degrado,
S. J.; Mizutani, H.; Hoveyda, A. H. J. Am. Chem. Soc. 2001, 123, 755–756; (i)
Yamanoi, Y.; Imamoto, T. J. Org. Chem. 1999, 64, 2988–2989.
We are grateful for the financial support of this work by the Na-
tional Natural Science Foundation of China (NSFC 20343005,
2
0473107, 20673130, 20773147, and 21073211).
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