Polyalkynylanthracenes-syntheses, structures and their behaviour towards UV irradiation

Article abstract of DOI:10.1039/c4ob00735b

A series of bis- and tris[(trimethylsilyl)ethynyl]anthracenes (1,5-, 1,8-, 9,10- and 1,8,10-) has been synthesised by multistep (cross coupling) reactions and the behaviour of the SiMe₃-functionalised alkynylanthracene derivatives towards UV irradiation was qualitatively studied by NMR spectroscopy. In the case of 9,10-bis[(trimethylsilyl)ethynyl]anthracene we observed a photodimerisation upon UV irradiation; the third example was reported for a symmetrically 9,10-difunctionalised anthracene derivative, besides those with small fluorine- and methyl-substituents. The anthracene dimerisation is completely thermally reversible and the temperature dependence of the cycloelimination reaction was studied by ¹H VT-NMR experiments. The (deprotected) 1,5- and 1,8-diethynylanthracenes were converted with (dimethylamino)trimethylstannane to obtain the corresponding SnMe ₃-functionalised alkynes, potentially useful as highly conjugated building blocks in Stille cross coupling reactions. The new anthracene compounds were completely characterised by multinuclear NMR spectroscopy, (high resolution) mass spectrometry and-in most cases-by X-ray diffraction experiments. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4ob00735b

Organic &
Biomolecular Chemistry
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Polyalkynylanthracenes – syntheses, structures
and their behaviour towards UV irradiation†
Cite this: Org. Biomol. Chem., 2014,
2, 7355
1
Jan-Hendrik Lamm, Johanna Glatthor, Jan-Henrik Weddeling, Andreas Mix,
Jasmin Chmiel, Beate Neumann, Hans-Georg Stammler and Norbert W. Mitzel*
A series of bis- and tris[(trimethylsilyl)ethynyl]anthracenes (1,5-, 1,8-, 9,10- and 1,8,10-) has been syn-
3
thesised by multistep (cross coupling) reactions and the behaviour of the SiMe -functionalised alkynyl-
anthracene derivatives towards UV irradiation was qualitatively studied by NMR spectroscopy. In the case
of 9,10-bis[(trimethylsilyl)ethynyl]anthracene we observed a photodimerisation upon UV irradiation; the
third example was reported for a symmetrically 9,10-difunctionalised anthracene derivative, besides those
with small fluorine- and methyl-substituents. The anthracene dimerisation is completely thermally revers-
1
ible and the temperature dependence of the cycloelimination reaction was studied by H VT-NMR experi-
ments. The (deprotected) 1,5- and 1,8-diethynylanthracenes were converted with (dimethylamino)-
Received 7th April 2014,
Accepted 24th July 2014
trimethylstannane to obtain the corresponding SnMe -functionalised alkynes, potentially useful as highly
3
conjugated building blocks in Stille cross coupling reactions. The new anthracene compounds were com-
DOI: 10.1039/c4ob00735b
pletely characterised by multinuclear NMR spectroscopy, (high resolution) mass spectrometry and – in
most cases – by X-ray diffraction experiments.
www.rsc.org/obc
their photodimerisation reactions are mostly found to be
Introduction
similar to unsubstituted anthracene, i.e. [4 + 4] cycloaddition
4
Anthracenes and their substituted derivatives undergo cyclo- leading to the 9,10:9′,10′ photodimer. However, other types of
1
addition reactions upon irradiation with UV light. In the case (mono-) substituted anthracene dimerisations, called non-
of functionalised anthracenes like 1,8-substituted ones, a classical photodimers, have been observed, e.g. in the case of
mixture of the so-called head to head- (A) and head to tail- (B) 9-(phenylethynyl)anthracene ([4 + 2] cycloaddition) or trans-1-
1
b,5
photodimers is obtained (Scheme 1). Owing to steric inter- (9-anthryl)-2-phenylethylene ([6 + 6] cycloaddition).
actions of the substituents, the head to tail isomer is the pre-
ferred product in most cases.
Due to steric repulsion of the substituents, the photodimer-
isation of 9,10-disubstituted anthracenes is rarely explored.
2
(
Di-) substituted anthracenes find various applications as Nevertheless, some examples are known. Some unsymmetri-
3
photoswitchable units, e.g. in supramolecular systems, as cally substituted anthracene derivatives have been found to
undergo photodimerisation yielding [4 + 4] cycloaddition pro-
1
b
ducts, which are thermally labile in most cases. Until now,
symmetrically 9,10-disubstituted anthracenes are known to be
6
difficult to dimerise, except for 9,10-difluoro- and 9,10-
7
dimethylanthracene.
Results and discussion
Scheme 1 Photodimerisation products of 1,8-substituted anthracene Syntheses and characterisation of the anthracene derivatives
derivatives.
The bis[(trimethylsilyl)ethynyl]-functionalised anthracenes 3, 4
and 10 were obtained by Kumada and Sonogashira-Hagihara
Universität Bielefeld, Fakultät für Chemie, Lehrstuhl für Anorganische Chemie und
Strukturchemie, Centrum für Molekulare Materialien CM , Universitätsstraße 25,
cross coupling reactions using 1,5- (1) and 1,8-dichloroanthra-
2
cene (2) as well as 9,10-dibromoanthracene (9), respectively
D-33615 Bielefeld, Germany. E-mail: mitzel@uni-bielefeld.de;
Fax: +49 521 106 6026; Tel: +49 521 106 6128
8,9
(
3
Scheme 2). After cleaving the SiMe groups, the deprotected
dialkynes 5 and 6 were converted with (dimethylamino)tri-
†
CCDC 994028–994034. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c4ob00735b
methylstannane and the SnMe -functionalised compounds 7
3
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We also tried to convert 9,10-diethynylanthracene (11) into
the corresponding SnMe3 substituted species. However, the
brownish product was found to be insoluble in common
organic solvents and could not be analysed so far.
The molecular structures in the crystalline state of com-
pounds 3, 4, 5, 7 and 8 are displayed in Fig. 1–4 (the structure
1
1
of 6 was previously published by us ). They were determined
Scheme 2 Syntheses of the 1,5-, 1,8- and 9,10-dialkynylsubstituted
anthracene derivatives. Reagents and conditions: (i) 1. Me
7 eq.), Ni(acac) , PPh , THF, reflux; 2. aq. workup, 82% (3), 92% (4); (ii)
, MeOH, r.t., 93% (5), 82% (6), 25% (11); (iii) Me SnNMe , THF,
0 °C, 4 h, quant. (7 and 8); (iv) 1. Me SiCuCH (2 eq.), CuI (10 mol%),
(PPh (5 mol%), (i-Pr) NH, reflux, 3 d; 2. aq. workup, 38%.
3
SiCuCMgBr
(
2
3
K
6
2
CO
3
3
2
3
PdCl
2
3
)
2
2
and 8 were obtained in quantitative yield. These terminally
SnMe -functionalised dialkynyl anthracenes might be appli-
3
cable as highly conjugated (photoswitchable) building blocks,
e.g. when two functionalities should be linked by Stille cross
1
0
coupling reactions. All compounds were characterised by
multinuclear NMR spectroscopy as well as (high resolution)
mass spectrometry. Tables 1 and 2 provide the H NMR spec-
troscopic shifts of the 1,5- and 1,8-substituted derivatives for
comparison.
1
Fig. 1 Molecular structures of compounds 3 (above) and 7 (below) in
the crystalline state. Displacement ellipsoids are drawn at the 50% prob-
ability level, hydrogen atoms are omitted for clarity. Selected bond
lengths and angles are listed in Table 3.
1
Table 1
3
H
NMR shifts of the 1,5-dialkynylsubstituted compounds
(500 MHz, 298 K). For NMR spectro-
(E = Si), 5 and 7 (E = Sn) in CDCl
3
scopic assignments see Scheme 7
H9/H10
H4/H8
H2/H6
H3/H7
CuC–H
3 3
E(CH )
3
5
7
8.88
8.93
8.93
8.06
8.10
8.04
7.74
7.79
7.72
7.44
7.46
7.42
—
3.60
—
0.39
—
0.48
1
Table 2
4
H
NMR shifts of the 1,8-dialkynylsubstituted compounds
(500 MHz, 298 K). For NMR spectro-
(E = Si), 6 and 8 (E = Sn) in CDCl
3
Fig. 2 Molecular structure of compound 5 in the crystalline state. Dis-
placement ellipsoids are drawn at the 50% probability level, hydrogen
atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]:
C(1)–C(2) 1.445(1), C(1)–C(14) 1.378(1), C(1)–C(15) 1.435(1), C(2)–C(3)
1.396(1), C(2)–C(11) 1.436(1), C(15)–C(16) 1.195(1); C(1)–C(2)–C(3)
122.3(1), C(1)–C(2)–C(11) 118.4(1), C(1)–C(15)–C(16) 178.5(1), C(2)–C(1)–
C(14) 120.2(1), C(2)–C(1)–C(15) 119.5(1).
scopic assignments see Scheme 7
H9
H10
H4/H5
H2/H7
H3/H6
CuC–H
3 3
E(CH )
4
6
8
9.32
9.44
9.43
8.42
8.45
8.40
7.98
8.03
8.95
7.79
7.80
7.76
7.42
7.45
7.40
—
3.62
—
0.39
—
0.46
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Table 3 Selected bond lengths [Å] and angles [°] of compounds 3 and
7
3
(E = Si)
7 (E = Sn)
C(1)–C(2)
C(1)–C(7)
C(1)–C(8)
C(2)–C(3)
C(2)–C(4)
C(8)–C(9)
C(9)–E(1)
C(10)–E(1)
C(1)–C(2)–C(3)
C(1)–C(2)–C(4)
C(1)–C(8)–C(9)
C(2)–C(1)–C(7)
C(2)–C(1)–C(8)
C(8)–C(9)–E(1)
1.447(1)
1.376(1)
1.437(1)
1.397(1)
1.436(1)
1.209(2)
1.844(1)
1.866(1)
122.4(1)
118.5(1)
175.5(1)
120.0(1)
119.1(1)
171.9(1)
1.452(3)
1.380(3)
1.434(3)
1.393(3)
1.433(3)
1.210(3)
2.113(2)
2.131(2)
122.4(2)
118.6(2)
175.2(2)
119.7(2)
118.6(2)
166.2(2)
Fig. 3 Molecular structure of compound 4 in the crystalline state. Dis-
placement ellipsoids are drawn at the 50% probability level. Hydrogen
atoms are omitted and only one molecule is shown for clarity. Selected
bond lengths [Å] and angles [°]: C(1)–C(2) 1.443(2), C(1)–C(14) 1.377(2),
C(1)–C(15) 1.440(2), C(2)–C(3) 1.396(2), C(2)–C(11) 1.438(2), C(5)–C(20)
planar with C–C distances ranging from 1.367(2) Å [C(5)–C(6), 3]
and 1.364(3) Å [C(5)–C(6), 7] to 1.447(1) Å [C(1)–C(2), 3] and
1
.437(2), C(6)–C(7) 1.416(2), C(16)–Si(1) 1.842(1), C(17)–Si(1) 1.864(2);
C(1)–C(2)–C(3) 122.6(1), C(1)–C(2)–C(11) 118.3(1), C(1)–C(15)–C(16) 1.452(3) Å [C(1)–C(2), 7], respectively. The alkynyl substituents
1
76.0(1), C(2)–C(1)–C(15) 120.5(1), C(5)–C(20)–C(21) 178.5(1), C(15)–
are nearly in the same plane as the anthracene backbone; this
is manifest from the surrounding angles of C(1), which are
close to 120° [maximum deviations are 0.9° (3) and 1.7° (7)].
The angles C(1)–C(8)–C(9) [175.5(2)° (3) and 175.2(2)° (7)] and
C(8)–C(9)–E(1) [171.9(2)° (3) and 166.2(2)° (7)] show the (tri-
methylelement)ethynyl groups to be slightly bent out of linear-
ity and they are found to be not in-plane with the anthracene
units as is indicated in the dihedral angles C(6)–C(7)–C(1)–C(8)
at 175.3(1)° (3) and 177.0(2)° (7), respectively. The silicon and
C(16)–Si(1) 173.9(1), C(20)–C(21)–Si(2) 177.1(1).
tin atoms are tetrahedrally coordinated with E(1)–C
dis-
Me
1
2
tances in the expected range. The CuC bond lengths of com-
pounds 3 [1.209(2) Å] and 7 [1.210(3) Å] are identical within
experimental error and with the standard triple bond length of
1
2
1.20 Å.
The molecular structure of the deprotected 1,5-diethynyl-
anthracene (5) depicted in Fig. 2 exhibits no unexpected bond
lengths and angles. Carbon atoms C(1) and C(8) are trigonal-
planar coordinated with the three surrounding angles being
close to 120°. The alkynyl substituents are found to be in-
plane with the planar anthracene skeleton. With “aromatic”
Fig. 4 Molecular structure of compound 8 in the crystalline state. Dis-
placement ellipsoids are drawn at the 50% probability level. Hydrogen
atoms are omitted and only one molecule is shown for clarity. Selected
bond lengths [Å] and angles [°]: C(1)–C(2) 1.448(2), C(1)–C(14) 1.381(2), C–C distances between 1.367(1) Å [C(5)–C(6)] and 1.436(1) Å
C(1)–C(15) 1.431(3), C(2)–C(3) 1.400(2), C(2)–C(11) 1.430(2), C(5)–C(20) [C(4)–C(9)], the structural parameters are well comparable with
1
.433(3), C(6)–C(7) 1.415(3), C(16)–Sn(1) 2.114(2), C(17)–Sn(1) 2.127(2);
C(1)–C(2)–C(3) 122.1(2), C(1)–C(2)–C(11) 118.6(2), C(1)–C(15)–C(16)
77.5(2), C(2)–C(1)–C(15) 120.1(2), C(5)–C(20)–C(21) 176.0(2), C(15)–
C(16)–Sn(1) 171.5(2), C(20)–C(21)–Sn(2) 174.7(2).
11
those of 1,8-diethynylanthracene (6).
The SiMe -substituted 1,8-dialkynylanthracene 4 is depicted
3
1
in Fig. 3 and the important structural parameters of both
molecules are listed in Table 4.
After recrystallisation from n-hexane, the molecular struc-
by X-ray diffraction experiments of single crystals grown from ture of the SnMe derivative 8 was also determined by X-ray
3
solutions by slow evaporation of the solvent (see the Experi- diffraction experiments (Fig. 4). In contrast to the corres-
mental section for details). Due to the fact that similar struc- ponding 1,5-substituted compound 7, four molecules of 1,8-
tural parameter values are observed for compounds 3 and 7, as bis[(trimethylstannyl)ethynyl]anthracene (8) and one n-hexane
well as for compounds 4 and 8, their molecular structures are molecule are found in the asymmetric unit. Selected value
described together.
The terminally SiMe - and SnMe -substituted 1,5-diethynyl- 8 are listed in Table 4 for comparison. A few remarkably
ranges of the corresponding bond lengths and angles of 4 and
3
3
anthracenes 3 and 7 exhibit inversion centres in the middle different values were measured demonstrating the variability
of their central anthracene rings. The aromatic systems are of structural parameters of independent molecules for the
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1
Table 4 Selected value ranges (minimum and maximum) of bond anthracenes, the H NMR spectrum recorded at ambient temp-
lengths [Å] and angles [°] of compounds 4 and 8
erature (298 K) in CDCl shows one downfield-shifted singlet
3
at δ = 9.44 ppm (H9), two doublets at 8.58 ppm (H4/H5) and
4
(E = Si)
8 (E = Sn)
7.78 ppm (H2/H7), as well as one doublet of doublets at
min.
max.
min.
max.
7.50 ppm (H3/H6). Two singlets at 0.49 ppm and 0.46 ppm
1
17
119
(
integral ratio 9 : 18) show typical
Sn- and
Sn-satellites,
CAr–Cu
1.437(2)
1.205(2)
1.842(1)
1.849(2)
1.356(2)
117.9(1)
118.9(1)
174.4(1)
173.9(1)
106.3(1)
109.5(2)
1.440(2)
1.209(2)
1.847(1)
1.864(2)
1.443(2)
122.6(1)
121.1(1)
178.5(1)
177.1(1)
109.4(1)
112.1(1)
1.427(3)
1.200(3)
2.105(2)
2.126(2)
1.355(3)
118.0(2)
119.2(2)
174.9(2)
170.2(2)
103.1(1)
108.9(1)
1.438(3)
1.210(3)
2.123(2) groups.
2.137(2)
indicating the availability of two different trimethylstannyl
–CuC–
uC–E
E–CMe
C
C
C
C
Ar–CAr
1.449(2)
Ar–CAr–CAr
Ar–CAr–Cu
Ar–CuC
122.4(2) Photodimerisation reactions
121.5(2)
179.6(2) To investigate the influence of the (trimethylsilyl)ethynyl sub-
CuC–E
uC–E–CMe
176.3(2)
109.0(1)
117.7(1)
stituent positions on the syn–anti ratio of the anthracene
dimerisation, the corresponding compounds were irradiated
CMe–E–CMe
with UV light (365 nm) at ambient temperature in CDCl . For
3
an exploratory qualitative assessment of the kinetics of these
same compound, a fact that has also been observed in the reactions simple NMR spectroscopic investigations were per-
1
1
X-ray diffraction results of 1,8-diethynylanthracene (6). Never- formed and one example was explored in more detail (see
theless, the bond lengths and angles determined for com- below). For this purpose, small amounts of compounds 3, 4,
3
pounds 4 and 8 are in the expected ranges and the values are 10, 13 and 14 were dissolved in CDCl and irradiated in an
comparable to those of the corresponding 1,5-substituted NMR tube for several hours, so that the reaction progress
1
derivatives 3 and 7 described above in more details. Exact could be easily monitored by H NMR spectroscopy. UV
values for certain molecules are given in Fig. 3 and 4.
irradiation of the 1,5- (3) and 1,8-bis[(trimethylsilyl)ethynyl]-
1
3
Starting from 10-bromo-1,8-dichloroanthracene (12), the anthracene (4) led to a complete conversion into the corres-
tris[(trimethylsilyl)ethynyl]-substituted species 14 was syn- ponding [4 + 4] cycloaddition products 17 and 18, respectively.
thesised in a two-step reaction via 1,8-dichloro-10-[(trimethyl- In the case of 3 only one photodimerised species was observed
1
silyl)ethynyl]anthracene (13), as is displayed in Scheme 3. 13 and H NMR spectroscopically identified as the head to tail-
can also be prepared (in lower yields) by conversion of 1,8- isomer, whereas a 49 : 51-mixture of the head to head (syn) and
dichloroanthracene-10-(9H)-one with [(trimethylsilyl)ethynyl]- head to tail (anti) photodimers was obtained when a CDCl
magnesium bromide in THF. Deprotection of the alkynyl solution of 1,8-bis[(trimethylsilyl)ethynyl]anthracene (4) was
units of 14 led to the formation of 15 which was converted irradiated with UV light (Scheme 4). This is in accordance with
3
1
4
with (dimethylamino)trimethylstannane to afford 1,8,10-tris- the literature for the photodimerisation of 1,8-dichloroanthra-
2
[(trimethylstannyl)ethynyl]anthracene (16).
cene (2) in various solvents. We did not observe the formation
However, compared to the 1,5- and 1,8-disubstituted com- of a syn–anti mixture of photodimers when the corresponding
pounds 7 and 8, the obtained product was found to be 1,5-substituted species 3 was irradiated, although a syn–anti
2
unstable towards air and moisture. Anyway, we found some mixture was reported for 1,5-dichloroanthracene (1).
evidence for the successful synthesis of the desired threefold
As expected, UV irradiation of the 1,8,10-substituted com-
SnMe
3
-substituted compound 16 stemming from H NMR data pound 14 led to a complete conversion into the corresponding
1
of the raw product. As expected for 1,8,10-trisubstituted
Scheme 3 Syntheses of the 1,8,10-trialkynylsubstituted anthracene
derivatives. Reagents and conditions: (i) 1. Me
10 mol%), PdCl (PPh (5 mol%), (i-Pr) NH, reflux, 3 d; 2. aq. workup,
5%; (ii) 1. Me SiCuCMgBr (10 eq.), Ni(acac) , PPh , THF, reflux; 2. aq.
workup, 83%; (iii) K CO , MeOH, r.t., 86%; (iv) Me SnNMe , THF, 60 °C,
h.
3
SiCuCH (2 eq.), CuI
(
8
2
3
)
2
2
3
2
3
2
3
3
2
Scheme 4 Photodimerisation of the monomers 3 and 4 to the dimeric
species 17 and 18 by UV irradiation in CDCl .
3
4
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Scheme 5 Photodimerisation of the monomers 13 and 14 to the
dimeric species 19 and 20 by UV irradiation in CDCl .
3
Fig. 5 Molecular structure of the anti-photo dimer of 1,8-bis[(tri-
methylsilyl)ethynyl]anthracene (anti-18). Displacement ellipsoids are
drawn at the 50% probability level, hydrogen atoms are omitted for
anti-[4 + 4] cycloaddition products 20 (Scheme 5). An increased
repulsive interaction of the bulky (trimethylsilyl)ethynyl substi-
tuents might be the reason for the selective anti-dimerisation clarity. Selected bond lengths [Å] and angles [°]: C(1)–C(2) 1.398(2),
reaction. In contrast to that, a syn–anti mixture (32 : 68) of 19 C(1)–C(14) 1.406(2), C(1)–C(15) 1.445(2), C(2)–C(3) 1.517(2), C(2)–C(11)
1
.407(2), C(3)–C(4) 1.519(2), C(3)–C(10’) 1.623(2), C(5)–C(20) 1.443(3),
was obtained when a solution of 1,8-dichloro-10-[(trimethyl-
silyl)ethynyl]anthracene (13) was irradiated under the same
conditions indicating a weaker interaction of the substituents
in positions 1, 8 and 10 of the syn-19 isomer.
C(15)–C(16) 1.207(2), C(16)–Si(1) 1.845(2), C(20)–C(21) 1.208(2), C(21)–
Si(2) 1.842(2); C(1)–C(2)–C(3) 122.4(1), C(1)–C(2)–C(11) 119.6(1), C(1)–
C(15)–C(16) 179.0(1), C(2)–C(1)–C(15) 121.0(1), C(2)–C(3)–C(4) 108.3(1),
C(2)–C(3)–C(10’) 112.2(1), C(4)–C(5)–C(20) 119.8(1), C(5)–C(20)–C(21)
In the case of the photodimerisation of 1,8-bis[(trimethyl- 173.4(1), C(15)–C(16)–Si(1) 175.4(1), C(20)–C(21)–Si(2) 173.9(1).
silyl)ethynyl]anthracene (4), as well as 1,8-dichloro-10-[(tri-
methylsilyl)ethynyl]anthracene (13), we determined the
molecular structures in the crystalline state of the corres-
ponding head-to-tail isomers anti-18 (Fig. 5) and anti-19
(Fig. 6), respectively.
Due to the [4 + 4] cycloaddition reaction, anti-18 contains
four isolated aromatic rings and an aliphatic tricyclic system.
The aromatic rings are planar and the dihedral angle between
their mean planes is 137.6(1)°. The phenyl C–C bond lengths
and angles are ranging from 1.390(2) Å [C(6)–C(7)] to 1.407(2)
Å [C(2)–C(11)] and from 119.2(2)° [C(5)–C(4)–C(9)] to 120.6(2)°
3
[
C(2)–C(11)–C(12)], respectively. As expected for sp carbon
atoms, the angles around C(3) and C(10) are close to tetra-
hedral geometry {107.9(2)° [C(9)–C(10)–C(11)] to 112.2(2)°
3
[
C(2)–C(3)–C(10′)]}. The C(sp )–CPh distances are between
1
.512(2) Å [C(10)–C(11)] and 1.519(2) Å [C(3)–C(4)], which is
3
2
12
slightly longer than a standard C(sp )–C(sp ) bond (1.50 Å ).
The C(3)–C(10′) [1.623(2) Å] bond is found to be remarkably
longer than a standard C(sp )–C(sp ) bond (1.54 Å ). A repul-
sive interaction between the TMS-substituted alkynyl units
results in an angle between the C(1)–Si(1)- and C(5)–Si(2)-
vectors [15.5(1)°]. Like in the case of 4 and 8, one of the
3
3
1
Fig. 6 Molecular structure of the anti-photo dimer of 1,8-bis[(tri-
methylsilyl)ethynyl]anthracene (anti-19). Displacement ellipsoids are
drawn at the 50% probability level, hydrogen atoms are omitted for
alkynyl substituents is nearly in plane with the aryl ring it is clarity. Selected bond lengths [Å] and angles [°]: C(1)–C(2) 1.391(3), C(1)–
C(14) 1.391(3), C(1)–Cl(1) 1.746(2), C(2)–C(3) 1.512(2), C(2)–C(11)
bonded to [the C(1)-bonded in anti-18], whereas the second
1.398(3), C(3)–C(4) 1.512(3), C(3)–C(10’) 1.643(2), C(10)–C(15) 1.471(3),
alkynyl unit is slightly bent, as denoted by the torsion angles
C(5)–C(20)–C(21) [173.4(2)°] and C(20)–C(21)–Si(1) [173.9(2)°].
Like in the case of anti-18, the photodimer of the 10-(tri-
C(15)–C(16) 1.209(3), C(16)–Si(1) 1.840(2), C(18)–Si(1) 1.864(2); C(1)–
C(2)–C(3) 123.1(2), C(1)–C(2)–C(11) 117.9(2), C(2)–C(1)–Cl(1) 120.2(1),
C(2)–C(3)–C(4) 109.1(1), C(2)–C(3)–C(10’) 112.2(1), C(10)–C(15)–C(16)
methylsilyl)ethynyl-substituted 1,8-dichloroanthracene (anti- 176.7(2), C(11)–C(10)–C(15) 112.3(2), C(15)–C(16)–Si(1) 171.2(2).
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9) crystallises in the triclinic space group P ˉ1 with one centro-
symmetric molecule in the unit cell.
The former anthracene units are linked by their central
rings, whereby the C(3)–C(10′)/C(10)–C(3′) bonds measure
1
1
.634(2) Å, slightly longer than the corresponding ones in anti-
8 [1.623(2) Å] and remarkably longer than the standard C–C
1
2
bond (1.54 Å ). The quaternary carbon atom C(10) adopts a
somewhat distorted tetrahedral coordination geometry, as is
indicated by its surrounding angles ranging from 106.5(2)°
[C(15)–C(10)–C(3′)] to 112.3(2)° [C(15)–C(10)–C(11)]. As is indi-
cated by the angles C(10)–C(15)–C(16) [176.7(2)°] and C(15)–
C(16)–Si(1) [171.2(2)°], the alkynyl substituents deviate little
from linearity. The chlorine atoms are found to be in-plane
with the aromatic rings they are bonded to. The dihedral angle
between these aromatic mean planes is 135.5(1)°, slightly
smaller than the corresponding one in compound anti-18
Fig. 7 Content of the photodimer 21 [%] vs. (irradiation-) time [min] at
[137.6(1)°].
298 K.
In all the cases mentioned above, a quantitative conversion
into the photodimers 17, 18, 19 and 20 was observed and they
are found to be thermally stable at ambient temperature for
several weeks.
1
monitored by recording its H NMR spectra. As shown in
Fig. 7, a complete cycloelimination reaction of 21 into the
corresponding monomer 10 was observed after ca. 6.5 hours,
when the sample was exposed to ambient temperature without
further UV irradiation.
A completely different behaviour was observed, when 9,10-
bis[(trimethylsilyl)ethynyl]anthracene (10) was irradiated
under the same conditions. Although a [4 + 4] cycloaddition
1
reaction occurs (indicated in a new set of resonances in the H
In order to monitor the influence of temperature on the
monomerisation (21 → 10) we performed kinetic NMR exper-
iments at 298 K, 303 K and 313 K. As can be concluded from
Fig. 8, a faster decay of the dimer concentration can be
observed at higher temperatures.
Starting with a photodimer-to-monomer ratio of 19.5%, a
complete conversion into the monomer 10 was observed after
more than 6 hours at 298 K. However, the reaction rate is
remarkably increased, when the sample is held at 303 K
NMR spectra), a quantitative conversion of 10 into its photo-
dimer 21 could not be achieved (Scheme 6). Solely a maximum
of 25% dimer 21 was formed after the sample was irradiated
with UV light for ca. 4 h at ambient temperature. Anyhow, a
proceeding irradiation (up to 5 hours) did not lead to an
increase of the dimer-to-monomer ratio under the given
circumstances.
Interestingly, we found that dimer compound 21 is much
more thermally labile, compared to the other (trimethylsilyl)-
ethynyl-substituted photodimers 17, 18, 19 and 20, which were
synthesised in this work. We investigated the kinetics of this
(
ca. 2.5 hours) or 313 K (ca. 1.5 hours), respectively (Fig. 8).
From the data shown in Fig. 8 we could calculate an estimate
for the barrier of activation E
A
of 94 kJ mol− . These results
1
1
cycloelimination reaction by a series of H NMR experiments.
suggest that 9,10-dialkynylanthracene derivatives might be
Therefore, a NMR sample of 9,10-bis[(trimethylsilyl)ethynyl]-
anthracene (10) in CDCl was irradiated with UV light for at
3
least 3.5 hours at ambient temperature (298 K), only inter-
rupted for ca. 3 minutes by recording proton NMR spectra.
After irradiation, the sample was left in the magnet at that
temperature and the decay of the dimer concentration was
Scheme 6 Photodimerisation of 9,10-bis[(trimethylsilyl)ethynyl]anthra-
cene (10) to the thermally (r.t.) unstable compound 21 by UV irradiation
Fig. 8 Content of the photodimer 21 [%] vs. time after stopping the UV
in CDCl
3
.
irradiation [min] at 298 K, 303 K and 313 K.
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8
9
applicable as molecular thermo-reversible photo switching cene (6), 9,10-bis[(trimethylsilyl)ethynyl]anthracene (10) and
units.
1
3
10-bromo-1,8-dichloroanthracene (12)
were synthesised
Due to this interesting behaviour in solution we further according to literature protocols. All reactions using organo-
assumed to dimerise 9,10-bis[(trimethylsilyl)ethynyl]anthra- metallic reagents were carried out under an anhydrous, inert
cene (10) in the solid state, according to experiments with e.g. atmosphere of nitrogen using standard Schlenk techniques in
1
5
diarylethene derivatives performed by Irie and coworkers.
dry THF (dried over potassium) or n-hexane (dried over
). The solvents were freshly distilled before being used
For this purpose, we fixed a single crystal of 10 on a glass fibre LiAlH
4
onto the goniometer of the diffractometer. After collecting the for the reactions. Column chromatography was performed on
monomer data, we used a blue-violet laser (402 nm) to irradi- silica gel 60 (0.04–0.063 mm mesh). NMR spectra were
ate the crystal (the ability of this light source for dimerisation recorded on a Bruker Avance III 300, a Bruker DRX 500, a
reactions was tested by irradiating a NMR sample of 10 in Bruker Avance III 500 and a Bruker Avance 600 instrument at
CDCl
3
). However, no photoreaction was observed by X-ray diffr- room temperature (298 K). The chemical shifts (δ) were
1
action investigations, also not when the irradiation exper- measured in ppm with respect to the solvent (CDCl : H NMR
iments were repeated several times between 243 K and 363 K. δ = 7.26 ppm, C NMR δ = 77.16 ppm) or referenced externally
This might be due to the fact that the 9,10-disubstituted ( Si: SiMe
3
1
3
2
9
119
4
,
4
Sn: SnMe ). EI mass spectra were recorded
anthracenes 10 are perpendicularly oriented to each other and using an Autospec X magnetic sector mass spectrometer with
no π–π interactions are found in its molecular structure in the EBE geometry (Vacuum Generators, Manchester, UK) equipped
1
6
solid state.
with a standard EI source. Samples were introduced by a push
rod in aluminium crucibles. Ions were accelerated by 8 kV. The
numbering scheme for NMR assignments (Scheme 7) is based
on IUPAC guidelines.
Conclusions
1
,8-Dichloro-10-[(trimethylsilyl)ethynyl]anthracene (13). 10-
Anthracenes with (trimethylsilyl)ethynyl substituents in 1,5- Bromo-1,8-dichloroanthracene (200 mg, 0.61 mmol) and (tri-
3), 1,8- (4) and 9,10-positions (10), as well as 1,8-dichloro-10- methylsilyl)acetylene (0.7 mL, 1.22 mmol) were dissolved in
(trimethylsilyl)ethynyl]- (13) and 1,8,10-tris[(trimethylsilyl)- diisopropylamine (40 mL). The solution was degassed by three
ethynyl]anthracene (14) were synthesised by cross coupling freeze–pump–thaw cycles and CuI (12 mg, 10 mol%) and
reactions. In addition, 1,5- (7) and 1,8-bis[(trimethylstannyl) PdCl (PPh (22 mg, 5 mol%) were then added. After heating
(
[
2
3 2
)
ethynyl]anthracene (8) have been quantitatively synthesised by to reflux for 3 d, the dark brownish mixture was filtered,
conversion of the corresponding ethynyl-substituted anthra- washed with n-pentane and added to water (50 mL). The
cene derivatives with (dimethylamino)trimethylstannane. The aqueous layer was extracted with n-pentane (3 × 25 mL) and
SnMe
Stille type cross coupling reactions.
CDCl solutions of the highly conjugated SiMe
3
-substituted dialkynes might be useful substrates in the combined organic phases were washed with brine and
dried over MgSO . The solvent was evaporated and the crude
4
3
3
-substituted yellow brownish solid was purified by column chromatography
systems were irradiated with UV light, whereby [4 + 4] cyclo- (∅ = 3 cm, l = 20 cm, eluent: n-pentane). Yield: 147 mg (71%).
addition reactions were observed. The anti-isomers were selec- For analytical data see ref. 14 (different synthetic protocols).
tively and quantitatively formed in the case of 3 and 14.
Irradiation of the 1,8- and 1,8,10-substituted species 4 and 13 according to ref. 9; for H and C NMR data see ref. 9. Si-
gave syn–anti mixtures [49 : 51 (4); 32 : 68 (13)] of the photo- { H} NMR (99 MHz, CDCl ): δ = −17.17 ppm. MS (EI, 70 eV):
dimerised products. Interestingly, 9,10-bis[(trimethylsilyl)- m/z [assignment] = 370 [M] , 355 [M − CH
ethynyl]anthracene (10) was found to dimerise to afford 21, (CH ]. HRMS: calculated for
9,10-Bis[(trimethylsilyl)ethynyl]anthracene (10). Synthesis
1
13
29
1
3
+
+
3
] , 297 [M − Si-
+
3
)
3
C
24
H
26Si
2
:
370.15676;
although symmetrically 9,10-substituted anthracenes with sub- measured: 370.15800.
stituents, except fluorine atoms or methyl groups, are known
1
b,6
for 28 years to be stable towards UV irradiation.
The influ- General procedure for Kumada coupling reactions
ence of the temperature upon monomerisation (cycloelimina-
tion) was qualitatively investigated by NMR experiments. Due
to the fact that ambient temperature is sufficient for the ther-
mally induced reaction of the photodimer 21, 9,10-dialkynyl-
anthracenes might be interesting objects of study e.g. for
detailed kinetic investigations.
Trimethylsilyl acetylene (Me
dropwise to a freshly prepared solution of ethylmagnesium
bromide in THF at 0 °C. The mixture was stirred at room temp-
3
SiCuCH, ca. 7 eq.) was added
Experimental
General
1
7
18
1
[
,5- (1) and 1,8-dichloroanthracene (2), as well as 1,8-bis-
Scheme 7 Numbering scheme exemplarily shown for a 1,8-substituted
8
(trimethylsilyl)ethynyl]anthracene (4), 1,8-diethynylanthra- anthracene derivative and its corresponding anti-photodimer.
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2
9
1
3 3 2 3
erature for 2 h and gas evolution was observed. The [(trimethyl- {[Si(CH ) ] } ppm. Si{ H} NMR (99 MHz, CDCl ): δ = −17.18
silyl)ethynyl]magnesium bromide suspension was transferred [Si(CH ) ], −17.35{[Si(CH ) ] } ppm. MS (EI, 70 eV): m/z
3
3
3 3 2
+
+
+
into a dropping funnel, fitted with glass wool for simultaneous [assignment] = 466 [M] , 451 [M − CH
filtering and slowly added to a solution of the dichloroanthra- HRMS: calculated for
3
] , 394 [M − Si(CH
3 3
) ] .
+
29 3
C H34Si : 466.19628; measured:
cene derivative, Ni(acac) and PPh in THF at room tempera- 466.19757.
2
3
ture, whereby the colour of the solution changed from yellow
to dark red. The mixture was heated to reflux and then
General procedure for the syntheses of the ethynyl-substituted
compounds 5, 6, 11 and 15
quenched with a saturated aqueous solution of NH Cl. The
4
aqueous layer was extracted with dichloromethane several The (trimethylsilyl)ethynyl substituted compounds were dis-
times. The combined organic phases were washed with brine solved in an adequate amount of boiling methanol. After
and dried over MgSO . The solvent was evaporated and the cooling to ambient temperature, K CO (ca. 1.2 eq. per alkyne
4
2
3
crude yellow brownish solid was purified by column chromato- unit) was added to the mixture stirred overnight. The solvent
graphy using different eluents (see below). was evaporated and the crude products were purified by
,5-Bis[(trimethylsilyl)ethynyl]anthracene (3). Synthesis column chromatography.
1
according to the general procedure for Kumada coupling reac-
1,5-Diethynylanthracene (5). Synthesis according to the
tions using 1,5-dichloroanthracene (1.60 g, 6.47 mmol), PPh
3
general procedure using 1,5-bis[(trimethylsilyl)ethynyl]anthra-
and Ni(acac) (one spatula tip of each compound), reflux for cene (1.70 g, 4.59 mmol) and K CO (1.14 g, 8.25 mmol) in
2
2
3
1
13 h. Column chromatography (∅ = 3 cm, l = 25 cm, eluent: MeOH (450 mL). Column chromatography (∅ = 3 cm, l =
n-pentane–dichloromethane 8 : 1) afforded 3 as bright yellow 11 cm, eluent: n-pentane) afforded 5 as bright yellow crystals.
1
1
crystals. Yield: 1.96 g (82%). H NMR (500 MHz, CDCl ): δ = Yield: 0.96 g (93%). H NMR (500 MHz, CDCl ): δ = 8.93 (s, 2H,
3
3
3
3
3
8
(
.88 (s, 2H, H9/H10), 8.06 (d, JH,H = 8.5 Hz, 2H, H4/H8), 7.74 H9/H10), 8.10 (d, JH,H = 8.6 Hz, 2H, H4/H8), 7.79 (d, JH,H =
3
3
3
d, JH,H = 6.8 Hz, 2H, H2/H6), 7.44 (dd, JH,H = 7.0, 8.5 Hz, 2H, 6.8 Hz, 2H, H2/H6), 7.46 (dd, JH,H = 7.0, 8.4 Hz, 2H, H3/H7),
1
3
1
13
1
H3/H7), 0.39 [s, 18H, Si(CH ) ] ppm. C{ H} NMR (125 MHz, 3.60 (s, 2H, CuC–H) ppm. C{ H} NMR (125 MHz, CDCl ): δ =
3
3
3
CDCl
3
): δ = 131.65, 131.45, 131.20 (C2/C6), 130.01 (C4/C8), 131.74 (C2/C6), 131.70, 131.51, 130.20 (C4/C8), 125.78 (C9/
1
25.94 (C9/C10), 125.12 (C3/C7), 120.87, 103.27 (CuC–Si), C10), 125.15 (C3/C7), 119.92, 82.72 (CuC–H), 81.94 (CuC–H)
2
9
1
+
1
00.34 (CuC–Si), 0.30 [Si(CH ) ] ppm. Si{ H} NMR (99 MHz, ppm. MS (EI, 70 eV): m/z [assignment] = 226 [M] , 200
3 3
+
+
CDCl ): δ = −17.36 ppm. MS (EI, 70 eV): m/z [assignment] = [M − CCH] . HRMS: calculated for C18H10 : 226.07770;
3
3
3
+
+
+
70 [M] , 355 [M − CH
70.15676; measured: 370.15590.
3
,8-Bis[(trimethylsilyl)ethynyl]anthracene (4). Synthesis Complete analytical data: H NMR (500 MHz, CDCl ): δ = 9.44
3
] . HRMS: calculated for C24
H
26Si
2
:
measured: 226.07662.
1,8-Diethynylanthracene (6). Synthesis according to ref. 8.
1
1
1
3
according to ref. 8. Complete analytical data: H NMR (s, 1H, H9), 8.45 (s, 1H, H10), 8.03 (d, JH,H = 8.6 Hz, 2H, H4/
3
3
(
(
500 MHz, CDCl ): δ = 9.32 (s, 1H, H9), 8.42 (s, 1H, H10), 7.98 H5), 7.80 (d, J
d, JH,H = 8.5 Hz, 2H, H4/H5), 7.79 (d, JH,H = 6.9 Hz, 2H, H2/ 8.5 Hz, 2H, H3/H6), 3.62 (s, 2H, CuC–H) ppm. C{ H} NMR
= 6.8 Hz, 2H, H2/H7), 7.45 (dd, J
= 7.0,
3
H,H
H,H
1
3
3
13
3
H7), 7.42 (dd,
3
JH,H = 7.0, 9.0 Hz, 2H, H3/H6), 0.39 [s, 18H, (125 MHz, CDCl ): δ = 131.72 (C2/C6), 131.47, 129.61 (C4/C5),
1
3
1
Si(CH ) ] ppm. C{ H} NMR (125 MHz, CDCl ): δ = 132.48 127.67 (C10), 125.14 (C3/C6), 123.90 (C9), 120.49, 82.78 (CuC–
3
3
3
(
(
0
C2/C6), 131.50, 131.37, 129.40 (C4/C5), 127.80 (C10), 125.09 H), 81.81 (CuC–H) ppm. MS (EI, 70 eV): m/z [assignment] =
+
+
C3/C6), 124.02 (C9), 121.43, 103.67 (CuC–Si), 99.94 (CuC–Si), 226 [M] . HRMS: calculated for C18H10 : 226.07770; measured:
2
9
1
.56 [Si(CH ) ] ppm. Si{ H} NMR (99 MHz, CDCl ): δ = 226.07599.
3
3
3
+
−
17.47 ppm. MS (EI, 70 eV): m/z [assignment] = 370 [M] , 355
9,10-Diethynylanthracene (11). Synthesis according to the
]. HRMS: calculated for general procedure using 9,10-bis[(trimethylsilyl)ethynyl]-
C H Si : 370.15676; measured: 370.15651. anthracene (0.45 g, 1.2 mmol) and K CO (0.42 g, 3.0 mmol) in
+
[M − CH
3
] , 267 [M − Si(CH
3
)
3
− 2 CH
3
+
2
4
26
2
2
3
1
,8,10-Tris[(trimethylsilyl)ethynyl]anthracene (14). Synthesis MeOH (250 mL). Column chromatography (∅ = 3 cm, l = 9 cm,
according to the general procedure for Kumada coupling eluent: n-pentane) afforded 11 as a yellow-brownish solid.
1
reactions
anthracene (210 mg, 0.62 mmol), PPh
spatula tip of each compound), reflux for 5 d. Column chrom- CuC–H) ppm. C{ H} NMR (150 MHz, CDCl
atography (∅ = 3 cm, l = 25 cm, eluent: n-pentane) afforded 14 127.19, 127.17, 117.96, 90.01 (CuC–H), 80.35 (CuC–H) ppm.
using
1,8-dichloro-10-[(trimethylsilyl)ethynyl]- Yield: 71 mg (25%). H NMR (500 MHz, CDCl ): δ = 8.62 (m,
3
3
2
and Ni(acac) (one 6H, H1/H4/H5/H8), 7.63 (m, 6H, H2/H3/H6/H7), 4.07 (s, 2H,
1
3
1
3
): δ = 132.62,
1
+
+
as bright yellow crystals. Yield: 217 mg (83%). H NMR MS (EI, 70 eV): m/z [assignment] = 226 [M] , 198 [M − CCH] .
3
+
(
2
500 MHz, CDCl
3
): δ = 9.35 (s, 1H, H9), 8.55 (d, JH,H = 8.7 Hz, HRMS: calculated for
C
18
H
10
:
226.07770; measured:
3
3
H, H4/H5), 7.81 (dd, J
= 6.9 Hz, J
= 0.7 Hz, 2H, H2/ 226.07663.
H,H
H,H
3
H7), 7.53 (dd,
Si(CH ) ], 0.38 {s, 18H, [Si(CH ) ] } ppm.
3 3 3 3 2
J
H,H = 7.0, 8.7 Hz, 2H, H3/H6), 0.41 [s, 9H,
1,8,10-Triethynylanthracene (15). Synthesis according to the
C{ H} NMR general procedure using 1,8,10-tris[(trimethylsilyl)ethynyl]-
125 MHz, CDCl ): δ = 132.82 (C2/C7), 132.70, 130.80, 128.01 anthracene (0.48 g, 1.03 mmol) and K CO (0.24 g, 1.75 mmol)
C4/C5), 126.34 (C3/C6), 125.40 (C9), 121.95, 118.69, 107.37 in MeOH (80 mL). Column chromatography (∅ = 3 cm, l =
CuC–Si(CH ], 103.47 {[CuC–Si(CH }, 101.28 [CuC– 8 cm, eluent: n-pentane) afforded 15 as a bright yellow solid.
1
3
1
(
(
3
2
3
[
3
)
3
3 3 2
) ]
1
Si(CH ) ], 100.52 {[CuC–Si(CH ) ] }, 0.52 [Si(CH ) ], 0.34 Yield: 0.22 g (86%). H NMR (500 MHz, CDCl ): δ = 9.52 (s, 1H,
3
3
3 3 2
3 3
3
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3
3
3
H9), 8.61 (d, JH,H = 8.8 Hz, 2H, H4/H5), 7.83 (d, JH,H = 6.8 Hz, 2H, H4/H5), 7.78 (d,
J
H,H = 6.5 Hz, 2H, H2/H7), 7.49 (dd,
3
3
2
1
H, H2/H7), 7.56 (dd, J
= 7.0, 8.7 Hz, 2H, H3/H6), 4.02 (s,
JH,H = 7.0, 8.7 Hz, 2H, H3/H6), 0.49 [s, 9H, Sn(CH ) ], 0.46
3 3
H,H
1
3
1
H, CuC–H), 3.63 [s, 2H, (CuC–H)
): δ = 132.79, 131.80 (C2/C7), 127.94 (C4/C5), reactant 15 under the experimental conditions, no further
26.18 (C3/C6), 125.80 (C9), 120.74, 89.04 (CuC–H), 83.10 characterisation of the product could be performed.
2 3 3 2
] ppm. C{ H} NMR {s, 18H, [Sn(CH ) ] } ppm. Due to rapid decomposition to the
(
1
125 MHz, CDCl
3
[
7
(CuC–H)
2
], 81.32 [(CuC–H)
2
], 79.86 (CuC–H) ppm. MS (EI,
+
+
General procedure for photodimerisation reactions
0 eV): m/z [assignment] = 250 [M] , 224 [M − CCH] . HRMS:
+
calculated for C H : 250.07770; measured: 250.07795.
Small amounts of the (trimethylsilyl)ethynyl substituted com-
2
0
10
pounds 3, 4, 10, 13 and 14 were dissolved in CDCl
ca. 0.55 mL) and irradiated with UV light (365 nm, UVP,
UVGL-25 Compact UV Lamp 254/365 nm, 4 W) in an NMR
3
General procedure for the syntheses of the trimethylstannyl-
substituted compounds 7, 8 and 16
(
The SnMe
3
functionalisation of the ethynyl substituted com- tube for several hours.
pounds was carried out analogous to a procedure described by
Photodimerisation of 1,5-bis[(trimethylsilyl)ethynyl]anthra-
1
9
Wrackmeyer and coworkers.
The corresponding ethynyl- cene. Synthesis according to the general procedure. Analytical
1
anthracene derivatives were dissolved in a small amount of dry data: H NMR (500 MHz, CDCl
THF. (Dimethylamino)trimethylstannane (ca. 2 eq. per alkyne H6), 7.44 (dd, JH,H = 7.2, 8.1 Hz, 4H, H3/H7), 6.38 (s, 4H, H9/
unit) was added dropwise to the solution and the mixture was H10), 0.31 [s, 36H, Si(CH ) ] ppm. C{ H} NMR (125 MHz,
3
): δ = 7.38 (m, 8H, H4/H8/H2/
3
1
3
1
3
3
3
heated to 60 °C for 4 h. After cooling to ambient temperature, CDCl ): δ = 139.93, 137.81, 131.17, 127.80 (C3/C7), 124.03,
all volatile compounds were removed in vacuo and the desired 118.87, 100.74 (CuC–Si), 99.81 (CuC–Si), 77.00 (C9/C10), 0.12
2
9
1
species were quantitatively obtained as yellow solids. Single [Si(CH ) ] ppm.
Si{ H} NMR (99 MHz, CDCl3): δ =
3
3
crystals of 7 and 8, suitable for X-ray diffraction experiments −17.03 ppm.
were afforded after recrystallisation from dry n-hexane. Photodimerisation of 1,8-bis[(trimethylsilyl)ethynyl]anthra-
,5-Bis[(trimethylstannyl)ethynyl]anthracene (7). Synthesis cene. Synthesis according to the general procedure gives a
according to the general procedure using 1,5-diethynylanthra- syn–anti mixture (49 : 51) of the photodimerised species.
1
1
3
cene (20 mg, 0.09 mmol), (dimethylamino)trimethylstannane Analytical data for the syn-isomer: H NMR (500 MHz, CDCl ,
1
3
3
(
0.08 mL, 0.49 mmol) and THF (6 mL). H NMR (500 MHz, 298 K): δ = 7.43 (d, J
= 7.9 Hz, 4H, H2/H7), 7.35 (d, J
=
H,H
H,H
3
3
CDCl ): δ = 8.93 (s, 2H, H9/H10), 8.04 (d, JH,H = 8.7 Hz, 2H, 7.2 Hz, 4H, H4/H5), 7.22 (m, 4H, H3/H6), 6.79 (s, 2H, H9), 5.96
3
13
1
H4/H8), 7.72 (m, 2H, H2/H6), 7.42 (dd, JH,H = 6.9, 8.5 Hz, 2H, (s, 2H, H10), 0.38 [s, 36H, Si(CH
3
)
3
] ppm. C{ H} NMR
1
3
1
H3/H7), 0.48 [s, 18H, Sn(CH ) ] ppm. C{ H} NMR (125 MHz, (125 MHz, CDCl ): δ = 138.30, 132.78 (C2/C7), 127.78 (C3/C6),
3
3
3
CDCl
3
): δ = 131.69, 131.53, 130.84 (C2/C6), 129.54 (C4/C8), 123.66 (C4/C5), 119.49, 101.28 (CuC–Si), 98.14 (CuC–Si),
] ppm. One signal
1
9
26.04 (C9/C10), 125.11 (C3/C7), 121.36, 107.04 (CuC–Sn), 78.95 (C10), 75.27 (C9), 0.63 [Si(CH
9.77 (CuC–Sn), −7.30 [Sn(CH ) ] ppm.
3
)
3
1
19
1
29
1
Sn{ H} NMR missing due to overlap or line broadening. Si{ H} NMR
3
3
(
186 MHz, CDCl
3
): δ = −63.15 ppm. MS (EI, 70 eV): m/z [assign- (99 MHz, CDCl
3
): δ = −17.08 ppm. Analytical data for the anti-
+
+
+
1
3
ment] = 552 [M] , 537 [M − CH
HRMS: calculated for C H Sn : 554.00730; measured: 7.3 Hz, 4H, H4/H5), 6.97 (dd, J
5
3
] , 226 [M − 2(SnCH
2
3
)
3
] . isomer: H NMR (500 MHz, CDCl
3
, 298 K): δ = 7.03 (d, JH,H
=
+
3
4
= 8.0 Hz, J
= 0.8 Hz, 4H,
H,H
2
4
26
H,H
3
54.00711.
H2/H7), 6.80 (m, 4H, H3/H6), 5.54 (d, JH,H = 11.0 Hz, 2H, H9),
3
1
,8-Bis[(trimethylstannyl)ethynyl]anthracene (8). Synthesis 4.54 (d, JH,H = 10.9 Hz, 2H, H10), 0.31 [s, 36H, Si(CH
3
)
3
] ppm.
1
3
1
according to the general procedure using 1,8-diethynylanthra-
cene (26 mg, 0.11 mmol), (dimethylamino)trimethylstannane (C2/C7), 126.40 (C4/C5), 125.74 (C3/C6), 121.83, 104.52 (CuC–
C{ H} NMR (125 MHz, CDCl ): δ = 144.14, 143.37, 130.25
3
1
3 3
(0.11 mL, 0.70 mmol) and THF (6 mL). H NMR (500 MHz, Si), 99.67 (CuC–Si), 52.23 (C9), 48.74 (C10), 0.35 [Si(CH ) ]
3
CDCl ): δ = 9.43 (s, 1H, H9), 8.40 (s, 1H, H10), 7.95 (d, J
=
ppm. One signal missing due to overlap or line broadening.
3
H,H
3
4
29
1
8
.4 Hz, 2H, H4/H5), 7.76 (dd, JH,H = 6.9 Hz, JH,H = 1.0 Hz, 2H,
Si{ H} NMR (99 MHz, CDCl
Photodimerisation of 9,10-bis[(trimethylsilyl)ethynyl]anthra-
Sn(CH ) ] ppm. C{ H} NMR (125 MHz, CDCl ): δ = 131.77 cene. Synthesis according to the general procedure. Analytical
3
): δ = −17.83 ppm.
3
H2/H7), 7.40 (dd, JH,H = 6.9, 8.5 Hz, 2H, H3/H6), 0.46 [s, 18H,
1
3
1
3
3
3
1
(
(
C2/C7), 131.57, 131.51, 128.92 (C4/C5), 127.58 (C10), 125.10 data: H NMR (600 MHz, CDCl
C3/C6), 124.44 (C9), 107.43 (CuC–Sn), 99.27 (CuC–Sn), −6.99 H4/H5/H8), 7.37 (m, 8H, H2/H3/H6/H7), 0.38 [s, 36H, Si(CH
3
, 298 K): δ = 7.69 (m, 8H, H1/
3 3
) ]
1
19
1
13
[Sn(CH ) ] ppm.
Sn{ H} NMR (186 MHz, CDCl ): δ = ppm. Due to the fast cycloelimination reaction, C NMR shifts
3
3
3
+
−
63.98 ppm. MS (EI, 70 eV): m/z [assignment] = 552 [M] , 537 of the photodimerised compound 21 were determined by
+
+
+
1
13
[M − CH
3
] , 390 [M − Sn(CH
3
)
3
] , 345 [M − Sn(CH
3
)
3
− 3CH
24 26
3
] ,
3
H, C HMBC and HSQC experiments at 278 K in CDCl . δ =
+
+
2
5
24 [M − 2(SnCH ) ] . HRMS: calculated for C H Sn : 136.86, 128.06, 122.82, 101.53, 79.08 (C9/C10) ppm. Signals
54.00730; measured: 554.00760.
3
3
2
missing due to overlap or line broadening.
1
,8,10-Tris[(trimethylstannyl)ethynyl]anthracene (16). Syn-
Photodimerisation of 1,8-dichloro-10-[(trimethylsilyl)-
thesis according to the general procedure using 1,8,10-triethy- ethynyl]anthracene. Synthesis according to the general pro-
nylanthracene (20 mg, 0.08 mmol), (dimethylamino)- cedure gives a syn–anti mixture (32 : 68) of the photodimerised
1
1
trimethyltin (0.1 mL, 0.6 mmol) and THF (19 mL). H NMR species. Analytical data for the syn-isomer: H NMR (500 MHz,
3
3
(
300 MHz, CDCl ): δ = 9.44 (s, 1H, H9), 8.58 (d, J
= 8.7 Hz, CDCl , 298 K): δ = 7.59 (d, J
= 7.3 Hz, 4H, H4/H5), 7.35 (d,
3
H,H
3
H,H
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Table 5 Crystallographic data for 3, 4, 5, 7, 8, anti-18 and anti-19
3
4
5
7
8
anti-18
anti-19
Emp. formula
C
24
H
26Si
2
C
24
H
26Si
2
C
18
H
10
C
24
H
26Sn
2
C
102
H
118Sn
8
C
48
H
52Si
4
38 4 2
C H32Cl Si
M
r
370.63
0.71073
100.0
396
Monoclinic
P2 /n
11.26970(2)
5.81937(7)
16.56046(2)
90
99.6391(1)
90
370.63
0.71073
100(2)
1584
Monoclinic
P2 /c
23.6928(2)
8.6313(1)
24.1592(2)
90
117.0424(5)
90
226.26
551.83
0.71073
100.0(1)
540
Monoclinic
P2 /n
11.4064(2)
6.07068(1)
16.7481(4)
90
94.669(2)
90
2293.48
0.71073
100.0(1)
2260
Triclinic
Pˉ1
15.3809(3)
15.4149(3)
21.7315(4)
80.698(2)
74.637(2)
86.960(2)
4902.7(2)
2
741.26
1.54178
100(2)
396
Triclinic
Pˉ1
686.62
0.71073
100(2)
356
Triclinic
Pˉ1
λ [Å]
T [K]
F(000)
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
0.71073
100.0(2)
472
Monoclinic
P2
10.93715(2)
11.26203(2)
9.96535(2)
90
105.9353(2)
90
1180.31(3)
4
1.273
1
1
1
/c
1
8.564(3)
7.5761(6)
10.244(4)
12.957(5)
79.45(3)
82.01(2)
76.34(1)
1080.5(7)
1
10.0339(8)
12.7454(8)
110.973(5)
99.303(5)
101.673(4)
856.5(1)
1
γ [°]
V [Å ]
3
1070.74(2)
2
1.150
4400.40(7)
8
1.119
1122.46(4)
2
1.633
Z
−3
ρcalcd. [g cm
]
1.554
2.045
1.139
1.502
1.331
0.442
−
1
μ [mm
]
0.170
0.166
0.072
2.229
θmax [°]
30.30
27.49
30.03
30.00
30.00
72.42
25.00
Index ranges h
Index ranges k
Index ranges l
Refl. collected
Indep. refl.
−15 ≤ h ≤ 15
−8 ≤ k ≤ 8
−23 ≤ l ≤ 23
59 469
3116
0.0343
2870
−30 ≤ h ≤ 30
−11 ≤ k ≤ 11
−31 ≤ l ≤ 31
93 358
10 078
0.034
−15 ≤ h ≤ 15
−15 ≤ k ≤ 15
−14 ≤ l ≤ 14
67 142
3436
0.0433
2987
−16 ≤ h ≤ 16
−8 ≤ k ≤ 8
−23 ≤ l ≤ 23
47 899
3274
0.0393
2966
−21 ≤ h ≤ 21
−21 ≤ k ≤ 21
−30 ≤ l ≤ 30
85 614
28 567
0.0256
−10 ≤ h ≤ 10
−12 ≤ k ≤ 12
−15 ≤ l ≤ 15
20 419
4051
0.0300
3821
−9 ≤ h ≤ 9
−11 ≤ k ≤ 11
−15 ≤ l ≤ 14
11 464
2930
R
int
0.044
2605
Observed refl., I > 2σ(I)
8795
24 838
Parameters
121
481
163
121
1017
0.0238
0.0465
0.0311
0.0490
1.032
a0.53/−0.54
241
202
R
1
, I > 2σ(I)
wR , I > 2σ(I)
(all data)
wR (all data)
GoF
0.0327
0.0937
0.0352
0.0963
1.063
0.0335
0.0936
0.0395
0.0980
1.039
0.0428
0.1229
0.0489
0.1277
1.068
0.0225
0.0532
0.0260
0.0558
1.068
0.0335
0.0901
0.0350
0.0912
1.062
0.0347
0.0876
0.0398
0.0915
1.039
2
R
1
2
max/ρmin [e Å−
3
]
0.43/−0.19
—
0.33/−0.30
—
0.43/−0.18
—
1.07/−0.60
—
0.41/−0.20
—
0.28/−0.33
—
ρ
Remarks
CCDC number
994028
994029
994030
994031
994032
994033
994034
a
Four molecules of 8 and one molecule of n-hexane are found in the asymmetric unit.
3
JH,H = 7.5 Hz, 4H, H2/H7), 7.29 (m, 4H, H3/H6), 6.89 (s, 2H, 99.74 {[CuC–Si(CH ) ] }, 75.72 (C10), 0.35 {[Si(CH ) ] }, 0.09
3 3 4
3 3 4
1
3
1
3 3 3 3 3 2
H9), 0.37 [s, 18H, Si(CH ) ]. C{ H} NMR (125 MHz, CDCl ): {[Si(CH ) ] } ppm. Signals were missing due to overlap or line
δ = 139.97, 134.66, 129.48, 129.22 (C3/C6), 129.05 (C2/C7), broadening. Si{ H} NMR (99 MHz, CDCl ): δ = −15.45
2
9
1
3
1
21.56 (C4/C5), 102.52 (CuC–Si), 92.58 (CuC–Si), 73.61 (C9), [Si(CH ) ], −17.08 {[Si(CH ) ] } ppm.
3
3
3 3 2
−
3 3
0.13 [Si(CH ) ] ppm. C10 signal was missing due to overlap
2
9
1
Crystal structure determination
3
or line broadening. Si{ H} NMR (99 MHz, CDCl ): δ =
1
−15.21 ppm. Analytical data for the anti-isomer: H NMR Suitable crystals of the compounds 3, 4, 5, 7, 8, anti-18, and
3
4
(
1
500 MHz, CDCl
3
, 298 K): δ = 7.70 (dd, JH,H = 7.4 Hz, JH,H
=
anti-19 were obtained by recrystallisation of dry n-hexane (7
.0 Hz, 4H, H4/H5), 6.95 (dd, JH,H = 8.0 Hz, JH,H = 1.2 Hz, 4H, and 8), by slow evaporation of saturated solutions of n-pentane
3
4
H2/H7), 6.91 (m, 4H, H3/H6), 5.99 (s, 2H, H9), 0.38 [s, 18H, (5 and anti-19), n-pentane/dichloromethane (3 and 4) and
1
3
1
Si(CH
33.33, 127.68 (C3/C6), 127.52 (C2/C7), 124.04 (C4/C5), 106.61 N oil, mounted on a glass fibre and transferred onto the gonio-
CuC–Si), 94.96 (CuC–Si), 56.08 (C9), 53.75 (C10), 0.26 meter of the diffractometer into a nitrogen gas cold stream
3 3 3
) ]. C{ H} NMR (125 MHz, CDCl ): δ = 143.74, 136.89, chloroform (anti-18). They were selected, coated with paratone-
1
(
2
9
1
[Si(CH
3
)
3
]
ppm.
Si{ H} NMR (99 MHz, CDCl
3
):
δ
=
solidifying the oil. Data collection was performed on a Super-
−17.18 ppm.
Nova, Dual, Cu at zero, Atlas diffractometer (3, 7 and 8), a
Photodimerisation of 1,8,10-tris[(trimethylsilyl)ethynyl]- SuperNova, Single Source at Offset, Eos diffractometer (5), a
anthracene. Synthesis according to the general procedure. Nonius KappaCCD diffractometer (4 and anti-19) and a Bruker
1
Analytical data: H NMR (500 MHz, CDCl , 298 K): δ = 7.63 (d, AXS X8 ProspectorUltra with APEX II diffractometer (anti-18).
3
3
3
JH,H = 7.2 Hz, 4H, H2/H7), 7.45 (dd, JH,H = 1.1, 7.9 Hz, 4H,
H4/H5), 7.27 (m, 4H, H3/H6), 6.81 (s, 2H, H10), 0.36 {s, 18H, by full-matrix least-squares cycles (program SHELX-97).
The structures were solved by direct methods and refined
2
0
1
3
1
[
(
(
Si(CH ) ] }, 0.30 {s, 36H, [Si(CH ) ] } ppm. C{ H} NMR Crystal and refinement details, as well as CCDC numbers are
3 3 2 3 3 4
125 MHz, CDCl ): δ = 138.37, 137.50, 133.16 (C4/C5), 127.72 provided in Table 5. CCDC 994028–994034 contain the sup-
3
3 3 2
C3/C6), 122.83 (C2/C7), 119.22, 101.24 {[CuC–Si(CH ) ] }, plementary crystallographic data for this paper.
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Paper
8
F. Vögtle, H. Koch and K. Rissanen, Chem. Ber., 1992, 125,
Acknowledgements
2129.
The authors thank Klaus-Peter Mester and Gerd Lipinski for
recording NMR spectra, as well as Jens Sproß and Heinz-
9 e.g. W. Fudickar and T. Linker, J. Am. Chem. Soc., 2012, 134,
15071.
Werner Patruck for measuring mass spectra. We gratefully 10 e.g. (a) J. K. Stille, Angew. Chem., 1986, 98, 504, (Angew.
acknowledge financial support from Deutsche Forschungsge-
meinschaft (DFG).
Chem., Int. Ed., 1986, 25, 508); (b) P. Espinet and
A. M. Echavarren, Angew. Chem., 2004, 116, 4808, (Angew.
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12 A. F. Holleman and E. Wiberg, Lehrbuch der Anorganischen
Chemie, Walter de Gruyter, Berlin, 1985, vol. 91–100, p. 133.
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1
7
1
This journal is © The Royal Society of Chemistry 2014
Org. Biomol. Chem., 2014, 12, 7355–7365 | 7365