(-)-dimenthyl malonate

Article abstract of DOI:10.1107/S0108270101019308

The C₂-symmetric dimenthyl malonate were synthesized as the model compound which would lead directly to enantiopure C₂ symmetric without contamination from the formation of other stereoisomers. The crude product was purified by flash

Full text of DOI:10.1107/S0108270101019308

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ture are consistent with C symmetry. We ascribe the confor-
2
mation of this molecule in the crystal state to packing effects.
The overall unit cell is pseudo-C -symmetric and contains two
2
ISSN 0108-2701
identical malonate molecules, as shown in Fig. 2.
The molecule is certainly not an enol derivative, with a C1Ð
ꢀ
C2ÐC3 bond angle of 111.5 (5) and not signi®cantly different
C1ÐC2 and C2ÐC3 bond lengths of 1.492 (7) and
Ê
(
±)-Dimenthyl malonate
1
.497 (8) A, respectively (Table 1). All the substituents on the
cyclohexyl ring are in the expected equatorial positions.
The most striking structural feature is the relative confor-
mation of both carbonyl groups, C1 O4 and C3 O3. They
are clearly twisted away from each other, as shown by the
Gregory S. Coumbarides, Jason Eames,* Majid Motevalli
and Yonas Yohannes
Department of Chemistry, Queen Mary, University of London, Mile End Road,
London E1 4NS, England
ꢀ
torsion angles of 138.3 (6) for O4ÐC1ÐC2ÐO3 and
ꢀ
Correspondence e-mail: j.eames@qmul.ac.uk
102.6 (6) for C1ÐC2ÐC3ÐO3. This is presumably due to a
combination of hyperconjugation effects at C2ÐH with both
Received 4 October 2001
Accepted 12 November 2001
Online 16 January 2002
The title compound, bis(2-isopropyl-5-methylcyclohex-1-yl)
malonate, C H O , crystallizes in the monoclinic space group
P2 . In the crystal, the molecule is not C symmetric.
2
3
40
4
1
2
Comment
A large number of substituted malonic acid derivatives are
known (Kanters & Kroon, 1972). Some attention has been
focused on related keto (Adhikesavalu & Venkatesan, 1983)
and aldehyde derivatives (Lundgren & Aurivillius, 1964), but
little attention has been paid to the corresponding malonate
ester derivatives. We were originally interested in the
conformational preference of simple 1,3-dicarbonyl-
containing molecules. To this aim, we synthesized the title C2-
symmetric dimenthyl malonate, (III), as our model compound.
We chose enantiopure (� )-menthol, (I), as our ester scaffold,
Figure 1
A view of the molecule of (III) with the atom-numbering scheme.
Displacement ellipsoids are drawn at the 50% probability level and H
atoms are shown as small spheres of arbitrary radii.
as this would lead directly to enantiopure C -symmetric (III)
2
without contamination resulting from the formation of other
stereoisomers. Addition of commercially available malonyl
dichloride, (II), to a stirred solution of natural (� )-menthol
and triethylamine in dichloromethane gave the required
(
� )-dimenthyl malonate, (III), as a cream-coloured pre-
cipitate in good yield (66%). The crude product was puri®ed
by ¯ash column chromatography on silica gel, eluting with a
light petroleum (313±333 K)±ether (19:1) mixture, and was
then vapour recrystallized from hexane to give colourless
needle-like crystals of (III).
X-ray diffraction of (III) revealed the structure illustrated
in Fig. 1. The stereochemistry was assigned by reference to
(
was not C symmetric in its solid phase, due to the non-
� )-menthol. It was immediately evident that this molecule
2
equivalence of the carbonyl groups, C1 O4 and C3 O3. By
comparison, solution-phase NMR studies at room tempera-
Figure 2
A packing diagram for (III), viewed along the b axis.
o84 # 2002 International Union of Crystallography
DOI: 10.1107/S0108270101019308
Acta Cryst. (2002). C58, o84±o85

organic compounds
carbonyl groups and a minimization of their relative dipole
moments. This can also be seen in a related twist involving the
other O atom in the ester motif, as shown by the torsion angles
Table 1
Selected geometric parameters (A, ).
Ê
ꢀ
C1ÐC2
1.492 (7)
C2ÐC3
1.497 (8)
ꢀ
ꢀ
of � 42.5 (6) for O1ÐC1ÐC2ÐC3 and � 73.4 (6) for C1Ð
C2ÐC3ÐO2. In contrast, both the ester groups strive for
C14ÐO1ÐC1ÐO4
C14ÐO1ÐC1ÐC2
O4ÐC1ÐC2ÐC3
O1ÐC1ÐC2ÐC3
� 0.8 (8)
� 180.0 (4)
138.3 (6)
� 42.5 (6)
C4ÐO2ÐC3ÐO3
C4ÐO2ÐC3ÐC2
C1ÐC2ÐC3ÐO3
C1ÐC2ÐC3ÐO2
� 9.5 (7)
166.6 (4)
102.6 (6)
� 73.4 (6)
ꢀ
ꢀ
planarity [� 9.5 (7) for C4ÐO2ÐC3ÐO3 and � 0.8 (8) for
C14ÐO1ÐC1ÐO4] through anomeric assistance (Table 1).
This type of antiparallel alignment has been reported in the
structural arrangement of diimidazolines (Brennan & McKee,
1
999), diones (Klein et al., 1999) and related malonic acid
Table 2
Hydrogen-bonding geometry (A, ).
derivatives (Kalsbeek, 1992). The effect of the non-equiva-
lence of the menthyl groups is more interesting and can be
seen more clearly by the non-equivalence of the ester groups.
The C14ÐO1ÐC1ÐC2 torsion angle of the ester group is
Ê
ꢀ
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
i
C15ÐH15BÁ Á ÁO4
0.99
1.00
2.44
2.54
3.374 (8)
3.351 (7)
157
138
ꢀ
ii
planar [� 180.0 (4) ], whereas the related C4ÐO2ÐC3ÐC2
C20ÐH20Á Á ÁO3
ꢀ
1
2
ester grouping certainly has a slight twist [166.6 (4) ] (Table 1).
Symmetry codes: (i) x; y � 1; z; (ii) 1 � x; ‡ y; 2 � z.
This is more than likely due to a combination of crystal-
packing effects and the presence of a local pseudo-twofold
axis (Table 2 and Fig. 2). This layer sequence is positioned in
an ABAB system, with layer B oriented antiparallel to layer A.
Re®nement
2
Re®nement on F
R(F) = 0.058
H atoms treated by a mixture of
independent and constrained
re®nement
2
wR(F ) = 0.163
S = 0.93
2
2
2
w = 1/[ꢆ (F
where P = (F
(Á/ꢆ)max = 0.003
Áꢇmax = 0.22 e A
Áꢇmin = � 0.21 e AÊ
o
) + (0.096P) ]
+ 2F )/3
o c
Experimental
2 2
2
2
194 re¯ections
51 parameters
Malonyl dichloride (5.0 g, 3.45 ml, 35.5 mmol) was slowly added to a
stirred solution of triethylamine (7.1 g, 9.90 ml, 70.9 mmol) and
Ê
� 3
� 3
(
� )-menthol (11.1 g, 70.9 mmol) in dichloromethane (100 ml), and
the resulting solution was stirred for 1 h. The reaction was quenched
slowly with water (30 ml) and the organic layer was extracted with
H atoms were placed in geometrical positions, with CÐH = 0.98±
Ê
.0 A. Uiso values were re®ned for the H atoms on C2; all other H
1
diethyl ether (3 Â 50 ml), dried (MgSO
4
) and evaporated under
atoms were treated as riding, with Uiso(H) = 1.2 or 1.5Ueq(C).
Data collection: CAD-4-PC Software (Enraf±Nonius, 1994); cell
re®nement: CAD-4-PC Software; data reduction: XCAD4 (Harms &
Wocadlo, 1995); program(s) used to solve structure: SHELXS97
reduced pressure. The residue was puri®ed by ¯ash column chro-
matography on silica gel, eluting with light petroleum (313±333 K)±
ether (19:1) to give the title compound, (III) (9.0 g, 66%), as a light-
cream solid. This solid was recrystallized using hexane to give
colourless needle crystals (m.p. 327±328 K). Spectroscopic analysis:
(
Sheldrick, 1997); program(s) used to re®ne structure: SHELXL97
Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997);
(
R
F
[light petroleum (313±333 K)±ether (9:1)] 0.75; IR (ꢀmax, ®lm,
software used to prepare material for publication: WinGX (Farrugia,
999).
�
1
1
cm ): 1725 (CO); [ꢁ]
CDCl
CH
D
� 83.7 (c 2.7 in acetone); H NMR (250 MHz,
1
3
, ꢂ, p.p.m.): 4.8 (2H, td, J = 10.8 and 4.4 Hz, CHO), 3.36 (2H, s,
2
CO), 2.15±0.85 (18H, m, 6 Â CH
), 0.85 (3H, d, J = 7.0 Hz, CHCH
, ꢂ, p.p.m.): 166.2, 75.5, 46.9, 42.4, 40.7, 34.2, 31.4, 26.1, 23.4,
2
and 6 Â CH), 1.1±0.95 (6H, m,
13
3
We are grateful to the Faculty of Natural Science at Queen
2
 CH
3
); C NMR (67 MHz,
Mary, University of London, the London University Central
Research Fund, the Nuf®eld Foundation (NUF±NAF 99) and
the Royal Society for their generous support.
CDCl
3
+
+
22.0, 20.8, 16.3; analysis found: M 381.3017; C23
41 4
H O requires M
381.3005; MS (m/z): 381 (80%, M), 243 (100, M � C10
H18).
Crystal data
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: NA1538). Services for accessing these data are
described at the back of the journal.
�
3
C
23
H
40
O
4
D
x
= 1.112 Mg m
r
M = 380.55
Mo Kꢁ radiation
Monoclinic, P21
Ê
a = 12.990 (2) A
Cell parameters from 25
re¯ections
Ê
b = 6.092 (3) A
ꢀ
References
ꢄ = 8.6±13.4
ꢅ = 0.07 mm
T = 180 (2) K
Ê
c = 14.528 (2) A
� 1
Adhikesavalu, D. & Venkatesan, K. (1983). Acta Cryst. C39, 1044±1048.
Brennan, C. J. & McKee, V. (1999). Acta Cryst. C55, 1492±1494.
Enraf±Nonius (1994). CAD-4-PC Software. Enraf±Nonius, Delft, The Nether-
lands.
ꢀ
ꢃ = 98.55 (2)
V = 1136.9 (6) A
Z = 2
Ê
3
Needle, colourless
0.4 Â 0.2 Â 0.2 mm
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837±838.
Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.
Kalsbeek, N. (1992). Acta Cryst. C48, 878±883.
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Lundgren, G. & Aurivillius, B. (1964). Acta Chem. Scand. 18, 1642±1652.
Sheldrick, G. M. (1997). SHELXL97 and SHELXS97. University of
G oÈ ttingen, Germany.
Data collection
ꢀ
Enraf±Nonius CAD-4
diffractometer
Non-pro®led !/2ꢄ scans
ꢄmax = 25
h = � 15 ! 15
k = 0 ! 7
2
2
1
285 measured re¯ections
194 independent re¯ections
234 re¯ections with I > 2ꢆ(I)
l = 0 ! 17
2 standard re¯ections
frequency: 60 min
intensity decay: 7%
Rint = 0.049
ꢁ
Acta Cryst. (2002). C58, o84±o85
Gregory S. Coumbarides et al.
23 40
C H O
4
o85