The application of chiral aminonaphthols in the enantioselective addition of diethylzinc to aryl aldehydes

Article abstract of DOI:10.1021/ol016341e

(Equation presented) Optically active aminonaphthol 3 obtained by condensation of 2-naphthol, benzaldehyde, and (S)-methylbenzylamine followed by N-methylation was found to catalyze the enantioselective ethylation of aryl aldehydes to secondary alcohols w

Full text of DOI:10.1021/ol016341e

ORGANIC
LETTERS
2001
Vol. 3, No. 17
2733-2735
The Application of Chiral
Aminonaphthols in the Enantioselective
Addition of Diethylzinc to Aryl
Aldehydes
Da-Xue Liu,† Li-Cheng Zhang,† Quan Wang,† Chao-Shan Da,† Zhuo-Qun Xin,†
,†
Rui Wang,* Michael C. K. Choi,‡ and Albert S. C. Chan‡
Open Laboratory of Chirotechnology, Department of Biochemistry and Molecular
Biology, School of Life Science, Lanzhou UniVersity, Lanzhou 730000, P. R. China,
and Open Laboratory of Chirotechnology, Department of Applied Biology and
Chemical Technology, The Hong Kong Polytechnic UniVersity,
Hong Kong, P. R. China
daxueliu@sohu.com
Received June 25, 2001
ABSTRACT
Optically active aminonaphthol 3 obtained by condensation of 2-naphthol, benzaldehyde, and (S)-methylbenzylamine followed by N-methylation
was found to catalyze the enantioselective ethylation of aryl aldehydes to secondary alcohols with high enantioselectivities (up to 99.8%) at
room temperature.
Catalytic asymmetric carbon-carbon bond formation is one
of the most active research areas in organic synthesis.1 In
this field, asymmetric additions of diethyl zinc (Et2Zn) to
aldehydes using catalytic amount of chiral catalysts have
attracted much attention.2 Numerous efforts of using chiral
ligands such as â-amino alcohols,3 amino thiols,4 pyridyl
alcohols,5 amines,6 aminonaphthol,7 o-hydroxylbenzylamines,8
BINOL,9 and metal complexes of them have been reported.10
The racemic aminonaphthol synthesized from condensation
of 2-naphthol with benzaldehyde and alkylamine must be
resolved through its diastereoisomeric tartaric acid salts to
obtain the optically active form.7 A practical asymmetric
synthesis of optically pure aminonaphthols is a challenging
endeavor.
† Lanzhou University.
(4) (a) Anderson, J. C.; Harding, M. Chem. Commun. 1998, 393. (b)
Rijnberg, E.; Jastrzebski, J. T. B. H.; Janssen, M. D.; Boersma, J.; Van
Koten, G. Tetrahedron Lett. 1994, 35, 6521.
(5) (a) Bolm, C.; Zehnder, M.; Bur, D. Angew. Chem., Int. Ed. Engl.
1990, 29, 205. (b) Ishizaki, M.; Fujita, K.; Shimamoto, M.; Hoshino, O.
Tetrahedron: Asymmetry 1994, 5, 411.
(6) (a) Chelucci, G.; Conti, S.; Falorni, M.; Giacomelli, G. Tetrahedron
1991, 47, 8251. (b) Conti, S.; Falorni, M.; Giacomelli, G.; Soccolini, F.
Tetrahedron 1992, 48, 8993.
(7) Cardellicchio, C.; Ciccarella, G.; Naso, F.; Perna, F.; Tortorella, P.
Tetrahedron 1999, 55, 14685.
(8) Palmieri, G. Tetrahedron: Asymmetry 2000, 11, 3361.
(9) (a) Yang, X. W.; Sheng, J. H.; Da, C. S.; Wang, H. S.; Su, W.; Wang,
R.; Chan, A. S. C. J. Org. Chem. 2000, 65, 295. (b) Yang, X. W.; Su, W.;
Liu, D. X.; Wang, H. S.; Sheng, J. H.; Da, C. S.; Wang, R.; Chan, A. S. C.
Tetrahedron 2000, 56, 3511.
‡ The Hong Kong Polytechnic University.
(1) (a) Qian, Y. L.; Chan, A. S. C. Organometallic Chemistry and
Catalysis; Chemical Industry Press: Beijing, 1997; pp 107-264. (b) Corey,
E. J.; Guzman-Perez, A. Angew. Chem., Int. Ed. Engl. 1998, 37, 388. (c)
Chan, A. S. C.; Zhang, F. Y.; Yip, C. W. J. Am. Chem. Soc. 1997, 119,
4080. (d) Wang, R.; Yang, X. W. Huaxue 1996, 54, 169.
(2) For reviews see: (a) Noyori, R.; Kitamura, M. Angew. Chem., Int.
Ed. Engl. 1991, 30, 49. (b) Soai, K.; Niwa, S. Chem. ReV. 1992, 92, 833.
(c) Knochel, P.; Singer, R. D. Chem. ReV. 1993, 93, 2117.
(3) (a) Kitamura, M.; Suga, S.; Kawai, K.; Noyori, R. J. Am. Chem.
Soc. 1986, 108, 6071. (b) Soai, K.; Ookawa, A.; Kaba, T.; Ogawa, K. J.
Am. Chem. Soc. 1987, 109, 7111. (c) Dai, W. M.; Zhu, H. J.; Hao, X. J.
Tetrahedron: Asymmetry 1996, 7, 1245. (d) Bringmann, G.; Breuning, M.
Tetrahedron: Asymmetry 1998, 9, 667. (e) Cho, B. T.; Chun, Y. S.
Tetrahedron: Asymmetry 1998, 9, 1489.
10.1021/ol016341e CCC: $20.00 © 2001 American Chemical Society
Published on Web 07/25/2001

Scheme 1
ee values (99.8%) were obtained with the tertiary amino-
naphthol 3.
Table 1. Diethyl Zinc Addition to Aldehydes in the Presence
of Chiral Aminonaphthols
entry
cat.
R
yield (%)a
ee (%)b
configc
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
1
1
1
1
1
1
1
2
2
2
2
2
2
2
3
3
3
3
3
3
H
97
90
87
88
82
86
70
96
91
89
86
84
88
76
95d
96d
97d
98d
86d
96d
72
92
80
87
85
65
84
33
46
46
28
30
32
23
99.4
99.8
52
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
p-Me
p-OMe
p-Cl
m-Me
o-OMe
m-OMe
H
p-Me
p-OMe
p-Cl
m-Me
o-OMe
m-OMe
H
Figure 1.
In this paper, we wish to report the application of optically
active aminonaphthols 1-3 in enantioselective additions of
diethylzinc to arylaldehydes. Optically active aminonaphthols
1 and 2 can be obtained by a simple and straightforward
one-pot condensation of the corresponding benzaldehyde and
isobutyric aldehyde with 2-naphthol and (S)-(-)-methylben-
zylamine.11 The S configuration of the R carbon is proved
by X-ray single-crystal analysis (Figure 1). Ligand 3 was
synthesized from the reaction of 1 with paraformaldehyde
and NaBH4 catalyzed by TFA.12
p-Me
p-OMe
p-Cl
p-NO2
m-Me
96
99.8
91
a Isolated yields. b Determined by chiral HPLC (Chiralcel OD). c Con-
figuration of the predominant enantiomer of the product. d Determined by
HPLC analysis.
The relevant results of the enantioselective addition of Et2-
Zn to aromatic aldehydes13 in Table 1 showing the highest
In summary, the main distinctive features of these ami-
nonaphthols are represented by an economical and simple
(10) (a) Zhang, F. Y.; Chan, A. S. C. Tetrahedron: Asymmetry 1997, 8,
3651. (b) Zhang, F. Y.; Yip, C. W.; Cao, R.; Chan, A. S. C. Tetrahedron:
Asymmetry 1997, 8, 585. (c) Seebach, D.; Beck, A. K.; Schmidt, B.; Wang,
Y. M. Tetrahedron 1994, 50, 4363. (d) Weber, B.; Seebach, D. Tetrahedron
1994, 50, 7473. (e) Schmidt, B.; Seebach, D. Angew. Chem., Int. Ed. Engl.
1991, 30, 1321. (f) P. B. Rheiner, H. Sellner, D. Seebach, HelV. Chem.
Acta 1997, 80, 2027.
(11) 1-((S)-Phenyl(((1′S)-1′-phenylethyl)amino)methyl)-2-naphthol (1).
Benzaldehyde (1.11 g, 10 mmol) was added to a solution of 2-naphthol
(1.00 g, 7.00 mmol) in 2 mL of ethanol. (S)-(-)-Methylbenzylamine (0.85
g, 7.00 mmol) was added dropwise to this solution with cooling to 0 °C.
The mixture was stirred at room temperature for 6 days. The precipitate
was recrystallized in methanol/acetone(3:1) after removal of ethanol in
reduced pressure. A prism crystal was obtained (1.73 g, 70%, 98% ee
2734
Org. Lett., Vol. 3, No. 17, 2001

asymmetric synthesis, involving cheap starting materials,
which merge to give a more complex compound without
side-products.
Acknowledgment. We are grateful to the National
Natural Science Foundation of China (no. 29972016), The
Hong Kong Polytechnic University ASD Fund, and the
Teaching and Research Award Program for Outstanding
Young Teachers in Higher Education Institutes of the
Ministry of Education of China for financial support.
determined by HPLC analysis using Chiralcel OD column): mp 147-148
°C; IR (KBr) 3311, 1621, 1236, 1095, 735, 699 cm-1; 1H NMR (400 MHz,
CDCl3) δ 1.51 (d, 3H, J ) 6.7 Hz), 1.53 (br s, 1H), 3.93 (q, 1H, J ) 6.7
Hz), 5.49 (s, 1H), 7.24-7.79 (m, 16H); MS (M + 1) 354.12. 1-((S)-Propyl-
(((1′S)-1′-phenylethyl)amino)methyl)-2-naphthol (2). The use of isobutyric
aldehyde with the same synthesis process as above produced a piece crystal
(yield 71%, >99.8% ee): mp 134-135 °C; IR (KBr) 3336, 1619, 1235,
Supporting Information Available: Detail spectra and
crystal data for ligands 1-3. This material is available free
of charge via the Internet at http://pubs.acs.org.
1
1101, 769, 700 cm-1; H NMR (200 MHz, CDCl3) δ 0.74 (d, 3H, J ) 5
Hz), 0.98 (d, 3H, J ) 6.7 Hz), 1.49 (d, 3H, J ) 6.7 Hz), 2.18 (senary, 1H,
J ) 6.7 Hz), 3.00 (t, 1H, J ) 6.7 Hz), 2.50 (br s, 1H), 4.15 (d, 1H, J ) 6
Hz), 7.05-7.70 (m, 11H), 13.01 (br s, 1H); MS (M + 1)320.16.
OL016341E
(12) 1-((S)-Phenyl(((1′S)-1′-phenylethyl)methylamino)methyl)-2-naph-
thol (3). To a solution of 1 (445 mg, 1.258 mmol) in 10 mL of THF were
added paraformaldehyde (377 mg, 12.58 mmol) and NaBH4 (476 mg, 12.58
mmol). Then the solution of THA (5 mL) in 30 mL of THF was added
dropwise (4 drops/min) under stirring acutely at room temperature; 351
mg (76% yield, >98% ee) was obtained after acid workup: mp 128-129
(14) Crystal data for 1: C25H23NO, MW ) 353.44, monoclinic, space
group P21/n, a ) 14.494(3), b ) 17.802(3), c ) 16.530(3) Å; R ) 90°, â
) 113.136(4)°, γ ) 90°, U ) 3922.1 Å3, T ) 294 K, Z ) 8, Dc ) 1.197
g cm-1, µ ) 0.072 mm-1, λ ) 0.9857-0.9787 Å, F(000) 1504, crystal
size 0.30 × 0.22 × 0.20 mm3, 9055 independent reflections (Rint ) 0.0542),
26195 reflections collected; refinement method, full-matrix least-squares
1
°C; IR(KBr) 3351, 1621, 1469, 1313 cm-1; H NMR (200 MHz, CDCl3)
δ 1.57 (d, 3H, J ) 6.6 Hz), 2.14 (s, 3H), 3.75 (q, 1H, J ) 6.6 Hz), 5.35 (s,
1H), 7.21-7.81 (m, 16H), 13.82 (br s, 1H); MS (M + 1) 368.16.
(13) Typical Procedure for the Asymmetric Addition of Et2Zn to
Benzaldehyde. To a solution of optically active aminonaphthol (1) (50.3
mg, 0.142 mmol) in toluene (1.4 mL) was added dropwise a solution of
Et2Zn (2.84 mL, 1 M in hexane) at room temperature. After the mixture
stirred for 1 h, benzaldehyde (100 mg, 0.947 mmol) was added at room
temperature, and the reaction was stirred for 24 h at room temperature.
Optically active 1-phenylpropan-1-ol (124 mg, 97%) was obtained after
acid workup and purification by silica gel TLC.
on F2; goodness-of-fit on F2 ) 0.741; final R indices [I > 2σ(I)] R1
)
0.0506, wR2 ) 0.1323, SADABS. Crystal data for 2: C22H25NO, MW )
319.43, orthorhombic, space group P212121, a ) 9.7303(14), b ) 10.5655-
(15), c ) 35.924(5) Å; R ) 90°, â ) 90°, γ ) 90°, U ) 3699.2(9) Å3, T
) 294 K, Z ) 8, Dc ) 1.149 g cm-1, µ ) 0.069 mm-1, λ ) 0.9849-
0.9795 Å, F(000) 1376, crystal size 0.30 × 0.22 × 0.22 mm3, 8536
independent reflections (Rint ) 0.0513), 25080 reflections collected;
refinement method, full-matrix least-squares on F2; goodness-of-fit on F2
) 0.739; final R indices [I > 2σ(I)] R1 ) 0.0460, WR2 ) 0.1190, SADABS
(semiempirical).
Org. Lett., Vol. 3, No. 17, 2001
2735