Enantioselective hydrogenation
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 10, October, 2001
1865
3.85 m. 13C NMR (acetone-d6), δ: 27.66 (CCH3); 46.74
and entry 3 in Table 4). Apparently, this is associated
with the fact that in the absence of coordination of the
(NCH3); 62.77 (CH2); 79.63 (CH); 109.11 (CCH3).
Complex [Rh(S,S-DIODMA)2]+CF3SO3 . The reagent
hydrogen molecule to the metal atom (pH = 1 atm),
2
CF3SO3Ag (25.7 mg, 0.1 mmol) was added to a mixture of
[(1,5-COD)RhCl]2 (0.05 mmol) and cyclooctadiene (0.1 mmol)
in degassed acetone (50 mL). The flocculent AgCl precipitate
that formed was filtered off and then S,S-DIODMA (1.2 equiv.,
27.6 mg, 0.127 mmol) in acetone (3 mL) was added portionwise
the diamine ligand is displaced from the coordination
sphere by the substrate molecules and subsequent hydro-
genation occurs at high pressure (pH = 35 atm) in the
2
presence of the resulting achiral rhodium complexes.
The results of multinuclear NMR spectroscopy dem-
onstrated that olefin is coordinated to complex 4 (or 11)
giving rise to olefin intermediates of type 10 (or 12) in
the absence of hydrogen and also, apparently, at the H2
pressure of ∼1 atm. Taking into account this fact and
the absence of signals of rhodium hydrides upon treat-
ment of complex 4 with hydrogen, the substrate mecha-
nism of hydrogenation on the bis-amine complex un-
der study can be proposed. The optical yield of
(+)-R-α-methylsuccinic acid increased and the optical
yield of (+)-S-N-acetylphenylalanine slightly decreased
as the H2 pressure was increased, which may be associ-
ated with the decrease in the difference between the
rates of hydrogenation of diastereomeric olefin interme-
diates. By varying substituents at the N atom in the
ligands of 1, the mechanism of hydrogenation on di-
amine rhodium complexes can be investigated in more
detail.
to the yellow solution of [Rh(COD)2]+CF3SO3 . The resulting
solution was concentrated to the volume of 3 mL. The complex
was precipitated with diethyl ether, successively washed with
diethyl ether and hexane, dried in vacuo, and sealed in tubes.
The yield was 0.04 g (60% with respect to the theoretical
1
value); m.p. 128132 °C. H NMR, δ: in a CD3ODC6D6
mixture: 1.38 (s, 6 H, Me2C); 2.47 (s, 12 H, NMe2); 2.79 (dd,
2 H, HA in CH2, 3JHH = 6.59 Hz, 2JH H = 13.2 Hz); 2.88 (d,
A
B
2
2 H, HB in CH2, JH H = 13.1 Hz); 3.90 (m, 2 H, CH); in
A
B
acetone-d6: 1.36 (s, 6 H, Me2C); 2.68 (s, 12 H, NMe2); 2.75
(m, 4 H, CH2); 3.89 (m, 2 H, CH). 13C NMR, δ: in acetone-d6:
27.23 (CCH3); 45.68 (NCH3); 60.60 (CH2); 77.90 (CH); in a
CD3ODC6D6 mixture: 27.23 (CCH3); 45.19 (NCH3); 60.93
(CH2); 77.20 (CH); 111.85 (CCH3). 19F NMR (CD3OD),
δ: 76.99.
Hydrogenation of itaconic and α-acetylaminocinnamic ac-
ids and their esters. A. In a swinging flask. Hydrogenation was
carried out with intense stirring in a glass temperature-con-
trolled swinging flask connected with a manometer and a
system for supplying hydrogen. The gas was purified and dried
according to a standard procedure. Methanol (5 mL) and the
substrate (∼1 mmol) were placed under a stream of hydrogen in
a swinging flask mounted on a shaker and the pressure was
raised to 1.21.4 atm. Then a solution of the individual
complex or the catalyst (ñRh = 2 mmol L1), which was
prepared in situ in an individual vessel under an atmosphere of
argon in a 2 : 1 mixture of methanol and benzene (5 mL), was
added with a syringe and the mixture was stirred.
Experimental
The IR spectra were recorded on an IKS-29 instrument in a
thin layer. The 1H, 13C, 19F, and 31P NMR spectra were
measured on a Bruker DPX 400 spectrometer (400, 100, 376,
and 162 MHz, respectively) for solutions in acetone-d6 with
HMDS as the internal standard. The chemical shifts are given
relative to Me4Si. The GLC analyses were carried out on an
LKhM-80 chromatograph equipped with a 1 m½3-mm column
packed with 5% SÅ-30 on Chromaton N-AW-DMCS (a ther-
mal conductivity detector; helium as the carrier gas). The
degrees of conversion of the substrates were determined by
GLC. The specific optical rotation was measured on a Polamat
A instrument at 546 nm and was scaled to the wavelength of
589 nm using the coefficient of 1.17543.
B. In an autoclave. The complex [(1,5-COD)2Rh]+CF3SO3
(0.02 mmol) was placed in a vessel, which was purged with dry
argon, and dissolved in a mixture of C6H6 (3 mL) and MeOH
(7 mL). Then two fractions of (+)-S,S-DIODMA were added.
The reaction mixture was stirred for 10 min, a weighed sample
of the substrate (0.130.22 g) was added, the mixture was
placed in a pre-evacuated autoclave, hydrogen was fed to the
autoclave under high pressure, and the autoclave was mounted
on a shaker. The treatment of the reaction mixture and isola-
tion of the products were carried out as described above.8
The chemical yield of the hydrogenation product was deter-
mined based on the ratio of the integral intensities of the signals
for the acetyl groups in the 1H NMR spectra of the initial
substrate and the hydrogenation product (for α-AACA and its
ester) or of the signals for the protons of the =CH2 groups in
the initial substrate and of the CH3 group in the hydrogenation
product (for itaconic acid). For α-AACA: δ(CH3CO)sat 1.88,
δ(CH3CO)unsat 2.08; for methyl ester of α-AACA: δ(CH3CO)sat
1.92, δ(CH3CO)unsat 2.12. For itaconic acid, δ(=CH2) 6.27.
For α-methylsuccinic acid, δ(CH3) 1.19 (d).
(4R,5R)-N4,N4,N5,N5,2,2-Hexamethyl-1,3-dioxolane-4,5-
dicarboxamide was prepared according to a procedure described
previously.7 M.p. 82 °C (cf. lit. data6: 8384 °C). 1H NMR, δ:
1.44 (s, 6 H, Me2C); 2.95 and 3.16 (both s, 6 H, NMe2); 5.22
(s, 2 H, CH) [cf. lit. data7: (CCl4): 1.38, 2.92, 3.16, 5.09 (all s)].
(+)-4S,5S-N4,N4,N5,N5,2,2-Hexamethyl-1,3-dioxolane-
4,5-dimethaneamine (1b) was prepared according to a proce-
dure described previously.7 B.p. 41 °C (1 Torr) (cf. lit. data7:
54 °C (0.8 Torr)). 1H NMR (CDCl3), δ: 1.39 (s, 6 H, Me2C);
2.28 (s, 12 H, NMe2); 2.38 (d, 2 H, HA in CH2); 2.50 (dd, 2 H,
HB in CH2, 2JH H = 12.6 Hz, 3JHH = 6.8 Hz); 3.77 (m, 2 H,
A
B
CH); in C6D6: 1.35 (s, 6 H, Me2C); 2.13 (s, 12 H, NMe2);
3
2.37 (d, 2 H, HA in CH2, JHH = 5.67 Hz); 2.47 (dd, 2 H,
References
HB in CH2, 2JH H = 12.9 Hz, 3JHH = 3.47 Hz); 3.91 (m, 2 H,
A
B
CH); in acetone-d6: 1.29 (s, 6 H, Me2C); 2.21 (s, 12 H,
NMe2); 2.37 (d, 2 H, HA in CH2, 3JHH = 6.03 Hz); 2.52 (dd,
2 H, HB in CH2, 2JH H = 13.0 Hz, 3JHH = 3.64 Hz); 3.80 (m,
1. H. Doucet, T. Ohkuma, K. Murata, T. Yokozawa,
M. Kozawa, E. Katayama, A. F. England, T. Ikariya, and
R. Noyori, Angew. Chem., 1998, 110, 1792.
A
B
2 H, CH); cf. lit. data7: (in CCl4): 1.32 s, 3.34* m, 3.50 m,
2. P. Gamez, F. Fache, and M. Lemaire, Tetrahedron Asym-
metry, 1995, 6, 705.
* The value is obviously erroneous; apparently, δ 2.34.