Non-hydroxylic clathrate hosts of [4 + 2]π cycloadducts of phencyclone and N-arylmaleimides: Recognition of aromatic guests

Article abstract of DOI:10.1039/b201915a

A series of non-hydroxylic crystalline host compounds, [4 + 2]π cycloadducts of phencyclone and N-arylmaleimides having a bicyclo[2.2.1]heptene-7-one system, was synthesized and their inclusion behavior investigated. X-Ray crystal analyses of the inclusion compounds of the N-(1-naphthyl) derivative with butan-2-one, the N-(m-tolyl) derivative with p-xylene, together with the guest-free host and the N-(p-tolyl) derivative with m-xylene indicate that the "space" surrounded by the phenanthrene ring, two phenyl rings and bridge carbonyl of the 1,3-diphenyl-1,3-dihydrocyclopenta[l]phenanthren-2-one moiety plays an important role, not only in the formation of inclusion complexes with the aromatic guests but also in host-host interactions. In every case, the N-aryl succinimide assists complex formation with the guests, in which the weak lattice forces due to C-H ... π and C-H ... O interactions are operative. Methyl-substituted benzenes are effectively recognized by the C-H ... π interactions between the guest molecules and the phenanthrene ring of the hosts.

Full text of DOI:10.1039/b201915a

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Non-hydroxylic clathrate hosts of [4 ؉ 2]ꢀ cycloadducts of
phencyclone and N-arylmaleimides:
recognition of aromatic guests†
2
Yasuyuki Yoshitake,a Junichi Misaka,a Koji Setoguchi,a Masaki Abe,a Tomohiro Kawaji,a
Masashi Etob and Kazunobu Harano*a
a Faculty of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-hon-machi,
Kumamoto 862-0973, Japan. E-mail: harano@gpo.kumamoto-u.ac.jp
b School of Agriculture, Kyushu Tokai University, 5435 Kawayo, Choyo-son, Aso-gun,
Kumamoto 869-1404, Japan
Received (in Cambridge, UK) 22nd February 2002, Accepted 27th June 2002
First published as an Advance Article on the web 16th July 2002
A series of non-hydroxylic crystalline host compounds, [4 ϩ 2]π cycloadducts of phencyclone and N-arylmaleimides
having a bicyclo[2.2.1]heptene-7-one system, was synthesized and their inclusion behavior investigated. X-Ray crystal
analyses of the inclusion compounds of the N-(1-naphthyl) derivative with butan-2-one, the N-(m-tolyl) derivative
with p-xylene, together with the guest-free host and the N-(p-tolyl) derivative with m-xylene indicate that the “space”
surrounded by the phenanthrene ring, two phenyl rings and bridge carbonyl of the 1,3-diphenyl-1,3-dihydrocyclo-
penta[l]phenanthren-2-one moiety plays an important role, not only in the formation of inclusion complexes with
the aromatic guests but also in host–host interactions. In every case, the N-aryl succinimide assists complex
formation with the guests, in which the weak lattice forces due to C–H ؒ ؒ ؒ π and C–H ؒ ؒ ؒ O interactions are
operative. Methyl-substituted benzenes are effectively recognized by the C–H ؒ ؒ ؒ π interactions between the
guest molecules and the phenanthrene ring of the hosts.
Introduction
Results
Crystalline inclusion compounds between simple organic
molecules are useful models for studying weak interatomic
interactions in molecular recognition and self-organization of
molecules.1a,b As hosts, organic compounds having various
functional groups have been designed and their clathrate form-
ing abilities tested.1c–h Characteristic examples are diol or
dicarboxylic host molecules, in which the hydroxy groups act
as H-bond sites for the guest, as well as assisting host–host
interactions.
In the course of studies of the pericyclic reaction behavior of
cyclopentadienones, the authors encountered the formation of
crystalline inclusion complexes with recrystallization solvents
(host : benzene : MeOH = 1 : 1 : 1) in the [4 ϩ 2]π cycloadducts
(Diels–Alder adducts) derived from the cycloaddition reactions
of phencyclone with p-bromostyrene and cyclooctatetraene.2
Inspection of the crystal data suggests that the phenanthrene
ring fused to the bicyclo[2.2.1]hepten-7-one moiety plays an
important role in the inclusion of the guest molecule. In con-
nection with this, we have published a communication describ-
ing a non-hydroxylic clathrate host of the [4 ϩ 2]π adduct of
phencyclone and N-(1-naphthyl)maleimide.3 The inclusion
behavior of the several [4 ϩ 2]π adducts of phencyclone and
N-(1-aryl)maleimides are discussed here with newly obtained
data to clarify the overall character of the non-hydroxylic hosts.
Synthesis
The cycloadducts 3a–k were synthesized by the cycloaddition
reaction of phencyclone 1a with N-substituted maleimides
except for the [4 ϩ 2]π adduct of N-(1-naphthylmethyl)-
maleimide 3e. The cycloadduct 3e was synthesized by the
reaction of the [4 ϩ 2]π cycloadduct of maleic anhydride and
phencyclone with 1-aminomethylnaphthalene (Scheme 1).
The configurations of the cycloadducts 3a–k were deter-
mined to be endo on the basis of the NMR spectroscopic
analysis of the C ؒ ؒ ؒ H correlation between the bridge carbonyl
carbon and the methine protons derived from the dienophiles.
Conformation of the N-aryl group of 3
In the cycloadducts 3c, 3f, 3i bearing unsymmetrical N-aryl
groups, but not the 3-methylphenyl derivative 3g, the 1H NMR
spectra were observed as mixtures of the isomers derived from
the restricted rotation about the N–Ar bond. The preferred
conformations of the unsymmetrical N-aryl groups of the
1
cycloadducts 3c, 3f, 3i were determined by H NMR spectro-
scopy. In the 2-methyl derivative 3f, the methyl proton resonates
at Ϫ0.03 (55%) and 2.03 (45%) ppm, remarkably high-field
shifts due to the phenanthrene-ring current effect. Compounds
3c and 3i also showed similar high-field shifted spectral pat-
terns. The 8Ј-H aromatic proton of 3c resonates at 4.62 ppm
and the ethyl protons of 3i appeared at Ϫ0.15 (CH3CH2–)
and 0.13 ppm (CH3CH2–). The populations (inner : outer)
in CDCl3 at room temperature are listed in Fig. 1. The
1-naphthyl, 2-methylphenyl and 2-ethylphenyl derivatives
prefer the inner orientation despite the steric repulsion between
the endo-orientated substituent and the phenanthrene moiety.
AM1 and PM3 molecular orbital (MO) calculations4a could
† Electronic supplementary information (ESI) available: X-ray crystal
reports for 3cؒbutan-2-one (1 : 1), 3g, 3gؒp-xylene (1 : 1) and
3hؒm-xylene (1 : 1) in .cif format; the distances between host and guest
for 3cؒbutan-2-one and distances between hosts for 3g; numbering
sequences of the compounds analyzed by X-ray crystallography; the
PM3 structures of the model inclusion compounds (host : guest = 1 : 1
and 3 : 1). See http://www.rsc.org/suppdata/p2/b2/b201915a/
DOI: 10.1039/b201915a
J. Chem. Soc., Perkin Trans. 2, 2002, 1611–1619
This journal is © The Royal Society of Chemistry 2002
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Differential scanning calorimetry (DSC) and thermogravi-
metry (TG) data for some important clathrates are summarized
in Table 2. The TG curve confirmed the host : guest stoichi-
ometry. For example, in the 3cؒbutanone complex, the total
weight loss was observed to be 10.6% in agreement with the
expected loss of 10.8% for a 1 : 1 ratio. The DSC data of
3cؒbutanone showed a broad endothermic pattern correspond-
ing to guest loss at 136 ЊC, followed by an endothermic peak at
272 ЊC caused by melting of the host. The desolvation temper-
ature is high in comparison to the boiling point of pure guest
liquid, indicating that the guest molecules are strongly held
within the host lattice. In contrast, aromatic guest compounds
form loose inclusion complexes, in which the desolvation
temperatures are lower than the boiling points of pure guests.
Single crystal X-ray analysis
In order to clarify the structures of the inclusion compounds,
the single crystal X-ray analyses were performed.
3cؒButan-2-one complex. A computer-generated drawing of
the packing arrangement of the 3cؒbutan-2-one inclusion com-
pound is shown in Fig. 2. The important distances between the
butan-2-one and the host are presented in Fig. 3 and further
Scheme 1
Fig. 2 Stereoview of the crystal packing of the 3cؒbutanone complex.
Fig. 1 1H NMR spectral data for conformational isomers due to
restricted rotation about the N–Ar bond in 3c, 3f and 3i.
not reproduce the conformational preference of the inner
orientation in 3c.4b
1
The H NMR spectrum of the 2-phenylphenyl derivative 3j
indicates that the 2-phenyl ring is forced to adopt the outer
conformation due to the serious steric repulsion in the inner
orientation.
Inclusion properties
Fig. 3 Intermolecular atom–plane distances (Å) of the 3cؒbutanone
complex.
A variety of solvents (10 solvents of three types: ketone, ether,
aromatic) were used to test the inclusion properties of the host
compounds 3a–k. Alcoholic solvents were not tested because of
the insolubility of the hosts. The inclusion compounds were
obtained by slow concentration of the solution of the host
compounds in the respective guest solvents under atmospheric
conditions. The results are summarized in Table 1. The host :
guest ratios were evaluated by 1H NMR spectral integration.
Compounds 3c, 3f and 3h are efficient inclusion hosts.
Compounds 3d, 3g and 3i allow fewer inclusions, while com-
pound 3b afforded no clathrates with solvents tested. Of the DA
adducts 3a–k, 3c, 3j formed crystalline inclusion compounds
with some polar solvents.
details are depicted in the electronic supporting information
(ESI-1†). The plane of the naphthalene ring is almost per-
pendicular to the maleimide ring and is covered with the phen-
anthrene ring in an ‘edge-to-face’ manner,5 in which the 8Ј-H
proton on the 1-naphthyl ring is located at a close-contact
perpendicular distance of 2.54 Å above the face of the
phenanthrene ring (Fig. 3).6 As described above, this special
geometrical feature is also observed in solution (see Fig. 1),
indicating that 3c prefers to adopt a congested T-shaped
conformation with an attractive intramolecular Ar–H ؒ ؒ ؒ π
interaction5 between the aromatic rings.
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Table 1 Crystalline inclusion compounds (host : guest molar ratio)
Host compound
Guest solvent
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
Acetone
–
–
–
2 : 1
2 : 1
1 : 1
1 : 1
–
1 : 1
1 : 1
–
–
–
–
–
–
–
–
–
–
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
–
–
–
–
–
–
–
–
–
–
3 : 2
–
1 : 1
–
–
–
–
1 : 1
2 : 1
1 : 1
1 : 1
2 : 1
1 : 1
1 : 1
1 : 1
–
–
–
–
–
–
–
1 : 1
–
–
–
–
–
–
–
1 : 1
–
–
–
–
1 : 1
2 : 1
2 : 1
1 : 1
–
–
–
–
–
–
–
–
–
–
1 : 1
1 : 1
–
1 : 1
–
Butan-2-one
Pentan-3-one
THF
1,4-Dioxane
Benzene
2 : 1
2 : 1
–
–
2 : 1
1 : 1
1 : 1
1 : 1
1 : 1
Toluene
o-Xylene
m-Xylene
p-Xylene
1 : 1
1 : 1
–
1 : 1
–
–
Table 2 Differential scanning calorimetry (DSC) and thermogravimetry (TG) data
Host molecule
3c
3g
3h
3j
3j
Guest molecule
Host : guest ratio
Butanone
1 : 1
p-Xylene
1 : 1
m-Xylene
1 : 1
Acetone
1 : 1
Butanone
2 : 1
Bp (guest)/ЊC
80
138
138
56
80
DSC:
Desorption endotherm onset temperature/ЊC
Host melting endotherm onset temperature/ЊC
TG:
136
272
110
287
98
277
143
284
135
284
Weight loss expected (%)
Weight loss observed (%)
10.8
10.6
15.6
13.0
15.6
15.7
8.2
8.4
5.2
5.4
The DA adduct (4c) of 2,3,4,5-tetraphenylcyclopentadienone
(tetracyclone) having a stilbene moiety did not show a clear
stoichiometric host–guest ratio with butan-2-one, which cannot
form the T-shaped conformation that the 1-naphthyl ring is
able to (see Scheme 1 for the structure of 4c).
As can be seen in Figs. 2 and 3, butan-2-one is located
between the parallel stacked walls of the neighboring naphthyl
and maleimide rings. The distance between the guest carbonyl
oxygen and the host maleimide-ring plane is 2.84 Å.7a The
distances between the naphthyl-ring plane and the methyl
and methylene carbons of the guest are 3.58 Å and 3.78 Å,
respectively [see also the supplementary informationESI-1†].
The guest methylene protons and carbonyl oxygen form
C–H ؒ ؒ ؒ O hydrogen bonds8 with the host carbonyl oxygen
and the naphthyl proton, respectively.7b
The edge-to-face type interaction is found between the
diphenyl rings and the adjacent phenanthrene rings in which
the distance between the phenyl hydrogen atom and the least-
squares plane of the phenanthrene ring is 2.46 Å [the distance
C–(H) ؒ ؒ ؒ plane = 3.55 Å]. The plane of the phenanthrene ring
of the free host 3g is remarkably distorted, in which the
dihedral angle (τ) C4–C4a–C4b–C5 is 7.00Њ.9a,b Distortion of
the phenanthrene ring from the ideal planar structure may be
accounted for by the closest approach10 of the phenyl hydrogen
atom to the phenanthrene ring plane constrained by other
crystal packing forces, wherein the back-side C–(H) ؒ ؒ ؒ O
interaction between the phenanthrene ring and the imide
carbonyl is operative (see Fig. 4b).
This distorted dihedral angle is reduced to 2.90Њ by inclusion
of the guest molecule. This may be attributable to the relief of
the strain due to the edge-to-face interactions between the host
molecules. This geometrical feature seems to be important in
connection with the recognition mode of aromatic guests by the
phenanthrene-condensed bicyclo[2.2.1]heptenone moiety.
Computer-generated drawings of the crystal structure of the
inclusion complex (3gؒp-xylene) are depicted in Figs. 5 and 6
(see also ESI-2†). Comparison of the packing diagrams of the
guest-free host 3g and 3gؒp-xylene complex indicates that the
arrangement mode of the host molecules in the complex is
almost the same as that of the free host 3g. In the 3gؒp-xylene
complex, the guest molecules intrude into the spaces occupied
by the edge-to-face interaction (phenanthrene ring–phenyl ring)
in the crystal structure of the free host 3g (Fig. 5). The guest
molecule is located almost parallel with both the succin-
imide ring and the plane of the bridge carbonyl group of
the neighboring host molecules. The geometry of the two
1,3-diphenylpropanone moieties is not largely altered by the
inclusion of the guest. This reflects the dimensions of the crys-
tal lattice constants: the b and c axes of the inclusion complex
are longer than those of the host by 2.5 Å and 1.5 Å,
respectively.
As an important host–host interaction, the phenyl ring of the
adjacent host molecule is located above the phenanthrene ring
(see Fig. 3).
3g and 3gؒp-xylene complex. A computer-generated drawing
of the crystal structure of the free host 3g is depicted in
Fig. 4a,b. The crystal packing of the free host 3g is interesting.
The molecules occur in the crystal as pairs of enantiomers
bonded together via an attractive π–π interaction between the
1,3-diphenylpropanone moieties across a center of symmetry.
The closest contact (3.02 Å) is found between the ketonic oxy-
gen atom and the carbon at the 2Ј-position of the facing phenyl
group. In addition, other short C ؒ ؒ ؒ C contacts (3.42 Å) are
found between the 2Ј-positions of the phenyl group and the
4Ј-positions of the one opposite.
These dimeric host molecules are intermolecularly linked by
a C–H ؒ ؒ ؒ O hydrogen bond and edge-to-face type interactions
between aromatic rings of the host molecules. The C–H ؒ ؒ ؒ O
hydrogen bonds are evident between the imide carbonyls and
the phenanthrene ring [C–(H) ؒ ؒ ؒ O, 3.30 Å] and phenyl ring
[C–(H) ؒ ؒ ؒ O, 3.32 Å] of neighboring host molecules. These
C–H ؒ ؒ ؒ O hydrogen bonds together with the close contacts
described above play a leading role in the construction of the
host framework.
One of the methyl groups of p-xylene makes a C–H ؒ ؒ ؒ O
hydrogen bond with a carbonyl group of the succinimide
moiety [C–(H) ؒ ؒ ؒ O, 3.52 Å] and an aromatic proton of
J. Chem. Soc., Perkin Trans. 2, 2002, 1611–1619
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Fig. 5 Comparison of the crystal packings for 3g (top) and 3gؒp-
xylene (bottom).
Fig. 4 (a) Short contacts in the crystal structure of the guest-free host
(3g). (b) Distortion of the phenanthrene ring in the crystal structure
of the guest-free host (3g). The horizontal dotted line (P) is the
undistorted phenanthrene plane (see ref. 10).
p-xylene also hydrogen-bonds with the bridge carbonyl
[C–(H) ؒ ؒ ؒ O, 3.34 Å] (see Fig. 6).
The plane of p-xylene makes the angle of 47.50Њ with the
phenanthrene ring and the “space” created by phenanthrene
ring, the bridge carbonyl and diphenyl groups hold a p-xylene
molecule which faces the succinimide ring with an interplane
distance of 3.6 Å. The importance of the role of the “space” is
also observed in the m-xyleneؒ3h (p-tolyl derivative) complex
described below.
The host 3g included only toluene and p-xylene. This
inclusion behavior is attributable to the nature of the cavity and
the strict steric requirement due to the different types of
CH ؒ ؒ ؒ O interaction.
Fig. 6 Crystal structure of the 3gؒp-xylene complex.
3hؒm-Xylene complex. The computer-generated drawings of
the inclusion complex 3hؒm-xylene are depicted in Figs. 7 and 8.
As the case of 3gؒp-xylene, the “space” on the phenanthrene
ring plays an important role in the holding of the guest. The
interplanar distance between the phenanthrene rings is 7.21 Å.
The intermolecular room created by the two “spaces” enclath-
rates two molecules of m-xylene (Me ؒ ؒ ؒ Me, 4.32 Å). The
distance between a methyl carbon of m-xylene and the
phenanthrene-ring plane is 3.70 Å. On the other hand, along
Fig. 7 Stereoview of the crystal packing of the 3hؒm-xylene complex.
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phenylphenyl) derivative 3j, this structural feature cannot be
attained because of the serious steric interference between the
phenanthrene ring and the 2-phenyl substituent, in which 3j
adopts
a conformation having the exo-oriented phenyl
substituent showing different inclusion behavior for ketones,
i.e., 2 : 1 complex formation.
From the X-ray analyses of the inclusion complexes of p- and
m-xylenes, an important inclusion mode becomes clear wherein
the “space” created by the phenanthrene ring, bridge carbonyl
and two phenyl groups of the bicyclo[2.2.1]heptenone moiety
plays a crucial role for inclusion of aromatic guest molecules. In
the 3cؒbutan-2-one complex, this “void space” is occupied by
the aromatic ring of the neighboring host molecule for the
stabilization of the host framework (Fig. 3). Therefore, the
opposite space (below the phenanthrene ring and by the side
of the naphthalene ring of the bicyclo[2.2.1]heptenone moiety)
is used for the inclusion of ketones. Similarly, in the guest-
free host 3g, the “space” is used for self-inclusion complex
formation stabilizing the host frame work.
Fig. 8 Location of the guest in 3hؒm-xylene.
In the cases of aromatic guests, the succinimide rings also
play an important role in formation of the host ؒ ؒ ؒ guest ؒ ؒ ؒ
host ؒ ؒ ؒ sequence, i.e., the face-to-face interaction in the 3gؒ
p-xylene complex and the >C᎐O ؒ ؒ ؒ H–CH – bond formation
the rectangular direction of this interaction, the methyl hydro-
gens of the guests are linked with the carbonyl oxygens of the
succinimide rings by a >C᎐O ؒ ؒ ؒ H–CH C H H C–H ؒ ؒ ؒ O᎐
᎐
᎐
2
6
4
2
᎐
2
C< type interaction (see Fig. 8). The distance between the
carbonyl oxygen atom of the maleimide and the methyl carbon
atom of the guest is ca. 3.5 Å, in which the C–H ؒ ؒ ؒ O distance
is ca. 2.5 Å and the angle is 170–177Њ. The p-tolyl ring makes the
angle of 45Њ with the plane of the maleimide ring and makes
face-to-face interaction with an adjacent p-tolyl ring at intervals
of 3.46 Å (the intermolecular distance between the carbon
atoms at the 2- or 3-position), stabilizing the host framework.
The guest molecules are enclathrated in the enclosure of the
aromatic rings of the hosts assisted by the C–H ؒ ؒ ؒ O
interactions.
in 3hؒm-xylene complex.
In connection with computer modeling technique in the field
of clathrate chemistry, we examined the usability of semi-
empirical MO calculations on the structural features of the
inclusion compounds. The partial structures extracted from the
host–guest complex were used for AM1 or PM3 calculations.
The PM3 MO method roughly reproduced the geometrical
features of the inclusion compounds of aromatic guests. The
stabilization energy due to C–H ؒ ؒ ؒ π interactions between
m-xylene and 3h was calculated to be 3.64 kcal molϪ1. The
PM3-calculated stabilization energy is assumed to be greater
than the actual value because the PM3 method is known to
overestimate non-bonding H ؒ ؒ ؒ H interaction energy. The
calculated energies and geometries of the 1 : 1 (host : guest)
models are shown in ESI-6–8† together with the geometries of
the 3 : 1 complex.
Reinvestigation of the previously reported X-ray crystal
structures of the (benzene and methanol)-included [4 ϩ 2]π
cycloadduct (3l) of 1a and p-bromostyrene2a and the 2 : 1
cycloadduct (3m) of 1a and bicyclo[4.2.0]octa-2,4,7-triene
(a valence isomer of cyclooctatetraene)2b indicates that the
inclusion behavior of these cycloadducts belongs to the
category of the present cases. In 3l, the guest molecule (benz-
ene) is held on the opposite side of the phenanthrene ring to the
bridge carbonyl group (Fig. 9).
Inspection of the X-ray structures indicated that the methyl-
substituted benzenes are recognized by three-point interactions
with the phenanthrene ring and benzene is located on the phen-
anthrene ring with two-point interactions. The aryl (host)–aryl
(host) interactions in guest-free 3g and butan-2-oneؒ2c are also
caused by similar recognition mechanisms.
The information of the present study seems to be very useful
for the design of clathrate hosts bearing aromatic rings. The
synthesis of some hosts which can enclathrate alcoholic guests
is in progress.
Discussion
As a characteristic feature of the [4 ϩ 2]π cycloadducts of
phencyclone as a clathrate host, we point out that the hosts do
not have any hydroxylic substituents which may act as
hydrogen-bond sites for the guest, as well as assisting host–host
interactions. The “space” above the phenanthrene plane is
occupied by the aromatic guest or the aryl group of the hosts.
The inclusion ability seems to depend upon the rigidity of
the N-aryl moiety of the hosts. Those hosts having conform-
ationally free N-phenyl (3b) or N-arylmethyl (3d, 3e) or
N-(substituted aryl) (3g, 3i, 3j, 3k) groups afford few inclusion
compounds. In the cases of 3c and 3f, whose rotations about
N ؒ ؒ ؒ aryl bonds are restricted by the σ–π interaction, a wide
range of inclusions were found. The N–Me derivative (3a) did
not include ketones.
In butan-2-oneؒ3c, the combination of the naphthalene ring
and the succinimide ring derived from the dienophile plays a
leading role in the inclusion of the guest molecule. The ketone
is considered to be included by coulomb interactions between
the carbonyl oxygen of butan-2-one and the electron-deficient
carbonyl carbons of the succinimide ring, assisted by the
C–H ؒ ؒ ؒ π interaction between the α-hydrogen atoms of butan-
2-one and the naphthalene ring (see ESI-1†), in which the
rotation about the N–naphthyl bond is restricted by the edge-
to-face interaction between the naphthalene and phenanthrene
rings. As stated above, the host 3a bearing an N–Me group did
not afford inclusion compounds with ketones, indicating that
the interaction with the N-aryl moiety is essential for inclusion
of ketones.
Experimental
Melting points were uncorrected. The IR spectra were taken
1
with a Hitachi 270–30 spectrophotometer. H NMR and 13C
NMR spectra were taken with JEOL JNM-EX 270 (270 MHz)
and JNM-A 500 (500 MHz) spectrometers for ca. 10% sol-
utions (CDCl3) with TMS as an internal standard; chemical
shifts are expressed as δ values and the coupling constants (J)
are expressed in Hz. Mass spectra were obtained using a JEOL
JMS-DX 303 instrument. UV spectra were recorded on a
Shimadzu UV-2500PC spectrophotometer. Thermal analyses
As can be seen in Table 1, the host 3f also enclathrates butan-
2-one. The inclusion mode of 3c seems to be applicable to the
host 3f in which the conformation of the 2-methylphenyl
ring may be fixed by the CH ؒ ؒ ؒ π interaction between the
phenanthrene ring and the methyl protons. In the N-(2-
J. Chem. Soc., Perkin Trans. 2, 2002, 1611–1619
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Fig. 9 Recognition of aromatic ring in guest–host and host–host interactions for the DA adducts of phencyclone: A, p-xyleneؒ3g; B, m-xyleneؒ3h;
C, 3c–3c interaction; D, guest-free 3g–3g interaction; E, benzene–3m–MeOH; F, benzene–3l–MeOH.
were performed on a Perkin Elmer 7 Series/UNIX DSC 7
(differential scanning calorimeter DSC), a Perkin Elmer 7
Series/UNIX TGA 7 (thermogravimetric analysis TG) and a
Shimadzu DTG-50/50H simultaneous TG/DTA instrument.
the precipitated crystals were collected and washed with cold
ether. The product was dried under vacuum to give a colorless
powder (4.3 g, yield 90%, mp 289 ЊC). IR (KBr)/cmϪ1 1784
(bridge >C᎐O). δH (500 MHz) 4.75 (2H, s, methine), 7.12–7.76
᎐
(16H, m, aromatic H), 8.69 (2H, d, J 8.43, protons at the 4,5-
positions of the phenanthrene moiety (Ha)). MS (m/z) 480
(Mϩ), 452 (Mϩ Ϫ CO). Anal. Calcd. for C33H20O4: C, 82.49;
H, 4.20. Found: C, 82.33; H, 4.11%.
Materials
Phencyclone (mp 245–255 ЊC) was prepared according to the
previously reported method using potassium hydroxide. The
product was washed with ethanol, yield 73%.11
Preparation of the [4 ؉ 2]ꢀcycloadduct of 1a and 1-aminomethyl-
naphthalene (3e)
Preparation of maleanilic acids (general procedure)
A mixture of 1a–MA (0.5 g, 1.04 mmol) and 1-amino-
methylnaphthalene (0.16 g, 1.02 mmol) in DMF was heated at
150 ЊC for 5 h. After cooling, the reaction product was poured
onto ice–water. The precipitate was collected and recrystallized
from acetone to give colorless needles 3e (0.62 g, yield 96%);
mp 287–288 ЊC (from acetone). IR (KBr)/cmϪ1 1786 (bridge
1-Aminonaphthalene (4.44 g, 0.03 mol) dissolved in small
amount of ether was added to a solution of maleic anhydride
(3.00 g, 0.03 mol) in ether with stirring. The crystals
precipitated were collected, washed with ether and dried under
vacuum to give pure crystals.
>C᎐O), 1702 (amide C᎐O). δ (270 MHz) 4.55 (2H, s,
᎐
᎐
H
Preparation of maleimides (general procedure)
methylene), 4.46 (2H, s, methine), 6.57 (2H, m, aromatic H),
6.95–7.74 (19H, m, aromatic H), 8.25 (2H, d, J 8, aromatic H),
8.35 (2H, d, J 7.9, Ha). MS (m/z) 619 (Mϩ), 591 (Mϩ Ϫ CO).
Anal. Calcd. C44H29O3N: C, 85.28; H, 4.72; N, 2.26. Found:
C, 85.10; H, 4.65; N, 2.38%.
A mixture of maleanilic acid (3.34 g, 0.01 mol), acetic
anhydride (16 ml) and anhydrous sodium acetate (0.55 g) was
stirred at 90–100 ЊC for 30 min. After being cooled, the reaction
mixture was poured onto ice–water and stirred until the pre-
cipitates appeared. The crystals were collected and washed with
2 × 10 ml of water and then with n-hexane (5 ml). The crystals
were dried under vacuum.
[4 ؉ 2]ꢀ Cycloadducts (3a–k) of 1a and maleimides (2a–k)
The cycloadducts were obtained according to the method
described in the [4 ϩ 2]π cycloadduct of 1a and maleic
anhydride using 1a (1.01 g, 0.03 mol), maleimide (0.03 mol) and
benzene (6 ml) as solvent.
The [4 ؉ 2]ꢀ cycloadduct (1a–MA) of 1a and maleic anhydride
(MA)
A solution of 1a (3.82 g, 0.01 mol), maleic anhydride (1.28 g,
11 mmol) in toluene (10 ml) was refluxed at 110 ЊC until the
dark green color had faded out (about 5 min). After cooling,
3a: with 2a, 74%, colorless needles; mp 292–293 ЊC (from
acetone). IR (KBr)/cmϪ1 1792 (bridge >C᎐O), 1702 (amide
᎐
>C᎐O). δ (270 MHz) 2.21 (3H, s, methyl), 4.43 (2H, s,
᎐
H
1616
J. Chem. Soc., Perkin Trans. 2, 2002, 1611–1619

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Table 3 Crystal data and intensity measurements for 3cؒbutan-2-
one(1 : 1)
methine), 7.12–7.75 (14H, m, aromatic H), 8.33 (2H, d, J 7.9,
aromatic H), 8.64 (2H, d, J 8.3, Ha). MS (m/z) 493 (Mϩ) 465
(Mϩ Ϫ CO). Anal. Calcd. C34H23O3N: C, 82.74; H, 4.70;
N, 2.84. Found: C, 82.60; H, 4.67; N, 3.05%.
Formula
Mp/ЊC
C43H27O3NؒC4H8O
272–273
3b: with 2b, 72%, colorless prisms; mp 295–296 ЊC (from
Formula weight
Crystal system
Lattice type
677.80
Monoclinic
Primitive
acetone). IR (KBr)/cmϪ1 1776 (bridge >C᎐O), 1718 (amide
᎐
>C᎐O). δH (270 MHz) 4.60 (2H, s, methine), 5.88 (2H, d, J 6.9,
᎐
Lattice parameters
a
b
c
β
V
C2Ј-H), 6.91–7.74 (17H, m, aromatic H), 8.36 (2H, d, J 7.9,
aromatic H), 8.58 (2H, d, J 8.6, Ha). MS (m/z) 555 (Mϩ) 527
(Mϩ Ϫ CO). Anal. Calcd. C39H25O3N: C, 84.31; H, 4.53;
N, 2.52. Found: C, 84.05; H, 4.68; N, 2.58%.
10.843(3) Å
13.916(2) Å
23.573(1) Å
91.144(10)Њ
3556.1(10) Å3
P21/n(No. 14)
4
3c: with 2c, 71%, colorless powder; mp 272–273 ЊC (from
benzene). IR (KBr)/cmϪ1 1780 (bridge >C᎐O), 1718 (amide
Space group
᎐
Z
>C᎐O). δ (270 MHz) 4.62 (0.6 of 1H, d, J 7.3, inner C8Ј-H),
᎐
H
Dc/g cmϪ3
1.266
4.63 (0.4 of 1H, d, J 7.3, outer C2Ј-H), 4.66 (1.2 of 2H, s, inner
methine), 4.74 (0.8 of 2H, s, outer methine), 6.03 (0.6 of 1H, t,
J 7.3, inner C7Ј-H), 6.71 (0.4 of 1H, t, J 7.3, outer C3Ј-H), 6.99
(0.6 of 1H, t, J 7.3, inner C6Ј-H), 7.12–7.69 (16H, m, aromatic
H), 8.35 (0.8 of 2H, d, J 8.1, aromatic H), 8.37 (1.2 of 2H, d,
J 8.1, aromatic H), 8.74 (0.8 of 2H, d, J 8.6, outer Ha), 8.80
(1.2 of 2H, d, J 8.6, inner Ha). MS (m/z) 604 (Mϩ ϩ 1), 576
(Mϩ ϩ 1 Ϫ CO). Anal. Calcd. C43H27O3N: C, 85.27; H, 4.49;
N, 2.31. Found: C, 85.15; H, 4.49; N, 2.48%.
Solvent
Radiation
Scan range
Reflections collected
Butan-2-one
Mo-Kα (λ = 0.71069 Å)
2θ < 55.0Њ
8937
Unique data collected
Unique data used [I > 2.00 σ(I )]
8499
4589
R
Rw
0.063
0.099
3d: with 2d, 84%, colorless needles; mp 286–287 ЊC (from
3j: with 2j, 94%, colorless needles; mp 284–285 ЊC (from
benzene). IR (KBr)/cmϪ1 1786 (bridge >C᎐O), 1704 (amide
᎐
toluene). IR (KBr)/cmϪ1 1788 (bridge >C᎐O), 1714 (amide
᎐
>C᎐O). δ (270 MHz) 4.07 (2H, s, methylene), 4.45 (2H, s,
᎐
H
>C᎐O). δH (270 MHz) 4.32 (2H, s, methine), 4.48 (1H, d, J 7.6,
᎐
methine), 6.25 (2H, d, J 6.9, C2Ј-H), 6.46 (2H, t, J 7.8, C3Ј-H),
6.79 (1H, t, J 7.5, C4Ј-H), 7.02–7.74 (14H, m, aromatic H), 8.35
(2H, d, J 7.6, aromatic H), 8.47 (2H, d, J 8.3, Ha). MS (m/z) 569
(Mϩ), 541 (Mϩ Ϫ CO). Anal. Calcd. C40H27O3N: C, 84.34;
H, 4.78; N, 2.46. Found: C, 84.58; H, 4.78; N, 2.63%.
C6Ј-H), 6.62–6.68 (1H, m, C5Ј-H), 7.09–7.70 (16H, m, aromatic
H), 8.22 (2H, d, J 7.9, aromatic H), 8.73 (2H, d, J 8.2, Ha).
MS (m/z) 630 (Mϩ Ϫ 1), 602 (Mϩ Ϫ 1 Ϫ CO). Anal. Calcd.
C45H29O3N: C, 85.56; H, 4.63; N, 2.22. Found: C, 85.30;
H, 4.74; N, 2.29%.
3f: with 2f, 91%, colorless prisms; mp 285–286 ЊC (from
3k: with 2k, 86%, colorless powder; mp 268–270 ЊC (from
p-xylene). IR (KBr)/cmϪ1 1788 (bridge >C᎐O), 1712 (amide
᎐
p-xylene). IR (KBr)/cmϪ1 1788 (bridge >C᎐O), 1712 (amide
᎐
>C᎐O). δ (270 MHz) Ϫ0.03 (1.64 of 3H, s, inner methyl), 2.03
᎐
H
>C᎐O). δ (270 MHz) 4.62 (2H, s, methine), 5.96 (2H, dd,
᎐
H
(1.36 of 3H, s, outer methyl), 4.36 (0.46 of 1H, d, J 7.3, C6Ј-H),
4.64 (2H, s, methine), 6.49 (0.46 of 1H, t, J 7.3, C5Ј-H), 6.76
(0.54 of 1H, d, J 7.3, C3Ј-H), 6.86–7.70 (15H, m, aromatic H),
8.37 (2H, t, J 8.6, aromatic H), 8.66 (1.08 of 2H, d, J 8.6, inner
Ha), 8.71 (0.92 of 2H, d, J 8.6, outer Ha). MS (m/z) 569 (Mϩ),
541 (Mϩ Ϫ CO). Anal. Calcd. C40H27O3N: C, 84.34; H, 4.78;
N, 2.46. Found: C, 84.52; H, 4.73; N, 2.54%.
J 1.96 and 6.6, C2Ј-H), 7.13–7.75 (21H, m, aromatic H), 8.39
(2H, d, J 7.9, aromatic H), 8.69 (2H, d, J 8.3, Ha). MS (m/z) 631
(Mϩ), 603 (Mϩ Ϫ CO). Anal. Calcd. C45H29O3N: C, 85.56;
H, 4.63; N, 2.22. Found: C, 85.52; H, 4.47; N, 2.19%.
Preparation of inclusion complexes
3g: with 2g, 86%, colorless prisms; mp 286–287 ЊC (from
The host compound was dissolved under heating in the
minimum amount of a guest solvent. The solution was allowed
to cool in a water bath to ensure crystallization of the inclusion
compounds. After standing for several days at 25 3 ЊC, the
crystals were collected by suction filtration and dried.
m-xylene). IR (KBr)/cmϪ1 1792 (bridge >C᎐O), 1710 (amide
᎐
>C᎐O). δ (270 MHz) 1.89 (3H, s, methyl), 4.57 (2H, s,
᎐
H
methine), 5.33 (1H, s, C2Ј-H), 5.88 (1H, d, J 6.9, C6Ј-H), 6.84
(1H, d, J 7.9, C4Ј-H), 6.87 (1H, t, J 7.6, C5Ј-H), 7.15–7.74
(14H, m, aromatic H), 8.36 (2H, d, J 7.9, aromatic H), 8.68 (2H,
d, J 8.6, Ha). MS (m/z) 569 (Mϩ), 541 (Mϩ Ϫ CO). Anal. Calcd.
C40H27O3N: C, 84.34; H, 4.78; N, 2.46. Found: C, 84.37;
H, 4.49; N, 2.70%.
Single crystal X-ray analysis‡
The crystal structure of 3cؒbutan-2-one (1 : 1) was determined
as follows. The reflection data (see Tables 3–5) were measured
on a Rigaku AFC7R four-circle autodiffractometer with
graphite monochromated Mo-Kα radiation (λ = 0.7107 Å) and
a rotating anode generator. The structures were solved by direct
methods. The hydrogen atoms were placed in calculated
positions. The non-hydrogen atoms were refined anisotropically
and the hydrogen atoms were refined isotropically. The final
residuals for reflections with I0 > 2.00σI) were R = 0.063 and
Rw = 0.099.
Similarly, the X-ray analyses of 3g, 3gؒp-xylene and 3hؒ
m-xylene were performed. The X-ray analysis data (crystal
data, final atomic coordinates, distance and angles) are sum-
marized in the supporting information. All calculations were
performed on a Silicon Graphics O2 WS with the teXsan12
crystal structure analysis package.
3h: with 2h, 81%, colorless powder; mp 277–278 ЊC (from
acetone). IR (KBr)/cmϪ1 1788 (bridge >C᎐O), 1712 (amide
᎐
>C᎐O). δ (270 MHz) 2.10 (3H, s, Me), 4.58 (2H, s, methine),
᎐
H
5.75 (2H, d, J 8.6, C2Ј-H), 6.75 (2H, d, J 8.3, C3Ј-H), 7.15–7.74
(14H, m, aromatic H), 8.39 (2H, d, J 7.5, aromatic H), 8.68 (2H,
d, J 8.6, Ha). MS (m/z) 569 (Mϩ), 541 (Mϩ Ϫ CO). Anal. Calcd.
C40H27O3N: C, 84.34; H, 4.78; N, 2.46. Found: C, 84.36;
H, 4.77; N, 2.46%.
3i: with 2i, 73%, colorless prisms; mp 279–280 ЊC (from
toluene). IR (KBr)/cmϪ1 1788 (bridge >C᎐O), 1712 (amide
᎐
>C᎐O). δ (270 MHz) Ϫ0.15 (1.8 of 3H, t, J 7.6, inner
᎐
H
CH2CH3), 0.13 (1.2 of 2H, q, J 7.6, inner CH2CH3), 1.10
(1.2 of 3H, t, J 7.6, outer CH2CH3), 2.35 (0.8 of 2H, q, J 7.6,
outer CH2CH3), 4.27 (0.4 of 1H, d, J 7.9, C6Ј-H), 4.65 (2H,
s, methine), 6.45 (0.4 of 1H, t, J 7.3, C5Ј-H), 6.82–7.73 (16H,
m, aromatic H), 8.37 (2H, t, J 8.3, aromatic H), 8.70 (0.8 of
2H, d, J 7.9, outer Ha), 8.73 (1.2 of 2H, d, J 7.9, inner Ha). MS
(m/z) 582 (Mϩ Ϫ 1), 554 (Mϩ Ϫ 1 Ϫ CO). Anal. Calcd.
C41H29O3N: C, 84.37; H, 5.01; N, 2.40. Found: C, 84.65;
H, 5.13; N, 2.53%.
‡ The crystal data have been deposited at the Cambridge Crystallo-
graphic Data Centre, CCDC reference numbers 180113–180116. See
http://www.rsc.org/suppdata/p2/b2/b201915a/ for crystallographic data
in .cif or other electronic format.
J. Chem. Soc., Perkin Trans. 2, 2002, 1611–1619
1617

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Table 4 Crystal data and intensity measurements for 3g and 3gؒp-xylene (1 : 1)
Compound
3g
3gؒp-xylene(1 : 1)
Formula
Mp/ЊC
Formula weight
C40H27O3N
290–291
569.66
C40H27O3NؒC8H10
290–291
675.83
Crystal system
Lattice type
Triclinic
Primitive
Triclinic
Primitive
Lattice parameters
a
b
c
α
β
γ
V
11.667(3) Å
14.264(3) Å
9.053(2) Å
90.09(2)Њ
100.01(2)Њ
77.15(2)Њ
1445.5(6) Å3
P1(Ϫ) (No. 2)
2
11.385(4)Å
16.895(5)Å
10.483(4)Å
101.11(3)Њ
114.33(2)Њ
95.93(3)Њ
1764(1) Å3
P1(Ϫ) (No. 2)
2
Space group
Z
Dc/g cmϪ3
1.309
1.272
Solvent
Radiation
Scan range
Reflections collected
Unique data collected
Unique data used [I > 3.00 σ(I)]
R
Rw
o-Xylene
Mo-Kα (λ = 0.71069 Å)
2θ < 55.0Њ
6963
6637
3632
p-Xylene
8513
8103
4962
0.050
0.078
0.052
0.075
Table 5 Crystal data and intensity measurements for 3hؒm-xylene
2 (a) M. Yasuda, K. Harano and K. Kanematsu, J. Org. Chem., 1980,
45, 659; (b) M. Yasuda, K. Harano and K. Kanematsu, J. Am.
Chem. Soc., 1981, 103, 3120.
3 M. Eto, K. Setoguchi, A. Harada, E. Sugiyama and K. Harano,
Tetrahedron Lett., 1998, 39, 9751.
(1 : 1)
Formula
Mp/ЊC
C40H27O3NؒC8H10
280–281
Formula weight
Crystal system
Lattice type
675.83
Monoclinic
Primitive
4 (a) AM1 and PM3 calculations were performed using MOPAC
ver. 6.0 (QCPE No. 445) and MOPAC97, Fujitsu Ltd, Tokyo,
Japan, 1998; (b) The heats of formation for the conformational
isomers of 3c calculated by semiempirical MO methods are as
Lattice parameters
a
b
c
β
V
14.802(2)Å
14.302(2)Å
16.739(2)Å
94.052(8)Њ
3534.9(6)Å3
P21/n (No. 14)
4
follows: AM1, inner 130.53 kcal molϪ1, outer 129.68 kcal molϪ1
;
PM3, inner 88.93 kcal molϪ1, outer 88.84 kcal molϪ1. The PM3
calculated energy difference in ∆∆H is 0.1 kcal molϪ1, suggesting
a 1 : 1.2 ratio in favor of the outer conformation. The AM1
calculated value is unreliable. The AM1 method perhaps
overestimates the electron–electron or core–core repulsion in
molecular association;4c (c) The intermolecular stabilization due to
molecules associating has proved difficult to accurately model using
MNDO and AM1 semiempirical methods J. J. P. Stewart, J. Comput.
Chem., 1989, 10, 239.
Space group
Z
Dcalc/g cmϪ3
Solvent
)
1.270
m-Xylene
Mo-Kα (λ = 0.71069 Å)
2θ < 55.0Њ
8768
Radiation
Scan range
Reflections collected
5 (a) M. Nishio and M. Hirota, Tetrahedron, 1989, 45, 7201;
(b) C. A. Hunter and J. K. M. Sanders, J. Am. Chem. Soc., 1990,
112, 5525; (c) T. Steiner, E. B. Starikov, A. M. Amada and
J. J. C. Texia-Dias, J. Chem. Soc., Perkin Trans. 2, 1995, 1321;
(d ) D. R. Boyd, T. A. Evans, W. B. Jennings, J. F. Malone, W.
O’Sullivan and A. Smith, J. Chem. Soc., Chem. Commun., 1996,
2269; (e) M. Nishio, M. Hirota and Y. Umezawa, The CH/π
Interaction; Evidence Nature and Consequences, Wiley, New York,
1998.
6 The calculated edge-to-face distances between the C8-H of the
naphthyl group and the phenanthrene plane are as follows: PM3,
2.574 Å; AM1, 2.722 Å; HF/6–31G*, 2.831 Å; B3LYP/6–31G*,
2.777 Å.
7 (a) The distances between the guest carbonyl oxygen and two
maleimide carbonyl carbons are 3.00 and 3.20 Å. A similar short
contact7c was found between the oxygen atom of a formamide
(guest) and the phthalimide carbonyl carbon of N-[2-(3,5-dinitro-
benzoylamino)-6-methylphenyl]phthalimide (host) K. Kishihara,
R. Takeuchi, S. Kohmoto, M. Yamamoto, K. Yamaguchi and
K. Yamada, J. Chem. Soc., Perkin Trans. 1, 1998, 1143;
Unique data collected
Unique data used [I > 3.00 σ(I )]
8452
5390
R
Rw
0.053
0.081
Acknowledgements
We thank Miss A. Harada, Miss E. Sugiyama, Miss
A. Kikuchi, Miss A. Saitoh and Miss R. Maehara for
experimental assistance.
References
1 (a) E. Weber, J. L. Atwood, J. E. D. Davies and D. D. MacNicol,
eds., Inclusion Compounds, Oxford University Press, Oxford, 1991,
vol. 4; (b) F. Vogtle, Supramolecular Chemistry, Wiley, Chichester,
1991; (c) E. Weber, I. Csoregh, J. Ahrendt, S. Finge and M. Czugler,
J. Org. Chem., 1988, 53, 5831; (d ) E. Weber, K. Skobridis, A. Wierig,
L. R. Nassimbeni and L. Johnson, J. Chem. Soc., Perkin Trans. 2,
1992, 2123; (e) K. Ochiai, Y. Mazaki, S. Nishikiori, K. Kobayashi
and S. Hayashi, J. Chem. Soc., Perkin Trans. 2, 1996, 1139;
( f ) E. Weber, T. Hens, Q. Li and T. C. W. Mak, Eur. J. Org. Chem.,
1999, 1115; (g) K. Kishikawa, S. Tsubokura, S. Kohmoto and
M. Yamamoto, J. Org. Chem., 1999, 64, 7568; (h) E. Weber, T. Hens,
T. Brehmer and I. Csoregh, J. Chem. Soc., Perkin Trans. 2, 2000, 235;
(i) M. R. Caira, L. R. Nassimbeni, D. Vujovic and E. Weber,
J. Chem. Soc., Perkin Trans. 2, 2001, 861; (j) E. Weber, S. Nitsche,
A. Wierig and I. Csoregh, Eur. J. Org. Chem., 2002, 856.
(b) the H ؒ ؒ ؒ O᎐C bond distances and angles are as follows:
᎐
CH3COCH(CH3)–H ؒ ؒ ؒ O᎐C(CH2)N–, 2.52 Å, 139.5Њ and
᎐
naphthyl-C2–H ؒ ؒ ؒ O᎐C< of butan-2-one, 2.57 Å, 161.3Њ; (c)
᎐
L. Pauling, The Nature of the Chemical Bond, Cornell University
Press, Ithaca, New York, 3rd edn., 1960.
8 (a) R. Taylor and O. Kennard, J. Am. Chem. Soc., 1982, 104, 5063;
(b) G. R. Desiraju, Acc. Chem. Res., 1991, 24, 290; (c) T. Steiner and
J. A. Kroon, J. Chem. Soc., Chem. Commun., 1996, 1277; (d ) Y. Gu,
T. Kar and S. Scheiner, J. Am. Chem. Soc., 1999, 9411.
9 (a) Similar twisted or puckered structures of the phenanthrene ring
were observed in several cases: the torsion angles of C4–C4a–C4b–
C5 of the DA adducts from the reactions of phencyclone with
1618
J. Chem. Soc., Perkin Trans. 2, 2002, 1611–1619

View Article Online
p-bromostyrene2a and cyclooctatetraene2b are 12.40 and 4.90,
respectively; (b) In 3g, the angles between the central benzene ring of
the phenanthrene moiety and the benzene rings on both sides are
7.00 and 6.50. The interplanar angle between the benzene rings of
either end of the phenanthrene ring is 12.5Њ, in which the C7 carbon
deviates 0.35 Å from the central benzene ring of the phenanthrene
moiety.
3.12 Å from the best plane of the central benzene ring of the
phenanthrene moiety.
11 For an efficient synthetic method for phencyclone, see W. R.
Forsyth, G. A. Weisenburger and K. W. Field, Trans. Illinois Acad.
Sci., 1996, 89, 37.
12 (a) teXsan: Crystal Structure Analysis Package, Version 1.11,
Molecular Structure Corporation, Rigaku Corporation, 2000;
(b) C. K. Johnson, ORTEP ORNL-3794, Oak Ridge National
Laboratory, Tennessee, USA, 1965.
10 If the bending of the phenanthrene ring did not occur, the edge-
to-face (Ph–H ؒ ؒ ؒ phenanthrene ring) distance is estimated to be
J. Chem. Soc., Perkin Trans. 2, 2002, 1611–1619
1619