Preparation of Optically Active Cyclic Carbonates and 1,2-Diols via Enantioselective Hydrogenation of α-Methylenedioxolanones Catalyzed by Chiral Ruthenium(II) Complexes

Article abstract of DOI:10.1021/jo961413e

The enantioselective hydrogenation of α-methylene-1,3-dioxolan-2-ones catalyzed by chiral (diphosphine)ruthenium complexes leads to optically active cyclic carbonates with high enantioselectivities.Their hydrolysis in methanol in the presence of potassium carbonate quantitatively affords optically active 1,2-diols.

Full text of DOI:10.1021/jo961413e

J . Org. Chem. 1996, 61, 8453-8455
8453
P r ep a r a tion of Op tica lly Active Cyclic Ca r bon a tes a n d 1,2-Diols
via En a n tioselective Hyd r ogen a tion of r-Meth ylen ed ioxola n on es
Ca ta lyzed by Ch ir a l Ru th en iu m (II) Com p lexes
Pierre Le Gendre, Thomas Braun, Christian Bruneau,* and Pierre H. Dixneuf*
Laboratoire de Chimie de Coordination Organique, URA CNRS 415, Campus de Beaulieu,
Universite´ de Rennes 1, 35042 Rennes Cedex, France
Received J uly 24, 1996X
The enantioselective hydrogenation of R-methylene-1,3-dioxolan-2-ones catalyzed by chiral (diphos-
phine)ruthenium complexes leads to optically active cyclic carbonates with high enantioselectivities.
Their hydrolysis in methanol in the presence of potassium carbonate quantitatively affords optically
active 1,2-diols.
Optically active carbonates offer selective routes to
polyfunctional molecules of interest. The ring-opening
of saturated cyclic carbonates by O- and N-nucleophiles
gives access to linear carbonates and urethanes,1 whereas
the cleavage by carbonucleophiles leads to selective
transformations into hydroxy esters.2 Cyclic carbonates
are now outstanding monomers for the preparation of
polycarbonates via ring-opening polymerization,3 and
they have been widely used for the preparation and the
protection of polyhydroxylated compounds4,5 and carbo-
hydrates.6 The preparation of optically pure cyclic
carbonates is based on the cyclization of diols found in
natural compounds or resulting from asymmetric dihy-
droxylation of olefins, with phosgene1 or activated car-
bonates.1,7 The insertion of CO2 into epoxides and allylic
epoxides catalyzed by zinc(II)8 or palladium(0)9 also
provides optically active cyclic carbonates. The latter
have also been prepared via diastereoselective cyclization
of [(alkenyloxy)carbonyl]oxy radicals,10 whereas the treat-
ment of â,γ-epoxycarbamates with various acids4b,6 has
led to the stereoselective formation of hydroxylated cyclic
carbonates.
hydrogenation of 5-methylene-1,3-dioxolan-2-ones 2a -
c, catalyzed by chiral ruthenium complexes and the
efficient synthesis of the cyclic carbonates 3a -c of high
enantiomeric purity, and we show that their hydrolysis
in methanol in the presence of potassium carbonate
affords the optically active 1,2-diols 4a -c (Scheme 1).
Resu lts a n d Discu ssion
En a n tioselective Hyd r ogen a tion of 5-Meth ylen e-
1,3-d ioxola n -2-on es. The starting carbonates 2a -c
were prepared in 97% (2a ),11 93% (2b), and 80% (2c)
yields in one step from the reaction of CO2 (5 MPa) with
the tertiary 1,1-disubstituted prop-2-yn-1-ols 1a -c con-
taining two identical substituents at C(1), in the presence
of tributylphosphine as catalyst.
The enantioselective hydrogenation of carbonates 2
was attempted with a variety of chiral ruthenium com-
plexes containing an optically active diphosphine ligand.
A typical hydrogenation was performed from 0.25 g (2
mmol) of carbonate 2, 0.01 mmol of ruthenium catalyst,
and 10 mL of dichloromethane, which were introduced
under inert atmosphere into a 125 mL autoclave. The
hydrogenation was then carried out under an initial
pressure of hydrogen (2-10 MPa), and the complete
conversion of the starting carbonate 2 was determined
by gas chromatography. The 1H NMR analyses of the
reaction products showed that the saturated cyclic car-
bonates 3 were the sole products of the reaction, indicat-
ing that the hydrogenation was very selective and no
cleavage of the cyclic carbonate took place. They were
isolated by distillation under reduced pressure in more
than 85% yield. The enantiomeric excesses of carbonates
3, obtained from a variety of optically active ruthenium
catalysts12 and determined by gas chromatography with
a chiral Lipodex capillary column, were in the range 84-
97% (Table 1).
The straightforward synthesis of R-methylene carbon-
11
ates from tertiary propargylic alcohols and CO2 cata-
lyzed by phosphine has offered a new step toward
optically active cyclic carbonates based on the enantio-
selective hydrogenation of their exocyclic CdC double
bond. We report here the first examples of asymmetric
* To whom correspondence should be addressed. Phone: 33 02 99
28 62 80. Fax: 33 02 99 28 69 39. E-mail: dixneuf@univ-rennes1.fr.
X Abstract published in Advance ACS Abstracts, November 1, 1996.
(1) Shaikh, A. G., Sivaram, S. Chem. Rev. 1996, 96, 951.
(2) Nicolaou, K. C.; Couladouros, E. A.; Nantermet, P. G.; Renaud,
J .; Guy, R. K.; Wrasidlo, W. Angew. Chem., Int. Ed. Engl. 1994, 33,
1581.
(3) Takata, T.; Kanamaru, M.; Endo, T. Macromolecules 1996, 29,
2315.
(4) (a) Roush, W. R.; Lesur, B. M. Tetrahedron Lett. 1983, 24, 2231.
(b) Corey, E. J .; Hopkins, P. B.; Munroe, J . E.; Marfat, A.; Hashimoto,
S. J . Am. Chem. Soc. 1980, 102, 7986.
(5) Bongini, A.; Cardillo, G.; Orena, M.; Porzi, G.; Sandri, S. J . Org.
Chem. 1982, 47, 4626.
(6) Roush, W. R.; Brown, R. J .; Dimare, M. J . Org. Chem. 1983, 48,
5033.
(7) (a) Burk, R. M.; Roof, M. B. Tetrahedron Lett. 1993, 34, 395. (b)
Kang, S.; J eon, J .; Nam, K.; Park, C.; Lee, H. Synth. Commun. 1994,
24, 305.
All the ruthenium catalyst precursors gave very good
results in terms of activity and enantioselectivity. For
the hydrogenation of 2a , bis(trifluoroacetate)(diphos-
phine)ruthenium complexes appeared to be the most
efficient catalysts precursors as enantioselectivities lo-
(8) Kisch, H.; Millini, R.; Wang, I. Chem. Ber. 1986, 119, 1090.
(9) Trost, B. M.; Angle, S. R. J . Am. Chem. Soc. 1985, 107, 6123.
(10) (a) Beckwith, A. L. J .; Davison, I. G. E. Tetrahedron Lett. 1991,
32, 49. (b) Newcomb, M.; Dhanabalasingam, B. Tetrahedron Lett. 1994,
35, 5193.
(11) (a) Fournier, J .; Bruneau, C.; Dixneuf, P. H. Tetrahedron Lett.
1989, 30, 3981. (b) J oumier, J . M.; Fournier, C.; Bruneau, C.; Dixneuf,
P. H. J . Chem. Soc., Perkin Trans. 1 1991, 3271.
(12) (a) Doucet, H.; Le Gendre, P.; Bruneau, C.; Dixneuf, P. H.;
Souvie, J . C. Tetrahedron: Asymmetry 1996, 7, 525. (b) Geneˆt, J . P.;
Pinel, C.; Ratovelomanana-Vidal, V.; Mallart, S.; Pfister, X.; Bischoff,
L.; Cano de Andrade, M. C.; Darses, S.; Galopin, C.; Laffitte, J . A.
Tetrahedron: Asymmetry 1994, 5, 675. (c) Ohta, T.; Takaya, H.; Noyori,
R. Inorg. Chem. 1988, 27, 566. (d) Heiser, B.; Broger, E. A.; Crameri,
Y. Tetrahedron: Asymmetry 1991, 2, 51.
S0022-3263(96)01413-2 CCC: $12.00 © 1996 American Chemical Society

8454 J . Org. Chem., Vol. 61, No. 24, 1996
Le Gendre et al.
Sch em e 1
Ta ble 1. Hyd r ogen a tion of Ca r bon a tes 2a -c in to 3a -c Ca ta lyzed by (Dip h osp h in e)Ru (II) Com p lexesa
run
catalyst
compd
H2 (MPa)
T (°C)
time (h)
eeb (%)
12a
12a
1
2
3
4
5
6
7
8
9
((S)-Binap)Ru(O2CCF3)2
((R)-Binap)Ru(O2CCF3)2
((R)-Binap)RuBr2
(+)-3a
(-)-3a
(-)-3a
(-)-3a
(-)-3a
(-)-3a
(-)-3a
(+)-3c
(-)-3c
(+)-3c
(-)-3c
(-)-3b
2
10
10
10
10
10
10
10
10
5
20
20
50
50
20
20
50
50
50
20
50
50
72
18
20
20
17
17
17
20
20
20
68
48
95
95
90
93
94
97
83c
84
80c
88
89
89
12b
12c
[((R)-Binap)RuCl2]NEt3
12d
((R)-MeO-Biphep)Ru(O2CCF3)2
((R)-Biphemp)Ru(O2CCF3)2
12d
((R)-Binap)Ru(O2CCF3)2
((S)-Binap)Ru(O2CCF3)2
((R)-Binap)Ru(O2CCF3)2
((S)-Binap)Ru(O2CCF3)2
((R)-Binap)Ru(O2CCF3)2
((R)-Binap)Ru(O2CCF3)2
10
11
12
2
10
a
b
Reactions carried out in CH2Cl2 with a ratio substrate/catalyst ) 200. ee were determined by gas chromatography with a capillary
column containing a chiral Lipodex phase (25 m × 0.25 mm). c Hydrogenation in methanol.
Ch a r t 1
cated in the range 90-97% were obtained with various
chiral diphosphines such as Binap, MeO-Biphep, or
Biphemp.13 The results in Table 1 show that the com-
plete conversion of the R-methylene carbonate 2a (88%
isolated yield in run 2) was reached in less than 20 h
when the hydrogenation was carried out under 10 MPa
of hydrogen, whereas 72 h were required under a 2 MPa
initial pressure of hydrogen to obtain 3a in 95% ee in
both cases (Table 1, runs 1 and 2). [(R)-Binap)RuCl2]-
NEt3 (Table 1, run 4) and the in situ prepared ((R)-
Binap)RuBr2 (Table 1, run 3) precursors gave similar
results as 90 and 93% ee, respectively, were obtained
under similar hydrogenation conditions. The best enan-
tioselectivity was obtained with the (Biphemp)Ru(O2-
Sch em e 2
affected by the bulk and the rigidity of the substituents
at the other cyclic carbon of the dioxolanone ring;
nevertheless, the best enantioselectivities are obtained
from carbonate 2a .
CCF3)2 catalyst, which led to 97% ee (Table 1, run 6).
The introduction of rigidity and steric hindrance at the
sp3 carbon atom in the R-methylene carbonates 2b and
2c did not improve the enantioselectivity of the hydro-
genation of the exocyclic double bond. Under our typical
conditions the use of (Binap)Ru(O2CCF3)2 catalyst pre-
cursor led to a complete conversion of the unsaturated
carbonates 2b-c and afforded the saturated cyclic car-
bonates 3b and 3c with 89% ee (Table 1, runs 11 and
12). It is noteworthy that the utilization of methanol as
the solvent led to lower enantioselectivities as 3a and
3c were obtained with only 83 and 80% ee, respectively,
after hydrogenation under 10 MPa of hydrogen at 50 °C
(Table 1, runs 7 and 9).
The excellent enantioselectivities might be due to the
fact that the cyclic carbonates 2a -c contain an exocyclic
CdC double bond and an adjacent oxygen atom, which
make possible the double chelation to the ruthenium
center and leads to high enantioface differentiation
(Chart 1). This chelation does not seem to be very
This explanation corresponds to that given by Takaya
et al.14 for the enantioselective hydrogenation of cyclic
enol esters and ethers. When methanol is used as the
solvent, the possible competition between the coordina-
tion of the carbonate oxygen and methanol, which only
allows the coordination of the CdC bond, might explain
the lower enantioselectivities obtained in this solvent.
Ca r bon a te Op en in g: Syn th esis of Op tica lly Ac-
tive Diols. The treatment of 1.34 mmol of carbonate 3a
with 2.00 mmol of potassium carbonate in 10 mL of
anhydrous methanol at 60 °C for 2.5 h led to the
quantitative conversion of the carbonate into the corre-
sponding diol (Scheme 2). After evaporation of the
solvent and dissolution of the salt in saturated NH4Cl,
the diol was extracted with diethyl ether and distilled
under reduced pressure. This procedure allowed the
isolation of the optically active diols (+)-4a -c from
(13) Binap: (1,1′-binaphthyl-2,2′-diyl)bis(diphenylphosphine). Bi-
phemp: (6,6′-dimethylbiphenyl-2,2′-diyl)bis(diphenylphosphine). MeO-
Biphep: (6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine).
(14) Ohta, T.; Miyake, T.; Seido, N.; Kuniobayashi, H.; Takaya, H.
J . Org. Chem. 1995, 60, 357.

Optically Active Cyclic Carbonates and 1,2-Diols
J . Org. Chem., Vol. 61, No. 24, 1996 8455
Cyclopen tan espir o-4′-5′-m eth yl-1′,3′-dioxolan -2′-on e (3b)
was isolated as a colorless liquid (82%) from the hydrogenation
of 0.250 g of carbonate 2b in CH2Cl2 under 10 MPa of hydrogen
at 50 °C for 19 h, in the presence of ((R)-Binap)Ru(O2CCF3)2
as catalyst: bp 110 °C (1.5 mmHg); IR (neat) ν 1790 cm-1; 1H
NMR (300.133 MHz, CDCl3) δ 4.59 (q, 1H, J ) 6.5 Hz), 2.03-
1.64 (m, 8H), 1.32 (d, 3H, J ) 6.5 Hz); 13C {1H} NMR (75.469
MHz, CDCl3) δ 154.31, 95.10, 79.06, 37.06, 32.09, 23.37, 22.61,
carbonates (-)-3a -c in 87, 85 and 85% yield, respec-
tively. Carbonate 3a led to the diol (+)-4a ([R]D) +9 (c
1.5, Et2O) corresponding to the diol with the (S) config-
uration previously prepared by deamination of 3-amino-
2-methylbutan-2-ol.15
As the ring opening of cyclic carbonates is known to
proceed with retention of configuration, this indicated
that the utilization of ((R)-diphosphine)ruthenium(O2-
CCF3)2 catalysts led to carbonate (-)-3a with the (S)
configuration. This method makes possible the prepara-
tion of 1-methyl-2,2-disubstituted diols containing two
identical substituents at C(2) in three steps from the
easily available corresponding prop-2-yn-1-ols16 and in-
volves the participation of CO2 as an essential synthetic
tool. It is noteworthy that the diol (S)-4a has already
been used as ligand in the molybdenum-mediated kinetic
resolution of oxiranes.17
15.68; [R]18 -23 (c ) 2, EtOH) (ee ) 89%). Anal. Calcd for
D
C8H12O3: C, 61.52; H, 7.74. Found: C, 61.50; H, 7.91.
Cycloh exan espir o-4′-5′-m eth yl-1′,3′-dioxolan -2′-on e (3c)
was isolated as a colorless liquid (80%) from the hydrogenation
of 0.250 g of carbonate 2c in CH2Cl2 under 2 MPa of hydrogen
at 20 °C for 68 h, in the presence of ((R)-Binap)Ru(O2CCF3)2
as catalyst: bp 140 °C (1.5 mmHg); IR (neat) ν 1798 cm-1; 1H
NMR (300.133 MHz, CDCl3) δ 4.30 (q, 1H, J ) 6.6 Hz), 2.03-
1.15 (m, 10H), 1.24 (d, 3H, J ) 6.6 Hz); 13C {1H} NMR (75.469
MHz, CDCl3) δ 154.25, 85.16, 81.51, 35.16, 30.06, 24.81, 22.01,
21.64, 14.43; [R]18D -30 (c ) 2, EtOH) (ee ) 89%). Anal. Calcd
for C9H14O3: C, 63.51; H, 8.29. Found: C, 63.63; H, 8.40.
Gen er a l P r oced u r e for th e P r ep a r a tion of Diols.
Carbonate 3a -c (1.34 mmol) and 2.0 mmol of potassium
carbonate were heated at 60 °C for 2.5 h in 10 mL of anhydrous
methanol. The solvent was then evaporated, and the reaction
mixture was dissolved in a saturated solution of NH4Cl and
extracted with diethyl ether. After the solution was dried with
MgSO4, the diols were collected by distillation under reduced
pressure as colorless liquids.
The above convenient syntheses of optically active
cyclic carbonates and 1,2-diols in two and three steps,
respectively, from carbon dioxide and prop-2-yn-1-ols
offer a potential for the synthesis of optically active
molecules and ligands without the utilization of phosgene
derivatives.
Exp er im en ta l Section
(S)-2-Meth yl-2,3-bu ta n ed iol (4a ): 87%; IR (neat) ν 3395
Cyclop en t a n esp ir o-4′-5′-Met h ylen e-1′,3′-d ioxola n -2′-
on e (2b). Ten mmol of the propargylic alcohol 1b and 0.2 mL
(0.8 mmol) of tributylphosphine were stirred for 20 h at 100
°C under CO2 pressure (5 MPa). The carbonate 2b (93%) was
isolated by chromatography over a silica gel column eluted
with a dichloromethane/pentane (3:1) mixture: IR (neat) ν
1
cm-1; H NMR (300.133 MHz, CDCl3) δ 3.54 (q, 1H, J ) 6.5
Hz), 2.70-2.46 (2s, broad signals, 2H), 1.16 (s, 3H,), 1.12 (s,
3H), 1.11 (d, 3H, J ) 6.4 Hz); 13C {1H} NMR (75.469 MHz,
CDCl3) δ 74.27, 73.32, 26.54-22. 65, 17.69; [R]18D +9 (c ) 1.5,
diethyl ether) ([R]D neat -5.15 for (R)-(4a )).15 Anal. Calcd for
C5H12O2: C, 57.66; H, 11.61. Found: C, 57.02; H, 11.69.
1823, 1683 cm-1 1H NMR (300.133 MHz, CDCl3) δ 4.73 (d,
;
1-(1-Hyd r oxyeth yl)cyclop en ta n -1-ol (4b): 85%; IR (neat)
1H, J ) 4.0 Hz), 4.31 (d, 1H, J ) 4.0 Hz), 2.18 (m, 8H); 13C
{1H} NMR (75.469 MHz, CDCl3) δ 155.68, 151.49, 94.27, 85.40,
40.63, 24.23. Anal. Calcd for C8H10O3: C, 62.33; H, 6.54.
Found: C, 62.71; H, 7.00.
1
ν 3405 cm-1; H NMR (300.133 MHz, CDCl3) δ 3.64 (q, 1H, J
) 6.4 Hz), 2.65 (s, 1H), 2.35 (s, 1H), 1.48-1.81 (m, 10H), 1.16
(d, 3H, J ) 6.4 Hz); 13C NMR (75.469 MHz, CDCl3) δ 84.95
(s), 73.54 (d, J ) 141.9 Hz), 38.15 (t, J ) 129.0 Hz), 35.39 (t,
J ) 127.6 Hz), 24.30 (t, J ) 128.3 Hz), 24.20 (t, J ) 128.3 Hz),
18.05 (q, J ) 126.0 Hz); [R]18D +6 (c ) 1.5, diethyl ether). Anal.
Calcd for C7H14O2: C, 64.58; H, 10.84. Found: C, 64.29; H,
11.00.
Gen er a l P r oced u r e for th e Hyd r ogen a tion of Cyclic
r-m eth ylen e ca r bon a tes. 5-Methylene-1,3-dioxolan-2-one
(0.250 g) and the ruthenium catalyst (0.5 mol %) were placed
in a 125 mL stainless steel autoclave. After addition of 10
mL of solvent under nitrogen atmosphere, the autoclave was
pressurized with hydrogen (2-10 MPa) and heated (see Table
1). The solvent was evaporated, and the hydrogenated car-
bonate was recovered by distillation under reduced pressure.
The enantiomeric excess was determined by GC using a chiral
Lipodex capillary column (25 m × 0.25 mm). The optical
rotation was measured on a Perkin-Elmer-241 polarimeter.
4,4,5-Tr im eth yl-1,3-d ioxola n -2-on e (3a ). Isolated as a
white solid (85%) from the hydrogenation of 0.250 g of
carbonate 2a in CH2Cl2 under 10 MPa of hydrogen at 20 °C
for 17 h, in the presence of ((R)-Biphemp)Ru(O2CCF3)2 as
catalyst: mp ) 64 °C; IR (KBr) ν 1795 cm-1; 1H NMR (300.133
MHz, CDCl3) δ 4.43 (q, 1H, J ) 6.5 Hz), 1.47, 1.35 (2 s, 6H),
1.34 (d, 3H, J ) 6.5 Hz); 13C {1H} NMR (75.469 MHz, CDCl3)
1-(1-Hyd r oxyeth yl)cycloh exa n -1-ol (4c): 85%; IR (neat)
1
ν 3402 cm-1; H NMR (300.133 MHz, CDCl3) δ 3.43 (q, 1H, J
) 6.5 Hz), 2.85 (s, 1H), 2.32 (s, 1H,), 1.10-1.58 (m, 10H), 1.08
(d, 3H, J ) 6.5 Hz); 13C NMR (75.469 MHz, CDCl3) δ 73.77 (d,
J ) 142.4 Hz), 73.52 (s), 34.18 (t, J ) 124.6 Hz), 31.28 (t, J )
122.1 Hz), 25.90 (t, J ) 123.3 Hz), 21.67 (t, J ) 132.2 Hz),
21.47 (t, J ) 147.5 Hz), 17.02 (q, J ) 125.9 Hz); [R]18 +5 (c )
D
1, diethyl ether). Anal. Calcd for C8H16O2: C, 66.63; H, 11.18.
Found: C, 65.76; H, 11.18.
Ack n ow led gm en t. The authors thank F. Hoffmann-
La Roche Ltd. (Basel) for a generous gift of Biphemp
and MeO-Biphep ligands, the E.U. for the Human
Capital and Mobility programme (Contract No. ERB-
CHRXCT 930147) for additional assistance, and the
Procope programme for a grant to T.B. of the University
of Wu¨rzburg. We are also very grateful to J ean-Claude
Souvie (Oril S.A.) for helpful discussions and Pascale
Authouart (Oril S.A.) for skillful analytical assistance.
δ 154.20, 84.18, 81.52, 25.78, 21.03, 14.53; [R]18 -24 (c ) 2,
D
EtOH) (ee ) 97%). Anal. Calcd for C6H10O3: C, 55.37; H, 7.74.
Found: C, 55.08; H, 8.01.
(15) Gu¨nther, B. R.; Kirmse, W. Liebigs Ann. Chem. 1980, 518.
(16) The propargylic alcohols were prepared from symmetrical
ketones and lithium acetylide at low temperature. See: Midland, M.
M. J . Org. Chem. 1975, 40, 2250.
(17) Schurig, V.; Betschinger, F. Bull. Soc. Chim. Fr. 1994, 131, 555.
J O961413E