Characterization of the crystalline nature of the racemates of novel chiral five-membered cyclic nitroxides

Article abstract of DOI:10.1080/15421400590957602

Racemic samples of chiral five-membered cyclic nitroxides, 2,2,5,5-tetrasubstituted pyrrolidine-1-oxyls bearing one or two 4-hydroxyphenyl groups on the stereogenic centers [C(2) or C(2) & C(5)] adjacent to the NO radical moiety, exist as a racemic conglo

Full text of DOI:10.1080/15421400590957602

This article was downloaded by: [Moskow State Univ Bibliote]
On: 19 January 2014, At: 07:22
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Molecular Crystals and Liquid
Crystals
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/gmcl20
Characterization of the
Crystalline Nature of the
Racemates of Novel Chiral
Five-Membered Cyclic
Nitroxides
Naohiko Ikuma a , Rui Tamura b , Satoshi Shimono c
,
Naoyuki Kawame c , Osamu Tamada c , Naoko Sakai c
, Yukio Yamamoto c & Jun Yamauchi d
a Graduate School of Global Environmental Studies ,
Kyoto University , Kyoto, Japan
b Graduate School of Global Environmental Studies
and Graduate School of Human & Environmental
Studies , Kyoto University , Kyoto, Japan
c Graduate School of Human & Environmental
Studies , Kyoto University , Kyoto, Japan
d Graduate School of Science , Kyoto University ,
Kyoto, Japan
Published online: 31 Aug 2006.
To cite this article: Naohiko Ikuma , Rui Tamura , Satoshi Shimono , Naoyuki
Kawame , Osamu Tamada , Naoko Sakai , Yukio Yamamoto & Jun Yamauchi (2005)
Characterization of the Crystalline Nature of the Racemates of Novel Chiral Five-
Membered Cyclic Nitroxides, Molecular Crystals and Liquid Crystals, 440:1, 23-35,
DOI: 10.1080/15421400590957602
To link to this article: http://dx.doi.org/10.1080/15421400590957602

PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the
Content should not be relied upon and should be independently verified with
primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,
and other liabilities whatsoever or howsoever caused arising directly or
indirectly in connection with, in relation to or arising out of the use of the
Content.
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions

Mol. Cryst. Liq. Cryst., Vol. 440, pp. 23–35, 2005
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400590957602
Characterization of the Crystalline Nature
of the Racemates of Novel Chiral Five-Membered
Cyclic Nitroxides
Naohiko Ikuma
Graduate School of Global Environmental Studies, Kyoto University,
Kyoto, Japan
Rui Tamura
Graduate School of Global Environmental Studies and Graduate School
of Human & Environmental Studies, Kyoto University, Kyoto, Japan
Satoshi Shimono
Naoyuki Kawame
Osamu Tamada
Naoko Sakai
Yukio Yamamoto
Graduate School of Human & Environmental Studies, Kyoto University,
Kyoto, Japan
Jun Yamauchi
Graduate School of Science, Kyoto University, Kyoto, Japan
Racemic samples of chiral five-membered cyclic nitroxides, 2,2,5,5-tetrasubstituted
pyrrolidine-1-oxyls bearing one or two 4-hydroxyphenyl groups on the stereogenic cen-
ters [C(2) or C(2) & C(5)] adjacent to the NO radical moiety, exist as a racemic con-
glomerate in the crystalline state, whereas those having one or two 3-hydroxyphenyl
groups at the same positions belong to a racemic compound. The key intermolecular
interactions in controlling whether these racemates crystallize in a homochiral way
or a heterochiral manner have been investigated by X-ray crystallographic analysis
and magnetic susceptibility measurements.
Keywords: chiral nitroxide radical; electron paramagnetic resonance spectroscopy;
magnetic susceptibility; racemic compound; racemic conglomerate; X-ray crystallographic
analysis
Address correspondence to Rui Tamura, Graduate School of Global Environmental Stu-
dies, Kyoto University, Kyoto 606-8501, Japan. E-mail: tamura-r@mbox.kudpc.kyoto-u.ac.jp
23

24
N. Ikuma et al.
INTRODUCTION
With a view to utilizing a chiral five-membered cyclic nitroxide frame-
work as a spin source in its core portion for the elaboration of chiral
paramagnetic liquid crystals, as well as providing a new chiral spin-
labeling reagent for EPR spectroscopic studies, we have synthesized
racemic and enantiomerically enriched nitroxides 1ꢀ5 with one or
two hydroxyphenyl groups on the stereogenic centers as synthetic
intermediates (Scheme 1). Among them, (ꢁ)-1, trans-(ꢁ)-2 and trans-
(ꢁ)-3 having 4-hydroxyphenyl groups were found to exist as a racemic
SCHEME 1 Preparation of chiralꢃ nitroxides 1ꢀ6. Reaction conditions:
a) MeReO3, ureaꢂ H2O2, MeOH, 0 C (60%); b) 1. R1MgBr, THF, ꢄ78ꢃC;
2. Cu(OAc)2, O2; c) 1. R2MgBr, THF, ꢄ78ꢃC; 2. Cu(OAc)2, O2; d) TBAF, THF, 0ꢃC.

Crystalline Nature of Chiral Cyclic Nitroxides
25
conglomerate (an equal mixture of R and S chiral crystals) [1], which
is very rare for chiral nitroxide radicals [2]. To examine the generality
of this conglomerate formation, we have characterized the crystalline
nature (i.e., classification as a racemic conglomerate, a racemic
compound or a racemic mixed crystal) of (ꢁ)-2-(3-hydroxyphenyl)-2,5,
5-trimethylpyrrolidine-1-oxyl (4) and trans-(ꢁ)-2,5-di(3-hydroxyphe-
nyl)-2,5-dimethylpyrrolidine-1-oxyl (5) by means of IR spectroscopy,
X-ray crystallographic analysis and magnetic susceptibility measure-
ments, and have compared their crystal structures and magnetic
properties with those of (ꢁ)-1, trans-(ꢁ)-3 and their parent compound,
trans-(ꢁ)-2,5-dimethyl-2,5-diphenylpyrrolidine-1-oxyl (6) [3].
Origin of the Formation of a Racemic Conglomerate with
Respect to (ꢁ)-1, trans-(ꢁ)-2 and trans-(ꢁ)-3
As shown in Figures 1–3 and Table 1, we reported that (ꢁ)-1, trans-(ꢁ)-
2 and trans-(ꢁ)-3 exist as the racemic conglomerates (common space
group P212121 and Z¼4) in their crystalline states. Each chiral crystal
commonly consists of a head-to-tail type of homochiral supramolecular
1D zigzag chains characterized by strong intermolecular hydrogen
bonds between the NO radical and the phenolic OH groups [1]. At first
glance, it was difficult to find out the primary interactions which must
control the homochiral packing of the homochiral 1D zigzag chains.
Therefore, the molar magnetic susceptibility vmol was measured for
1, trans-2 and trans-3 at temperatures ranging between 2 and 300 K
using a SQUID susceptometer at an applied field of 0.5 T, because
the measurement of the temperature-dependence of the magnetic sus-
ceptibility of molecular magnetic materials often affords useful infor-
mation on the weak intermolecular interactions present in the
crystal lattice [4]. Consequently, three typical magnetic behaviors
such as weak ferro- and antiferro-magnetic interactions, and isolated
paramagnetic interactions were observed for 1, trans-2 and trans-3,
respectively [1]. The racemic sample showed the same magnetic
behaviour as the enantiomerically enriched one for each of 1, trans-2
and trans-3, because of their existence as racemic conglomerates.
Appearance of weak ferromagnetic interactions for 1 is consistent
with its chiral crystal structure in which the intra- and inter-molecular
spin polarization exchange coupling can be transmitted ferromagneti-
cally in accord with the McConnell mechanism [5]. The sandwich-type
weak C(sp3)ꢄHꢂꢂꢂOꢂꢂꢂHꢄC(sp3) interactions [HꢂꢂꢂO distances: 3.380(4)
˚
and 3.541(4) A] between the NO group of a molecule and the two methyl
groups on the pyrrolidinyl C(5) of the adjacent molecule, which give a
homochiral 1D zigzag chain along the a axis, seems responsible for

26
N. Ikuma et al.
FIGURE 1 Crystal structure of (ꢁ)-1 (P212121, Z ¼ 4) viewed down the (a) a
axis, (b) b axis and (c) c axis [1] and (d) schematic representation of the homo-
chiral 3D network structure. The carbon, hydrogen, nitrogen, and oxygen
atoms are represented by large open, small open, crosshatched, and closed cir-
cles, respectively. Hydrogen atoms except the OH group and the two methyl
groups on the pyrrolidinyl C(5) are omitted.
the weak ferromagnetic interactions (Fig. 1b). This zigzag chain along
the a axis, and the foregoing homochiral 1D zigzag chain along the c
axis formed by strong OꢄHꢂꢂꢂOꢄN hydrogen bonds [OꢂꢂꢂO distance:
˚
2.725(6) A] (Fig. 1a), are alternately weaved along the b axis into the
homochiral 3D network structure (Fig. 1d).
The observed weak antiferromagnetic behavior of trans-2 is
explained by the through-space NOꢂꢂꢂON interactions among the NO
˚
groups [the shortest OꢂꢂꢂO distance: 6.399(3) A] aligned along the c axis
(Fig. 2b). The 1D zigzag chains along the b axis, which were formed by
˚
OꢄHꢂꢂꢂOꢄN hydrogen bonds [OꢂꢂꢂO distance: 2.752(3) A], were further
connected with one another on the ab plane by C(sp3)ꢄHꢂꢂꢂOꢄN inter-
˚
actions [HꢂꢂꢂO distance: 2.875(2) A] between the pyrrolidinyl C(4)Hs of
a homochiral chain and the nearest NꢄO groups of the neighbouring
chain to give a sheet structure (Fig. 2a). Thus, the above dipole–dipole

Crystalline Nature of Chiral Cyclic Nitroxides
27
FIGURE 2 Crystal structure of trans-(ꢁ)-2 (P212121, Z ¼ 4) viewed down the (a)
c axis and (b) a axis [1]. The carbon, hydrogen, nitrogen, and oxygen atoms are
represented by large open, small open, crosshatched, and closed circles, respect-
ively. Hydrogen atoms except the OH group and one hydrogen atom on the
pyrrolidinyl C(4) are omitted in (a), while all hydrogen atoms are done in (b).

28
N. Ikuma et al.
FIGURE 3 Crystal structure of trans-(ꢁ)-3 (P212121, Z ¼ 4) viewed down the
(a) b axis and (b) c axis [1]. The carbon, hydrogen, nitrogen, and oxygen atoms
are represented by large open, small open, crosshatched, and closed circles,
respectively. Hydrogen atoms except the OH group are omitted in (a), while
those except the two OH groups and the two hydrogen atoms on the pyrro-
lidinyl C(3) are omitted in (b).
interactions between the NO groups along the c axis may be responsible
for the homochiral stacking of the homochiral ab sheets along the c axis.
In the paramagnetic crystals of trans-3, in which the OꢂꢂꢂO distance
˚
(7.547 A) between the nearest NO groups is too long to show an anti-
ferromagnetic behavior, a combination of the hydrogen bonds between
˚
the neighboring phenolic OH groups [OꢂꢂꢂO distance: 2.761(5) A] with
˚
the strong OꢄHꢂꢂꢂOꢄN hydrogen bonds [OꢂꢂꢂO distance: 2.665(5) A]
provides a homochiral 1D ribbon structure along the c axis (Fig. 3a).

Crystalline Nature of Chiral Cyclic Nitroxides
29
TABLE 1 Melting Points, Specific Rotations, ESR g-factors and Hyperfine
Coupling Constants, and Magnetic Data for Nitroxides 1-6
ESRd
mp
(ꢃC)a
Ce=emu
K molꢀ1
Compound
ee=%b
[a]2D5c
g
aN (mT)
hf=K
(S)-1g
161.7
151.0
180.8
168.5
177.2
173.8
160.9
120.9
168.7
191.7
130.5
100.5
88
ꢀ
ꢀ118.7
ꢀ
2.0067
2.0073
2.0070
2.0070
2.0067
2.0080
2.0065
2.0064
2.0066
2.0072
2.0070
2.0070
1.38
1.38
1.33
1.33
1.34
1.35
1.39
1.38
1.34
1.33
1.34
1.33
0.38
0.37
0.38
0.37
0.38
0.38
0.38
0.38
0.38
0.38
0.38
0.38
þ0.20
þ0.15
ꢀ0.33
ꢀ0.30
ꢀ0.01
ꢀ0.02
ꢀ3.40
ꢀ1.28
ꢀ1.01
ꢀ0.70
ꢀ1.34
ꢀ1.37
(ꢂ)-1g
(2S,5S)-2g
(ꢂ)-2g
97
ꢀ
ꢀ202.2
ꢀ
(2S,5S)-3g
(ꢂ)-3g
97
ꢀ
ꢀ187.3
ꢀ
(S)-4
98
ꢀ
ꢀ99.4
ꢀ
(ꢂ)-4
(2S,5S)-5
(ꢂ)-5
93
ꢀ
ꢀ142.0
ꢀ
(2S,5S)-6
(ꢂ)-6
96
ꢀ
ꢀ181.7
ꢀ
aMeasured by DSC. All samples were decomposed at the indicated temperature.
bDetermined by HPLC analysis using a chiral stationary phase column (Daicel
Chiralcel OD-H, 0.4 ꢄ 25 cm) and a mixture of hexane and 2-propanol (9:1) as the mobile
phase.
cMeasured in THF. c 1.00.
dMeasured in THF at 25ꢃC.
eCurie constants.
fWeiss temperature.
gData quoted from Ref. 1.
The homochiral ribbons further interact with one another along the b
axis by two C(sp3)ꢀHꢁꢁꢁOꢀN interactions [HꢁꢁꢁO distances: 2.760(4)
˚
and 2.916(3) A] between the two pyrrolidinyl C(3)Hs of a homochiral
ribbon and the nearest NO groups of the neighbouring ribbons to give
the homochiral 3D network structure (Fig. 3b).
Thus, the origin of the conglomerate formation with respect to 1,
trans-2 and trans-3 can be interpreted in terms of the formation of
homochiral 1D zigzag chains by the strong intermolecular OꢀHꢁꢁꢁOꢀN
OꢀN hydrogen bonds, together with weak attractive forces such as
dipole–dipole interactions between the NO groups and C(spn)–
HꢁꢁꢁOꢀN interactions [1].
Preparation of 4 and trans-5
Racemic and enantiomerically enriched nitroxides 4 and trans-5 were
prepared analogously to the preparation of trans-(ꢂ)- and trans-(2S,5S)-6

30
N. Ikuma et al.
[3,6] from trans-(ꢁ)- and trans-(2R,5R)-2,5-dimethylpyrrolidine, respect-
ively (Scheme 1) [7]. The phenolic hydroxy group was protected by a
tert-butyldimethylsilyl (TBDMS) group prior to the Grignard reaction
and then was deprotected in the final step using tetrabutylammonium flu-
oride (TBAF) to give phenolic nitroxides 4 and trans-5. These were purified
by flash column chromatography on silica gel eluting with CH2Cl2=Et2O,
followed by recrystallization from CH2Cl2 or MeOH, respectively. The
single crystals of (ꢁ)-4, trans-(ꢁ)-5 and trans-(ꢁ)-6 for X-ray crystallo-
graphic analysis were obtained by recrystallization from CH2Cl2, MeOH
or hexane, respectively. Their thermal, optical and magnetic properties
are summarized in Table 1, together with those of nitroxides 1, trans-2
and trans-3 [1].
Origin of the Formation of a Racemic Compound with Respect
to (ꢁ)-4, trans-(ꢁ)-5 and trans-(ꢁ)-6
As expected from the comparison of IR spectra between the enantio-
merically enriched material and the racemate (Fig. 4), all of the racemic
samples of 4, trans-5 and trans-6 have been found to exist as a racemic
compound consisting of a pair of R and S molecules by X-ray crystal-
lographic analysis.
The temperature-dependence of the molar magnetic susceptibility
vmol measured for the polycrystalline samples of (ꢁ)-4, trans-(ꢁ)-5
and trans-(ꢁ)-6 is shown in the vT vs. T plot in Figure 5. These solid
materials uniformly show weak antiferromagnetic interactions below
20 K. The vT value at 300 K for each compound corresponds to the free
S¼1=2 spin with a g-factor of 2.0, indicating that the radical purity of
the obtained nitroxides is satisfactory.
The crystal structure of (ꢁ)-4 (space group P21=c, Z¼4) is character-
ized by a centrosymmetric head-to-head cyclic dimer which is formed
by hydrogen bonds between the NO and the OH groups [OꢂꢂꢂO
˚
distance: 2.720(2) A] in a pair of R and S molecules. The cyclic dimers
interact with each other in a cyclic manner around an inversion center
by means of weak C(sp3)ꢄHꢂꢂꢂOꢄN interactions [HꢂꢂꢂO distance:
˚
3.1479(13) A] between one of the two methyl groups on the pyrrolidinyl
C(5) of one dimer and the NO group of the neighboring dimer, eventu-
ally forming heterochiral 1D chains along the c axis (Fig. 6). The OꢂꢂꢂO
distances among the NO groups in the 1D chain are alternately
˚
4.282(2) and 5.554(2) A. No appreciable interchain interaction other
than van der Waals forces is seen in the crystal lattice. Accordingly,
the observed weak antiferromagnetic behavior of (ꢁ)-4 below 20 K is
explained by the through-space NOꢂꢂꢂON interactions among the NO
groups which form an alternating linear chain.

Crystalline Nature of Chiral Cyclic Nitroxides
31
FIGURE 4 Comparison of the diffuse reflectance IR spectra between the
enantiomerically enriched material and the racemate with respect to (a) 4,
(b) trans-5 and (c) trans-6.

32
N. Ikuma et al.
FIGURE 5 Temperature dependence of the magnetic susceptibility for (ꢁ)-4
(represented by squares), trans-(ꢁ)-5 (triangles) and trans-(ꢁ)-6 (circles).
The crystal structure of trans-(ꢁ)-5 (space group Pbcn, Z¼4) is
characterized by a bifurcated hydrogen bond formed by the two facing
phenolic hydroxy groups and the NO groups [OꢂꢂꢂO distance:
˚
2.810(2) A] to give a heterochiral 1D ribbon structure composed of
FIGURE 6 Crystal structure of (ꢁ)-4 (P21=c, Z ¼ 4) viewed down the b axis.
The carbon, hydrogen, nitrogen, and oxygen atoms are represented by large
open, small open, crosshatched, and closed circles, respectively.

Crystalline Nature of Chiral Cyclic Nitroxides
33
FIGURE 7 Crystal structure of trans-(ꢁ)-5 (Pbcn, Z ¼ 4) viewed down the a
axis. The carbon, hydrogen, nitrogen, and oxygen atoms are represented by
large open, small open, crosshatched, and closed circles, respectively. Hydro-
gen atoms except the two OH group are omitted.
centrosymmetric cyclic dimers along the c axis (Fig. 7). The OꢂꢂꢂO dis-
˚
tance among the NO groups in the 1D ribbon is uniformly 4.6311(9) A.
No appreciable inter-ribbon interaction other than van der Waals
forces is seen in the crystal lattice. Accordingly, the observed weak
antiferromagnetic behavior is also interpreted in terms of the
through-space NOꢂꢂꢂON interactions among the NO groups which
form a regular linear chain.
The crystal structure of trans-(ꢁ)-6 (space group Pbcn, Z¼4) is iso-
morphous with that of trans-(ꢁ)-5 (Fig. 8). In this case, each NO group
FIGURE 8 Crystal structure of trans-(ꢁ)-6 (Pbcn, Z ¼ 4) viewed down the b
axis. The carbon, hydrogen, nitrogen, and oxygen atoms are represented by
large open, small open, crosshatched, and closed circles, respectively. Hydro-
gen atoms except one of the two meta hydrogen atoms for each phenyl group
are omitted.

34
N. Ikuma et al.
interacts with two meta hydrogen atoms on the two facing phenyl
2
˚
groups [OꢂꢂꢂHꢄC(sp ) distances: 2.8775(10) A], giving a heterochiral
1D ribbon structure along the c axis (Fig. 8). No appreciable inter-
ribbon interaction other than van der Waals forces is observed in
the crystal lattice. The OꢂꢂꢂO distance among the NO groups in the
˚
1D ribbon is uniformly 4.4324(6) A, which is shorter than that
˚
[4.6311(9) A] present in trans-(ꢁ)-5. For this reason, the antiferromag-
netic interactions (h¼ ꢄ1.37 K) observed for trans-(ꢁ)-6, which are rel-
evant to the through-space NOꢂꢂꢂON interactions, are stronger than
those (h¼ꢄ0.70 K) for trans-(ꢁ)-5.
Thus, the origin of the racemic compound formation with respect to
(ꢁ)-4, trans-(ꢁ)-5 and trans-(ꢁ)-6 can be accounted for by the formation
of a centrosymmetric cyclic dimer structure arising from the strong
intermolecular OꢄHꢂꢂꢂOꢄN hydrogen bonds, along with additional
weak attractive forces such as dipole–dipole interactions between
the NO groups and C(spn)ꢄHꢂꢂꢂOꢄN interactions.
CONCLUSIONS
It has been revealed that OꢄHꢂꢂꢂOꢄN hydrogen bonds play an impor-
tant role in the formation of both the racemic conglomerates for 1,
trans-2 and trans-3 and the racemic compounds for (ꢁ)-4, trans-(ꢁ)-5
and trans-(ꢁ)-6. Therefore, the presence of at least one 4-hydroxyphe-
nyl group on the stereogenic centers has turned out to be essential to
the formation of a racemic conglomerate with respect to the 2,2,5,
5-tetrasubstituted pyrrolidine-1-oxyl system.
REFERENCES
[1] Ikuma, N., Tamura, R., Shimono, S., Kawame, N., Tamada, O., Sakai, N.,
Yamauchi, J., & Yamamoto, Y. (2003). Mendeleev Commun., 109.
[2] (a) Tamura, R., Susuki, S., Azuma, N., Matsumoto, A., Toda, F., Kamimura, A., &
Hori, K. (1994). Angew. Chem. Int. Ed., 33, 878.
(b) Tamura, R., Susuki, S., Azuma, N., Matsumoto, A., Toda, F., Takui, T.,
Shiomi, D., & Itoh, K. (1995). Mol. Cryst. Liq. Cryst., 271, 91.
(c) Tamura, R., Susuki, S., Azuma, N., Matsumoto, A., Toda, F., & Ishii, Y. (1995).
J. Org. Chem., 60, 6820.
[3] Nicholas, B., Steenbock, M., Klapper, M., Mu¨llen, K., Enkelman, V., & Cabera, K.
(1996). Liebigs Ann. Chem., 1413.
[4] Miller, J. S. & Drillon, M. (Eds.), (2001). Magnetism: Molecules to Materials II,
Wiley-VCH: Weinheim.
[5] McConnell, H. M. (1963). J. Chem. Phys., 39, 1910.
[6] Einhorn, J., Einhorn, C., Ratajczak, F., Gautier-Luneau, J., & Pierre, J.-L. (1997).
J. Org. Chem., 62, 9385.
[7] Short, R. P., Kennedy, R. M., & Masamune, S. (1989). J. Org. Chem., 54, 1755.

Crystalline Nature of Chiral Cyclic Nitroxides
35
[8] The X-ray data were collected at 298 K on an Enraf-Nonius Kappa CCD diffract-
ometer. The crystal structures were solved by the direct methods and refined by
full-matrix least squares. All non-hydrogen atoms were refined anisotropically. All
of the crystallographic calculations were performed by using maXus software pack-
age. Crystal data for (ꢁ)-4: C13H18NO2, Mr¼220.29, 0.29 ꢅ 0.25 ꢅ 0.20 mm, monocli-
ꢃ
˚
nic, space group P21=c, a¼8.1217(5), b¼20.2165(7), c¼8.0943(5) A, b¼110.403(2) ,
ꢃ
V¼1245.65(12) A , Z¼4, qcalcd ¼1.175 g cmꢄ3, 2hmax¼53.5 , MoKa (k¼0.71073 A),
l¼0.79 cmꢄ1, /–xscans, T¼298 K, 2655 independent reflections, 1605 observed
reflections (I > 2.0r(I)), 149 refined parameters, R¼0.051, Rw¼0.126, Dqmax¼0.187
3
˚
˚
ꢄ3
ꢄ3
.
˚
˚
eA
,
Dqmin¼ ꢄ0.281 eA
Crystal data for trans-(ꢁ)-5: C18H20NO3, Mr ¼
298.36, 0.26 ꢅ 0.16 ꢅ 0.06 mm, orthorhombic, space group Pbcn, a¼19.178(2),
b¼8.9422(8), c¼9.0107(4) A, V¼1545.3(2) A , Z¼4, qcalcd¼1.282 g cmꢄ3, 2hmax
¼
3
˚
˚
ꢃ
54.2 , MoKa (k¼0.71073 A), l¼0.87 cmꢄ1, /–xscans, T¼298 K, 1717 independent
˚
reflections, 887 observed reflections (I > 2.0r(I)), 103 refined parameters, R¼
0.052, Rw¼0.128, Dqmax¼0.241 eAꢄ3, Dqmin¼ ꢄ0.328 eAꢄ3. Crystal data for trans-(ꢁ)-
˚
˚
6: C18H20NO, Mr¼266.36, 0.30 ꢅ 0.24 ꢅ 0.20mm, orthorhombic, space group Pbcn,
a¼19.3353(6), b¼9.2424(6), c¼8.5632(5) A, V¼1530.3(1) A , Z¼4, qcalcd¼1.156 g cmꢄ 3
,
3
˚
˚
ꢃ
3, 2hmax¼58.3 , MoKa (k¼0.71073 A), l¼0.71 cmꢄ1, /–xscans, T¼298 K, 2063 inde-
˚
pendent reflections, 1284 observed reflections (I > 2.0r(I)), 103 refined parameters,
R¼0.055, Rw¼0.156, Dqmax¼0.251 eAꢄ3, Dqmin¼ ꢄ0.452eAꢄ3. CCDC-217527-217529
contains the supplementary crystallographic data for this paper. These data can be
obtained online free of charge (or from the Cambridge Crystallographic Data Centre,
12, Union Road, Cambridge CB2 1EZ, UK; fax: (þ44) 1223-336-033; or deposit@ccdc.
cam.ac.uk).
˚
˚