Synthesis and Properties of Functional Twisted Tolanes

Article abstract of DOI:10.1002/chem.201701519

The synthesis and optical properties of several novel fluorescent and/or phosphorescent bridged tolanes (tolanophanes) are reported and their optical and structural properties are investigated. Specifically, diiodinated and bisalkynylated tolanophanes were obtained, and characterized by spectroscopy and computational methods. They represent attractive building blocks for novel polymers and emissive solid-state materials.

Full text of DOI:10.1002/chem.201701519

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Accepted Article
Title: Synthesis and Properties of Functional Twisted Tolanes
Authors: Uwe Heiko Bunz, Yuri Kozhemyakin, andreas kretzschmar,
Frank Rominger, Maximilian Krämer, and andreas dreuw
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Synthesis and Properties of Functional Twisted Tolanes
Yury Kozhemyakin,[a] Andreas Kretzschmar,[a] Maximilian Krämer,[b] Frank Rominger,[a] Andreas
Dreuw[b,c] and Uwe H. F. Bunz*[a,c]
Dedication ((optional))
Abstract: The synthesis and optical properties of several novel
fluorescent and/or phosphorescent bridged tolanes (tolanophanes)
are reported. Their optical and structural properties are investigated.
Specifically, diiodinated and bisalkynylated tolanophanes were
obtained and spectroscopically as well as computationally charac-
terized; they represent attractive building blocks for novel polymers
and emissive solid state materials.
solution. A striking property of TTs is their long phosphorescence,
which might lead to unusual applications in organic electronic
devices. Herein we describe the synthesis and synthetic protocols
to prepare new and functionalized twisted tolanes, and
characterize their properties spectroscopically and theoretically.
RESULTS AND DISCUSSION
INTRODUCTION
Synthesis: As there are no functionalized twisted tolanes (TT)
described and only very few TTs exist in general, we started with
the synthesis of TT 4, which contains amide instead of ester
bridges and which should be robust against hydrolysis etc.
Iodobenzylic alcohol 1 (Scheme 1) was mesylated, treated with
methyl amine and then Boc-protected to give 2. Sonogashira
coupling of 2 with acetylene provided the bis-ammonium salt 3
after deprotection with acid. In the last step, the ring was closed,
employing malonic acid chloride (42% yield) to give TT 4.
We herein describe the synthesis and optical properties of novel,
functional, twisted tolanes (TT).[1,2] Tolane, diphenylacetylene,[3]
is one of the fundamental motifs and the building block for the
preparation of conjugated polymers of the poly(para-phenylene-
ethynylene) (PPE) type.[ 4 ] PPEs are of great importance in
sensory applications but also useful in organic electronics.[5,6] Due
to the rigidity of the PPE-backbone they possess only one degree
of freedom, the twisting of adjacent phenyl rings with respect to
each other.[7] This twisting motion is almost energy neutral and
the fully twisted conformation in tolane, but also in PPEs, is less
than 0.5 kcal/M above that of the planar conformation.[8] In the
solid state, tolane but also PPEs are generally planar, as that
allows the optimal packing of the molecules; in solution there is
reasonably free rotation and the different rotamers are Boltz-
]
mann-distributed.[3, 9 As kT is 0.6 kcal/M, all rotamers are
indiscriminately populated. This rotational freedom has important
consequences. For monomeric tolane, absorption in solution is
sharp and structured, suggesting that absorption is only efficient
when the molecule is in the planar state,[3] as for the twisted states
the extinction coefficient is lower. For tolane, most of the
molecules are in the planar ground state. For the PPEs the
situation is different, a broad absorption envelope results as the
long, conjugated chain supports multiple conformers of tolane
subunits; the planar ground state is only achieved in the solid.
An attractive proposition engineers the torsion angle of tolanes
and PPEs into materials with frozen pre-selected and dialed-in
twist angles. Such materials would be of interest, as twisted
tolanes show unique optical properties and these should translate
into the properties of PPEs when investigated in thin films or
Scheme 1. Synthesis of TT 4.
[a]
Y. Kozhemyakin, A. Kretzschmar, Dr. F. Rominger, Prof. U. H. F.
Bunz
Organisch-Chemisches Institut, Ruprecht-Karls-Universitat Heidelberg
̈
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
E-Mail: uwe.bunz@oci.uni-heidelberg.de
M. Krämer, Prof. Dr. A. Dreuw
Interdisziplinäres Zentrum für Wissenschaftliches Rechnen
Ruprecht-Karls-Universität Heidelberg
Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
Prof. Dr. U. H. F. Bunz, Prof. Dr. A. Dreuw
Centre for Advanced Materials
[b]
[c]
Scheme 2. Synthesis of the TT 7 using the salts 6a or 6b.
In a similar way, the mixed ester-amide TT 7 was prepared
(Scheme 2). Starting from 1, Sonogashira coupling and
subsequent deprotection gave 5, which was again coupled with 2
to furnish the salts 6a or 6b, depending upon the acid employed
for deprotection of the Boc group. The tolane 6 is then closed to
Ruprecht-Karls-Universitat Heidelberg
Im Neuenheimer Feld 225, 69120 Heidelberg, Germany
̈
Supporting information for this article, including experimental details,
full scaled absorption and emission spectra, cyclic voltammograms,
additional information on theoretical calculations and NMR-spectra (1H
and 13C), is available on the WWW
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the ester-amide TT 7 in 23 or 56 % yield, depending upon the
starting salt. The difference in the yields can be explained by a
deactivation of the hydroxyl group. A mixed anhydride could form
from malonyl chloride and the TFA-anion which would convert the
OH-group of 6a into a triflate, unreactive to the malonyl chloride.
To investigate the twist angle of the two TTs we have obtained
single crystalline specimen suitable for diffraction. Figure 1 shows
the ORTEPs of the two structures. For the bisamide TT 4, the twist
angles are only 43° and 58o in the solid state, while for the ester-
amide TT 7, the twist angle is much closer to perpendicular.
To obtain alkynylated TTs such as 12 (Scheme 4), the diiodide 11
was coupled to TIPS-acetylene in a Sonogashira reaction to
afford TT 12 in 81% yield. Alternatively, 10 was alkynylated into
13, which then was treated with malonic acid in the presence of
toluene sulfonic acid to give 12 (40% yield). If the ring closure is
performed by malonic acid chloride, only an 8% yield of 12 is
isolated but in addition, a 30% yield of the dimer 14 is obtained.
Figure 1. ORTEP of 4 (left) and 7 (right). The twist angles for 4 are 43 and 58°
(left) while the twist angle for 7 (right) is 86° in the solid state.
The fairly involved synthesis of the amide and ester-amide TTs let
us revert to the diester TTs for the access to functionalized
derivatives. Scheme 3 shows the synthesis of the diiodo TT 11.
Starting from 8, reduction and iodination gave 9, which was
coupled with acetylene and then subjected to
a double
Sandmeyer-reaction after diazotation to provide the tolane 10 in
65% yield. The acid-catalyzed ring closure with malonic acid
delivered the TT 11 in 48% yield.
Figure 3. Single crystal X-ray diffraction of 12 and 14. In 12 the twist is 61°,
while in 14 the distance between the two benzene rings is 3.6 Å.
Scheme 3. Synthesis of the diiodo-TT 11.
Scheme 5. Shotgun-synthesis of 16-18 using the diol 15.
To investigate the solid-state structure of 12 and 14 we could grow
single crystalline specimen. The bond lengths and bond angles
are inconspicuous, but we see that in 12 the two phenyl rings are
twisted by an angle of 61°, while for 14 the two benzene rings
overlap and are roughly coplanar with a distance of around 3.6 Å.
To investigate, if the formation of dimers and higher oligomers is
common in this system (Scheme 5) we treated 15 with either
malonic acid chloride or with malonic acid under toluene sulfonic
acid catalysis to obtain the monomer-trimer in yields of 36% (16),
1% (17) and 6% (18) after careful chromatography. While the
Fischer esterification gives overwhelmingly 16, the malonic-acid
cyclization also provides cyclo-oligomers.
Scheme 4. Synthesis of 12 and cyclodimer 13 starting from 10.
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To obtain the dimer 21 we could couple 19 sequentially with
malonyl dichloride to obtain linear 20 in reasonable yield.
However, the ring closure of 20 under dilution conditions was
disappointing and furnished the dimer 21 in only 16 % isolated
yield, besides insoluble polymeric material.
Figure 5 shows the room temperature and the low temperature
emission spectra of compounds 4, 7, 11, 12, 14 and 21 in solution
and in a low temperature glass at 77 K. The diiodide 11 is non-
fluorescent in solution at room temperature. The compounds 4
and 7 emit both at 313 nm, the compound 12 and 14 at 356 and
355 nm in EPA solution at room temperature. The room
temperature emission spectra of 12 and 14 are identical, since
both possess identical emitting chromophores. The red shift in 12
and 14 (in comparison to that of 16) is caused by the extension of
the -system through the alkyne groups.
Scheme 6. Synthesis of 21 using a stepwise approach.
Optical and Electronic Properties: The optical and emissive
properties of the tolanes are broadly defined by their twist angle
and their substituent patterns. At room temperature the tolanes
are all more or less fluorescent and twisted representatives show
invariably significantly a blue-shifted absorption (vide infra).
Figure 5. Emission spectra of 4, 7, 11, 12, 14 and 21 in EPA (diethyl
ether/isopentane/ethanol 5:5:2, v/v) at room temperature (top) compared to low
temperature (77 K, bottom).
At cryogenic temperatures, un-substituted and iodinated twisted
tolanes give moderate to strong phosphorescence and can show
additional fluorescence. Upon addition of conjugated substi-
tuents, the phosphorescence is suppressed (vide infra,
computational details) and fluorescence is restored, irrespective
of the twist angle.
With this overview in mind, Figure 4 shows the room temperature
UV-Vis spectra of the TTs 4, 7 and 11. The UV-properties of 7
and 11 are similar, while the features of 4 are red-shifted with a
significant vibrational structure pointing to a larger twist angle in 7
and 11 than in 4. Comparison with the X-ray crystal structure
suggests that twisting of TTs 7 and 11 in the solid state is not due
to crystal packing but is also observed in their dilute solutions.
This was further supported by DFT calculations in gas phase,
where 4 adopts a torsion angle of 46°, 7 of 78° and 11 of 72°.
Figure 6. Top: Absorption (dashed line) and emission (solid line) spectra of 12
and 14 in n-hexane at room temperature. Bottom: Comparison of the absorption
spectra of 12 and 14 in n-hexane (dashed line) and emission in EPA at -196°C
(solid line).
Upon going into a cryogenic glass, the emission spectra of 4 and
7 do not change much, suggesting their photochemistry is
unaltered: in the excited state they still planarize, even at low
temperatures. For 11 the situation is different. It is non-emissive
at room temperature but shows both phosphorescence and weak
fluorescence at low temperature. The strong phosphorescence is
Figure 4. Absorption spectra of 4, 7, 11 and 16 compared to 15 (n-hexane, room
temperature). Vertical lines show the calculated vertical excitation energies of
the first excited state of the corresponding tolanophane shifted by +0.37 eV,
corresponding to the difference between the experimental and calculated max
values of tolanophane 4.
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accompanied by a less intense fluorescence that is blue-shifted
and suggests that iodinated 11 remains twisted in this cryogenic
glass.
still twisted, the attachment of alkynyl substituents leads to a
suppression of intersystem crossing and instead to a well-
resolved but blue-shifted fluorescence peak (vide infra). The
emission of the dimer 14 is temperature independent, as 14
seems to fluoresce always out of the planarized state. That is also
observed by the comparison of the emission spectra of the
monomeric ester amide 7 and dimeric 21 (Figure 9).
Figure 7. Emission spectra of 16, 17 and 18 at room temperature (dotted line)
compared to low (solid line) temperature (-196°C) in EPA (diethyl
ether/isopentane/ethanol 5:5:2, v/v).
Figure 10. Reduced molecular model systems I-III (left to right) for the
computational investigation of the optical properties of the different TTs. Also
for clarification (bottom) the trans bent mode of tolane in its excited state.
The series 16-18 is also of interest. The emission spectra of 16
show the literature known phosphorescence at low
temperature,[1b] while the spectra of dimer 17 and trimer 18 show
much less or none of the contribution from phosphorescence.
Instead of the phosphorescence we observe at room temperature
in the cyclo-oligomers a red-shifted feature at around 380 nm,
perhaps due to some intramolecular excimer formation, which
however disappears at cryogenic temperatures.
Quantum chemical calculations: Tolanes can be divided into
groups, depending on their torsion angle. Planar tolanes show
fluorescence at room temperature and at 77 K, but exhibit no
phosphorescence. Twisted tolanes (TTs), on the other hand,
show fluorescence at room temperature, but at 77 K they also
phosphoresce. For phosphorescence to occur, it is necessary to
populate the global S1 minimum, which has a trans-stilbene like
structure and is a „dark state“ - the precursor for the triplet state.
Since twisted tolanes are generally excited at higher energies,
they overcome the energy barrier and populate the trans-bent
minimum. The excitation energy of planar tolanes is generally not
sufficient to traverse this barrier, so they populate the linear-
planar S1 minimum from which fluorescence occurs. To explain
the different behavior of the various TTs, three model systems
were investigated at the theoretical level of DFT/TDDFT cam-
B3LYP/cc-pVDZ (Figure 10, for further information see the SI).
Model system I represents 4 and 7 and possesses a global trans-
bent S1 minimum, which is about 0.4 eV (10 kcal/mol) lower in
energy than the linear-planar minimum. Since both tethered
molecules 4 and 7 exhibit a twisted ground-state structure, they
possess enough excess energy after photoexcitation for some
part of the excited molecules to overcome the barrier to the trans-
bent minimum where ISC occurs. This explains why these tolane
derivatives show fluorescence at room temperature and also
phosphorescence at 77 K.
Figure 8. Absorption (dashed line) and emission (solid line) spectra of 17 and
18 compared to 16 (dichloromethane).
Figure 9. Absorption (dotted line, n-hexane), emission at 298K (solid line,
n-hexane) and emission at 77K (dashed line, EPA), spectra of 7 compared to
21.
Also, the presence of the iodo substituents in 11 increases the
intersystem crossing rate due to the heavy-atom effect,[10] leading
to the intense observed phosphorescence in 11. 4 and 7 show
some phosphorescence in the cryogenic matrix but it is
considerably weaker than that of the diiodo-11. A second
interesting observation is the change of the emission spectrum of
12 under cryogenic conditions (Figures 5-8). The absorption data
in hexane suggest that 12 is fully twisted at room temperature,
while the dimer 14 would be planar. The twisting of 12 is also
corroborated by its single crystal structure and that of 14 (Figure
3) and computations. However, at cryogenic temperatures, the
emission spectrum of 12 blue-shifts significantly, and 12 does not
show any sign of phosphorescence. We assume that, while 12 is
In case of model system II, which represents 11, the same
excited-state properties were observed. The trans-bent minimum
is the global S1 minimum and it is about 0.2 eV (5 kcal/mol) lower
in energy than the linear-planar structure. Due to the well-known
heavy-atom effect of the two iodine atoms, ISC is strongly
enhanced and fluorescence is fully quenched.
The behavior of model system III, i.e. molecule 12, is different. In
comparison to the other two model systems, the global S1 is not
the trans-bent like minimum, but instead it is about 0.02 eV (0.5
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Table 1. Photophysical Properties and DFT Calculations for the Twisted Tolanes
Fluorescence Fluore-
[c]
Emmax
Absmax
Emmax
77K (λex
[nm]
Stokes-
Shift
[nm]
Molar extinction
coefficient
[104 L⋅mol−1⋅cm-1]
Phosphorescence
[j]
[j]
Quantum
yield
scence
lifetime[a]
[ps]
λabs
λem
Cpd
298K (λex
)
)
lifetime[c]
[s]
[nm]
[eV]
[eV]
[nm]
[%]
286[a]
302[a,d]
288[b]
309[f]
448[g]
(285)
314[a] (287)
317[b] (287)
12[a]
10[b]
26[a]
12[b]
2.36[b]
410
1.3
1.0
4.69
3.94
4
307[b,d]
271[a]
283[a,d]
301[a,d]
274[b]
285[b,d]
303[b,d]
310[f]
461[g]
(285)
312[a] (285)
315[b] (285)
9[a]
12[b]
8[a]
10[b]
1.33[b]
300
4.97
4.74
4.51
3.99
3.63
3.59
7
276[a]
327[a,e]
272[b]
282[b,d]
302[b,d]
300[f]
457[g]
(285)
--[a,i]
1.7
11
12
--[a,b,i]
--[a,b,i]
--[a,b,i]
0[a,b,i]
297[a]
309[a,d]
351[a,e]
300[b]
313[b,d]
355[b,e]
338[f]
not observed[g]
(297)
356[a] (297)
360[b] (300)
89[a]
88[b]
720
--[i]
5[a,b]
6.76[b]
326[a]
349[a]
328[b]
351[b]
357[f]
not observed[g]
(325)
355[a] (326)
359[b] (328)
6[a]
8[b]
90[a]
87[b]
750
--[i]
--
--
--
--
14
16
11.2[b]
265[a]
284[a,d]
339[a,e]
268[b,d]
290[b,d]
302[f]
438[g]
(264)
312[a] (280)
315[b] (280)
28
25
31[a,h]
4[b,h]
108[h]
1.4[h]
1.32[b,h]
273[a]
304[a,d]
287[b]
312[f]
466[g,e]
(285)
310[a] (273)
314[b] (287)
6[a]
9[b]
--
--
--
--
17
--
--
305[b]
339[b,e]
--[a,i]
310[f]
463[g,e]
(285)
<100
290
0.8
0.9
--
--
--
--
18
21
288[b]
306[b]
314[b] (285)
8[b]
8.03[b]
1.34[b]
8[b]
285[a]
303[a]
287[b]
305[b]
311[f]
466[g,e]
(285)
310[a] (285)
314[b] (287)
7[a]
9[b]
7[b]
[a] In n-hexane. [b] In dichloromethane. [c] In EPA (diethyl ether/isopentane/ethanol 5:5:2, v/v). [d] Shoulder. [e] Low intensity. [f] Fluorescence maximum. [g]
Phosphorescence maximum. [h] See references[1a,1b]. [i] Low intensity (also due to insufficient solubility). [j] Calculations were performed at the time-dependent
density functional theory (TDDFT) level with method cam-B3LYP and the basis set cc-pVDZ.
planarize well at cryogenic conditions, yet does not show
phosphorescence. For an in-depth study of the non-alkynylated
not populate the trans-bent minimum and ISC is unlikely to occur,
species 16 see reference.[3]
kcal/mol) higher in energy. As a consequence, excited TTs 12 do
and thus 12 shows only fluorescence. A reason for the blue shift
of the fluorescence of 12 at 77 K cannot be provided based on
our gas-phase calculations, however, it seems 12 does not
CONCLUSIONS AND OUTLOOK
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In conclusion, we have prepared a series of novel, functionalized
tolanophanes. In some cases, the ring closure gives cyclodimers
and cyclotrimers in addition to the monomeric species, a
consequence of the reaction conditions. For the monomeric
tolanophanes, depending upon the chemical nature of the bridge,
we see planar or twisted conformations in the ground state.
49.5, 91.4, 117.3 (q; 1JCF 301 Hz; CF3), 122.5, 129.2, 129.5, 129.7, 132.8,
133.3, 158.4 (q; 2JCF 31 Hz; CO) ppm; IR: ν
̃=3080 (w), 2688 (w), 2430 (w),
1657 (s), 1614 (s), 1495 (m), 1456 (m), 1432 (m), 1198 (vs), 1179 (vs),
1125 (vs), 1132 (m), 833 (s), 797 (s), 759 (s), 720 (s), 464 cm-1 (m); HRMS
(ESI+) m/z: [M+H]+ of corresponding diamine calcd for C18H21N2: 265.1699;
found: 265.1695 correct isotope distribution; elemental analysis calcd (%)
for C22H22F6N2O4: C 53.66, H 4.50, N 5.69; found: C 53.67, H 4.47, N 5.80.
Attachment of iodine substituents gives
a functionalized
tolanophane that can be alkynylated. The alkynylated
tolanophane 12, with an increased -system do not show any
phosphorescence at low temperature, probably due to the
enlarged conjugation and the absence of an easily populated
trans-bent excited state that allows facile ISC into the triplet state.
The synthesized iodinated and ethynylated tolanophanes are
attractive building blocks for the synthesis of novel poly(para-
phenyleneethynylene)s with highly twisted backbones and
attractive emissive properties.
6,10-Dimethyl-16,17-didehydro-10,11-dihydro-5H-
dibenzo[g,k][1,5]diazacyclotridecine-7,9(6H,8H)-dione (4)
A solution of N,N-diisopropylethylamine (0.60 mL, 3.448 mmol, 6.0 equiv)
in dry dichloromethane (120 mL) was prepared at rt under nitrogen. To this
solution we added simultaneously during 4 h solutions of 3 (0.283 g, 0.575
mmol, 1.0 equiv) in a mixture of dry dichloromethane and acetonitrile (40
mL, 1:1, v/v) and malonyl chloride (61µL, 0.632 mmol, 1.1 equiv) in dry
dichloromethane (40 mL). After stirring overnight, the reaction mixture was
quenched by addition of saturated NaHCO3 solution (30 mL) and the water
phase was extracted with dichloromethane (3×20 mL). The combined
organic layers were washed with brine (1×10 mL), dried over MgSO4 and
the solvent was removed in vacuo. Purification by column chromatography
(silica gel; dichloromethane/methanol 30:1, v/v) yielded 4 as colorless
solid. Yield: 0.083 g (0.250 mmol, 42%).
Experimental Section
Materials and Methods are in the Supporting Information. Compound 2
was synthesized according to a published procedure.[11]
Rf=0.42 (dichloromethane/methanol 10:1, v/v); m.p.=213°C; seen complex
signal distribution due to tautomer mixture 1H NMR (CDCl3, 600.25 MHz):
δ=2.76 (s), 2.92 (s), 2.94 (s), 2.98 (s), 3.55.–3.68 (m), 4.03–4.12 (m), 4.66
(br), 5.69–5.73 (m), 5.91–6.01 (m), 7.23–7.40 (m), 7.53–7.55 (m), 7.56–
7.62 (m) ppm; 13C NMR (CDCl3, 150.93 MHz): δ=33.1, 33.8, 34.5, 35.2,
42.2, 43.7, 44.8, 50.3, 50.8, 53.1, 53.2, 91.2, 91.6, 91.7, 122.2, 122.5,
123.1, 123.5, 127.7, 127.9, 128.2, 128.5, 128.7, 129.1, 130.2, 130.3,
130.5, 131.2, 134.1, 134.8, 135.0, 135.2, 137.2, 137.4, 137.9, 166.6,
Di-tert-butyl {ethyne-1,2-diylbis[(2,1-phenylene)methylene]}bis(me-
thylcarbamate) (22)
A published procedure was used.[1a] To a degassed solution of 2 (371 mg,
1.069 mmol, 1.00 equiv) in piperidine (1.3 mL) were added Pd(PPh3)4 (12
mg, 10.7 µmol, 0.01 equiv) and CuI (4 mg, 21.4 µmol, 0.02 equiv). After
that the solution was frozen in a bath of liquid nitrogen and held under
vacuum for 30 min. Then a balloon filled with acetylene gas was attached
and the reaction mixture was allowed to melt and stir under acetylene
atmosphere at room temperature (rt). After 2 h the reaction mixture was
diluted with DCM until homogenization occurred. Celite was added
followed by concentration in vacuo. The precipitate was purified by column
chromatography (silica gel; petroleum ether/ethyl acetate gradient from
20:1 to 5:1, v/v) to yield 22 as yellowish oil, which crystallizes later. Yield:
0.216 g (0.465 mmol, 86%).
Rf=0.51 (petroleum ether/ethyl acetate 2:1, v/v); m.p.=73°C; 1H NMR
(CDCl3, 300.51 MHz): δ=1.34–1.57 (m; 18H; tBu-H), 2.79–2.99 (m; 6H;
NCH3), 4.70 (s; 4H; ArCH2), 7.19–7.40 (m; 6H; HAr) 7.49–7.59 (m; 2H; HAr)
ppm; 13C NMR (CDCl3, 75.57 MHz): δ=28.2, 34.2, 50.0 (0.5C), 50.7 (0.5C),
79.5, 91.7, 121.6 (0.5C), 121.9 (0.5C), 125.9, 126.7, 128.7, 132.1, 139.5,
167.0, 167.4 ppm; IR: ν̃=2925 (w), 1651 (s), 1628 (vs), 1492 (m), 1434
(m), 1392 (s), 1352 (m), 1208 (m), 1168 (m), 1102 (m), 1080 (m), 756 (vs),
648 (s), 601 (m), 454 cm-1 (m); HRMS (ESI+) m/z: [M+Na]+ calcd for
C21H20N2NaO2: 355.1417; found: 355.1417 correct isotope distribution;
elemental analysis calcd (%) for C21H20N2O2: C 75.88, H 6.06, N 8.43;
found: C 76.01, H 6.21, N 8.47; crystal data: C21H20N2O2, Mw=332.39,
colourless crystal (plate), obtained by slow cooling of a solution of 4 in
ethanol, dimensions 0.210×0.120×0.020 mm3, triclinic crystal system,
space group P1, Z=4, a=9.3207(7) Å, b=9.9560(7) Å, c=19.4297(15) Å,
α=102.8874(19)°, β=97.9994(19)°, γ=96.2809(19)°, V=1722.0(2) Å3,
ρ=1.28 g·cm–3, T=200(2) K, Θmax=25.085°, radiation MoKα, λ=0.71073 Å,
21598 reflections measured, 6080 unique (Rint=0.0560), 3823 observed (I
> 2σ(I)), final residual values R1(F)=0.055, wR(F2)=0.111 for observed
reflections.
155.9 ppm; IR: ν̃=2972 (w), 2932 (w), 2862 (w), 1692 (s), 1480 (m), 1453
(m), 1389 (s), 1365 (s), 1300 (m), 1244 (m), 1173 (m), 1142 (s), 1022 (w),
881 (m), 755 (s), 666 cm-1 (w); HRMS (DART+) m/z: [M+H]+ calcd for
C28H37N2O4: 465.2748; found: 465.2763 correct isotope distribution;
elemental analysis calcd (%) for C28H36N2O4: C 72.39, H 7.81, N 6.03;
found: C 72.36, H 8.02, N 6.13.
(2-Ethynylphenyl)methanol (5)
For Sonogashira coupling reaction[13] and deprotection[14]literature known
procedures were applied.
Rf=0.52 (petroleum ether/ethyl acetate 1:1, v/v); m.p.=66°C; 1H NMR
(CDCl3, 300.51 MHz): δ=2.20 (s; 1H; OH), 3.34 (s; 1H; ArCCH), 4.04 (s;
2H; ArCH2), 7.23–7.30 (m; 1H; HAr), 7.34–7.41 (m, 1H, HAr), 7.42–7.54 (m,
2H, HAr) ppm; 13C NMR (CDCl3, 75.56 MHz): δ=63.7, 81.2, 81.9, 120.2,
N,N'-{ethyne-1,2-diylbis[(2,1-phenylene)methylene]}dimethanamini-
um bis(trifluoroacetate) (3)
A published procedure was used.[12] To a solution of 22 (0.890 g, 1.916
mmol, 1 equiv) in dichloromethane (45 mL) was added trifluoracetic acid
(4.5 mL, 58.0 mmol, 30 equiv) in one portion at rt. The resulting mixture
was allowed to stir at these conditions for 2 h. After removal of all volatiles
in vacuo, toluene (60 mL) was added and the mixture was concentrated
again. The obtained solid was washed by decantation with toluene (6×10
mL). Yield: 0.802 g (1.629 mmol, 85%) brownish solid.
Rf=0.10 (dichloromethane/methanol 10:1, v/v); m.p.=173°C; 1H NMR
(DMSO-d6, 400.33 MHz): δ=2.68 (s; 6H; NCH3), 4.41 (s; 4H; ArCH2),
7.50–7.59 (m; 4H; HAr), 7.63–7.67 (m; 2H; HAr), 7.76–7.80 (m; 2H; HAr),
9.21 (br s; 4H; NH2) ppm; 13C NMR (DMSO-d6, 100.66 MHz): δ=32.5,
127.3, 127.4, 129.2, 132.8, 143.2 ppm; IR: ν̃=3281 (w), 3257 (s), 2915 (m),
2862 (m), 2103 (vw), 1478 (s), 1450 (m), 1368 (s), 1044 (s), 757 (vs), 705
(vs), 641 (s), 622 (s), 566 cm-1 (s); HRMS (EI+) m/z: [M]+ calcd for C9H8O:
132.0570; found: 132.0559; elemental analysis calcd (%) for C9H8O: C
81.79, H 6.10; found: C 81.76, H 5.98.
tert-Butyl (2-((2-(hydroxymethyl)phenyl)ethynyl)benzyl)(methyl)carb-
amate (19).[10]
A degassed solution of 2 (2.837 g, 8.172 mmol, 1.00 equiv), Pd(PPh3)2Cl2
(287 mg, 409 µmol, 0.05 equiv) and CuI (156 mg, 817 µmol; 0.1 equiv) in
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10.1002/chem.201701519
Chemistry - A European Journal
FULL PAPER
a mixture of tetrahydrofuran (36 mL) and diethylamine (18 mL) was added
to (2-ethynylphenyl) methanol 5 (1.080 g, 8.172 mmol, 1.00 equiv) under
nitrogen. The resulting mixture was allowed to stir at rt for 3 h, after that
dichloromethane (40 mL) and celite were added and all volatiles were
removed in vacuo. The precipitate was purified by column chromatography
(silica gel; petroleum ether/ethyl acetate gradient from 10:1 to 2:1, v/v) to
yield 19 as yellowish oil. Yield: 2.326 g (6.619 mmol, 81%).
91.2, 122.3, 122.4, 122.8, 123.3, 128.1, 128.5, 128.7, 128.8, 128.9, 129.0,
129.4, 130.2, 130.5, 131.1, 131.9, 133.0, 133.6, 133.7, 136.4, 136.5,
136.9, 138.2, 165.0, 165.3, 167.0, 167.4 ppm; IR: ν̃=3061 (vw), 2947 (w),
1742 (s), 1635 (s), 1232 (s), 1012 (s), 757 (s), 624 (m), 502 cm-1 (m);
HRMS (DART+) m/z: [M+H]+ calcd for C20H18NO3: 320.1281; found:
320.1295 correct isotope distribution; elemental analysis calcd (%) for
C20H17NO3: C 75.22, H 5.37, N 4.39; found: C 75.09, H 5.36, N 4.32; crystal
data: C20H17NO3, Mw=319.35, colourless crystal (polyhedron), obtained by
slow diffusion of pentane vapour into a solution of 7 in tetrahydrofurane,
dimensions 0.100×0.090×0.080 mm3, orthorhombic crystal system, space
group P212121, Z=4, a=8.4867(10) Å, b=9.2750(11) Å, c=20.323(2) Å,
α=90°, β=90°, γ=90°, V=1599.7(3) Å3, ρ=1.326 g·cm–3, T=200(2) K,
Θmax=22.331°, radiation MoKα, λ=0.71073 Å, 9986 reflections measured,
2029 unique (Rint=0.0479), 1648 observed (I > 2σ(I)), final residual values
R1(F)=0.068, wR(F2)=0.178 for observed reflections.
Rf=0.46 (petroleum ether/ethyl acetate 1:1, v/v); 1H NMR (CDCl3, 400.33
MHz): δ=1.42 (s; 9H; tBu-H), 2.84 (br s, 1H, OH), 4.70 (s, 2H, ArCH2), 4.90
(s, 2H, ArCH2), 7.22–7.29 (m, 3H, HAr), 7.30–7.38 (m, 2H, HAr), 7.48–7.55
(m, 3H, HAr) ppm; seen complex signal distribution due to tautomer mixture
13C NMR (CDCl3, 100.66 MHz): δ=28.3, 34.1, 50.3, 50.9, 63.6, 79.8, 91.5,
91.6, 121.2, 121.7, 122.3, 126.3, 127.0, 127.3, 127.5, 128.8, 132.1, 132.4,
139.6, 142.5, 156.0 ppm; IR: ν̃=3437 (w), 2975 (w), 2927 (w), 1691 (s),
1668 (s), 1479 (m), 1451 (m), 1391 (s), 1367 (m), 1145 (s), 1044 (m), 879
(m), 756 cm-1 (vs); HRMS (ESI+) m/z: [M+Na]+ calcd for C22H25NNaO3:
374.1727; found: 374.1731 correct isotope distribution; elemental analysis
calcd (%) for C22H25NO3: C 75.19, H 7.17, N 3.99; found: C 75.08, H 7.34,
N 3.86.
(5-Amino-2-iodophenyl)methanol (9)
Reduction of 3-aminobenzoic acid 8 was accomplished according to ref.[15]
1-(2-((2-(Hydroxymethyl)phenyl)ethynyl)phenyl)-N-methylmethana-
minium chloride (6b)
A commercially available 1M solution of ICl in dichloromethane (1.8 mL,
1.79 mmol, 1.1.equiv) was added dropwise to an ice cooled solution of 3-
aminobenzylalkohol (0.200 g, 1.624 mmol, 1.0 equiv) in methanol (5 mL).
The ice bad was removed and the reaction mixture was allowed to stir at
rt for 40 min followed by concentration in vacuo. The solid was washed
with dichloromethane and partitioned between a 1M aqueous solution of
NaOH (5 mL) and ethyl acetate (10 mL). The organic phase was washed
with 1M aqueous solution of NaOH (1×25 mL) and the combined aqueous
layers were extracted with ethyl acetate (2×10 mL). The organic phase
was washed with brine (1×20 mL) and dried over MgSO4. Column
chromatography (silica gel; petroleum ether/ethyl acetate gradient from 2:1
to 1:1, v/v, then ethyl acetate) yielded a brownish solid. Yield: 0.302 g
(1.212 mmol, 74%).
To a solution of 19 (0.407 g, 1.158 mmol) in acetonitrile (23 mL) was
added a 2M solution of HCl in water (23 mL); the reaction mixture was
allowed to stay overnight at rt. After evaporation of all volatiles in vacuo
the brownish solid was washed with chloroform (3×10 mL) and petroleum
ether (1×10 mL) yielding 6b as beige solid. Yield: 0.275 g (0.986 mmol,
85%).
M.p.=180°C; 1H NMR (DMSO-d6, 600.44 MHz): δ=2.61 (s; 3H; NCH3),
4.37 (s, 2H, ArCH2), 4.75 (s, 2H, ArCH2), 5.45 (br, 1H, OH), 7.32–7.36 (m,
1H, HAr), 7.44–7.54 (m, 3H, HAr), 7.55–7.58 (m, 1H, HAr), 7.60–7.63 (m,
1H, HAr), 7.66–7.68 (m, 1H, HAr), 7.75–7.77 (m, 1H, HAr), 9.49 (br, 2H, NH2)
ppm; 13C NMR (DMSO-d6, 150.93 MHz): δ=32.3, 49.4, 61.5, 90.7, 92.4,
119.7, 123.1, 126.9, 127.0, 129.15, 129.17, 129.24, 130.2, 131.9, 132.3,
Rf=0.45 (ethyl acetate); m.p.=125°C; 1H NMR (DMSO-d6, 300.51 MHz):
δ=4.27 (d; J 5.48 Hz; 2H; ArCH2), 5.21–5.28 (m; 3H; OH, NH2), 6.27 (dd;
J 2.79, 8.37 Hz; 1H; HAr), 6.81 (d; J 2.79 Hz; 1H; HAr), 7.33 (d; J 8.37; 1H,
HAr) ppm; 13C NMR (DMSO-d6, 75.56 MHz): δ=67.3, 77.9, 113.8, 114.7,
133.3, 144.0 ppm; IR: ν=̃ 3377 (m), 2943 (m), 2788 (w), 2715 (w), 2426 (w),
1495 (w), 1472 (w), 1457 (w), 1434 (w), 1404 (w), 1191 (w), 1005 (m), 753
(s), 563 cm-1 (m); HRMS (ESI+) m/z: [M+H]+ of corresponding amine calcd
for C17H18NO: 252.1383; found: 252.1384 correct isotope distribution;
elemental analysis calcd (%) for C17H18ClNO: C 70.95, H 6.30, N 4.87;
found: C 70.75, H 6.16, N 4.65.
138.2, 143.5, 149.0 ppm; IR: ν̃=3357 (w), 3191 (w), 2837 (w), 1594 (m),
1571 (m), 1665 (m), 1445 (m), 1293 (m), 1228 (m), 1168 (m), 1042 (s),
1012 (s), 803 (vs), 686 (s), 574 cm-1 (s); HRMS (ESI+) m/z: [M+H]+ calcd
for C7H9INO: 249.9723; found: 249.9726 correct isotope distribution;
elemental analysis calcd (%) for C7H8INO: C 33.76, H 3.24, N 5.62; found:
C 33.93, H 3.29, N 5.46.
10-Methyl-16,17-didehydro-10,11-
dihydrodibenzo[g,k][1,5]oxazacyclotridecine-7,9(5H,8H)-dione (7)
(Ethyne-1,2-diylbis(5-iodo-2,1-phenylene))dimethanol (10)[16]
Under
a nitrogen atmosphere were simultaneously added at room
temperature during 4.5 h, to a mixture of NaHCO3 (0.271 g, 3.222 mmol,
3.0 equiv) and N,N-diisopropylethylamine (0.36 mL, 2.148 mmol, 2.0
equiv) in dichloromethane (215 mL), a solution of malonyl chloride (157
µL, 1.611 mmol, 1.5 equiv) in dry dichloromethane (30 mL) and a solution
of 6b (0.309 g, 1.074 mmol, 1.0 equiv) together with N,N-
diisopropylethylamine (0.37 mL, 2.148 mmol, 2.0 equiv) in dry
dichloromethane (30 mL). The reaction mixture was allowed to stir
overnight, after that water (50 mL) was added. The water phase was
separated and extracted with dichloromethane (2×40 mL). The organic
phase was washed with brine (1×50 mL) and dried over MgSO4.
Concentration and purification by column chromatography (silica gel;
petroleum ether/ethyl acetate 1:1, v/v then ethyl acetate) yielded 7 as
colorless solid. Yield: 0.193 g (0.604 mmol, 56%).
Under nitrogen atmosphere a degassed mixture of 9 (15.00 g, 60.23 mmol,
1 equiv), Pd(PPh3)2Cl2 (2.114 g, 3.011 mmol, 0.05 equiv) and CuI (1.047
g, 6.023 mmol, 0.1 equiv) in diethylamine (30 mL) was frozen in a liquid
nitrogen bath, held under vacuum and filled with acetylene gas and
allowed to melt. After stirring overnight under acetylene atmosphere at rt,
the diethylamine was evaporated and dichloromethane was added. Solids
were filtered, washed with dichloromethane (5×20 mL) and dried, yielding
5.799 g of a brown solid, which, without further purification was suspended
in a warm solution of 8.6 mL of concentrated H2SO4 in water (35 mL). The
suspension was cooled with ice and the solution of NaNO2 (3.726 g, 54.00
mmol) in water (18 mL) was added at such a rate, that the internal
temperature remained under 5°C. After stirring for an additional 15 min the
reaction mixture was added in small portions (foaming) into a solution of
KI (35.86 g, 216.0 mmol) in water (43 mL) at rt. After stirring for an
additional 2 h, the black solid was filtered, washed with water (3×20 mL),
sodium hydrogen sulfite solution (3×20 mL), again with water (2×20 mL)
and dried. Chromatographic purification (silica gel; petroleum
Rf=0.38 (ethyl acetate); m.p.=147°C; seen complex signal distribution due
to tautomer mixture 1H NMR (DMSO-d6, 300.13 MHz): δ=2.70 (s), 3.10–
3.20 (m), 3.60 (s), 3.68–3.90 (m), 4.69 (s), 4.98–5.17 (m), 5.22 (s), 5.43–
5.52 (m), 5.75 (s), 7.34–7.68 (m) ppm; 13C NMR (DMSO-d6, 75.48 MHz):
δ=31.1, 33.9, 42.0, 43.0, 49.5, 52.2, 54.9, 66.1, 66.2, 90.2, 90.3, 90.8,
This article is protected by copyright. All rights reserved.

10.1002/chem.201701519
Chemistry - A European Journal
FULL PAPER
ether/tetrahydrofuran gradient from 3:1 to 1:1, v/v) yielded a brown solid.
25540 reflections measured, 7025 unique (Rint=0.0429), 4983 observed (I
> 2σ(I)), final residual values R1(F)=0.050, wR(F2)=0.117 for observed
reflections.
Yield: 9.59 g (19.57 mmol, 65%).
Rf=0.51 (petroleum ether/tetrahydrofuran 1:1, v/v); m.p.=205°C; 1H NMR
(DMSO-d6, 300.51 MHz): δ=4.68 (d; J 5.43 Hz; 4H; ArCH2), 5.48 (m; 2H;
OH), 7.29 (d; J 8.02 Hz; 2H; HAr), 7.67 (d; J 8.02 Hz; 2H, HAr), 7.89 (s; 2H;
HAr) ppm; 13C NMR (DMSO-d6, 75.56 MHz): δ=60.7, 91.9, 95.9, 118.8,
[Ethyne-1,2-diylbis(5-{[tri(propan-2-yl)silyl]ethynyl}-2,1-phenylene)]-
dimethanol (13)[14]
133.2, 134.9, 135.5, 146.0 ppm; IR: ν=̃ 3224 (m), 2878 (m), 1586 (w), 1480
(m), 1392 (m), 1358 (m), 1187 (m), 1069 (s), 1042 (s), 868 (m), 811 (s),
541 cm-1 (m); HRMS (ESI+) m/z: [M+Na]+ calcd for C16H12I2NaO2:
512.8819; found: 512.8827 correct isotope distribution; elemental analysis
calcd (%) for C16H12I2O2: C 39.21, H 2.47; found: C 39.43, H 2.49.
To a degassed solution of 10 (250 mg, 510.1 µmol, 1.0 equiv),
Pd(PPh3)2Cl2 (36 mg, 51.01 µmol, 0.1 equiv) and CuI (19 mg, 102.0 µmol,
0.2 equiv) in triethylamine (6 mL) under nitrogen atmosphere, was added
ethynyltriisopropylsilane (0.29 mL, 1.275 mmol, 2.5 equiv) and then the
reaction mixture was heated to 45°C for 2 h. After cooling, addition of celite
and dilution with dichloromethane (5 mL) the reaction mixture was
concentrated in vacuo. Purification by column chromatography (silica gel;
petroleum ether/ethyl acetate gradient from 20:1 to 5:1, v/v) yielded a
brownish solid. Yield: 0.220 g (367.3 µmol, 72 %).
Rf=0.73 (petroleum ether/ethyl acetate 1:1, v/v); m.p.=119°C; 1H NMR
(CDCl3, 300.51 MHz): δ=1.14 (s; 42H; iPr-H), 2.33 (br s; 2H; OH), 4.83 (s;
4H; ArCH2), 7.41 (dd; J 1.55, 7.89 Hz; 2H; HAr), 7.49 (d; J 7.89 Hz; 2H; HAr)
ppm; 13C NMR (CDCl3, 75.56 MHz): δ=11.3, 18.7, 64.0, 93.0, 93.3, 106.4,
3,13-Diiodo-16,17-didehydro-5,11-dihydro-7H-dibenzo[g,k][1,5]-
dioxacyclotridecyne-7,9(8H)-dione (11)
A mixture of 10 (300 mg, 612.1 µmol, 1.0 equiv), malonic acid (76 mg,
734.6 µmol, 1.2 equiv) and p-toluenesulfonic acid monohydrate (12 mg,
61.21 µmol, 0.1 equiv) in toluene (120 mL) was heated at reflux at a Dean-
Stark separator for 19 h. After cooling, water (40 mL) was added and layers
were separated. The aqueous layer was extracted with toluene (3×20 mL)
and the combined organic layer was washed with saturated NaHCO3
solution (1×10 mL) and brine (1×30 mL) and dried over MgSO4.
Concentration and purification by column chromatography (silica gel;
petroleum ether/dichloromethane gradient from 1:1 to 2:3, v/v) yielded a
pale yellowish solid. Yield: 0.165 g (295.6 µmol, 48%).
Rf=0.60 (petroleum ether/ethyl acetate 1:1, v/v); m.p.=235°C; 1H NMR
(CDCl3, 400.33 MHz): δ=3.38 (s; 2H; COCH2CO), 5.06 (s; 4H; ArCH2),
7.25–7.28 (m; 2H; HAr), 7.71–7.75 (m; 4H, HAr) ppm; 13C NMR (CDCl3,
100.66 MHz): δ=41.7, 66.6, 91.1, 94.5, 123.4, 133.8, 138.8, 138.3, 139.4,
121.6, 124.0, 131.3, 131.6, 132.2, 142.3 ppm; IR: ν̃=3285 (w), 2941 (m),
2862 (s), 2143 (m), 1495 (m), 1463 (m), 1040 (m), 997 (m), 882 (s), 831
(s), 756 (s), 677 (s), 661 (vs), 621 (vs), 459 cm-1 (s); HRMS (ESI+) m/z:
[M+Na]+ calcd for C38H54NaO2Si2: 621.3555; found: 621.3551 correct
isotope distribution; elemental analysis calcd (%) for C38H54O2Si2: C 76.19,
H 9.09; found: C 76.13, H 9.02.
3-{[Tri(propan-2-yl)silyl]ethynyl}-13-{3-[tri(propan-2-yl)silyl]prop-2-
yn-1-yl}-16,17-didehydro-5,11-dihydro-7H-dibenzo[g,k][1,5]dioxacy-
clotridecyne-7,9(8H)-dione (12) from 13
165.8 ppm; IR: ν̃=3046 (w), 2976 (w), 1732 (s), 1708 (s), 1487 (m), 1303
(s), 1195 (s), 1074 (m), 1006 (s), 972 (m), 882 (s), 872 (m), 819 (s), 811
cm-1 (s); HRMS (ESI+) m/z: [M+Na]+ calcd for C19H12I2NaO4: 580.8717;
found: 580.8737 correct isotope distribution; elemental analysis calcd (%)
for C19H12I2O4: C 40.89, H 2.17; found: C 41.08, H 2.33.
A mixture of 13 (60 mg, 100 µmol, 1.0 equiv), malonic acid (13 mg, 120
µmol, 1.2 equiv) and p-toluenesulfonic acid monohydrate (2 mg, 10 µmol,
0.1 equiv) in toluene (20 mL) was heated to reflux at a Dean-Stark
separator for 4 h. After cooling, saturated NaHCO3 solution (5 mL) was
added and layers were separated. The water layer was extracted with
toluene (3×10 mL) and the combined organic layer was washed with brine
(1×10 mL) and dried over MgSO4. Concentration and separation by
column chromatography (silica gel; petroleum ether/dichloromethane
gradient from 2:1 to 1:1, v/v) yielded the tolane 12 as pale yellowish solid
and tolane 14 as colorless solid. Yield: 12 (26 mg. 38.98 µmol, 39%), 14
(6 mg, 4.497 µmol, 8%).
3-{[Tri(propan-2-yl)silyl]ethynyl}-13-{3-[tri(propan-2-yl)silyl]prop-2-
yn-1-yl}-16,17-didehydro-5,11-dihydro-7H-
dibenzo[g,k][1,5]dioxacyclotridecine-7,9(8H)-dione (12) from 11[17]
To
a degassed solution of 11 (161 mg, 288.5 µmol, 1.0 equiv)
Pd(PPh3)2Cl2 (20 mg, 28.85 µmol, 0.1 equiv) and CuI (11 mg, 57.70 µmol,
0.2 equiv) in triethylamine (4 mL) under a nitrogen atmosphere, was added
ethynyltriisopropylsilane (0.26 mL, 1.154 mmol, 4 equiv) and then reaction
mixture was heated to 45°C for 4 h and kept overnight at rt. After addition
of celite and dilution with dichloromethane (5 mL) the mixture was
concentrated in vacuo. Purification by column chromatography (silica gel;
petroleum ether/dichloromethane gradient from 1:1 to 1:2, v/v) yielded 12
as colorless solid. Yield: 0.157 g (235.4 µmol, 81 %).
Rf=0.71 (petroleum ether/ethyl acetate 2:1, v/v); m.p.=176°C; 1H NMR
(CDCl3, 400.33 MHz): δ=1.13–1.15 (m; 42H; iPr-H), 3.38 (s; 2H;
COCH2CO), 5.10 (s; 4H; ArCH2), 7.45–7.50 (m; 6H; HAr) ppm; 13C NMR
(CDCl3, 100.66 MHz): δ=11.3, 18.7, 41.7, 67.1, 91.9, 93.9, 105.8, 123.7,
2,9,19,26-Tetrakis{[tri(propan-2-yl)silyl]ethynyl}-5,6,22,23-tetradehy-
dro-11,17,28,34-tetrahydro-13H,30H-tetrabenzo[g,k,t,x][1,5,14,18]te-
traoxacyclohexacosine-13,15,30,32(14H,31H)-tetrone (14) from 13[18]
To a solution of 13 (200 mg, 333.9 µmol, 1 equiv) and pyridine (54 µL, 668
µmol, 2 equiv) in dry dichloromethane (22 mL) under nitrogen atmosphere
was added during 7 h a solution of malonyl chloride (64 µL, 668 µmol, 2
equiv) in dry dichloromethane (25 mL). After stirring for additional 2 d,
water (10 mL) was added, layers were separated and the water layer was
extracted with dichloromethane (3×10 mL). The combined organic layers
were washed with saturated NaHCO3 solution (1×5 mL), brine (1×10 mL)
and dried over MgSO4. Concentration and separation by column
chromatography (silica gel; petroleum ether/dichloromethane gradient
from 2:1 to 1:1, v/v) yielded tolane 12 and tolane 14 as colorless solids.
Yield: 12 (19 mg, 28.48 µmol, 8%), 14 (68 mg, 50.97 µmol, 30%).
124.2, 132.49, 132.50, 134.0, 136.3, 165.9 ppm; IR: ν̃=2941 (m), 2864
(m), 2147 (w), 1756 (m), 1735 (s), 1502 (m), 1459 (m), 1294 (s), 1278 (s),
1207 (m), 1157 (m), 1010 (m), 993 (m), 880 (s), 831 (m), 776 (m), 675 (s),
656 (s), 617 cm-1 (s); HRMS (ESI+) m/z: [M+Na]+ calcd for C41H54NaO4Si2:
689.3453; found: 689.3454 correct isotope distribution; elemental analysis
calcd (%) for C41H54O4Si2: C 73.83, H 8.16; found: C 73.74, H 8.19; crystal
data: C41H54O4Si2, Mw=667.02, colourless crystal (plate), obtained by slow
cooling of a solution of 12 in the mixture of acetone and methanol (2:1,
v/v), dimensions 0.250 0.170 0.080 mm3, triclinic crystal system, space
group P1 , Z=2, a=8.7838(5) Å, b=12.0180(7) Å, c=19.4191(11) Å,
α=104.2904(16)°, β=92.1446(16)°, γ=94.2181(16)°, V=1977.9(2) Å3,
ρ=1.120 g·cm–3, T=200(2) K, Θmax=25.090°, radiation MoKα, λ=0.71073 Å,
Tolane 14. Rf=0.86 (petroleum ether/ethyl acetate 2:1, v/v); m.p.=186°C;
1H NMR (CDCl3, 400.33 MHz): δ=1.14 (s; 84H; iPr-H), 3.52 (s; 4H;
COCH2CO), 5.32 (s; 8H; ArCH2), 7.38 (dd; J 1.51, 8.00 Hz; 4H; HAr), 7.46
(d; J 8.00 Hz; 4H; HAr), 7.48 (d; J 1.21 Hz; 4H; HAr) ppm; 13C NMR (CDCl3,
100.66 MHz): δ=11.3, 18.7, 41.3, 65.2, 92.6, 93.7, 106.2, 122.2, 124.2,
131.9, 132.2, 132.3, 136.8, 166.1 ppm; IR: ν̃=2942 (m), 2864 (m), 2148
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(w), 1759 (m), 1739 (s), 1501 (m), 1462 (m), 1258 (m), 1146 (s), 1013 (m),
995 (m), 881 (s), 831 (m), 761 (s), 658 (s), 621 cm-1 (s); HRMS (ESI+) m/z:
[M+Na]+ calcd for C82H108NaO8Si4: 1355.7013; found: 1356.7044 correct
isotope distribution; elemental analysis calcd (%) for C82H108O8Si4: C
73.83, H 8.16; found: C 73.63, H 8.35; crystal data: C84H112Cl4O8Si4,
Mw=1503.89, colorless crystals (plate), obtained by slow diffusion of
pentane vapor into a solution of 14 in dichloromethane, dimensions
0.320×0.110×0.040 mm3, monoclinic crystal system, space group P21/n,
Z=4, a=8.3361(9) Å, b=40.091(4) Å, c=26.570(3) Å, α=90°, β=98.968(3)°,
γ=90°, V=8771.1(16) Å3, ρ=1.139 g·cm–3, T=200(2) K, Θmax=20.913°,
radiation MoKα, λ=0.71073 Å, 41514 reflections measured, 9344 unique
(Rint=0.0605), 6604 observed (I > 2σ(I)), final residual values R1(F)=0.101,
wR(F2)=0.262 for observed reflections.
ArCH2), 7.23–7.29 (m; 12H; HAr), 7.33–7.37 (s; 6H; HAr), 7.48–7.52 (m; 6H;
HAr) ppm; 13C NMR (CDCl3, 150.95 MHz): δ=41.3, 65.5, 91.3, 122.4, 128.3,
128.8, 132.3, 136.7, 166.2 ppm; IR: ν̃=2952 (w), 1748 (s), 1722 (vs), 1495
(m), 1343 (m), 1313 (m), 1260 (s), 1226 (s), 1155 (s), 1015 (s), 992 (m),
756 (vs), 712 (m), 587 cm-1 (m); HRMS (ESI+) m/z: [M+Na]+ calcd for
C57H42NaO12: 941.2568; found: 941.2571 correct isotope distribution;
elemental analysis calcd (%) for C57H42O12: C 74.50, H 4.61; found: C
74.27, H 4.68.
Bis({2-[(2-{[(tert-butoxycarbonyl)(methyl)amino]methyl}phenyl)-
ethynyl]phenyl}methyl) propanedioate (20)
To an ice cooled solution of 19 (1.858 g, 5.287 mmol, 1.0 equiv) and
pyridine (3.4 mL, 42.3 mmol, 8.0 equiv) in dry dichloromethane (260 mL)
held under nitrogen was added during1 h a solution of malonyl chloride
(1.03 mL, 10.6 mmol, 2.0 equiv) in dry dichloromethane (20 mL). After
additional stirring for 30 min at rt TLC showed consumption of the starting
materials. The reaction mixture was filtered through a silica gel plug (1×6
cm, eluent ethyl acetate 3×20 mL), celite was added and all volatiles were
removed in vacuo. Purification by column chromatography (silica gel;
dichloromethane/diethyl ether gradient from 50:1 to 10:1, v/v) yielded 20
as pale yellow oil. Yield 1.337 g (1.734 mmol, 65%).
Rf=0.66 (petroleum ether/ethyl acetate 1:1, v/v); 1H NMR (CDCl3, 600.25
MHz): δ=1.37–1.54 (m; 18H; tBu-H), 2.80–2.96 (m; 6H; NCH3), 3.54 (s;
2H; COCH2CO), 4.64–4.76 (m; 4H; ArCH2), 5.43 (s; 4H; ArCH2), 7.20–7.43
(m; 12H; HAr), 7.50–7.58 (m; 4H; HAr) ppm;13C NMR (CDCl3, 150.95 MHz):
δ=28.3, 34.2, 34.4, 41.3, 50.1, 50.9, 65.5, 79.6, 79.7, 91.0, 91.2, 92.0,
92.1, 121.3, 121.8, 122.3, 122.4, 126.0, 126.9, 128.2, 128.3, 128.6, 128.7,
128.9, 132.16, 132.24, 132.4, 136.4, 139.5, 139.8, 155.9, 156.1, 166.0
16,17-Didehydro-5,11-dihydro-7H-dibenzo[g,k][1,5]dioxacyclotri-
decyne-7,9(8H)-dione (16)
A mixture of 15 (179 mg, 751 µmol, 1.0 equiv), malonic acid (94 mg, 901
µmol, 1.2 equiv) and p-toluenesulfonic acid monohydrate (14 mg, 75 µmol,
0.1 equiv) in toluene (25 mL) was heated to reflux at a Dean-Stark
separator for 4 h. After cooling, NaHCO3 solution (30 mL) was added and
layers were separated. The water layer was extracted with toluene (3×10
mL) and the combined organic layers were washed with brine (1×10 mL)
and dried over MgSO4. Concentration and purification by column
chromatography (silica gel; petroleum ether/ethyl acetate gradient from 4:1
to 2:1, v/v) yielded tolane 16 as colorless solid. Yield: 83 mg (271.0 µmol,
36%). Analytical data was in agreement with published.[1b]
5,6,22,23-Tetradehydro-11,17,28,34-tetrahydro-13H,30H-tetrabenzo-
[g,k,t,x][1,5,14,18]tetraoxacyclohexacosine-13,15,30,32(14H,31H)-tet-
rone (17) and 16,17,33,34,50,51-hexadehydro-5,11,22,28,39,45-hexa-
hydro-7H,24H,41H-hexabenzo[g,k,t,x,g1,k1][1,5,14,18,27,31]-hexao-
xacyclononatriacontyne-7,9,24,26,41,43(8H,25H,42H)-hexone (18)
ppm; IR: ν=̃ 2974 (w), 2930 (w), 1736 (m), 1688 (vs), 1480 (m), 1451 (w),
1390 (s), 1365 (m), 1247 (m), 1141 (vs), 1009 (w), 882 (m), 757 cm-1 (s);
HRMS (ESI+) m/z: [M+Na]+ calcd for C47H50N2NaO8: 793.3459; found:
793.3461 correct isotope distribution; elemental analysis calcd (%) for
C47H50N2O8: C 73.23, H 6.54, N 3.63; found: C 69.49, H 6.50, N 3.41.
To a suspension of 15 (179 mg, 751.2 µmol, 1.0 equiv) and NaHCO3 (316
mg, 3.76 mmol, 5.0 equiv) in dry dichloromethane (25 mL) under nitrogen
atmosphere, was added during 1 h at rt a solution of malonyl chloride (37
µL, 376 µmol, 0.5 equiv) in dry dichloromethane (5 mL). After stirring for 2
h the reaction mixture was diluted with dry dichloromethane (125 mL) and
another portion of malonyl chloride (37 µL, 376 µmol, 0.5 equiv) solution
in dry dichloromethane (5 mL) was added during 1.5 h and the stirring was
continued overnight. The reaction was quenched with water (50 mL),
layers were separated and the aqueous phase was extracted with
dichloromethane (2×20 mL). The combined organic layers were washed
with brine (1×20 mL) and dried over MgSO4. Concentration and separation
by column chromatography (silica gel; petroleum ether/ethyl acetate
gradient from 4:1 to 2:1, v/v) yielded tolanes 17 and 18 as colorless solids.
Yield 17: 3 mg (4.897 µmol, 1%); yield 18: 17 mg (18.50 µmol, 7%).
Tolane 17. Rf=0.64 (petroleum ether/ethyl acetate 1:1, v/v); 1H NMR
(CDCl3, 300.51 MHz): δ=3.49 (s; 4H; COCH2CO), 5.35 (s; 8H; ArCH2),
29,33-Dimethyl-5,6,22,23-tetradehydro-28,29,33,34-tetrahydro-11H,
13H-tetrabenzo[g,k,t,x][1,5,14,18]dioxadiazacyclohexacosyne-13,15,
30,32(14H,17H,31H)-tetrone (21)
To a solution of 20 (1.327 g, 1.721 mmol, 1 equiv) in dichloromethane (20
mL) was added trifluoracetic acid (3.43 mL, 44.8 mmol, 26 equiv) at rt in
one portion. The mixture was stirred for 5.5 h (gas evaluation). After
removal of all volatiles in vacuo toluene (10 mL) was added, the mixture
was concentrated and a brownish oil obtained that was used in the next
step without further purification.
To a solution of N,N-diisopropylethylamine (1.80 mL, 10.3 mmol, 6.0
equiv) and 4-(dimethylamino)pyridine (0.126 g, 1.033 mmol, 0.6 equiv) in
dry dichloromethane (350 mL) held under nitrogen, were simultaneously
added at rt in 4.5 h solutions of malonyl chloride (0.250 mL, 2.58 mmol,
7.28–7.41 (m; 12H; HAr), 7.50–7.57 (m; 4H; HAr) ppm; IR: ν=
̃
3064 (w), 2949
1.5 equiv) in dry dichloromethane (30 mL) and a solution of the
(w), 2160 (w), 1762 (s), 1724 (s), 1379 (m), 1335 (s), 1162 (vs), 1149 (vs),
1031 (s), 1018 (s), 756 cm-1 (vs); HRMS (ESI+) m/z: [M+Na]+ calcd for
C38H28NaO8: 635.1676; found: 635.1686 correct isotope distribution;
crystal data: C38H28O8, Mw=612.63, colourless crystal (needle), obtained
by slow diffusion of petroleum ether into a solution of 17 in CDCl3,
dimensions 0.590×0.040×0.020 mm3, monoclinic crystal system, space
group P21/c, Z=2, a=17.4119(19) Å, b=4.8650(5) Å, c=4.8650(5) Å, α=90°,
β=107.657(3)°, γ=90°, V=1435.9(3) Å3, ρ=1.417 g·cm–3, T=200(2) K,
Θmax=25.404°, radiation MoKα, λ=0.71073 Å, 17633 reflections measured,
2640 unique (Rint=0.0743), 1792 observed (I > 2σ(I)), final residual values
R1(F)= 0.055, wR(F2)= 0.118 for observed reflections.
deprotected product (from the previous step) in dry dichloromethane (30
mL). After stirring for additional 24 h, water (20 mL) was added, layers
were separated and the water phase was extracted with dichloromethane
(2×50 mL). Combined organic layers were washed with brine (1×20 mL)
and dried over MgSO4. Concentration and purification by column
chromatography (silica gel; petroleum ether/ethyl acetate gradient from 2:1
to 1:1, v/v, then ethyl acetate) followed by preparative HPLC
(dichloromethane/ethyl acetate 1:1, v/v) yielded 21 as colorless solid. Yield
0.182 g (284.9 µmol, 16%).
Rf=0.36 (ethyl acetate); m.p.=177°C; seen complex signal distribution due
to tautomer mixture 1H NMR (CDCl3, 600.25 MHz): δ=2.88–3.10 (m; 6H;
NCH3), 3.34 (s; 0.6H; COCH2CO), 3.43 (s; 1.1H; COCH2CO), 3.48 (s;
0.3H; COCH2CO), 3.57–3.69 (m; 2H; COCH2CO), 4.70–4.96 (m; 4H;
Tolane 18. Rf=0.58 (petroleum ether/ethyl acetate 1:1, v/v); m.p.=163°C;
1H NMR (CDCl3, 600.25 MHz): δ=3.46 (s; 6H; COCH2CO), 5.32 (s; 12H;
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10.1002/chem.201701519
Chemistry - A European Journal
FULL PAPER
[18] N. Chronakis, T. Brandmüller, C. Kovacs, U. Reuther, W.
Donaubauer, F. Hampel, F. Fischer, F. Diederich, A. Hirsch,
Eur. J. Org. Chem. 2006, 2296-2308.
ArCH2), 5.22–5.41 (m; 4H, ArCH2), 7.18–7.46 (m; 12H; HAr), 7.48–7.62 (m;
4H; HAr) ppm; 13C NMR (CDCl3, 150.95 MHz): δ=34.0, 34.4, 35.4, 35.5,
40.1, 40.9, 41.15, 41.19, 49.0, 49.2, 52.6, 52.8, 65.8, 66.1, 66.20, 66.23,
91.1, 91.17, 91.18, 91.20, 91.80, 91.82, 92.1, 121.1, 121.4, 122.1, 122.4,
122.6, 123.2, 123.3, 123.7, 125.6, 125.7, 127.1, 127.3, 127.4, 127.6,
127.8, 128.5, 128.65, 128.69, 128.7, 128.8, 128.9, 129.1, 129.2, 129.26,
129.29, 129.4, 130.0, 130.3, 132.1, 132.2, 132.3, 132.45, 132.47, 132.53,
132.7, 136.0, 136.1, 136.2, 136.6, 138.2, 138.4, 138.7, 138.8, 166.05,
166.15, 166.2, 166.4, 167.0, 167.4, 168.1, 168.3 ppm; IR: ν̃=3065 (vw),
2935 (w), 1745 (m), 1725 (m), 1630 (s), 1788 (m), 1399 (m), 1335 (m),
1152 (m), 1132 (m), 1122 (m), 957.5 (m), 956.9 (s), 712 (m), 609 (w), 442
cm-1 (m); HRMS (ESI+) m/z: [M+Na]+ calcd for C40H34N2NaO6: 661.2309;
found: 661.2309 correct isotope distribution; elemental analysis calcd (%)
for C40H34N2O6: C 75.22, H 5.37, N 4.39; found: C 74.87, H 5.60, N 4.33.
Acknowledgements
This work was financed by the “Deutsche Forschungs-
gemeinschaft (DFG) BU771/12-1.
Keywords: tolane • conformation • ring closing • twisted •
alkynylation
References
[1]
a) S. Menning, M. Krämer, A. Duckworth, F. Rominger, A.
Beeby, A. Dreuw, U. H. F. Bunz, J. Org. Chem. 2014, 79, 6571-
6578; b) S. Menning, M. Krämer, B. A. Coombs, F. Rominger,
A. Beeby, A. Dreuw, U. H. F. Bunz, J. Am. Chem. Soc. 2013,
135, 2160-2163; c) G. Brizius, K. Billingsley, M. D. Smith, U. H.
F. Bunz, Org. Lett. 2003, 5, 3951-3954.
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Vollhardt, Chem. Commun. 2005, 2606-2608.
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b) J. Kim, T. M. Swager, Nature 2001, 411, 1030-1034; c) T.
Miteva, L. Palmer, L. Kloppenburg, D. Neher, U. H. F. Bunz,
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[8]
[9]
[10] Y. Shimizu, T. Azumi, J. Phys. Chem., 1982, 86, 22-26.
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FULL PAPER
Entry for the Table of Contents
FULL PAPER
Lets twist again: We access a family
of twisted tolanes carrying iodine and
alkynyl substitutents. The functiona-
lized twisted tolanes show optical and
Yury Kozhemyakin, Andreas Kretzschmar,
Maximilian Krämer, Frank Rominger,
Andreas Dreuw and Uwe H. F. Bunz*
Page No. – Page No.
A
electronic
properties
that
are
surprisingly different from those of the
unsubstituted twisted tolane.
1
2
3
4
5
6
7
8
9
a) S. Menning, M. Krämer, A. Duckworth, F. Rominger, A. Beeby, A. Dreuw, U. H. F. Bunz, J. Org. Chem. 2014, 79, 6571-6578; b) S. Menning, M. Krämer, B. A. Coombs, F. Rominger, A. Beeby, A. Dreuw, U. H. F. Bunz, J. Am. Chem. Soc. 2013, 135, 2160-2163; c) G. Brizius, K. Billingsley, M. D. Smith, U. H. F. Bunz, Org. Lett. 2003, 5, 3951-3954.
a) G. T. Crisp, T. P. Bubner, Tetrahedron 1997, 53, 11881-11898; b) S. Toyota, Chem. Rev. 2010, 110, 5398-5424; c) O. S. Miljanic, S. D. Han, D. Holmes, G. R. Schaller, K. P. C. Vollhardt, Chem. Commun. 2005, 2606-2608.
M. Krämer, U. H. F. Bunz, A. Dreuw, J. Phys. Chem.
A 2017, 121, 946-953.
U. H. F. Bunz, K. Seehafer, M. Bender, M. Porz, Chem. Soc. Rev. 2015, 44, 4322-4336; c) U. H. F. Bunz, Chem. Rev. 2000, 100, 1605-1644; d) U. H. F. Bunz, Acc. Chem. Res. 2001, 34, 998-1010; e) U. H. F. Bunz, Macromol. Rapid Commun. 2009, 30, 772-805; f) U. H. F. Bunz, Adv. Polym. Sci. 2005, 177, 1-52.
U. H. F. Bunz, K. Seehafer, M. Bender, M. Porz, Chem. Soc. Rev. 2015, 44, 4322-4336.
S. Schmid, A. K. Kast, R. R. Schröder, U. H. F. Bunz, C. Melzer, Macromol. Rapid Comm. 2014, 35, 1770-1775.
a) M. I. Sluch, A. Godt, U. H. F. Bunz, M. A. Berg, J. Am. Chem. Soc. 2001, 123, 6447-6448; b) L. T. Liu, D. Yaron, M.I. Sluch, M. A. Berg, J. Phys. Chem.
J. M. Seminario, A. G. Zacarias, J. M. Tour, J. Am. Chem. Soc. 2000, 122, 3015-3020.
a) U. H. F. Bunz, J. M. Imhof, R. K. Bly, C. G. Bangcuyo, L. Rozanski, D. A. V. Bout, Macromolecules 2005, 38, 5892-5896; b) J. Kim, T. M. Swager, Nature 2001, 411, 1030-1034; c) T. Miteva, L. Palmer, L. Kloppenburg, D. Neher, U. H. F. Bunz, Macromolecules 2000, 33, 652-654.
B 2006, 110, 18844-18852.
10 Heavy atom effect
11 K. Miyawaki, F. Ueno, I. Ueda, Heterocycles 2001, 54, 887-900.
12 A. V. Dubrovskiy, P. Jain, F. Shi, G. H. Lushington, C. Santini, P. Porubsky, R. C. Larock, ACS Comb. Sci. 2013, 15, 193-201.
13 H. Sashida, K. Ohyanagi, M. Minoura, K. Akiba, J. Chem. Soc., Perkin Trans. 1 2002, 606-612.
14 H. Wu, Y. He, L. Gong, Org. Lett. 2013, 15, 460-463.
15 I. Sucholeiki, V. Lynch, L. Phan, C. S. Wilcox, J. Org. Chem. 1988, 53, 98-104.
16 M. A. Fox, J. A. K. Howard, J. A. H. MacBride, A. Mackinnon, K. Wade, J. Organomet. Chem. 2003, 680, 155-164.
17 T. Peterle, P. Ringler, M. Mayor, Adv. Funct. Mater. 2009, 19, 3497-3506.
18 N. Chronakis, T. Brandmüller, C. Kovacs, U. Reuther, W. Donaubauer, F. Hampel, F. Fischer, F. Diederich, A. Hirsch, Eur. J. Org. Chem. 2006, 2296-
2308.
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