The effect of bulky substituents on the formation of symmetrically trisubstituted triptycenes

Article abstract of DOI:10.1002/ejoc.201000354

A series of 1,8-dichloroanthracene precursor molecules with substituents in C-10 position of different steric demand (cyclohexyl, tert-butyl, methyl, isopropyl, n-butyl, phenyl, benzyl, trimethylsilylethinyl) were synthesised and subjected to electrocyclic cycloadditions with chlorobenzyne generated from 3-chloroanthranilic acid. The aim was to steer the regioselectivity of the addition reaction by the steric repulsion between this C-10 substituent and the chlorine substituent at: the benzyne intermediate. With H as C-10 substituent the reaction leads to 23 % syn and 77 % anti form. With the small methyl group a syn/anti ratio of 37:63 was achieved. Contrary to our expectations the large C-10 substituent tert-butyl leads to 100% selectivity for the anti form. The best results were achieved for the C-10 substituent n-butyl with a syn/anti ratio of 40:60. The crystal structures of five 1,8dichloroanthracenes with C-10 substituents were determined, namely those with tert-butyl, cyclohexyl, n-butyl and phenyl groups. As expected the backbone of the tert-butyl compound shows marked distortion of the planarity. Additionally, the crystal structures of three triptycenes were determined, namely those of the syn compound 1,8,13-trichlorotriptycene and those of the anti compounds 10-terbutyl-1,8,16- trichlorotriptycene and 1,8,16-trichloro-10methyltriptycene.

Full text of DOI:10.1002/ejoc.201000354

FULL PAPER
DOI: 10.1002/ejoc.201000354
The Effect of Bulky Substituents on the Formation of Symmetrically
Trisubstituted Triptycenes
Jasmin Chmiel,[a] Ingo Heesemann,[a] Andreas Mix,[a] Beate Neumann,[a]
Hans-Georg Stammler,[a] and Norbert W. Mitzel*[a]
Keywords: Anthracene / Triptycene / Cycloaddition / Isomers / Solid-state structures
A series of 1,8-dichloroanthracene precursor molecules with
substituents in C-10 position of different steric demand (cy-
clohexyl, tert-butyl, methyl, isopropyl, n-butyl, phenyl, benz-
yl, trimethylsilylethinyl) were synthesised and subjected to
electrocyclic cycloadditions with chlorobenzyne generated
leads to 100% selectivity for the anti form. The best results
were achieved for the C-10 substituent n-butyl with a
syn/anti ratio of 40:60. The crystal structures of five 1,8-
dichloroanthracenes with C-10 substituents were deter-
mined, namely those with tert-butyl, cyclohexyl, n-butyl and
from 3-chloroanthranilic acid. The aim was to steer the re- phenyl groups. As expected the backbone of the tert-butyl
gioselectivity of the addition reaction by the steric repulsion
between this C-10 substituent and the chlorine substituent at
the benzyne intermediate. With H as C-10 substituent the
reaction leads to 23% syn and 77% anti form. With the small
compound shows marked distortion of the planarity. Ad-
ditionally, the crystal structures of three triptycenes were de-
termined, namely those of the syn compound 1,8,13-tri-
chlorotriptycene and those of the anti compounds 10-tert-
methyl group a syn/anti ratio of 37:63 was achieved. Con- butyl-1,8,16-trichlorotriptycene
and
1,8,16-trichloro-10-
trary to our expectations the large C-10 substituent tert-butyl
methyltriptycene.
tems could serve for the recognition of anions and bases in
general and for the activation of small molecules.[10]
Introduction
In 1942 the first triptycene was obtained by Bartlett
et al.[1] by Diels–Alder cycloaddition of anthracene and p-
benzoquinone. Due to its structure the [2.2.2] bridgehead
system keeps the angle between the planes of the aromatic
rings at about 120°. Triptycenes are useful in the generation
of rigid backbones and for creating structures with well-
defined geometries.[2] One example is the preparation of
cage compounds for potential applications such as storage[3]
and recognition,[4] inspired by nano-sized compounds in
biological systems.[5] Some of these self-assembled supra-
molecular cages use the ability of a coordination bond or a
hydrogen bond for a direct orientation of the desired com-
ponents.[6]
A rigid backbone of C3-symmetry would be perfectly
given by a triptycene with functional groups at the 1-, 8-,
and 13-positions.[11] The introduction of chloro functions
in these positions offers various ways of derivatisation, e.g.
their direct replacement by Lewis-acids or rigid spacer-units
like alkynes via Kumada coupling reactions.[12] Scheme 1
illustrates the synthesis of trisubstituted triptycenes by the
Diels–Alder cycloaddition of disubstituted anthracenes
We became interested in functionalised triptycenes
through a project for the synthesis of new poly-Lewis-
acids[7] with defined positions of the acceptor sites. Poly-
Lewis-acids are an active field of research,[8] but there is a
distinct paucity of suitable rigid hydrocarbon backbones
with defined structures capable of tolerating strong Lewis-
acidic functionalities. In order to achieve selectivity in asso-
ciation with Lewis-bases, host molecules were synthesized
with Lewis-acid functions in suitably close proximity and
oriented such that they can act simultaneously.[9] These sys-
[a] Fakultät für Chemie, Lehrstuhl für Anorganische Chemie und
Strukturchemie, Universität Bielefeld,
Universitätsstraße 25, 33615 Bielefeld, Germany
Fax: +49-521-1066-026
Scheme 1. General outline for the synthesis of trisubstituted trip-
tycenes.
E-mail: mitzel@uni-bielefeld.de
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(diene) with a monosubstituted benzyne (dienophile).[13]
The disubstituted anthracenes employed in the reactions are
accessible from the commercially available 1,8-dichloro-
anthraquinone. Benzyne itself can be generated in situ by
addition of the monosubstituted anthranilic acid (dissolved
in DME) to a solution of disubstituted anthracene and
isoamyl nitrite in DME with elimination of N2 and
CO2.[14]
Herein we describe the syntheses of eight modified an-
thracenes and investigations of their influence on the for-
mation of syn- and anti-trichlorotriptycenes.
Results and Discussion
Syntheses of the Modified Anthracenes
As a prerequisite for exploring the triptycene-formation
reactions, we first prepared a series of 1,8-dichloroan-
thracenes modified by substituents of different steric de-
mand at C-10. We found that individual protocols for the
introduction of substituents in C-10 position had to be de-
veloped (Scheme 2).
Scheme 3. For compounds 1, 2 and 3: a) RMgBr, THF/Ether, b)
3  HCl, c) toluene P2O5; for compounds 4 and 5: a) RMgBr, ether,
b) and c) NH4Cl; for compound 6: a) RMgBr, ether, b) NH4Cl, c)
P2O5; for compounds 7 and 8: a) RLi, toluene, b) and c) 3  HCl.
group under acidic conditions. Subsequently, a proton is
abstracted from another methyl-group to form a propylenyl
substituent at C-10.
Scheme 2.
For instance the 10-tert-butyl-1,8-dichloroanthracene (3)
could only be synthesised by the reaction of the corre-
sponding anthrone with the tert-butyl-Grignard reagent.
The reaction with tert-butyllithium did not lead to the ex-
pected product, but to a complicated mixture of products
difficult to separate and identify. Moreover, in the case of
anthracenes with a bulky substituent in C-10 position, the
elimination of water and the subsequently initiated aroma-
tisation of the anthrone reaction products with metal alkyls
could only be achieved by heating these compounds several
times with P2O5 in toluene or tetrachloromethane
(Scheme 3). Care has to be applied to find the right reaction
conditions for each case, because the reaction with P2O5
does not only result in dehydration, but may also lead to
rearrangements in the substituent substructures.
Figure 1. Crystal structure of 1,8-dichloro-10-methyl-10-(prop-1-
en-2-yl)-9,10-dihydroanthracene (16). Only some selected hydro-
gen-atoms are pictured for a better overview. Selected bond lengths
[Å] and angles [°]: C(2)–C(3) 1.503(2), C(3)–C(4) 1.503(2), C(9)–
C(10) 1.547(2), C(10)–C(11) 1.531(2), C(10)–C(15) 1.556(3), C(10)–
C(16) 1.524(2), C(2)–C(11) 1.394(2), C(4)–C(9) 1.392(2), C(4)–C(5)
1.401(2), C(11)–C(12) 1.400(2), C(1)–C(2)–C(3) 120.1(2), C(2)–
C(3)–C(4) 114.6(2), C(4)–C(5)–C(6) 123.4(1), C(7)–C(8)–C(9)
121.3(2), C(9)–C(10)–C(11) 112.3(1).
Syntheses of the Triptycenes
After hydrolytic work-up the resulting alcohol from the
reaction of 1,8-dichloroanthrone with tert-BuMgBr un-
Based on the work of Rogers and Averill,[15] we repeated
dergoes decay reactions upon treatment with P2O5. We ob- the attempt to prepare the symmetrically substituted tri-
served the formation of 1,8-dichloro-10-methyl-10-(prop-1- chlorotriptycene by reaction of 1,8-dichloroanthracene with
en-2-yl)-9,10-dihydroanthracene (16), which was identified 6-chloroanthranilic acid. Analogous to their report, the tri-
by crystal structure determination (Figure 1). This is obvi- chlorotriptycene was obtained in a mixture of 21% syn and
ously a by-product of a Wagner–Meerwein-type rearrange- 79% anti form. They found that the isomeric ratio depends
ment of one methyl-group from the tert-butyl substituent on the substituents of the diene and dienophile and investi-
to a carbocation resulting from water elimination of the OH gated different substituents at the anthranilic acid in 6-posi-
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Trisubstituted Triptycenes
tion and different 1,8-substituents at the anthracene. It STO3G), the results of which can be summarised as follows.
turned out that in particular the functionalities at the inter- As argued earlier by others,[17] the regiochemistry of the
mediate benzyne are important in dictating the observed addition of arynes depends on the nature of substituents,
regiochemistry. With methyl as substituent the formation of which may influence their polarities. In the case of 3-chloro-
the syn isomer is found to be preferred, but with chloro benzyne, we calculated a small negative charge on C-2 and
substitution, the anti isomer is the preferably formed one.
a neutral charge at C-1, i.e. the negative end of the dien-
Considering this information we started studying the ophil at C-2 or towards the chlorine substituent. In the par-
syn/anti ratio of similar reactions of C-10-substituted 1,8- ent diene (1,8-dichloroanthracene), C-9 and C-10 have al-
dichloroanthracene with 6-chloroanthranilic acid and most the same charges, so that an equal preference for syn
found that these C-10 substituents have indeed an effect on and anti orientation of the resulting triptycene could be pre-
the isomeric ratio. A summary of the results of these experi- dicted, with the repulsive steric interaction between the
ments is provided in Table 1.
chlorine atoms favouring slightly the anti form. This is what
the experiments of Rogers and Averill have shown.[15]
Methyl substitution at C-10 makes the C-10 position more
positive, i.e. this should preferably interact with 3-chloro-
benzyne to result in anti-triptycenes, but here the Cl–Me
repulsion is also increased. An even more pronounced
charge distribution δ+(C-10) and δ–(C-9) is achieved by tert-
butyl substitution, which seems to be sufficiently regio-di-
recting to override any steric argument.
The calculations predict that the situation could be
changed by substitution at C-9, but this would be ac-
companied by an intolerable increase in synthetic complex-
ity. The most promising prediction is the effect of silylation
at C-10, as this reverses the polarity compared to above-
mentioned cases.
Table 1. Ratio of syn- and anti-triptycene formed in the reaction
between with 6-chloroanthranilic acid and C-10-substituted 1,8-
dichloroanthracenes depending on the C-10 substituent.
R at C-10
% anti
% syn
% Yield[a]
9
H
79
79
100
63
70
60
75
–
21
21
0
37
30
40
25
–
16
60
43
42
40
22
28
0
10
11
12
13
14
15
c-C6H11
Me3C–
Me
Me2CH–
n-C4H9
Ph
PhCH2–
Me3Si–CϵC–
–
–
0
[a] All yields are given for the mixture of syn- and anti-triptycene.
The relatively low yields in most cases can be explained
by the fact that 3-chlorobenzyne is not easily produced via
aprotic diazotization of 3-chloroanthranilic acid. The high
contribution of 75% anti-structure in the case of the tri-
chlorophenyltriptycene (15) can be rationalised by ad-
ditional intramolecular interactions between the π-system
and the chloro function (of the benzyne) as reported by
Öki.[16]
Astonishing are the results of the Diels–Alder reactions
with the benzyl- and (trimethylsilyl)ethynyl-substituted an-
thracenes. They led only to trace amounts of the expected
triptycenes, barely detectable by NMR spectroscopy. Even
the application of longer reaction times and different work-
up procedures (column chromatography) resulted almost
exclusively in the recovery of starting material.
NMR Studies on the Isomeric Mixture of Substituted
Triptycenes
The exact classification of syn- and anti-triptycenes and
their ratio could be achieved by using two-dimensional
NMR spectroscopy, NOESY and HMQC (Figure 2). Rog-
ers and Averill reported[15] that “the most effective way to
differentiate the isomeric pairs of triptycenes was by 1H
NMR spectra”. They described the typical patterns for the
aromatic protons as well as the two singlets generated by
Except for the entry with the tert-butyl group, the results
in Table 1 indicate, that a C-10 substituent induces only lit-
tle influence on the isomeric ratio to a slightly increased
amount of the syn product. However, this influence is ac-
companied by other factors like polarity, which explains the
non-linear behaviour of the syn-amount in relation to the
steric demand of the C-10 substituent. Nevertheless, we ex-
pected to take the most pronounced influence on the ad-
dition reaction by using the sterically most demanding sub-
stituent, which was the tert-butyl group in our series of ex-
periments. However, this assumption was disproved by the
formation of 100% anti-10-tert-butyl-1,8,16-trichlorotrip-
tycene (11). Clearly, the exclusive formation of the anti
structure indicates that electronic factors override the steric
ones.
Figure 2. Section of the HMQC spectrum of a mixture of 1,8,13-
trichloro-10-methyltriptycene (syn-12) and 1,8,16-trichloro-10-
methyltriptycene (anti-12) showing the signals of the bridgehead
In order to rationalise these findings we performed quan-
tumchemical calculations on an exploratory level (HF/ positions.
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N. W. Mitzel et al.
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the bridgehead protons. It is also mentioned by Kidd et
al.[18] that the shifts of these singlets depend on the aromatic
substituents and that the bridgehead proton of the syn-iso-
mer experiences a larger shift ∆δ than that of the anti-iso-
mer. In general we approve these results, but found in ad-
dition that in the case of the modified 1,8,13-trichlorotrip-
tycenes, due to the close arrangement of three chloro func-
tions, the corresponding bridgehead proton, pointing to the
same side as the chloro substituents, is so strongly deshi-
elded that its signal overlaps with the proton signals of the
aromatic system. A clear assignment in these cases can
therefore only be achieved by two-dimensional NMR spec-
troscopy.
The syn/anti mixture of the methyl-substituted trichloro-
triptycene 12 can serve as a representative example for all
synthesised triptycene systems. Its 13C NMR spectrum con-
tains signals for the aromatic ring at 149.25–119.22 ppm
and signals corresponding to the methyl substituents at δ =
17.48 and 13.51 ppm. Resonances at δ = 51.88 and
50.23 ppm (C-10) and 46.90 and 42.82 ppm (C-9) corre-
spond to the bridgehead carbon atoms, respectively. In a
1H-13C HMQC experiment these carbon atoms induce cross
peaks with the directly bonded bridgehead protons of the
syn- and anti-triptycene at δ = 7.08 and 6.43 ppm. For a
proper assignment of these proton signals of the triptycene
isomers, we carried out NOESY experiments: only the
bridgehead proton of the anti-isomer shows a through-
space interaction with one of the aromatic protons leading
to a cross-peak in the corresponding spectra.
Figure 3. Molecular structure of 10-tert-butyl-1,8-dichloroan-
thracene (3).
For all compounds, the ratio of syn- and anti-triptycene
was either determined by integration of the bridgehead pro-
ton signals or by integration of the signals induced by the
C-10 substituent. The NMR spectra of compounds 10, 11,
13, 14 and 15 show almost identical chemical shifts and
splittings.
Figure 4. Molecular structure of 1,8-dichloro-10-cyclohexylan-
thracene (1).
Molecular Structures of Modified Dichloroanthracenes
Single crystals of compounds 1, 5, 7 and 8 suitable for
X-ray diffraction were obtained by slow evaporation of the
solvent from the solutions obtained in the preparative pro-
cedures described above. Crystals of 10-tert-butyl-1,8-
dichloroanthracene (3) were obtained from a pentane/
dichloromethane mixture at room temperature as yellow
plates.
The molecular structures of compounds 1, 3, 5, 7 and 8
were determined by single-crystal X-ray diffraction and are
displayed in Figures 3, 4, 5, 6, and 7. Some selected struc-
tural parameter values are compiled in Table 2 for compari-
son. Compounds 1, 3, 5, 7 and 8 show two different struc-
tural motifs of the anthracene backbone depending on the
substituent in C-10 position. 1, 5, 7 and 8 have in common
a planar anthracene skeleton.
In contrast, the anthracene backbone of 10-tert-butyl-
1,8-dichloroanthracene (3) shows a butterfly-like defor-
mation caused by the steric bulk of the tert-butyl group. In
Figure 5. Molecular structure of 1,8-dichloro-10-[(trimethylsilyl)-
this respect the structure is concordant with the known ethynyl]anthracene (5).
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Trisubstituted Triptycenes
fluence of the latter is small and the Cl atoms are found
in plane with the almost planar side rings they are bonded
to. The bond C(10)–C(15) connecting the tert-butyl group
to anthracene is 1.561(2) Å long, i.e. longer than standard
C–C bonds. Also compared to 10-butyl-1,8-dichloro-
anthracene (7) this bond is 0.043 Å longer, which can be
attributed to the steric repulsion between the hydrogen
atoms in 4- and 5-position of the anthracene system and
those of the tert-butyl group. The tert-butyl group itself
seems to be only little affected, as the bond lengths of
1.549(2) Å and the angles around C(15) of 109.1(1)° [C(17)–
C(15)–C(16)], 110.2(1)° [C(17)–C(15)–C(18)] are indicating
no distortions, and only a somewhat compressed angle of
102.7(1)° [C(16)–C(15)–C(18)] indicates some influence by
repulsive interactions.
The structural parameter values of compounds 1, 5, 7
and 8 can be described together due to the fact that the
anthracene backbone is undistorted regarding planarity.
The C–Cl distances are 1.745(3) Å (cyclohexyl), 1.744(2) Å
(trimethylsilylethynyl), 1.738(2) Å (butyl) and 1.748(2) Å
(phenyl) and agree well with the value 1.749 Å reported for
1,8-dichloro-10-methylanthracene[20] and are just slightly
shorter than in 1,8-dichloroanthracene [1.751(3) Å].[21] The
Cl atoms of the structures are in plane with the anthracene
backbone. The bond lengths for the aromatic system of 1, 5,
7 and 8 vary from the common C–C bond length in benzene
(1.398 Å) but show trends comparable to literature known
anthracene structures, such as the parent non-substituted
anthracene (1.37 to 1.43 Å).[22] In all four structures, the
bonds of C(1)–C(14), C(2)–C(3) and C(12)–C(13) are
shorter (average bond length of 1.37 Å) than the other
bonds of the aromatic system (average bond length of
1.42 Å). The C(10)–C(15) distances between the different
substituents and the anthracene are 1.532(4) Å (cyclohexyl),
1.437(2) Å (trimethylsilylethynyl), 1.518 Å (butyl) and
1.505(2) Å (phenyl).
Figure 6. Molecular structure of 10-butyl-1,8-dichloroanthracene
(7).
Figure 7. Molecular structure of 1,8-dichloro-10-phenylanthracene
In 1,8-dichloro-10-cyclohexylanthracene (1), the cyclo-
hexyl substituent adopts the expected chair conformation
and is nearly orthogonal to the anthracene backbone thus
minimising the steric interferences of the hydrogen atoms.
In the case of 1,8-dichloro-10-[(trimethylsilyl)ethynyl]-
anthracene (5), the angle of C(10)–C(15)–C(16) is 177.8(2)°
and the C(15)–C(16)–Si angle is, i.e. the acetylene unit is
almost perfectly linear. It is also nearly in plane with the
anthracene system. The silicon atom adopts a tetrahedral
coordination with C–Si–C angles ranging from 108.2(1)° to
111.2(1)°.
The butyl group in compound 7 shows no significant de-
formations or structural characteristics. The C–C bond
lengths of the substituent are 1.511(3) to 1.528(3) Å and the
C–C–C angles 111.6(2) to 113.9(2)°.
The C–C bond lengths of the phenyl substituent in
1,8-dichloro-10-phenylanthracene (8) are 1.394(2) to
1.387(2) Å, which fits well with C–C bond lengths of benz-
ene. With respect to steric interactions with the peri-dis-
(8).
Table 2. Selected bond lengths [Å] and angles [°] of 1, 3, 5, 7
and 8.
1
3
5
7
8
Cl(1)–C(1)
C(2)–C(3)
C(2)–C(11)
C(10)–C(11)
1.745(3) 1.741(1) 1.744(2) 1.739(2) 1.748(2)
1.388(4) 1.393(2) 1.394(2) 1.393(2) 1.391(2)
1.444(4) 1.440(2) 1.436(2) 1.437(3) 1.443(2)
1.418(4) 1.425(2) 1.416(2) 1.409(3) 1.407(2)
1.532(4) 1.561(2) 1.437(2) 1.518(3) 1.505(2)
119.2(2) 118.9(1) 118.8(2) 118.9(1) 118.6(1)
118.1(2) 118.3(1) 118.8(2) 118.5(1) 118.7(1)
122.0(3) 121.9(1) 123.1(2) 122.1(2) 122.6(1)
121.4(3) 119.9(1) 121.3(2) 120.7(2) 121.3(1)
123.9(3) 123.0(1) 121.9(2) 122.5(2) 122.5(1)
119.7(3) 116.9(1) 121.2(2) 119.9(2) 120.7(1)
121.2(2) 122.1(1) 119.3(2) 120.1(1) 118.8(1)
119.0(2) 120.9(1) 119.4(2) 120.0(2) 120.5(1)
C(10)–C(15)
Cl(1)–C(1)–C(2)
Cl(1)–C(1)–C(14)
C(1)–C(2)–C(3)
C(2)–C(3)–C(4)
C(10)–C(11)–C(12)
C(9)–C(10)–C(11)
C(9)–C(10)–C(15)
C(11)–C(10)–C(15)
crystal structure of 9-tert-butylanthracene.[19] As both posed C–H groups in the anthracene backbone, the phenyl
chloro functions are located at the opposite side of the an- substituent resides at a dihedral angle of 76.9° and 81.1°
thracene system relative to the tert-butyl group, the in- (because of two independent molecules in the asymmetric
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N. W. Mitzel et al.
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unit) relative to the plane of the anthracene core. In the
similar 6-phenylpentacene, this angle is 81.1° and
89.6°.[23]
Molecular Structure of 1,8,13-Trichlorotriptycene (9)
1,8,13-Trichlorotriptycene (9) crystallises in the mono-
clinic system in the space group P21/m. The molecule is
close to threefold rotational symmetry,[24] but does only
contain a mirror plane as crystallographical element of
symmetry. The dihedral angles between the planes of the
benzene rings are 121.5 and 117.0°. All three chlorine atoms
point to the same direction and are oriented nearly parallel
to each other. The average C(sp2)–Cl bond length in aro-
matic compounds is 1.76 Å[25] and the two C–Cl bond
lengths in 9 are 1.743(2) and 1.739(1) Å. The average C–C
bond length in the benzene rings is 1.39 Å. All three rings
are parallel to the C(3)–C(10) axis and the eight-membered
cage shows no significant distortion. The bonds to the
atoms C(3) and C(10) have nearly the same length (1.52 Å).
In addition, all angles about the atoms C(3) and C(10) are
close to 105°: C(2)–C(3)–C(4) 105.5(1)°, C(4Ј)–C(3)–C(4)
105.1(1)° and all C–C–C angles around C(10) are 105.8(1)°.
Figure 9. Molecular structure of 10-tert-butyl-1,8,16-trichloro-
triptycene (11).
Table 3. Selected bond lengths [Å] and angles [°] of structures 11
and 12.
11
12
Cl(1)–C(1)
Cl(2)–C(5)
Cl(3)–C(19)
C(3)–C(4)
C(3)–C(15)
C(4)–C(9)
C(9)–C(10)
C(10)–C(20)
C(15)–C(20)
1.742(2)
1.746(1)
1.740(2)
1.507(2)
1.514(2)
1.404(2)
1.574(2)
1.590(2)
1.419(2)
1.575(2)
118.9(1)
119.0(1)
127.1(1)
111.6(1)
121.4(2)
105.4(1)
114.4(1)
111.2(1)
102.7(1)
113.1(1)
118.4(1)
1.742(4)
1.739(4)
1.739(5)
1.530(5)
1.516(6)
1.395(6)
1.536(6)
1.556(6)
1.402(6)
1.526(6)
118.6(3)
118.5(3)
124.1(3)
115.8(3)
120.1(4)
105.1(3)
114.3(3)
112.6(4)
102.8(3)
112.2(3)
118.1(4)
Molecular Structure of Modified anti-Trichlorotriptycenes
In general triptycene has a paddlewheel configuration
with a structure close to D3h symmetry, which is lowered by
substitution. The maximum possible symmetry for an anti-
trisubstituted triptycene is Cs. Steric interactions between
the chloro function at C(19) and the substituent at C(10) C(10)–C(21)
Cl(1)–C(1)–C(14)
Cl(2)–C(5)–C(6)
lead to a small distortion of the eight-membered cage of
the triptycene.[26] We determined the structures of two such
anti-trichlorotriptycenes, 11 and 12 (see Figures 8 and 9).
For comparison, the structural parameter values for com-
pounds 11 and 12 are listed together in Table 3.
Cl(3)–C(19)–C(20)
Cl(3)–C(19)–C(18)
C(18)–C(19)–C(20)
C(4)–C(3)–C(15)
C(4)–C(9)–C(10)
C(15)–C(20)–C(10)
C(9)–C(10)–C(20)
C(9)–C(10)–C(21)
C(20)–C(10)–C(21)
Figure 8. Molecular structure of 1,8,13-trichlorotriptycene (9). Se-
lected bond lengths [Å] and angles [°]: Cl(1)–C(1) 1.743(2), Cl(2)–
C(5) 1.739(1), C(1)–C(14) 1.395(2), C(2)–C(3) 1.521(2), C(3)–C(4)
1.522(1), C(4)–C(5) 1.385(2), C(4)–C(9) 1.402(2), C(9)–C(10)
1.525(1), C(10)–C(11) 1.522(2), Cl(1)–C(1)–C(2) 120.3(1), Cl(1)–
C(1)–C(14) 118.8(2), C(14)–C(1)–C(2) 120.9(2), C(2)–C(3)–C(4)
105.5(1), C(09)–C(10)–C(11) 105.8(1).
In compounds 11 and 12 (Figures 9 and 10), the bond
lengths C(10)–C(20) are 0.076 Å (11) and 0.040 Å (12)
Figure 10. Molecular structure of 1,8,16-trichloro-10-methyl-
longer than the C(3)–C(15) bond. This may be rationalised triptycene (12).
3902
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 3897–3907

Trisubstituted Triptycenes
by the steric repulsion between Cl(3) and the substituent at
Future work will be directed to alternative strategies for
C(10). In addition, the angles C(20)–C(10)–C(21) are ex- a selective 1,8,13-substitution of the triptycene framework.
panded to 118.4(1)° (11) and 118.1(4)° (12), whereas the Such strategies could include templated metallation.
C(9)–C(10)–C(21) angles are compressed to 113.1(1)° (11)
and 112.2(3)° (12).
Experimental Section
Further proof for this repulsion stems from the dissym-
metry of the angles about C(19) as the chlorine atom Cl(3)
at this position is dislocated from an “ideal” bonding situa-
tion at an arene core. Though the sum of angles about
C(19) at 360.0(2)° show it expectedly to be planar, Cl(3) is
General Remarks: NMR spectra were recorded with a Bruker DRX
500 and a Bruker Avance 600 instrument at room temperature; the
chemical shifts (δ) were measured in ppm with respect to the sol-
1
vent (CDCl3, H NMR δ = 7.26 ppm, 13C NMR δ = 77.13 ppm).
bent away from the substituent at C(10). The angles Cl(3)– MS were recorded with a Shimadzu GCIMS-QP2010S mass spec-
trometer. Melting points (m.p.) were determined on Büchi melting
point B-545 melting point apparatus. Crystallographic structure de-
C(19)–C(20) are drastically widened at 127.1(1)° (11) and
124.1(3)° (12), while the angles Cl(3)–C(19)–C(18) are
found to be compressed at 111.6(1)° (11) and 115.8(3)° (12).
This result thus gives an idea of the high degree of steric
repulsion build up during the triptycene formation by elec-
trocyclic reactions and clearly demonstrates electronic ef-
fects to be more important than steric repulsion.
terminations were carried out with Mo-Kα radiation (λ
=
0.71073 Å). The structures were solved by direct methods and re-
fined by full-matrix least-squares cycles programs SHELXS-97 and
SHELXL-97. Column chromatography was performed on silica gel
60 (0.04–0.063 mm mesh). Methylmagnesiumbromide solution (3 
in diethyl ether), n-butyllithium solution (1.6  in hexane), isoamyl
nitrite and 1-chloroanthranilic acid were commercially available.
4,5-Dichloro-9-anthrone was prepared by a published procedure.[30]
The bond lengths in the benzene rings partly vary about
0.02 Å from the standard bond length of benzene (1.398 Å),
which is the same result as reported for triptycene itself.[27] 1,8-Dichloro-10-cyclohexylanthracene (1), 10-benzyl-1,8-dichlo-
roanthracene (2), 10-tert-butyl-1,8-dichloroanthracene (3), 1,8-
dichloro-10-methylanthracene (4) and 1,8-dichloro-10-isopropylan-
thracene (6) were synthesized by a modified procedure of Toyota
et al.[31] 10-Butyl-1,8-dichloroanthracene (7) and 1,8-dichloro-10-
phenylanthracene (8) were also synthesized by a modified pro-
cedure of Toyota et al.[32] All triptycenes were synthesised by the
method described by Rogers and Averill[15] with a variation in
work-up depending on the substituents. The reactions were carried
out by using freshly distilled and dry solvents from solvent stills.
The numbering scheme for NMR assignments (Scheme 4) is based
on IUPAC and Hellwinkel guidelines.
The C–C(Cl)–C angles involving the chlorine-substituted
carbon atom are nearly 120° [120.4(1)° (11), 121.4(2)° (12)].
This distortion can be rationalised by the steric interference
between the tert-butyl group and the chloro atom.
The C–Cl bond lengths are 1.740(2) to 1.746(1) Å for 11
and 1.739(4) to 1.742(4) for 12. This is not in line with the
results on 10-tert-butyl-1,2,3,4-tetrachlorotriptycene (1.716,
1.723, 1.725 and 1.743 Å) which is in good agreement
with the C(sp2)–Cl bond length in trichlorobenzene
[1.719(5) Å].[28,29]
Conclusions
Influence on the selectivity of syn- and anti-forms of tri-
chlorotriptycenes can be taken by varying the substituents
in C-10 position of the 1,8-dichloroanthracene precursor
molecules. Without substituents the reaction of 1,8-dichlo-
roanthracene with in situ generated chlorobenzyne leads to
23% syn and 77% anti form. With smaller C-10 substitu-
ents at the 1,8-dichloroanthracene like methyl the relation
of syn and anti triptycenes changes to 37% syn and 63%
anti. Contrary to expectations the relatively large C-10 sub-
stituent tert-butyl leads to 100% selectivity for the anti form
of 10-tert-butyl-trichlorotriptycene (11).
Scheme 4. Numbering scheme for NMR assignments.
General Procedure for the Syntheses of 1,8-Dichloro-10-cyclohex-
ylanthracene (1), 10-Benzyl-1,8-dichloroanthracene (2) and 10-tert-
Butyl-1,8-dichloroanthracene (3): The Grignard reagent was pre-
pared by the reaction of magnesium and alkyl bromide in diethyl
The crystal structures of the 10-tert-butyl-1,8,16-tri-
chlorotriptycene (12), 1,8,16-trichloro-10-methyltriptycene ether in the ordinary manner. The resulting mixture was added
dropwise to a cooled solution of 4,5-dichloro-9-anthrone (1 equiv.
anthrone to 5 equiv. Grignard reagent) in THF and stirred over-
night at room temperature. For the following work up 3  HCl was
used to quench the reaction. The organic layer was separated and
the aqueous layer was extracted with dichloromethane. Afterwards
the combined organic solution was washed with aq. NaCl, dried
with MgSO4 and the solvents evaporated. For the complete elimi-
nation of water, the residue was dissolved in little amount of tolu-
ene and heated to 80 °C in the presents of P2O5. The solid was
removed by filtration, and the filtrate was washed with water and
the solvents evaporated. The crude product was purified by
(12) demonstrate that there is a severe repulsive steric inter-
action between these C-10 substituent and the chloro func-
tion introduced by the chlorobenzyne. This interaction must
also be present during the electrocyclic reaction between the
chlorobenzyne and the C-10-substituted 1,8-dichloroan-
thracenes. Calculations show on the other hand, that C-10
substituents always change the orbital coefficients in a way
to favour the anti over the syn form, and the experiments
demonstrate that such electronic effects clearly override ste-
ric repulsion effects during the reaction.
Eur. J. Org. Chem. 2010, 3897–3907
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3903

N. W. Mitzel et al.
FULL PAPER
chromatography on silica gel with eluents depending on the dif-
ferent fragments.
pentane. A previously elimination of water by heating the residue
with P2O5 was not necessary; bright yellow solid; yield 288 mg
(56%); m.p. 154.8 °C. 1H NMR (500 MHz, CDCl3, 25 °C): δ = 9.29
(s, 1 H, H9), 8.51 (d, JH,H = 8.6 Hz, 2 H, H2/H7), 7.67 (d, JH,H
= 7.2 Hz, 2 H, H4/H5), 7.53 (dd, 3JH,H = 7.7, 7.2 Hz, 2 H, H3/H6),
0.42 (s, 9 H, methyl-H) ppm. 13C NMR (125 MHz, CDCl3): δ =
133.80, 132.94, 128.94, 126.79, 126.37, 126.12, 123.89, 122.02,
107.67 (CϵC-Si), 100.75 (CϵC-Si), 0.13 (C methyl) ppm. 29Si
NMR (99 MHz, CDCl3): δ = –17.0 ppm. MS (EI, 70 eV): m/z =
341.8 [M+], 326.8 [M+ – Me], 97.1 [CϵCSiMe3].
1,8-Dichloro-10-cyclohexylanthracene (1): The desired product was
obtained by chromatography on silica gel with pentane; bright yel-
low solid; yield 191 mg (33%); m.p. 167.0 °C. 1H NMR (500 MHz,
CDCl3, 25 °C): δ = 9.33 (s, 1 H, H9), 8.61–8.36 (2br. s, 2 H), 7.62
3
3
3
3
(d, JH,H = 6.9 Hz, 2 H, H2/H7), 7.40 (br. s, 2 H), 4.10 (tt, JH,H
= 3.6, 12.7 Hz, 1 H, H15), 2.50 (m, 2 H), 2.04–1.92 (m, 4 H), 1.57
(m, 4 H) ppm. 13C NMR (125 MHz, CDCl3): δ = 141.36, 133.66,
128.18, 127.71, 125.62, 120.69, 41.39 (C15), 32.34 (C16/C20), 28.07
(C17/C19), 26.49 (C18) (signals missing due to overlap or broaden-
ing) ppm. MS (EI, 70 eV): m/z = 328.1 [M+], 293.1 [M+ – Cl],
259.0 [M+ – 2 Cl], 83.1 [C6H10], 35.0 [Cl]. HRMS: calculated for
C20H18Cl2: 328.0786; measured: 328.0778.
1,8-Dichloro-10-isopropylanthracene (6): According to the litera-
ture, treatment of the intermediate with P2O5 in toluene for 1 h at
85 °C resulted in water elimination and aromatisation. Purification
of the product was carried out by column chromatography with
pentane; bright yellow solid; yield 202 mg (39%). Analytical studies
were published by Toyota et al.[31]
10-Benzyl-1,8-dichloroanthracene (2): The product was purified by
column chromatography with pentane/toluene, 1:1 as eluent; bright
yellow solid; yield 280 mg (40%); m.p. 162.2 °C. 1H NMR
General Procedure for the Syntheses of 10-Butyl-1,8-dichloro-
anthracene (7) and 1,8-Dichloro-10-phenylanthracene (8): The
lithiated species (5 mmol) in toluene was cooled to –78 °C and 4,5-
dichloro-9-anthrone (2 mmol) in toluene was slowly added. After
warmed to room temp. and stirred overnight, the mixture was
quenched by the addition of 3  hydrochloric acid. After the com-
pound was refluxed for 30 min, the organic materials were ex-
tracted with toluene and the toluene solution was washed with aq.
NaCl, dried with MgSO4 and concentrated. The crude product was
purified by chromatography on silica gel with hexane as eluent.
3
(500 MHz, CDCl3, 25 °C): δ = 9.37, (s, 1 H, H9), 8.15 (d, JH,H
=
3
9.1 Hz, 2 H, H2/H7), 7.64 (d, JH,H = 7.1 Hz, 2 H, H4/H5), 7.41
(dd, 3JH,H = 7.7, 8.5 Hz, 2 H, H3/H6), 7.22–7.16 (m, 3 H, m-H and
3
p-H), 7.06 (d, JH,H = 7.2 Hz, 2 H, o-H), 5.00 (s, 2 H, benzyl-H)
ppm. 13C NMR (125 MHz, CDCl3): δ = 140.15, 133.48, 133.30,
131.64, 129.37, 128.59, 127.98, 126.23, 126.01, 125.74, 124.08,
120.89, 34.16 (C-benzyl) ppm. MS (EI, 70 eV): m/z = 336.1 [M+],
301.1 [M+ – Cl], 266.2 [M+ – 2 Cl], 91.1 [CH2 – C6H5]. HRMS:
calculated for C21H14Cl2: 336.0473; measured: 336.0446.
10-tert-Butyl-1,8-dichloroanthracene (3): Purification of the product
10-Butyl-1,8-dichloroanthracene (7): Bright yellow solid; yield
was carried out by column chromatography with pentane; bright
1
339 mg (59%); m.p. 77.3 °C. H NMR (500 MHz, CDCl3, 25 °C):
yellow solid; yield 69 mg (12%); m.p. 156.0 °C. 1H NMR
3
δ = 9.26 (s, 1 H, H9), 8.21 (d, JH,H = 8.9 Hz, 2 H, H2/H7), 7.64
3
(500 MHz, CDCl3, 25 °C): δ = 9.28 (s, 1 H, H9), 8.46 (d, JH,H
=
3
3
(d, JH,H = 7.1 Hz, 2 H, H4/H5), 7.44 (dd, JH,H = 7.1, 7.2 Hz, 2
3
9.2 Hz, 2 H, H2/H7), 7.57 (d, JH,H = 7.1 Hz, 2 H, H4/H5), 7.26
(dd, 3JH,H = 6.9, 7.2 Hz, 2 H, H3/H6), 1.90 (s, 9 H, methyl-H) ppm.
13C NMR (125 MHz, CDCl3): δ = 141.72–122.62, 35.42 (C15),
28.67 (C-methyl) ppm. MS (EI, 70 eV): m/z = 302.1 [M+], 287.1
[M+ – Me], 276.1 [M+ – Cl], 232.1 [M+ – 2 Cl], 57.1 [C4H9]. HRMS:
calculated for C18H16Cl2: 302.0629; measured: 302.0616.
H, H3/H6), 3.59 (t, 3JH,H = 8.2 Hz, 2 H, H15), 1.78 (m, 2 H, H16),
1.60 (m, 2 H, H17), 1.03 (t, JH,H = 7.5 Hz, 3 H, methyl-H) ppm.
3
13C NMR (125 MHz, CDCl3): δ = 137.16, 133.30, 130.62, 129.31,
125.59, 125.42, 123.74, 119.74, 33.64 (C15), 28.50 (C16), 23.34
(C17), 14.02 (C-methyl) ppm. MS (EI, 70 eV): m/z = 301.9 [M+],
258.9 [M+ – CH2CH2CH3], 245.8 [M+ – CH2CH2CH2CH]. HRMS:
calculated for C18H16Cl2: 302.0629; measured: 302.0618.
General Procedure for the Syntheses of 1,8-Dichloro-10-methylan-
thracene (4), 1,8-Dichloro-10-[(trimethylsilyl)ethynyl]anthracene (5)
and 1,8-Dichloro-10-isopropylanthracene (6): The Grignard reagents
were either available commercially or synthesized by the way de-
scribed before. To a solution of alkyl-Grignard in diethyl ether was
added 4,5-dichloro-9-anthrone (1 equiv. anthrone to 3 equiv. Grig-
nard reagent). The mixture was stirred overnight and quenched by
the addition of aq. NH4Cl. The organic layer was separated and the
aqueous layer was extracted with dichloromethane. The combined
organic layers have been washed with aq. NaCl, dried with MgSO4
and concentrated.
1,8-Dichloro-10-phenylanthracene (8): Bright yellow solid; yield
371 mg (59%); m.p. 172.4 °C. 1H NMR (500 MHz, CDCl3, 25 °C):
δ = 9.43 (s, 1 H, H9), 7.63–7.26 (m, 11 H, aryl-H) ppm. 13C NMR
(125 MHz, CDCl3): δ = 141.97, 138.24, 132.65, 131.04, 128.50,
127.91, 127.29, 126.28, 125.83, 125.41, 122.26, 121.01 ppm. MS
(EI, 70 eV): m/z = 321.8 [M+], 285.9 [M+ – Cl], 251.9 [M+ – 2 Cl].
HRMS: calculated for C20H12Cl2: 322.0316; measured: 322.0291.
General Procedure for the Syntheses of Triptycenes: All triptycenes
were synthesized by the method published by Rogers and Averill.[15]
To enhance the yields the reaction time and the amount of an-
thranilic acid and isoamyl nitrite was modified. All triptycenes were
purified by sublimation (120 °C, 0.007 mbar). The isomers were not
separated by column chromatography. All yields and NMR-data
reference to a mixture of syn and anti isomer. Only the classifiable
NMR-signals are described in detail.
1,8-Dichloro-10-methylanthracene (4): Purification of the product
was carried out by column chromatography with pentane. A pre-
viously elimination of water by heating the residue with P2O5 was
not necessary; bright yellow solid; yield 248 mg (63%); m.p.
156.1 °C. 1H NMR (500 MHz, CDCl3, 25 °C): δ = 9.24 (s, 1 H,
H9), 8.22 (d, 3JH,H = 8.8 Hz, 2 H, H2/H7), 7.63 (d, 3JH,H = 7.1 Hz,
3
2 H, H4/H5), 7.46 (dd, JH,H = 7.2, 7.3 Hz, 2 H, H3/H6), 3.10 (s,
1,8,13-Trichlorotriptycene and 1,8,16-Trichlorotriptycene (9):[15]
White solid; yield 260 mg (23%); m.p. 350.3 °C. 1H NMR
(600 MHz, CDCl3, 25 °C): δ = 7.44 (m, 3 H, H4/H5/H16 syn), 7.39
3 H, methyl-H) ppm. 13C NMR (125 MHz, CDCl3): δ = 133.21,
131.88, 133.16, 129.13, 125.64, 125.33, 123.97, 119.59, 29.74 (C-
methyl) (one signal missing due to overlapping or broadening)
ppm. MS (EI, 70 eV): m/z = 259.9 [M+], 224.9 [M+ – Cl], 189.0
[M+ – 2 Cl]. HRMS: calculated for C15H10Cl2: 260.0160; measured:
260.0139.
3
3
(d, JH,H = 7.5 Hz, 1 H, H13 anti), 7.34 (d, JH,H = 7.3 Hz, 2 H,
H4/H5 anti), 7.08 (m, 3 H, H2/H7/H15 anti), 7.02 (m, 4 H, H3/H6/
H9/H15 syn), 6.99 (m, 6 H, H2/H7/H14 syn, H3/H6/H14 anti), 6.44
(s, 1 H, H9 anti), 5.93 (s, 1 H, H10 anti), 5.91 (s, 1 H, H10 syn)
ppm. 13C NMR (75 MHz, CDCl3): δ = 147.28–122.09 (C-aryl syn
and anti), 51.02 (C10 anti), 50.21 (C10 syn), 47.42 (C9 anti), 43.39
1,8-Dichloro-10-[(trimethylsilyl)ethynyl]anthracene (5): Purification
of the product was carried out by column chromatography with
3904
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 3897–3907

Trisubstituted Triptycenes
(C9 syn) ppm. MS (EI, 70 eV): m/z = 355.9 [M+], 321.0 [M+ – Cl],
286.0 [M+ – 2 Cl], 250.0 [M+ – 3 Cl].
(C9), 38.35 (C-methyl), 32.67 (C-methyl), 32.60 [C(CH3)3] ppm.
MS (EI, 70 eV): m/z = 412.0 [M+], 397.0 [M+ – CH3], 377.1 [M+
Cl], 355.0 [M+
C4H9]. HRMS: calculated for C24H19Cl3:
412.0552; measured: 412.0552.
–
–
1,8,13-Trichloro-10-cyclohexyltriptycene and 1,8,16-Trichloro-10-cy-
clohexyltriptycene (10): White solid; yield 154 mg (58%); m.p.
1
3
298.9 °C. H NMR (500 MHz, CDCl3, 25 °C): δ = 8.07 (d, JH,H 1,8,13-Trichloro-10-methyltriptycene and 1,8,16-Trichloro-10-meth-
3
3
= 8.0 Hz), 7.32 (d, JH,H = 7.1 Hz), 7.30 (d, JH,H = 7.1 Hz, 1 H,
yltriptycene (12): White solid; yield 228 mg (42%); m.p. 350.4 °C.
3
3
H13 anti), 7.25 (d, JH,H = 7.4 Hz, 3 H, H4/H5/H16 syn), 7.19 (d,
1H NMR (600 MHz, CDCl3, 25 °C): δ = 7.39 (d, JH,H = 7.1 Hz,
3JH,H = 8.0 Hz), 7.11 (s, 1 H, H9 syn), 6.98 (m), 6.92 (dd, JH,H
=
1 H, H13 anti), 7.33 (d, JH,H = 7.5 Hz, 2 H, H4/H5 anti), 7.26 (d,
3
3
3
7.8, 7.9 Hz, H3/H6/H15 syn), 6.85 (dd, JH,H = 7.6 Hz, 1 H, H14
3JH,H = 7.5 Hz, 3 H, H4/H5/H16 syn), 7.10 (m, 5 H, H2/H7/H14
syn, H2/H7 anti), 7.08 (s, 1 H, H9 syn), 7.03 (m, 6 H, H3/H6/H15
3
anti), 6.39 (s, 1 H, H9 anti), 3.70 (t, JH,H = 11.5 Hz, cyclohexyl-H
anti), 2.99 (t, JH,H = 11.4 Hz, cyclohexyl-H syn), 2.66–1.54 (m, syn, H3/H6/H15 anti), 6.94 (dd, 3JH,H = 7.5, 7.8 Hz 1 H, H14 anti),
3
cyclohexyl-H syn and anti) (signals missing due to overlapping or
6.43 (s, 1 H, H9 anti), 2.72 (s, 3 H, methyl-H anti), 2.38 (s, 3 H,
broadening) ppm. 13C NMR (125 MHz, CDCl3): δ = 149.91–
methyl-H syn) ppm. 13C NMR (75 MHz, CDCl3): δ = 149.25–
121.97 (C-aryl syn and anti), 60.51 (C10 anti), 58.19 (C10 syn), 119.22 (C-aryl syn and anti), 51.88 (C10 anti), 50.23 (C10 syn),
48.12 (C9 anti), 43.95 (C9 syn), 39.57–27.38 (C-cyclohexyl) ppm. 46.90 (C9 anti), 42.82 (C9 syn), 17.48 (C-methyl anti), 13.51 (C-
MS (EI, 70 eV): m/z = 438.1 [M+], 403.1 [M+ – Cl], 367.1 [M+
–
methyl syn) ppm. MS (EI, 70 eV): m/z = 370.0 [M+], 354.9 [M+
–
2 Cl], 320.0 [M+ – Cl – C6H10]. HRMS: calculated for C26H21Cl3: CH3], 335.0 [M+ – 2 Cl], 266.1 [M+ – 3 Cl].
438.0709; measured: 438.0700.
1,8,13-Trichloro-10-isopropyltriptycene and 1,8,16-Trichloro-10-iso-
10-tert-Butyl-1,8,16-trichlorotriptycene (11): White solid; yield
propyltriptycene (13): White solid; yield 80 mg (40%); m.p.
1
1
3
85 mg (41%); m.p. 283.7 °C. H NMR (600 MHz, CDCl3, 25 °C): 317.2 °C. H NMR (600 MHz, CDCl3, 25 °C): δ = 7.78 (d, JH,H
3
3
3
3
δ = 7.84 (d, JH,H = 8.1 Hz, 2 H, H4/H5), 7.40 (d, JH,H = 7.0 Hz,
= 7.8 Hz, 1 H, H4 anti), 7.62 (d, JH,H = 7.7 Hz), 7.40 (d, JH,H =
3
3
3
1 H, H13), 7.16 (d, JH,H = 8.8 Hz, 1 H, H15), 7.11 (d, JH,H
=
7.2 Hz, 1 H, H5 anti), 7.33 (d, JH,H = 7.3 Hz, 4 H, H4/H5/H16
7.9 Hz, 2 H, H2/H7), 6.96 (m, 3 H, H3/H6/H14), 6.53 (s, 1 H, H9),
syn, H13 anti), 7.20 (m), 7.11 (s, 1 H, H9 syn), 7.03 (m, H3/H6/
3
2.29 (s, 6 H, methyl-H), 2.01 (s, 3 H, methyl-H) ppm. 13C NMR H15 anti), 6.91 (dd, JH,H = 7.8, 7.9 Hz, 1 H, H14 anti), 6.86 (dd,
(125 MHz, [D8]THF): δ = 150.39–124.18 (C-aryl), 70.07, 48.91 3JH,H = 7.4, 7.6 Hz, 3 H, H3/H6/H15 syn), 6.41 (s, 1 H, H9 anti),
Table 4. Crystallographic data for 1, 3, 5, 7, 8, 9, 11, 12 and 16.
1
3
5
7
8
9
11
12
16
Empirical
formula
Mr
F(000)
Colour
Crystal form
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C20H18Cl2
C18H16Cl2
C19H16Cl2Si
C18H16Cl2
2C20H12Cl2
0.5CH2Cl2
688.86
2824
yellow
C20H11Cl3
C24H19Cl3
C21H13Cl3
C18H16Cl2
329.24
688
colourless
fragment
orthorhombic triclinic
P21212
11.323(1)
19.812(1)
6.944(1)
90
303.21
316
yellow
plate
343.31
712
colourless
needles
monoclinic
P21/c
15.162(1)
14.855(1)
7.402(1)
90
94.55(1)
90
1662.0(2)
4
1.372
0.456
27.47
303.21
632
pale yellow
needles
357.64
364
413.74
856
colourless
fragment
monoclinic
P21/c
8.395(1)
11.070(1)
19.908(1)
90
95.15(1)
90
1842.4(1)
4
1.492
0.504
27.46
371.66
380
colourless
plate
triclinic
¯
P1
7.963(1)
8.089(1)
13.391(2)
79.57(1)
89.20(1)
74.89(1)
818.5(2)
2
303.21
632
colourless
needle
monoclinic
P21/m
7.891(1)
13.523(1)
7.972(1)
90
112.42(1)
90
786.4(1)
2
colourless
fragment
orthorhombic
P212121
7.313(1)
10.154(1)
19.752(1)
90
90
90
1466.7(1)
4
1.373
fragment
orthorhombic monoclinic
¯
P1
P212121
4.700(1)
12.194(2)
25.929(3)
90
C2/c
9.533(1)
9.641(1)
9.929(1)
115.59(1)
105.28(1)
104.49(1)
721.1(1)
2
40.109(1)
8.221(1)
23.058(1)
90
124.87(1)
90
6237.0(2)
8
1.467
0.497
30
90
90
90
90
γ [°]
V [Å3]
Z
1557.7(2)
4
1.404
0.410
25
1486.0(3)
4
1.355
0.423
30.03
ρcalcd. [gcm–3
]
1.397
0.436
30
1.510
0.578
30
1.508
0.558
24.99
µ [mm–1
θmax [°]
]
0.429
30
Index ranges h
Index ranges k
Index ranges l
Refl. collected
Independent refl. 2750
Rint
–13 Յ h Յ 13 –13 Յ h Յ 13 –19 Յ h Յ 19 –6ՆhՆ6
–23 Յ k Յ 23 –13 Յ k Յ 13 –19 Յ k Յ 18 –17ՆkՆ17
–55 Յ h Յ 56 –11 Յ h Յ 11 –10 Յ h Յ 10 0 Յ h Յ 9
–11 Յ k Յ 11 –18 Յ k Յ 19 –14 Յ k Յ 14 –8 Յ k Յ 9
–10 Յ h Յ 10
–14 Յ k Յ 14
–8 Յ l Յ 8
14682
–13 Յ l Յ 13 –9 Յ l Յ 8
–36ՆlՆ36
17144
4346
–32 Յ l Յ 32 –11 Յ l Յ 11 25 Յ l Յ 25
–15 Յ l Յ 15 –27 Յ l Յ 27
29376
4207
0.034
3546
19114
3667
0.056
2867
79833
9089
0.052
6945
9269
2380
0.016
2144
44475
4204
0.041
3611
9322
2881
0.071
2069
39724
4279
0.034
4003
0.089
2198
0.043
3639
Observed refl.,
IϾ2σ(I)
Parameters
R1, IϾ2σ(I)
wR2, IϾ2σ(I)
R1 (all data)
wR2 (all data)
GoF
199
184
202
182
411
118
247
218
184
0.0403
0.0813
0.0613
0.0888
1.027
0.199
–0.230
0.0330
0.0849
0.0418
0.0896
1.036
0.361
–0.288
–
0.0375
0.0894
0.0544
0.0967
1.025
0.236
–0.339
–
0.0431
0.0884
0.0567
0.0931
1.045
0.0340
0.0837
0.0522
0.0905
1.045
0.398
–0.390
–
0.0283
0.0802
0.0319
0.0838
1.045
0.503
–0.215
–
0.0353
0.0942
0.0424
0.0983
1.043
0.745
–0.382
–
0.0593
0.1371
0.0934
0.1552
1.031
0.911
–0.375
–
0.0360
0.0927
0.0395
0.0949
1.025
ρmax [eÅ–3
ρmin [eÅ–3
]
]
0.365
0.869
–0.253
0.02(6)
768542
–0.237
0.56(5)
768547
Flack parameter 0.52(8)
CCDC numbers 768539
768540
768541
768543
768544
768545
768546
Eur. J. Org. Chem. 2010, 3897–3907
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3905

N. W. Mitzel et al.
FULL PAPER
4.29 (m, 1 H, CHCH3 anti), 3.55 (m, 1 H, CHCH3 syn), 1.92 (d,
litz (laboratory assistant, Bielefeld), Marius Strunk (undergraduate
student, Münster) and Stefanie Pelzer (undergraduate student,
3
3JH,H = 6.6 Hz, 3 H, methyl-H anti), 1.85 (d, JH,H = 6.7 Hz, 6 H,
3
methyl-H syn), 1.74 (d, JH,H = 6.7 Hz, 3 H, methyl-H anti) ppm. Bielefeld) for their help in the laboratory, Dr. Matthias Letzel and
13C NMR (150 MHz, CDCl3): δ = 149.90–122.13 (C-aryl syn and Oliver Kollas for recording mass spectra as well as the NRW Grad-
anti), 71.61 (CHCH3 syn), 62.87 (C10 anti), 59.07 (C10 syn), 48.04 uate School of Chemistry (GSC-MS) and the Deutsche For-
(C9 anti), 43.55 (C9 syn), 25.83 (CHCH3 anti), 24.55 (C-methyl
anti), 21.71 (C-methyl syn), 21.40 (C-methyl anti) ppm. MS (EI,
70 eV): m/z = 398.0 [M+], 363.1 [M+ – Cl], 321.0 [M+ – Cl – C3H7],
250.0 [M+ – 3 Cl – C3H7]. HRMS: calculated for C23H17Cl3:
398.0396; measured: 398.0392.
schungsgemeinschaft (DFG) for financial support.
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10-Butyl-1,8,13-trichlorotriptycene and 10-Butyl-1,8,16-trichloro-
1
triptycene (14): White solid; yield 103 mg (22%); m.p. 284.1 °C. H
3
NMR (600 MHz, CDCl3, 25 °C): δ = 7.41 (d, JH,H = 7.3 Hz, 2 H,
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2 H, H3/H6 anti), 6.98 (dd, JH,H = 7.7, 7.8 Hz, 4 H, H3/H6/H15
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=
7.7 Hz,
2
H,
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3
6 H, CH2CH3 syn and anti, CH2CH2CH3 anti), 1.15 (t, JH,H
=
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3
7.3 Hz, 3 H, methyl-H syn), 1.11 (t, JH,H = 7.1 Hz, 3 H, methyl-
H anti) ppm. 13C NMR (75 MHz, CDCl3): δ = 143.13–123.28 (C-
aryl syn and anti), 55.03 (C10), 47.56 (C9 anti), 43.34 (C9 syn),
28.26 (CH2CH2CH2CH3 syn), 27.32 (CH2CH2CH3 syn) 24.78
(CH2CH3 and CH2CH2CH3 anti), 24.55 (CH2CH3 syn), 14.30 (C-
methyl) (signals missing due to overlapping or broadening) ppm.
MS (EI, 70 eV): m/z = 412.0 [M+], 377.1 [M+ – Cl], 356.9 [M+
–
C4H9], 342.1 [M+ – 2 Cl]. HRMS: calculated for C24H19Cl3:
412.0552; measured: 412.0531.
1,8,13-Trichloro-10-phenyltriptycene and 1,8,16-Trichloro-10-phen-
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3
1H NMR (600 MHz, CDCl3, 25 °C): δ = 8.02 (d, JH,H = 7.9 Hz,
3
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3
7.66 (dd, JH,H = 7.6 Hz, 3 H, H3/H6/H15 syn), 7.55 (m, 5 H, H2/
3
H7/H14 syn, H3/H6 anti), 7.52 (d, JH,H = 7.1 Hz, 2 H, H2/H7
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=
3
7.9 Hz, 1 H, H15 anti), 6.97 (dd, JH,H = 7.3, 7.8 Hz 1 H, H14
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Acknowledgments
We thank Drs. Stuart A. Hayes and Raphael J. F. Berger for the
calculations on the anthracene, benzyne and triptycene, Irina Lang-
3906
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 3897–3907

Trisubstituted Triptycenes
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Eur. J. Org. Chem. 2010, 3897–3907
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3907