Asymmetric synthesis XXVIII: Novel chiral aminophosphine phosphinite ligand and its application in homogeneous catalytic asymmetric hydrogenation of dehydroamino acid derivatives

Article abstract of DOI:10.1055/s-1998-1821

Novel chiral aminophosphine phosphinite, DPAMPP was designed and synthesized from (1S,2R)-1,2-diphenyl-2-aminoethanol. Its cationic rhodium complex has been found to be an excellent catalyst for enantioselective hydrogenation of dehydroamino acids (more t

Full text of DOI:10.1055/s-1998-1821

August 1998
SYNLETT
847
Asymmetric Synthesis XXVIII: Novel Chiral Aminophosphine Phosphinite Ligand and Its
Application in Homogeneous Catalytic Asymmetric Hydrogenation of Dehydroamino Acid
Derivatives
a
a
b
Aiqiao Mi, * Rongliang Lou, Yaozhong Jiang, * Jingen Deng, Yong Qin, Fangmin Fu, Zhi Li, Wenhao Hu, and Albert S. C. Chan *
a
Union Laboratory of Asymmetric Synthesis, Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, China
b
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong
Fax: (0086) (028) 5223978, E-mail: clf@mail.sc.cninfo.net
Received 26 May 1998
Abstract: Novel chiral aminophosphine phosphinite, DPAMPP was
designed and synthesized from (1S,2R)-1,2-diphenyl-2-aminoethanol.
Its cationic rhodium complex has been found to be an excellent catalyst
for enantioselective hydrogenation of dehydroamino acids (more than
95.0%e.e.).
Scheme 2
The homogeneous catalytic asymmetric hydrogenation of prochiral
olefins using transition metal complexes containing chiral bidentate
2a
2c
2h
PROLOPHOS, 80; NEtAlaNOP, 48; PINDOPHOS, 90. Besides
this, it was also compared to those achieved with the best well-known
chiral phosphine-rhodium or phosphinite-rhodium catalysts, for
example, the e.e. values (%) of the asymmetric hydrogenation of methyl
ligands is one of the most important advancements in modern organic
1
synthesis. During the last ten years, much attention has been paid to
chiral aminophosphine phosphinite (AMPP) ligands because of their
easiness of preparation. A great variety of chiral AMPPs have been
investigated and used as ligands for rhodium-catalyzed asymmetric
5
6
(Z)-2-acetamidocinnamate are as follows: DuPHOS, 99; DIPAMP, 96;
TRAP, 92; DIOP, 55; CAPP,95.6; BPPFA, 21; Ph-β-Glup, 91.5;
spirOP, 95.7. The phenyl at C(2) of 1 was important for the
enantioselectivity. Pracejus reported that the stereoselectivity was
poor (75%e.e. and 55%e.e. respectively) when (1R,2S)-N,O-
bis(diphenylphosphino)-1-phenyl-2-(N-methyl) aminopropanol (5,
Figure 1) and (R)-N,O-bis(diphenyl-phosphino)-1-phenyl-2-(N-
methyl)aminoethanol (6, Figure 1) were used as ligands.
7
8
9
10
11
2
hydrogenation. However, the development of chiral AMPP for
12
asymmetric hydrogenation has been less successful compared with
chiral phosphine ligand. Far fewer of very notable examples (>90% e.e.)
have been reported.
2b
More recently, we developed a series of chiral ligands derived from
(1R,2S) or (1S,2R)-1,2-diphenyl-2-aminoethanol, and found them to be
3
effective in asymmetric catalytic reactions, for example, diethylzinc
3a,b
3c
addition,
reduction of ketones,
trimethylsilylcyanation of
3d,e
aldehyde.
These results indicated that the backbone of chiral 1,2-
diphenyl-2-aminoethanol is beneficial to asymmetric induction. Here
we reported a novel chiral aminophosphine phosphinite, (1S,2R)-(+)-
N,O-bis(diphenylphosphino)-1,2-diphenyl-2-(N-methyl)aminoethanol
(abbreviated 1S, 2R-DPAMPP, 1), which was derived from (1S,2R)-1,2-
diphenyl-2-aminoethanol, and its application in homogeneous catalytic
asymmetric hydrogenation of dehydroamino acid derivatives.
Compound 1 was conveniently prepared through the reaction
of chlorodiphenylphosphine with the corresponding aminoethanol 2
Figure 1
Extensive studies of the using [Rh(COD)(1)]BF in asymmetric
hydrogenation of
demonstrated that the high enantioselectivity was quite general in more
than 95.0%e.e. The results were shown in Table 1.
4
a variety of dehydroamino acid derivatives
4
( Scheme 1 ).
In conclusion, we have developed a novel, highly effective chiral
aminophosphine phosphinite ligand for the catalytic asymmetric
hydrogenation of dehydroamino acids. The remarkably high catalytic
activity and enantioselectivity of its rhodium complex for the
hydrogenation as well as the ease of preparation indicated a good
potential for wide application. Further studies of its application in
asymmetric reactions are in progress.
Scheme 1
When a cationic rhodium catalyst containing 1 was used in the
asymmetric hydrogenation of methyl (Z)-2-acetamidocinnamate (3) at
Experimental Section
ambient temperature and 50 atm H , the desired methyl (R)-2-
2
Preparation of compound 1 : 100mg of 2 (0.44mmol) was placed in a
10 ml Schlenk flask and degassed by 3 cycles of vacuum/argon. 0.13ml
of triethylamine (0.90mmol) in 3ml of anhydrous benzene (freshly
distilled under nitrogen) was added. The mixture was stirred well with a
magnetic stirrer and the solution was cooled to 0°C in an ice bath. A
solution of 0.16ml of chlorodiphenylphosphine (0.90mmol) in 1ml of
anhydrous benzene was added dropwise to the mixture. After all of the
chlorodiphenylphosphine was added, the ice bath was removed and the
stirring was continue at ambient temperature for 24 h. Filtration of the
triethylammonium chloride followed by flash column chromatography
on silica gel (benzene as eluent) gave 141 mg of 1 (53.9% theoretical
acetamido-3-phenylpropionate (4) was obtained in 98.3%
enantioselective excess (e.e.) and 100% conversion ( Scheme 2 ). The
catalytic activity of this new DPAMPP-rhodium catalyst was
remarkably high. Even though a substrate/catalyst ratio of 10 000 was
used, 100% conversion of methyl (Z)-2-acetamidocinnamate to methyl
2-acetamido-3-phenylpropionate (97.0%e.e.) was observed in 16 h.
To our knowledge, this was the best result among those of AMPPs
2
reported so far. For example, the e.e. values (%) of the asymmetric
hydrogenation of methyl (Z)-2-acetamidocinnamate are as follows:

848
LETTERS
SYNLETT
GC with a Chirasil-L-Val column or chiral HPLC with a Chiralcel OD
column.
Acknowledgement We thank the National Natural Science Foundation
of China (No.29790124) and Union Laboratory of Asymmetric
Synthesis in Chengdu for financial support of this study.
References
(1) Noyori, R. Asymmetric Catalysis in Organic Synthesis; Wiley:
New York, 1994; pp 16.
(2) (a) Cesarotti, E.; Chiesa, A.; D’Alfonso, G. Tetrahedron Lett.
1982, 23, 2995. (b) Pracejus, G.; Pracejus, H. J. Mol. Cat. 1984,
24, 227. (c) Karim, A.; Mortreux, A.; Petit, F.; Buono, G.; Peiffer,
G. J. Organomet. Chem. 1986, 317, 93. (d) Karim, A.; Mortreux,
A.; Petit, F. J. Organomet. Chem. 1986, 312, 375. (e) Dobler, Chr.;
Kreuzfeld, H. J.; Pracejus, H. J. Organomet. Chem. 1988, 344, 89.
(f) Krause, H. W.; Kreuzfeld, H. J.; Dobler, Chr. Tetrahedron:
Asymmetry 1992, 3, 555. (g) Dobler, Chr.; Schmidt, U.; Krause, H.
W.; Kreuzfeld, H. J.; Michalik,M. Tetrahedron: Asymmetry 1995,
6, 385. (h) Kreuzfeld, H. J.; Schmidt, U.; Dobler, Chr.; Krause, H.
W. Tetrahedron: Asymmetry 1996, 7, 1011.
20
yield) as a white solid. Analytic data: m.p.=94~96°C. [α] = +37.6
D
(3) (a) Li, S. J.; Jiang, Y. Z.; Mi, A. Q. Tetrahedron: Asymmetry 1992,
3, 1467. (b) Li, S. J.; Jiang, Y. Z.; Mi, A. Q.; Yang, G. S. J. Chem.
Soc. Perkin Trans.I 1993, 885. (c) Jiang, Y. Z.; Qing, Y.; Mi, A. Q.
Tetrahedron: Asymmetry 1994, 5, 1211. (d) Jiang, Y. Z.; Zhou, X.
G.; Hu, W. H.; Wu, L. J.; Mi,A.Q. Tetrahedron: Asymmetry 1995,
6, 405. (e) Jiang, Y. Z.; Zhou, X. G.; Hu, W. H.; Li, Z.; Mi, A. Q.
Tetrahedron: Asymmetry 1995, 6, 2915.
31
(c=0.218, benzene). P-NMR (CDCl ): 65.9(s, P
), 113.3(s, P
(O)
3
(N)
1
)ppm. H-NMR (CDCl ): 2.21(d, 3H, J =2.4Hz, CH ), 4.94(dd, 1H,
3
P-H
3
J
=10.0Hz, J =14.4Hz, NCH), 5.57(dd, 1H, J =10.4Hz, J
P-H H-H P-
H-H
=8.4Hz, OCH), 6.53~7.74(m, 30H, 6Ph)ppm.
H
Preparation of cationic catalyst [Rh(COD)(1)]BF in situ: In an
argon-filled dry box, 9.2mg of [Rh(COD)Cl] (0.0187 mmol), 7.4mg of
AgBF (0.0380 mmol) and 2 ml of anhydrous THF (freshly distilled
under nitrogen) were placed in a 5ml Schlenk flask and stirred for 3 h.
The formed silver chloride was filtered off. To the filtered solution was
added 22.4mg of 1 in 1ml of anhydrous THF. After 1 h of stirring, the
4
2
4
(4) Mi, A. Q.; Lou, R. L.; Qin, Y.; Jiang, Y. Z.; Hu, W. H.; Chan, A. S.
C. CN Appl. 97 1 07608.1.
(5) Burk, M. J. J. Am. Chem. Soc. 1991, 113, 8518.
(6) Knowles, W. S. J. Chem. Edu. 1986, 63, 222.
THF solution of [Rh(COD)(1)]BF (2.6ml volume, C=0.014 mM) thus
4
obtained was ready to use for asymmetric hydrogenation.
(7) Sawamura, M.; Kuwano, R.; Ito, Y. J. Am. Chem. Soc. 1995, 117,
A general procedure for asymmetric hydrogenation: In a 50 ml
stainless steel autoclave was added appropriate substrate (0.114mmol),
0.08ml of catalyst (0.00112 mmol, prepared according to the above-
mentioned procedure) and 1ml of degassed MeOH under the argon
atmosphere. Subsequently, the reactor was connected with a hydrogen
cylinder. The argon atmosphere was replaced with hydrogen by 3 cycles
of pressurizing. The hydrogenation was run under the reaction
conditions given in text. The solvent was removed under reduced
pressure. The e.e. values and conversion rates were determined by chiral
9602.
(8) Kagan, H. B.; Dang, T. P. J. Am. Chem. Soc. 1972, 94, 6429.
(9) Ojima, I.; Yoda, N. Tetrahedron Lett. 1980, 21, 1051.
(10) Hayashi, T.; Kumada, M. Acc. Chem. Res. 1982, 15, 395.
(11) Selke, R.; Pracejus, H. J. Mol. Cat. 1986, 37, 213.
(12) Chan, A. S. C.; Jiang, Y. Z.; Hu, W. H.; Mi, A. Q.; Yan, M.; Pai, C.
C.; Sun, J.; Lau, C. P.; Lou, R. L.; Deng, J. G. J. Am. Chem. Soc.
1997, 119, 9570.