Synthesis of modified H4-BINOL ligands and their applications in the asymmetric addition of diethylzinc to aromatic aldehydes

Article abstract of DOI:10.1016/j.tetasy.2006.06.042

Two new ligands (S,S)-3-(1,1′-bi-2-naphthol-3-yl)-5,6,7,8-tetrahydro-1,1′-bi-2-naphthol [(S,S)-1] and (S)-3-(morpholin-4-ylmethyl)-H₄-BINOL [(S)-2] have been synthesized via Suzuki cross-coupling reaction and a Mannich-type reaction, respectively. In the presence of titanium tetraisopropoxide, 0.8 mol % of ligand (S,S)-1 catalyzed the asymmetric addition of diethylzinc to aromatic aldehydes in good yield and with high enantioselectivity.

Full text of DOI:10.1016/j.tetasy.2006.06.042

Tetrahedron: Asymmetry 17 (2006) 1842–1845
Synthesis of modified H -BINOL ligands and their applications in
4
the asymmetric addition of diethylzinc to aromatic aldehydes
Yong-Na Lu, Qun-Sheng Guo, Fu-Yong Jiang and Jin-Shan Li*
State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PR China
Received 17 May 2006; accepted 23 June 2006
Available online 25 July 2006
0
0
Abstract—Two new ligands (S,S)-3-(1,1 -bi-2-naphthol-3-yl)-5,6,7,8-tetrahydro-1,1 -bi-2-naphthol [(S,S)-1] and (S)-3-(morpholin-4-yl-
methyl)-H -BINOL [(S)-2] have been synthesized via Suzuki cross-coupling reaction and a Mannich-type reaction, respectively. In
4
the presence of titanium tetraisopropoxide, 0.8 mol % of ligand (S,S)-1 catalyzed the asymmetric addition of diethylzinc to aromatic
aldehydes in good yield and with high enantioselectivity.
ꢀ
2006 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results and discussion
0
1
,1 -Bi-2-naphthol (BINOL) is one of the most effective
Ligand (S,S)-1 was synthesized by a Suzuki cross-cou-
pling reaction (Scheme 1). The hydroxyl groups of (S)-BI-
NOL were protected with methoxymethyl (MOM) groups
1
chiral ligands in asymmetric catalysis. Recent research
showed that catalysts based on the partially hydrogenated
BINOL ligands, 5,5 ,6,6 ,7,7 ,8,8 -octahydro-1,1 -bi-2-
naphthol (H -BINOL) and 5,6,7,8-tetrahydro-1,1 -bi-2-
naphthol (H -BINOL), exhibited better efficiency and
enantioselectivity for asymmetric reactions than those ob-
tained from their BINOL ligands, due to the steric and
electronic modulation in the binaphthyl backbone. How-
ever, very few substituted H -BINOL ligands have been
0
0
0
0
0
0
0
0
to afford (S)-2,2 -bis(methoxymethoxy)-1,1 -binaphthalene
2
6
(S)-3. The lithium salt of (S)-3 reacted with B(OMe) and
8
3
3
the mixture was hydrolyzed with 2 M HCl to afford (S)-
4
0
0
2,2 -bis(methoxymethoxy)-1,1 -binaphthyl-3-boronic acid
4
(S)-4 in pure form in 55% yield after purification by col-
5
7
umn chromatography on silica gel. The bromination of
4
h
(S)-5 gave 3-bromo-H -BINOL (S)-6 in excellent yield.
4
4
3
,4h
synthesized and studied.
of two new modified H -BINOL ligands (S,S)-1 and (S)-2
Fig. 1) and their catalytic activity in titanium complex cat-
Herein, we report the synthesis
The hydroxyl groups of (S)-6 were protected with meth-
oxymethyl (MOM) groups to afford (S)-7. After Suzuki
4
8
(
cross-coupling of (S)-7 with (S)-4 in the presence of aq
alyzed enantioselective addition of diethylzinc to aromatic
aldehydes.
Na CO and Pd(PPh ) in THF at reflux for 36 h and
deprotection of the MOM groups compound (S,S)-1
2
3
3 4
was obtained.
We conducted the reaction of the enantiomerically pure
N
O
(
S)-H -BINOL with paraformaldehyde and morpholine
4
9
OH
OH
in dioxane at 60 ꢁC. This one-pot process led to the forma-
tion of (S)-3-(morpholin-4-ylmethyl)-H -BINOL [(S)-2] in
OH
OH
HO
HO
4
98% yield (Scheme 2).
(S,S)-1
(S)-2
The plate-like colorless single crystals of (S)-2 were ob-
tained from Et O–CH Cl –petroleum ether solution. The
2
2
2
Figure 1.
crystal structure of (S)-2 was determined by X-ray diffrac-
1
0
tion as shown in Figure 2. The dihedral angle between the
two naphthalene systems is 108.6(3)ꢁ. The bond angle
C(3)–C(21)–N(1) is 111.3(2)ꢁ and slightly larger than the
*
Corresponding author. Tel.: +86 22 23504230; fax: +86 22 23503627;
e-mail: jinshanl@nankai.edu.cn
0957-4166/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2006.06.042

Y.-N. Lu et al. / Tetrahedron: Asymmetry 17 (2006) 1842–1845
1843
B(OH)2
a
55%
OMOM
OMOM
OMOM
OMOM
d
(S)-3
(S)-4
(S,S)-1
51%
Br
Br
c
b
OH
OH
OH
OH
OMOM
OMOM
9
8%
(
S)-5
(S)-6
(S)-7
Scheme 1. Reagents and conditions: (a) (i) 1.1 equiv n-BuLi, ꢀ78 ꢁC, (ii) B(OMe)
3
, ꢀ78 ꢁC, (iii) 2 M HCl, 0 ꢁC, 55%; (b) 1.2 equiv Br
2
, 12 h, 98%; (c)
K
2
CO
3
, ClCH
2
3 3 4 2 3
OCH , acetone, rt; (d) (i) Pd(PPh ) , aq Na CO , THF/reflux, 36 h; (ii) 2 M HCl, 0 ꢁC.
Table 1. Catalytic asymmetric addition of diethylzinc (1.0 M in toluene)
to 1-naphthaldehyde
N
O
(
HCHO)n
dioxane, 60 ˚C
OH
OH
OH
OH
HO
∗
CHO
HN
O
i
*
Ti(O Pr) /L
4
+
Et Zn
2
9
8% yield
toluene
(S)-5
(S)-2
a
b
c
d
Entry
Ligand (mol %)
Yield (%)
ee (%)
Config.
4
Scheme 2. Synthesis of 3-morphoplinylmethyl-H -BINOL.
1
2
3
4
5
6
7
8
9
(S,S)-1 (10)
(S,S)-1 (5)
(S,S)-1 (4)
(S,S)-1 (3)
(S,S)-1 (2)
(S,S)-1 (1)
(S,S)-1 (0.8)
(S,S)-1 (0.6)
(S,S)-1 (0.5)
(S,S)-1 (0.4)
(S,S)-1 (0.2)
(S,S)-1 (0.1)
(S)-2 (20)
95
92
96
92
95
92
96
91
92
91
85
92
96
89
80
88.3
88.2
88.0
87.8
87.5
82.7
84.7
82.8
77.7
77.8
74.6
57.1
79.3
78.8
68.6
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
10
11
12
13
14
15
(S)-2 (10)
(S)-2 (5)
a
i
Ti(O Pr)
4 2
/Et Zn/1-naphthaldehyde = 1.2:3:1; reaction temperature:
0
ꢁC; reaction time: 5 h.
b
c
Isolated yield.
Data were determined by GC analysis: initial 100 ꢁC, 1 ꢁC/min to 200 ꢁC
on a Chiral beta-DEX 120 capillary column.
d
2
Figure 2. The molecular structure of (S)-2 including one Et O molecule.
The absolute configuration of the product was determined by comparing
13
the specific rotation with the literature data.
ideal tetrahedral value of 109.5ꢁ. The conformation of the
morpholine ring is a stable chair form.
With conditions optimized for 1-naphthaldehyde, the use
of ligands (S,S)-1 and (S)-2 was extended to the asymmet-
ric addition of diethylzinc to other aromatic aldehydes. The
The effectiveness of the two ligands in the titanium complex
catalyzed enantioselective addition of diethylzinc to 1-
i
molar ratio of (S,S)-1/Ti(O Pr) /Et Zn/aldehyde was set up
4
2
1
1
i
naphthaldehyde was tested. The active catalyst was
formed in situ by mixing the ligand with titanium tetraiso-
to be 0.008:1.2:3:1 and that of (S)-2/Ti(O Pr) /Et Zn/alde-
4 2
hyde was set up to be 0.1:1.2:3:1. The results are summa-
rized in Table 2. (S,S)-1 showed high enantioselectivity in
this reaction while (S)-2 only showed moderate enantio-
1
2
propoxide in toluene. The amount of ligand (S,S)-1
varied from 10 to 0.1 mol %. It was found that the enantio-
selectivity was still high (84.7% ee) when using 0.8 mol % of
0
selectivity. For (S,S)-1, introducing 1,1 -binaphthol-3-yl
0
(
(
S,S)-1. (Table 1, entries 1–12). Decreasing the amount of
S)-2 from 20 to 5 mol % led to a large decrease in the
group at the 3 position of 5,6,7,8-tetrahydro-1,1 -binaph-
thol possibly tended to create a larger dihedral angle
and thus led to high enantioselectivity.
4
f
enantioselectivity (Table 1, entries 13–15).

1844
Y.-N. Lu et al. / Tetrahedron: Asymmetry 17 (2006) 1842–1845
Table 2. Enantioselective addition of diethylzinc (1.0 M in toluene) to
aldehydes with (S,S)-1 and (S)-2
THF (40 mL), H O (20 mL), and Na CO (3.3 g,
2 2 3
31.2 mmol). The resulting mixture was heated at reflux
for 36 h. The organic layer was separated and the aqueous
layer extracted with AcOEt. The combined organic phases
O
i
OH
∗
Ti(OPr) /L*
4
+
Et Zn
2
Ar
H
toluene
Ar
were dried over MgSO . After removal of the solvent, the
4
a
b
c
e
residue was resolved in CH Cl (35 mL) and MeOH
2
2
Entry Ligand (%) Ar
Yield (%) ee (%) Config.
(
35 mL). To this solution was added 15 mL HCl (12 M)
at 0 ꢁC. The mixture was stirred at room temperature for
2 h and poured into water (80 mL), extracted with
CH Cl , washed with water, and then saturated NaHCO ,
d
14
1
2
3
4
5
6
7
8
9
1
1
(S,S)-1
(S,S)-1
(S,S)-1
(S,S)-1
(S,S)-1
(S,S)-1
(S)-2
(S)-2
(S)-2
(S)-2
(S)-2
Ph
p-ClC
p-BrC
p-MeOC
o-MeOC
1-Naphthyl 96
Ph
p-ClC
p-BrC
o-MeOC H
6 4
80
70
89
71
91
82.5
81.1
82.4
81.3
83.4
84.7
77.8
64.8
70.0
63.8
78.8
S
S
S
S
S
S
S
S
S
S
S
1
5
6
6
H
4
1
1
6
H
4
d
17
2
2
3
6
H
4
18
and dried over Na SO . After removal of the solvent in
2 4
6
H
4
vacuo, the residue was submitted to column chromatogra-
phy on silica gel with petroleum ether/ethyl acetate (3:1) as
94
75
96
98
6
H
4
eluent to give a khaki oil. After recrystallization in Et O
2
6
H
4
and petroleum ether, compound (S,S)-1 was obtained as
a khaki powder (2.3 g, 51.3% yield). Mp 210–212 ꢁC;
0
1
2
D
5
1
1-Naphthyl 89
½
aꢁ ¼ ꢀ19:51 (c 1.01, CHCl ); H NMR (300 MHz,
3
a
i
i
(
S,S)-1/Ti(O Pr)
4
/Et
2
Zn/aldehyde = 0.008:1.2:3:1; (S)-2/Ti(O Pr)
/Et
4 2
Zn/
CDCl ): d 1.51–1.65 (m, 2H), 1.66–1.74 (m, 2H), 2.09–
3
aldehyde = 0.1:1.2:3:1; solvent: toluene; reaction temperature: 0 ꢁC;
reaction time: 5 h.
Isolated yield.
Data were determined by GC analysis using a chiral column (Chiral beta-
DEX 120 capillary column).
Data were determined by HPLC analysis using a chiral OD column.
The absolute configuration of the product was determined by comparing
the specific rotation with the literature data.
2.30 (m, 2H), 2.80 (t, J = 6.6 Hz, 2H), 4.98 (s, 1H), 5.15
(s, 1H), 5.17 (s, 1H), 5.34 (s, 1H), 7.15–7.43 (m, 11H),
b
c
7
8
2
1
1
1
1
.75 (d, J = 10.5 Hz, 1H) 7.89–8.01 (m, 4H), 8.10 (s, 1H),
1
3
.21 (s, 1H); C NMR (75 MHz, CDCl ): d 22.75, 22.75,
3
5.98, 29.16, 107.56, 111.53, 112.04, 112.54, 113.77,
17.84, 118.02, 119.55, 123.82, 124.09, 124.30, 124.40,
24.45, 127.46, 127.46, 128.45, 128.49, 129.04, 129.12,
29.34, 129.52, 129.58, 130.52, 130.98, 131.90, 132.03,
33.00, 133.00, 133.50, 133.73, 133.73, 138.70, 149.00,
d
e
3. Conclusion
150.50, 151.44, 152.7; IR (KBr): 3514, 3222, 3056, 2927,
ꢀ
1
2847, 1620, 1509, 1456, 1189, 866, 812 cm ; HRMS (EI)
We have synthesized two new modified H -BINOL ligands
calcd for C H O : 574.2144; found: 574.2136.
4
40 30
4
(
S,S)-1 and (S)-2, respectively, via a Suzuki cross-coupling
reaction and Mannich-type reaction. The titanium complex
of (S,S)-1 was found to be a very effective catalyst in the
asymmetric addition of diethylzinc to a variety of aromatic
aldehydes.
4.3. Synthesis of (S)-3-(morpholin-4-ylmethyl)-5,6,7,8-tetra-
hydro-1,1 -bi-2-naphthol (S)-2
0
Paraformaldehyde (9.0 g, 300 mmol) was placed in a round
bottom flask. Morpholine (26.1 g, 300 mmol) was added
dropwise over 1 h with vigorous stirring. Since this was a
strongly exothermic reaction, the addition rate was ad-
justed in order to keep the oil bath temperature at 60–
70 ꢁC. Then the reaction mixture was heated at 60 ꢁC for
4. Experimental
4
.1. General
about 12 h until it became a clear yellow solution. H -BI-
4
1
13
The H and C NMR spectra were recorded on a Bruker
NOL (2.9 g, 10 mmol) and dioxane (10 mL) were added
and the solution was stirred at 60 ꢁC for an additional
12 h. The residue was dissolved in CH Cl , washed with
AC-300 instrument in CDCl solution with TMS as inter-
3
nal standard. Optical rotations were measured on a Per-
kin–Elmer 241 polarimeter. IR spectra were recorded as
KBr plates on a Bruker Equinox 55 spectrometer. Elemen-
tal analysis was performed with a Yanaco CHN Corder
MT-3 elemental analyzer. The high-resolution mass spectra
2
2
1 M HCl (3 · 10 mL) and water (3 · 10 mL), and dried
over Na SO . After removal of solvent, the residue was
2
4
submitted to column chromatography on silica gel with
petroleum ether/ethyl acetate (2:1) as eluent to give (S)-2
(3.8 g, 98% yield) as a colorless oil. The colorless crystals
of (S)-2 were obtained from Et O–CH Cl –petroleum
(
(
EI-HRMS) were measured on an Autospec-AltimaETOF
UK, Micromass) spectrometer. All experiments which are
2
2
2
2
D
5
1
sensitive to moisture or air were carried out under an argon
atmosphere using standard Schlenk techniques. Diethyl-
zinc (1.0 M solution in toluene) was prepared according
ether. Mp 103–105 ꢁC; ½aꢁ ¼ ꢀ30:8 (c 1.05, CHCl ); H
3
NMR (300 MHz, CDCl ): d 1.54–1.62 (m, 2H), 1.68–1.76
3
(m, 2H), 2.07–2.31 (m, 2H), 2.59 (br s, 4H), 2.75 (t,
1
9
to literature method. Pd(PPh3)4 was purchased from
Aldrich. All anhydrous solvents were purified and dried
by standard techniques just before use.
J = 6.15 Hz, 2H), 3.67 (br s, 4H), 3.76 (s, 2H), 6.90 (s,
1
3
1H), 7.21–7.33 (m, 4H), 7.80–7.83 (m, 2H); C NMR
(75 MHz, CDCl ): d 23.49, 23.05, 25.91, 29.29, 52.99,
3
5
2.99, 61.84, 66.60, 66.59, 116.49, 117.31, 118.75, 119.12,
0
4.2. Synthesis of (S,S)-3-(1,1 -bi-2-naphthol-3-yl)-5,6,7,8-
tetrahydro-1,1 -bi-2-naphthol (S,S)-1
123.15, 124.15, 125.41, 128.32, 128.79, 129.24, 129.39,
130.31, 133.04, 138.48, 150.38, 153.98; IR (KBr): 3514,
0
3
222, 3056, 2927, 2847, 1620, 1509, 1456, 1189, 866,
ꢀ1
Under argon, (S)-4 (3.25 g, 7.8 mmol) was combined with
812 cm ; Anal. Calcd for C H NO : C, 77.09; H, 6.99;
25 27 3
(
S)-7 (2.87 g, 7.8 mmol), Pd(PPh3)4 (0.46 g, 0.4 mmol),
N, 3.60. Found: C, 76.02; H, 6.51; N, 3.80.

Y.-N. Lu et al. / Tetrahedron: Asymmetry 17 (2006) 1842–1845
1845
4.4. A typical procedure for the asymmetric addition of
diethylzinc to benzaldehyde
H. Organometallics 2002, 21, 409–417; (h) Long, J.; Hu, J.;
Shen, X.; Ji, B.; Ding, K. J. Am. Chem. Soc. 2002, 124, 10–11.
. For recent examples, see (a) Zhang, F. Y.; Pai, C. C.; Chan,
A. S. C. J. Am. Chem. Soc. 1998, 120, 5808–5809; (b)
Uemura, T.; Zhang, X.; Matsumura, K.; Sayo, N.; Kumo-
bayashi, H.; Ohta, T.; Nozaki, K.; Takaya, H. J. Org. Chem.
5
Titanium tetraisopropoxide (0.34 g, 1.2 mmol) was added
to a solution of ligand (S,S)-1 (0.0046 g, 0.008 mmol) in
5
mL of toluene at room temperature and the reaction mix-
1
996, 61, 5510–5516.
. Kitajima, H.; Aoki, Y.; Ito, K.; Katsuki, T. Chem. Lett. 1995,
113–1114.
ture was stirred for 15 min followed by the addition of
diethylzinc (3.0 mL, 1.0 M solution in toluene) with contin-
ued stirring for 15 min. The solution was cooled to 0 ꢁC
and benzaldehyde (0.10 mL, 1.0 mmol) was introduced
with a syringe. The reaction mixture was stirred at 0 ꢁC
for 5 h. The reaction was quenched with 20 mL of satu-
6
1
7. Bai, X. L.; Liu, X. D.; Wang, M.; Kang, C. Q.; Gao, L. X.
Synthesis 2005, 458–464.
8. (a) Hu, Q. S.; Zheng, X. F.; Pu, L. J. Org. Chem. 1996, 61,
5
200–5201; (b) Simonson, D. L.; Kinsbury, K.; Xu, M. H.;
Hu, Q. S.; Sabat, M.; Pu, L. Tetrahedron 2002, 58, 8189–8193;
c) Ma, L.; White, P. S.; Lin, W. B. J. Org. Chem. 2002, 67,
577–7586; (d) Bai, X. L.; Liu, X. D.; Wang, M.; Kang, C.
rated NH Cl solution. The mixture was extracted with
4
(
7
ethyl acetate (3 · 10 mL). The combined organic layers
were dried over MgSO and concentrated to solvent free.
4
Q.; Gao, L. X. Synthesis 2005, 3, 0458–0464.
. (a) Fabris, F.; Lucchi, O. D.; Lucchini, V. J. Org. Chem.
The residue was purified by column chromatography on
silica gel affording 1-phenyl-1-propanol (0.11 g, 80% yield)
as a colorless liquid. The optical rotation was measured.
The enantiomeric excess of product was determined by
HPLC on a Chiralcel OD column.
9
1
997, 62, 7156–7164; (b) Liu, L.; Pu, L. Tetrahedron 2004, 60,
7
427–7430.
10. Crystal data for (S)-2: C H NO , M = 463.60, orthorhom-
2
9
37
4
˚
bic, space group P2(1)2(1)2(1), a = 10.553(2) A, b =
c = 21.591(5) A,
623.0(11) A , Z = 4, D = 1.174 g cm
˚
˚
1
2
0
1.512(3) A,
a = b = c = 90ꢁ,
V =
MoKa (k =
, crystal size
˚
3
ꢀ3
,
˚
ꢀ1
.71073 A), T = 293(2) K, l = 0.077 mm
Acknowledgment
(
mm) 0.24 · 0.22 · 0.19. Area detector data collected on a
Bruker Smart 1000 diffractometer. A total of 14,387 reflec-
tions were collected (1.89 < h < 25.01). Structure solution by
direct method (SHELXS-97), refinement by full-matrix least-
squares using all reflections, R = 0.0472, wR = 0.1125,
This work was supported by The National Natural Science
Foundation of China (Grant No. 20372037).
1
2
GOF = 1.032. Crystallographic data has been deposited with
the Cambridge Crystallographic Data Centre as supplemen-
tary publication number CCDC 607833. Copies of the data
can be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK. Fax: +44 1223
336033 or e-mail: deposit@ccdc.cam.ac.uk.
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