Asymmetric hydrogenation of the C{double bond, long}O bond with the recycling of an organometal catalyst deposited on a solid organic polyelectrolyte

Full text of DOI:10.1016/j.mencom.2007.01.008

Mendeleev
Communications
Mendeleev Commun., 2007, 17, 20–21
Asymmetric hydrogenation of the C=O bond with the recycling of an
organometal catalyst deposited on a solid organic polyelectrolyte
Eugenia V. Starodubtseva, Olga V. Turova, Maxim G. Vinogradov,* Vladimir A. Ferapontov,
Ilya V. Razmanov, Sergei G. Zlotin and Alexander S. Kucherenko
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 495 135 5328; e-mail: ving@ioc.ac.ru
DOI: 10.1016/j.mencom.2007.01.008
The asymmetric hydrogenation of methyl levulinate to chiral γ-valerolactone has been performed with the recycling of a RuII–BINAP
catalyst deposited on a solid organic polyelectrolyte; enantioselectivity up to 99% ee has been achieved at high conversion of
substrate after three recycles of the catalyst.
The recycling of expensive transition metal chiral catalysts
(TMCCs) is of considerable current interest. An approach to
solve the problem of the catalyst recovery is the immobilization
of TMCCs on mineral or polymer carriers.1–6 However, it often
gives rise to a decrease in catalytic reaction rate. Recently, a
method of TMCC recycling by ‘immobilization’ in organic salt
solutions including ionic liquids has attracted considerable
attention.7–14 Another promising approach to TMCC recycling
is based on the use of ionic polymers, polyelectrolytes (PEs), as
catalyst carriers. In particular, an efficient catalyst system for
asymmetric aldol reaction between aldehydes and ketones based
on L-proline supported on organic PE, poly(diallyldimethylammo-
nium salt) 1, has been recently elaborated.15 This heterogeneous
system retained high activity after several reaction cycles without
decreasing enantioselectivity.
Table 1 Asymmetric catalytic hydrogenation of ketoester 2 with the re-
cycling of the catalyst deposited on PE 1a–c.a
Composition of the
reaction products (mol%)
Series
of runs
Reaction Conversion
PE
cycle
of 2 (%)
ee (S)
3b
4b
(%)c
I
—
1a
1b
1c
1
1
1
1
72
63
74
72
0
100
81
88
99
19
12
0
98.5
98.5
99
100
II
1b
1b
1b
1
2
3
99
12
14
1
21
20
99
79
80
97.5
98
98.5
III
1c
1c
1c
1c
1c
1
2
3
4
5
100
98
94
52
22
0
1
1
2
24
100
99
98
98
76
99
99
98.5
98
98
H2C
CH2
n
aSolvent: abs. MeOH, [2] = 1.6 M, catalyst system: RuII–(S)-BINAP–HCl;
PE, 100 mg, [2]:[Ru] = 200; 40 atm. (H2), 40 °C, 2 h (series of runs I);
60 atm (H2), 60 °C, 3 h (series of runs II and III). bNMR data. cGLC data.
a X = Cl, n = 1800–2250
b X = BF4, n = 1800–2250
c X = PF6, n = 1800–2250
d X = PF6, n = 450–900
N
X
1a–d
It was found that the use of PE 1b or 1c did not reduce sub-
strate 2 conversion compared with a control experiment performed
under homogeneous conditions, whereas in the case of PE 1a
the conversion of 2 decreased by ~10% (Table 1, series I). The
4:3 product ratio depended on the PE anion nature increasing in
the order: 1a (81:19) < 1b (88:12) < 1c (> 99:1).
Here, we report on the first use of solid organic PEs bearing
no additional components† for TMCC recycling. The asymmetric
hydrogenation of methyl levulinate 2 to γ-hydroxyvaleric acid
methyl ester 3 in the presence of the RuII–BINAP–HCl–PE
catalyst system was used as a model reaction. The cyclization
of hydroxyester 3 under reaction conditions afforded chiral
γ-valerolactone 4, a versatile building block that can be used
for the synthesis of medications and other useful products
(Scheme 1).
PEs 1b and 1c, which showed better results, were applied as
carriers in the catalyst recycling experiments. We found that the
use of recovered RuII–BINAP–1b catalyst system resulted in a
decrease of the conversion of 2; the enantioselectivity remained
high even after three cycles (series II). The best results were
obtained in experiments with PE 1c having hexafluorophos-
phate anions (series III).‡ The second and third hydrogenation
cycles proceeded with an only slight decrease of the substrate
conversion (by 2 and 6%, respectively). The activity of the
catalyst deposited on PE 1c noticably fell in the fourth reaction
cycle; nevertheless, the enantioselectivity remained unchanged
in at least five cycles. The length of the PE chain plays an
important role. The use of shorter-chain PE 1d with the same
counter-ion (PF6–) led to a substantial decrease of the substrate
conversion in the first hydrogenation cycle.
COOMe
H2 /RuII–BINAP–HCl
1
O
2
COOMe
*
*
+
O
O
OH
3
4
Scheme 1
†
Earlier,13 the asymmetric hydrogenation of C=C and C=O bonds was
studied in the presence of Rh- and Ru-containing recyclable hetero-
geneous systems consisting of PE in which both the ionic liquid and
TMCC are incorporated.
In each cycle, after the addition of MeOH to solid PE
containing an adsorbed catalyst, the solvent grew yellow, the
– 20 –

Mendeleev Commun., 2007, 17, 20–21
colour typical of RuII bisphosphine dihalide complex solution.16
We believe that the proposed approach to recycling organo-
metal catalysts by using solid organic PE carriers may be used
in other TMCC-catalysed reactions.
Evidently, an equilibrium between adsorbed and desorbed cata-
lysts was established in the reaction mixture, and both forms
may be active in the hydrogenation reaction. The equilibrium
shifted towards a supported catalyst upon MeOH removal
(evaporation). No marked leaching of the catalyst deposited on
PE 1c was observed during product extraction with hexane.‡
This work was supported by the Presidium of the Russian
Academy of Sciences (Basic Research Programme 08) and by
the Russian Foundation for Basic Research (project no. 06-03-
32603).
‡
Asymmetric hydrogenation of 2 with the recycling of a RuII–BINAP
References
catalyst. Commercial (S)-BINAP (Fluka) and (COD)Ru(2-methylallyl)2
(Acros) were used. Polymers 1a–c were synthesised as described earlier;15
PE 1d was similarly prepared from poly(diallyldimethylammonium)
chloride (Aldrich) (MM 100000–200000 Da) 20% aqueous solution by
the anion exchange reaction. Methyl ester 2 was prepared from levulinic
acid (Acros) according to a standard procedure. MeOH was dehydrated
and distilled under argon before use. Ar was purified by passing through
columns packed with a nickel–chromium catalyst, copper on Kieselguhr
(80 °C), and molecular sieves (4 Å). H2 was purified by passing through
columns packed with a nickel–chromium catalyst and molecular sieves
(4 Å). All manipulations with the catalyst, including its regeneration,
were carried out under purified argon. The conversion of keto ester 2
and the composition of hydrogenation products were determined by
1H NMR spectroscopy on a Bruker AM-300 instrument. Enantiomeric
GLC analysis of lactone 4 was performed on a Biochrom-21 chromato-
graph, a quartz capillary column (30 m×0.25 mm×0.25 µm) coated with
2,6-dipentyl-3-trifluoroacetyl-β-cyclodextrine, He (1 ml min–1), 130 °C.
Retention times of the test components (min): CH4 (unsorbed), 3.5;
(R)-4, 12; (S)-4, 15.3.
1
2
W. Tang and X. Zhang, Chem. Rev., 2003, 103, 3029.
E. Cariati, D. Roberto, R. Ugo and E. Lucenti, Chem. Rev., 2003, 103,
3401.
3
4
5
C. Gennan and U. Piarulli, Chem. Rev., 2003, 103, 3071.
C. Saluzzo and M. Lemaire, Adv. Synth. Catal., 2002, 344, 915.
P. Guerreiro, V. Ratovelomanana-Vidal, J.-P. Genet and P. Dellis,
Tetrahedron Lett., 2001, 42, 3423.
6
7
8
9
D. J. Bayston, J. L. Fraser, M. R. Ashton, A. D. Baxter, M. E. C. Polywka
and E. Moses, J. Org. Chem., 1998, 63, 3137.
Y. Chauvin, L. Mussmann and H. Olivier, Angew. Chem., Int. Ed.
Engl., 1995, 34, 2698.
A. L. Monteiro, F. K. Zinn, R. F. de Souza and J. Dupont, Tetrahedron:
Asymmetry, 1997, 8, 177.
A. Berger, R. F. de Souza, M. R. Delgado and J. Dupont, Tetrahedron:
Asymmetry, 2001, 12, 1825.
10 R. A. Brown, P. Pollet, E. McKoon, C. A. Eckert, C. L. Liotta and
P. G. Jessop, J. Am. Chem. Soc., 2001, 123, 1254.
11 S. Guernik, A. Wolfson, M. Herskowitz, N. Greenspoon and S. Geresh,
Chem. Commun., 2001, 2314.
PE 1c (100 mg), (COD)Ru(2-methylallyl)2 (4.8 mg, 0.015 mmol) and
(S)-BINAP (9.4 mg, 0.15 mmol) were placed in a glass tube, which was
evacuated and filled with argon three times; then, preliminary degassed
solutions of methyl levulinate (490 mg, 3 mmol) in MeOH (2 ml) and
3 M HCl in anhydrous MeOH (50 µl, 0.15 mmol) were added. The tube
was placed in a stainless-steel autoclave (50 ml) filled with argon; the
autoclave was pressured with hydrogen up to 60 atm, and the reaction
mixture was agitated with a magnetic stirrer at 60 °C for 3 h. Methanol
was distilled off; the products were extracted with degassed hexane
(3×5 ml), and combined extracts were passed through a 1 cm thick silica
bed. The solvent was removed, and the products were analysed by NMR
spectroscopy and GLC. The tube containing the catalyst deposited on PE
was evacuated, filled with argon and used in subsequent hydrogenation
experiments; 30 µl of 3 M methanolic HCl were added in each sub-
sequent cycle.
12 H. L. Ngo, A. Hu and W. Lin, Chem. Commun., 2003, 1912.
13 A. Wolfson, I. F. J. Vankelecom and P. A. Jacobs, Tetrahedron Lett.,
2003, 44, 1195.
14 E. V. Starodubtseva, M. G. Vinogradov, V. A. Pavlov, L. S. Gorshkova
and V. A. Ferapontov, Izv. Akad. Nauk, Ser. Khim., 2004, 2079 (Russ.
Chem. Bull., Int. Ed., 2004, 53, 2172).
15 A. S. Kucherenko, M. I. Struchkova and S. G. Zlotin, Eur. J. Org.
Chem., 2006, 2000.
~
16 J. P. Genêt, V. Ratovelomanana-Vidal, M. C. Cano de Andrade, X. Pfister,
P. Guerreiro and J. Y. Lenoir, Tetrahedron Lett., 1995, 36, 4801.
Received: 19th July 2006; Com. 06/2755
– 21 –