Thiophene-Based Double Helices: Syntheses, X-ray Structures, and Chiroptical Properties

Article abstract of DOI:10.1021/jacs.6b05709

We demonstrate facile and efficient construction of conjugated double helical ladder oligomers from the saddle-shaped cyclooctatetrathiophene (COTh) building blocks. The key step involves deprotonation of tetra[3,4]thienylene (β,β-COTh) with n-BuLi which displays remarkably high ipsilateral selectivity. Three racemic double helical ladder oligomers, rac-DH-1, rac-DH-2, and rac-DH-3, containing two, three, and five COTh annelated moieties are efficiently synthesized by diastereoselective coupling of the racemic precursors. The X-ray crystallographic studies of rac-DH-1, rac-DH-2 and rac-DH-3 unambiguously revealed that each double helical scaffold has two single helices intertwined with each other via the C-C single bonds. Following removal of TMS groups, double helical ladder oligomer rac-DH-1-D had sufficient solubility to be resolved via chiral HPLC, thus enabling determination of its chirooptical properties such as CD spectra and optical rotation. (+)-DH-1-D has a large barrier for racemization, with lower limit of ΔG^? > 48 kcal mol^-1, which may be compared to DFT-computed barrier of 51 kcal mol^-1. The enantiomers of DH-1-D show 1 order of magnitude stronger chirooptical properties than the carbon-sulfur [7]helicene, as determined by the anisotropy factor g = Δ?/? = -0.039, based on Δ?_max = -11 and ? = 2.8 × 10² L mol^-1 cm^-1 in cyclohexane at 327 nm.

Full text of DOI:10.1021/jacs.6b05709

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Article
Thiophene-based Double Helices: Syntheses,
X-ray Structures and Chiroptical Properties
Sheng Zhang, Xinming Liu, Chunli Li, Lu Li, Jinsheng Song, Jianwu
Shi, Martha D. Morton, Suchada Rajca, Andrzej Rajca, and Hua Wang
J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 21 Jul 2016
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Grapic Abstract
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Thiophene-based Double Helices: Syntheses, X-ray Struc-
tures and Chiroptical Properties
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Sheng Zhang , Xinming Liu , Chunli Li , Lu Li , Jinsheng Song *, Jianwu Shi , Martha Morton , Su-
‡
‡
†§
chada Rajca , Andrzej Rajca *, and Hua Wang *
†
Engineering Research Center for Nanomaterials, Henan University, Kaifeng 475004, China
‡
Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, USA.
§
Collaborative Innovation Center of Nano Functional Materials and Applications of Henan Province, Kaifeng 475004, China
ABSTRACT: We demonstrate facile and efficient construction of conjugated double helical ladder oligomers from the saddle-
shaped cyclooctatetrathiophene (COTh) building blocks. The key step involves deprotonation of tetra[3,4]thienylene (β,β-COTh)
with n-BuLi which displays remarkably high ipsilateral selectivity. Three racemic double helical ladder oligomers, rac-DH-1, rac-
DH-2 and rac-DH-3, containing two, three and five COTh annelated moieties are efficiently synthesized by diastereoselective
coupling of the racemic precursors. The X-ray crystallographic studies of rac-DH-1, rac-DH-2 and rac-DH-3 unambiguously re-
vealed that each double helical scaffold has two single helices intertwined with each other via the C-C single bonds. Following
removal of TMS groups, double helical ladder oligomer rac-DH-1-D had sufficient solubility to be resolved via chiral HPLC, thus
enabling determination of its chirooptical properties such as CD spectra and optical rotation. (+)-DH-1-D has a large barrier for

-1
-1
racemization, with lower limit of G > 48 kcal mol , which may be compared to DFT-computed barrier of 51 kcal mol . The en-
antiomers of DH-1-D show an order of magnitude stronger chirooptical properties than the carbon-sulfur [7]helicene, as determined
2
–1
–1
by the anisotropy factor g = Δε/ε = –0.039, based on Δεmax = –11 and ε = 2.8 × 10 L mol cm in cyclohexane at 327 nm.
INTRODUCTION
cyclooctatetrathiophene, α,β-COTh) and tetra[3,4]thienylene
β,β-cyclooctatetrathiophene, β,β-COTh) (Figure 2) may be
(
Thiophene-based oligomers and polymers play prominent
role in the development of organic materials for technological
conceived as composed of double helical polymers with alter-
nating connectivity of α,β-COTh and β,β-COTh. Likewise,
the all-thiophene double helices may be viewed as conjugated
[1,2]
applications.
The mainstream research has largely focused
on linear α-oligothiophenes, such as α-sexithiophene, and their
analogous fused thiophenes (thienoacene) oligomers, such as
pentathienoacene (Figure 1).
made in the design of highly annelated oligothiophenes that
lead to novel zero- and one-dimensional (0-D and 1-D) car-
bon-sulfur molecules and oligomers. Among notable examples
[8]
double helical ladder oligomers. Such oligomers are of par-
ticular interest, due to their imaginative and extraordinary
aesthetically pleasing structures with potential to possess very
high racemization barriers, propensity for strong intermolecu-
[
1-3]
Significant effort has been
[9-12]
lar interactions, and strong chirooptical properties.
[4]
are sulflower (0-D), and helical annelated -oligothiophene,
2
Figure 2. D -symmetric fragment of two-dimensional (2D)
carbon-sulfur structure (geometry optimized at the AM1-level)
and all-thiophene double helices with alternating connectivity
[5,6]
such as [7]helicene (1-D) (Figure 1). These novel structures
have received considerable attention because not only that
they are aesthetically pleasing, but also with great potential in
the design of organic functional materials with unique and
[7]
tunable optical/electronic properties.
S
S
S
S
S
S

-sexithiophene
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
pentathienoacene
S
S
S
[7]helicene
sulflower
of α,β-COTh and β,β-COTh.
Figure 1. Oligothiophenes and annelated carbon-sulfur
molecules and oligomers.
The double helical motifs connected by covalent bonds per-
tain to exotic macromolecules that are distinct from those non-
covalently linked helices derived from supramolecular assem-
We are motivated to explore the two-dimensional (2-D) car-
bon-sulfur structure. Alternating connectivity of the saddle-
shaped tetraarylenes such as tetra[2,3]thienylene (α,β-
[13]
bly of single strands by metal ion complexation, aromatic
[14,15]
[16,17]
interaction
and hydrogen bonding.
Design and syn-
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thesis of such macromolecules with double helical motif is
try that is enforced by covalent C-C bond linkage. We note the
two critical factors for this strategy. First, selective control of
stepwise ipsilateral deprotonation of the highly strained oli-
gomers with bulky substituents must be efficient. Second, the
highly twisted racemic double helices and the thienylene
building blocks should induce significant diastereoselectivity
in the CC-bond forming coupling reaction.
highly challenging. The primary challenge lies in diastereose-
lective (homochiral) connection of sterically hindered precur-
sors.
[
9]
[10,18]
In the pioneering work by Rajca , Marsella,
and
[11]
Wong, pre-installation of halogens into the building blocks
were pivotal for chemoselectivities and couplings (Figure 3).
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Scheme 1. The synthetic route to double helices.
Here we report the iterative ipsilateral deprotona-
tion/coupling strategy to construct the double helical motifs
from α,β-COTh and β,β-COTh building blocks (Scheme 1
and 4). With this synthetic strategy, we obtain racemic double
helices rac-DH-1, rac-DH-2 and rac-DH-3 (Chart 1) in re-
markable yields (26%–42%). Rac-DH-3 is the longest π-
conjugated thiophene-based double helix, possessing
6
bithienylene units. X-ray crystallographic studies of rac-DH-1,
rac-DH-2 and rac-DH-3 unambiguously reveal that each dou-
ble helical scaffold has two single helices intertwined with
each other via the C-C single bonds.
Figure 3. Syntheses of double helical molecules.
Chart 1.
Rajca’s tetra-o-phenylene-based double helix 1, with four
biphenyl moieties, was synthesized in 4% yield via CuBr -
2
promoted oxidative homocoupling of a racemic tetra-o-
phenylene precursor. As a continuation of Rajca’s work,
[11]
Wong recently synthesized the optically pure homologues
of octaphenylene 1 with 3, 4, 5, and 6 biphenyl moieties via
the Suzuki cross-coupling reaction and the copper-mediated
oxidative homo-coupling reaction; in particular, starting from
2
enantiopure tetra-o-phenylene precursor, the CuCl -mediated
homo-coupling gave octaphenylene 1a, an analogue of 1, in 16%
yield. Octaphenylene 1a and its higher homologues were ob-
tained in low yields (5–9%) via random homo-coupling of
enantiopure precursors with two and three biphenyl moieties
[11]
(Figure 3).
Marsella’s conjugated double helical oc-
tathienylene 2 was obtained in 28% yield via Sonogashira
cross-coupling of the saddle-shaped racemic α,β-COTh build-
ing block. The building blocks with bulky substituents and low
diastereoselectivities presumably contributed to the reported
low CC-bond coupling efficiencies, starting from racemic
precursors, although the introduction of the bridging acetylene
units should help release the steric hindrance in the latter case.
RESULTS AND DISCUSSION
Regioselective deprotonation of ,-COTh. We first ex-
plored the possibility of regioselective deprotonation of ,-
COTh, which is the key for successful construction of double
helical motif. Although the first synthesis of ,-COTh was
[18]
[
21]
reported by Kauffmann in 1978, there has been no report on
its regioselective deprotonation.
Development of convenient and efficient approaches to
double helical oligomers is still highly sought, which should in
turn spur the advances of this challenging field.
Scheme 2. Regioselective deprotonation of ,-COTh.
Our groups have been actively involved in the synthesis of
[5,6,19,20]
oligo(thienylene) derivatives.
COTh-TMS
We discover that rac-β,β-
4
(rac-3) preferentially undergoes stepwise ipsi-
lateral deprotonation. This prompts us to explore iterative
deprotonation/coupling strategy for the synthesis of double
helical molecules and oligomers, as shown in Scheme 1. In
principle, these oligomers should adopt double helical geome-
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We first attempted to deprotonate all eight α-CH positions
Scheme 3. Regioselective deprotonation of rac-3.
o
in ,-COTh using 10 equivalents of n-BuLi in THF at –78 C.
I
I
o
After the reaction mixture was warmed to 60 C for 2 hours,
S
S
S
S
S
S
S
n-BuLi
4.5 eq)
n-BuLi
(2.0 eq)
TMS
TMS
and quenched with TMS-Cl, to our surprise, only the product
with four TMS substituents (3) was obtained in 73% yield
Scheme 2), rather than the anticipated octa-TMS-substituted
TMS
TMS
TMS
TMS
TMS
TMS
(
rac-3
I
2
I
2
(
S
product. The ipsilateral substitution patterns were also notable,
I
I
I
I
4
70 %
[22]
5
possibly due to lithium chelation. We reason that selective
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69 %
deprotonation of ,-COTh might originate in the intermedi-
ate (,-COTh-Li
4
) bearing a double-bridged dilithium moie-
Syntheses of rac-DH-1, rac-DH-2 and rac-DH-3. The suc-
cess in highly selective deprotonations of ,-COTh and 3
offered us the possible synthetic pathway to novel double heli-
cal oligomers, as summarized in Scheme 4. The synthesis has
three main features: (1) the precursors are racemic, (2) direct
annelation of two building blocks, ,-COTh and ,-COTh,
without any linkage, and (3) TMS groups provide protection
and solubility.
[23,24]
ties, as suggested by Xi
in the case of 1,4-dilithio-1,3-
butadiene. This might be the key factor for the observed selec-
tivity. We then explored the loading range of n-BuLi from 4 to
0 equivalents and obtained the same results. We next careful-
ly investigated the effect of temperature. We found that the
1
deprotonation of β,β-COTh with n-BuLi showed very low
o
efficiency below -60 C, but greatly improved in the tempera-
o
ture range of -30 – 60 C, in which 3 was obtained in the
yields of 74–80% (Table S1, SI). We also carried out reactions
using s-BuLi and t-BuLi and found similar results to that of n-
BuLi (Table S2, SI). Lastly, even weaker base such as LDA
provided 3 in 67% yield. When the reaction of β,β-COTh with
Scheme 4. The synthetic route to racemic double helical mol-
ecules
1
) n-BuLi (2.1 eq)
60 o
1) n-BuLi (2.1 eq)
0 o
) CuBr
n-BuLi was quenched with D
2
O, 99% yield of β,β-COTh-d
4
C
6
C
2
2) ZnCl (2.5 eq)
was obtained (Table S2, SI). Therefore, we conclude that
deprotonation of ,-COTh is highly selective to give carbo-
tetraanion/salt when >4 equiv of n-BuLi is used. The carbo-
tetraanion/salt of β,β-COTh are quite stable over a wide tem-
2
2
(2.5 eq)
O, -78 oC to rt
2
) 6, Pd(PPh
3 4
3 )
O, 120 o
Et
Et
2
C
rac-DH-2
rac-DH-1
rac-3
4
2%
33%
o
perature range, even as high as 60 C. The structure of 3 was
TMS
TMS
1
) n-BuLi (2.1 eq)
confirmed by X-ray crystal diffraction analysis (Figure 4).
6
=
0 o
S
S
6
C
Br Br
Next, we turned our attention to the deprotonation of 3,
which has four equivalent peripheral α-CH positions. Note that
regioselective formation of carbodianion/salt via ipsilateral
deprotonation of 3 is the prerequisite for our synthetic ap-
proach to double helices (Scheme 1). Treatment of 3 with 2.0
2) CuCl
2
(2.5 eq)
Et
2
O, -78 oC to rt
TMS
TMS TMS
S
TMS TMS
S
TMS
TMS
S
S
S
S
S
S
S
Cl
Cl
o
rac-DH-3
equiv n-BuLi in diethyl ether at –78 C, then warming up to 60
+
26%
o
C for 2 h, and then quenching with iodine provided the ex-
S
S
S
pected ipsilateral diodide 4 in 70% yield (Scheme 3). Similarly
to the deprotonation of ,-COTh, the deprotonation of 3
shows temperature dependence (Table S3, SI). The yields of 4
can reach up to 65–72% when the reaction temperature was in
TMS
TMS TMS
TMS TMS
meso-DDH-1-Cl2
11%
+
o
the 0–60 C range. When 4.5 equiv n-BuLi was employed, a
TMS TMS
S
TMS
TMS
tetra-iodo substituted compound 5 was produced in 69% yield
(Scheme 3). Structures of both 4 and 5 were confirmed by X-
ray crystal analyses (Figure 4). We speculate that deprotona-
tion of 3 may have occurred in a stepwise fashion, i.e., two
ipsilateral deprotonations in sequence.
S
S
S
S
Cl
Cl
S
TMS TMS
DH-1-Cl2
22%
Figure 4. The crystal structures of 3, 4 and 5 (from left to right). Carbon, silicon, sulfur and iodine atoms are depicted with thermal
ellipsoids set at the 30% probability level. All hydrogen atoms are omitted for clarity.
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Figure 5. The possible formation of rac-DH-3 from rac-DH-1. (R)/(S) labels indicate configuration of chiral axes associated with
3
,3’-bithienylene moieties.
the efficiency of the iterative deprotonation/coupling strategy
in the construction of the double helical oligomers.
The tris(bithienylene) rac-DH-1 was obtained by treatment
of rac-3 with 2 equiv of n-BuLi followed by trapping with
ZnCl and subsequent Negishi coupling with 2,2'-dibromo-
,5'-di(trimethylsilyl)-3,3'-bithiophene (6). The overall yield
was 33%. Likewise, the tetrakis(bithienylene) rac-DH-2 was
readily produced by CuBr -mediated oxidative coupling of
rac-3-Li in a higher 42% yield over two steps. Further depro-
tonation of the rac-DH-1 at its only two α-CH positions, using
.5 equiv of n-BuLi at 60 C, again displays high ipsilateral
selectivity, as evidenced by isolation d -quenching product
rac-DH-1-d in 99% yield. Upon treatment of rac-DH-1 with
+ equiv of n-BuLi, followed by the addition of CuCl , result-
ed in oxidative dimerization of the likely rac-DH-1-Li inter-
[19a,21,26,27]
2
As evident in preparation of COThs,
construction
5
of eight-membered thienylene-derived rings generally results
in very low yields, presumably due to highly disfavored strain
residing in the products. In comparison, the more twisted ge-
ometries in the double helical motifs should induce additional
molecular strains, and consequently gives poorer yields (e.g., 4%
2
2
[
9]
2
coupling yield for making octaphenylene 1 by Rajca ). How-
ever, our approach to the double helical oligomers exhibits
reasonably good coupling efficiency. The key attribute is the
formation of highly stable lithiated carbodianions after ipsilat-
2
2
2
2
o
2
eral deprotonation of the TMS-thienylene precursors at 60 C.
mediate. As a result, a higher order homologous double helix,
namely hexakis(bithienylene), rac-DH-3 was obtained in 26%
yield (over 2 steps). Two side products were also identified to
The subsequent coupling provides rac-DH-1, rac-DH-2 and
rac-DH-3 in 33%, 42% and 26% yields, respectively. Very
low yields of products and various side products were ob-
o
be DH-1 bearing two Cl groups, such as meso-DDH-1-Cl
DH-1-Cl isolated in 11% and 22% yields, respectively
Scheme 4).
rac-DH-2, produced by CuBr
rac-3-Li , indicate absence of similar bromo-substituted by-
products (Figure S24, SI). These results clearly demonstrate
2
and
tained if the deprotonation reactions were run at –78 C, possi-
2
bly due to a slow or incomplete deprotonation process. We
believe that highly efficient formation of lithiated carboanions
is the key for preparation of the double helical oligomers.
[9,25]
(
NMR spectra of crude reaction mixtures for
-mediated oxidative coupling of
2
2
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Figure 6. X-ray crystal structures of rac-DH-1 (a), rac-DH-2 (b), rac-DH-3 (c), the crystal cell of rac-DH-3 (d) and meso-DDH-1-Cl (e)
(side view). rac-DH-3 (d) showing two repeat units of one supramolecular polymer chain that form across the two vertex angles of cell.
Carbon, silicon, sulfur and chlorine atoms are depicted with thermal ellipsoids set at the 30% probability level. All hydrogen atoms are
omitted for clarity.
a
Table 1. Data for X-ray crystal structures
Averaged Dihedral Angle (°)
Averaged Inner Angle (°)
Compound
a[27]
[27]
4
TMS -α,-COTh
37.7 (A)
128.4 (A)
a
4
TMS -,-COTh (3)
51.0 (B)
121.9 (B)
A
1
B
1
A
2
B
2
A
3
A
1
B
1
A
2
B
2
A
3
rac-DH-1
rac-DH-2
rac-DH-3
42.0
42.0
40.7
51.1
49.7
50.1
---
---
---
---
---
126.6
126.5
127.1
121.9
122.2
122.3
---
---
---
---
---
51.6
50.3
122.7
122.2
39.0
40.6
127.7
127.2
a
4 4
A corresponds to TMS -α,-COTh moiety and B corresponds to TMS -,-COTh (3) moiety.
pertain to the three 3,3’-bithienylene moieties, as the precursor
for DH-3. We note that DH-3 has six chiral axes, which
means only three isomers, two enantiomers (R,R,R,R,R,R)-
DH-3 and (S,S,S,S,S,S)-DH-3, and a plausible meso-DH-3
could be obtained from dimers A, B and C (Figure 5), respec-
To date, the syntheses of chiral double helices strictly re-
[
11,25,28]
quires optically pure starting materials.
work, we utilized a racemic mixture ((R,R,R)-DH-1 and
S,S,S)-DH-1), where the (R)/(S) labels for three chiral axes
In the present
(
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tively. The dimers A, B and C might be formed by coupling of
conformations because the angles θ and α within the moieties
are similar to those in α,-COTh and ,-COTh molecules.
This suggests that little, if any, extra strain is introduced in the
annelation process leading to the double helical oligomers.
(R,R,R)-DH-1 and (S,S,S)-DH-1. The next ring closure cou-
pling can occur within the dimer A and B to generate rac-DH-
3 in 26% yield. Meanwhile, the side-product, meso-DDH-1-
Cl , was generated in 11% yield, due to the failure of the ring
2
closure of dimer-C (meso compound). The yield of rac-DH-3
The electronic absorption spectra of double helical oligo-
mers. UV-vis absorption spectra of α,-COTh and ,-COTh
were used to evaluate electron delocalization in rac-DH-1,
rac-DH-2 and rac-DH-3 (Figure 7). ,-COTh shows two
is about twice to that of meso-DDH-1-Cl , which implies a
2
significant diastereoselectivity for the initial C-C bond for-
0
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2
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0
mation between homochiral DH-1 building blocks leading to
[29]
4
peaks at 232 nm and 265 nm (shoulder). Meanwhile, (TMS) -
dimers A and B.
α,-COTh shows two peaks at 234 nm and 290 nm, and a
weak band at ~350 nm. Double helices rac-DH-1, rac-DH-2
and rac-DH-3 show four absorption bands at ~230 nm, ~265
nm (shoulder), ~300 nm, and a very weak band at ~350 nm
The X-ray crystal structure analyses of double helical oli-
gomers. The three double helical oligomers, rac-DH-1, rac-
DH-2, and rac-DH-3, as well as meso-DDH-1-Cl , can be
2
crystallized from chloroform/methanol; they crystallize in
monoclinic/space point P2(1)/c, monoclinic/space point C2/c,
triclinic/space point P-1 and triclinic/space point P-1, respec-
tively. Their crystal structures are shown in Figure 6, from
which the double helical molecular structures can be visual-
ized directly. Rac-DH-1, rac-DH-2 and rac-DH-3 have two,
three and five COTh moieties, respectively. These COTh moi-
eties are sequentially annelated together in the molecules,
which contain double helical structures intertwined with each
other via the CC single bonds. The molecular lengths extend
from 7.884 Å (S2…C26) to 11.921 Å (C39…C53) and 17.956
Å (C11…C69) for rac-DH-1, rac-DH-2 and rac-DH-3, re-
spectively. In addition, the dihedral angle of the two terminal
thiophene rings of each strand (blue or red strand, Fig.5) in the
double helical oligomer are measured, and the average value
increased from 127 to 196 and 298 for rac-DH-1, rac-DH-
(shoulder). Besides the significant increases in absorbance,
peaks at ~ 230 nm remain at the same wavelength, while the
other bands show small bathochromic shifts with increasing
length of the double helix. We rationalize this behavior by
noting that α,-COTh and ,-COTh moieties are sequential-
ly annelated in the double helical oligomers, forming cross-
conjugated -system of 2,2’-bithienyls, which shows signifi-
cant increases in absorbance but weak bathochromic shifts.
This behavior is analogous to that observed in cross-
[5,28,31]
conjugated carbon-sulfur [n]helicenes (Figure 1).
,-COTh
3
0.6
0.3
0.0
TMS4--COTh
rac-DH-1
rac-DH-2
rac-DH-3
2
and rac-DH-3, respectively.
In packing of rac-DH-3, two enantiomers ((R,R,R,R,R,R)-
DH-3 and (S,S,S,S,S,S)-DH-3) per unit cell are shown in Fig-
ure 6d. Only two H1A···H12A short interactions (2.261 Å)
between the repeat two enantiomer units form one supramo-
lecular polymer chain across the two vertex angles of cell.
Similar observations were reported in the self-aggregation of
200
250
300
350
400
450
[30]
[18]
Wavelength (nm)
helicenes, and tetra(phenylacetyl)-α,-COTh. In addition,
another two H11B···H44A short interactions (2.325 Å) be-
tween two adjacent enantiomers from two neighboring supra-
molecular polymer chains link the polymer chains to form
crystal packing pattern.
Figure 7. UV-vis absorption spectra in dichloromethane at
−
5
room temperature ([C] = 1 × 10 M).
Resolution of double helix DH-1-D: barrier for racemi-
zation and chirooptical properties. For resolution of double
helical oligomers, we chose chiral AD-H column, which gave
baseline resolution of enantiomers in racemic carbon-sulfur
2
In the crystal of meso-DDH-1-Cl , one molecule per unit
cell packing one by one is shown along the a-axis. Only in-
termolecular interaction between S1···H27C is observed with
distance of 2.911 Å. Each molecule combines with two mol-
ecules of chloroform. The distance between two Cl1 atoms is
[5de,28,31]
[n]helicenes (n = 7, 9, 11).
Thus, we were disappoint-
ed to find out that the chromatograms for rac-DH-1, rac-DH-2
and rac-DH-3 showed only a single sharp peak (Figures S1-
S3, SI). Therefore, we removed TMS groups using trifluoroa-
cetic acid to obtain cleanly the corresponding deprotected
double helices rac-DH-1-D, rac-DH-2-D and rac-DH-3-D.
However, only rac-DH-1-D had sufficient solubility in organ-
7
.505 Å, and the distance between two C16 atoms (Figure 6e)
is 7.093 Å. Such distance implies significant disfavored steric
interaction for ring closure coupling to generate meso-DH-3
from dimer-C.
[32]
ic solvents to permit resolution with chiral HPLC; we ob-
More interestingly, rac-DH-1, rac-DH-2 and rac-DH-3 are
independently constructed by one α,-COTh and one ,-
COTh, one α,-COTh and two ,-COTh, and three α,-
COTh and two ,-COTh, respectively. The averaged dihedral
angles (θ) and averaged inner angles (α) of α,-COTh and ,-
COTh moieites bearing four TMS groups are measured to be
tained a fraction of mg of (+)-DH-1-D and (-)-DH-1-D with
99+% enantiomeric excess (ee) (Figure S1, SI).
Since pure enantiomers had a melting point of 294 C, we
attempted racemization of (+)-enantiomer at 298 C on air
using melting point capillaries and following the progress of
the reaction by chiral HPLC. However, even after heating at
298 C for 120 min, the chromatograms of these samples show
only one peak, with a broad shoulder near the baseline (Figure
3
7.7, 51.0 and 128.4, 121.9 (Table 1), respectively. It is
also interesting to note that all α,-COTh and ,-COTh moie-
ties in the three double helical oligomers retain their parent
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S4, SI). Thus, assuming that up to 5% of (-)-enantiomer has
formed, we estimate the lower limit for the barrier for racemi-
ular architecture for the emerging field of chiral organic con-
[40]
ducting systems.

-1
zation as G > 48 kcal mol . This barrier is significantly
DFT modelling of barrier for racemization and CD spectra
for DH-1-D. All geometries were optimized at the B3LYP/6-
31G(d,p)+ZPVE level of theory; transition states were charac-

-1
higher than the barrier G = 43.5 kcal mol for racemization
[33]
of [9]helicene but most likely lower than B3LYP and MP2-
computed barrier of about 79 kcal mol for ring inversion in
-1
[41]
terized by intrinsic reaction coordinate (IRC) computations.
[34,35]
tetra-o-phenylene.
As expected, global minimum structures for α,-COTh,
0
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Enantiomers of double helix DH-1-D possess moderate op-
tical rotations, e.g., for (-)-enantiomer, [α]  –176 (c 0.036,
which is significantly

,-COTh and DH-1-D possess D
of symmetry, respectively (Table 2). The planar structures of
α,-COTh, ,-COTh and DH-1-D, with D2h-, D4h-, and C2v
2 2
, D2d, and C point groups
D
-1
2
-1 [36a,b]
cyclohexane) 10 deg cm g ,
weaker than [α]
-
-1
2
-1
= –1019 10 deg cm g for carbon-sulfur
-1
D
symmetries, are at 29.77, 47.09, and 138.03 kcal mol above
their corresponding global minimum structures and correspond
to the critical points with multiple imaginary frequencies. The
transition states (one imaginary frequency) for ring flip in α,-
COTh and ,-COTh, with C and D point groups of sym-
[7]helicene. CD spectra show helicene-like spectral pattern
with the sign of the longest wavelength Cotton effect corre-
sponding to the sign of [α] , i.e., the sign is negative for the (-
D
–
1
–1
)-enantiomer with Δε ≈ –11.0 L mol cm at 327 nm (Fig-
max
[36b,c]
i
4
ure 8).
-1
metry, are at 29.51 and 45.24 kcal mol above their corre-
sponding global minimum structures, that is, only slightly
below the planar structures.
Table 2. Barriers for ring inversion (racemization) in
tetrathienylenes and in double helix DH-1-D at the B3LYP/6-
3
1G(d,p)+ZPVE level of theory.
Point group of
symmetry
Relative
energy
Critical
point
(number of
Compound
-1
imaginary
(kcal mol
)
frequencies)
α,-COTh
α,-COTh
α,-COTh
D
2
(0)
(1)
minimum
TS
0.00
29.51
29.77
0.00
C
i
D
2h (3)
2d (0)

,-COTh
,-COTh
D
minimum
TS

D
4
(1)
45.24
47.09
0.00
,-COTh
DH-1-D
DH-1-D
DH-1-D
DH-1-D
DH-1-D
D4h (4)
C
C
C
C
2
2
2
1
(0)
(0)
(1)
(1)
minimum
minimum
TS
39.52
42.75
51.03
138.03
Figure 8. UV-vis absorption spectra and CD spectra for DH-
[36c]
TS
1
-D in cyclohexane (solid lines).
TD DFT-computed spec-
tra at the CAM-B3LYP/6-31+G(d,p)/IEF-PCM-UFF (cyclo-
hexane) level of theory. Both computed spectra were shifted
by -0.15 eV and scaled vertically.
C2v (7)
For DH-1-D, two transition states were identified at 42.75
-1
and 51.03 kcal mol above the global minimum. The C2-
symmetric global minimum structure may be viewed as pos-
sessing three 3,3’-bithienylene moieties associated with the
three chiral axes of the same configuration. IRC computations
revealed that both transition states are connected to the global
The strength of chiroptical properties in absorption may be
measured by the corresponding anisotropy factors (g-
[37,38]
values).
Thus for (-)-DH-1-D, g = Δε/ε = –0.039, based
2 –1 –1
on Δεmax = –11.0 and ε = 2.8 × 10 L mol cm at 327 nm in
–
3
cyclohexane, may be compared to g = Δε/ε = –4 × 10 for
carbon-sulfur [7]helicene, in which Δεmax = –117 and ε = 3.1 ×
minimum on one side and to the second C -symmetric mini-
2
-1
4
–1
–1
[28,38]
mum on the other side, which is 39.52 kcal mol higher in
energy. The second minimum structure possesses two terminal
10 L mol cm at 285 nm.
This implies significantly
stronger chirooptical properties for the double helix (-)-DH-1-
D than for carbon-sulfur [7]helicene.
3
,3’-bithienylene moieties with opposite configurations and
the center 3,3’-bithienylene moiety is flattened. The process of
racemization of DH-1-D is complex because it involves inver-
sion of the chiral axes associated with three 3,3’-bithienylene
moieties (Figure 9). This process of racemization may be
thought as involving two chiral axes at the same time. First,
the two 3,3’-bithienylene moieties flatten, forming the lower
energy transition state with nearly planar α,-COTh moiety.
High barrier for racemization and the significant strength of
chiroptical properties in DH-1-D indicate thiophene-based
double helical oligomers with their unique structures have a
potential to become a significant player in the field of chiral
[12,39]
materials, analogously to tetraphenylenes.
Moreover, thi-
ophene-based double helices may provide a new chiral molec-
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Second, the terminal 3,3’-bithienylene moiety within α,-
COTh moiety acquires inverted configuration forming the
ASSOCIATED CONTENT
Supporting Information. Complete reference 41, general exper-
imental procedures, synthesis, spectroscopic data ( H-NMR, C-
NMR, and HRMS), chiral HPLC chromatograms, crystal data in
CIF and DFT computational results for the corresponding prod-
ucts are included. This material is available free of charge via the
Internet at http://pubs.acs.org.
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2
2
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second minimum structure, and then next the other terminal
3,3’-bithienylene moiety flattens, forming the highest energy
transition state with nearly planar ,-COTh moiety. Finally,
the two 3,3’-bithienylene moieties within nearly planar ,-
COTh moiety invert their configuration, thus forming enanti-
omer of DH-1-D.
0
1
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3
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2
3
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0
AUTHOR INFORMATION
Theoretical modelling of the UV-vis absorption and CD
spectra was carried out at the CAM-B3LYP/6-31+G(d,p) level
in IEF-PCM-UFF-modelled cyclohexane and using B3LYP/6-
Corresponding Author
Dr. Jinsheng Song, Dr. Andrzej Rajca, and Dr. Hua Wang
[41]
3
1G(d,p)-optimized geometries.
Both computed spectra
Email:
songjs@henu.edu.cn,
arajca1@unl.edu,
and
were shifted by -0.15 eV and scaled vertically to obtain rea-
sonable fit to the experimental data (Figure 8).
hwang@henu.edu.cn
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
51.03
We gratefully acknowledge the support of this research by the
National Science Foundation (US, CHE-1362454) and the Na-
tional Natural Science Foundation of China (21270255, 20972041,
21404031), as well as Innovation Scientists and Technicians
Troop Construction Projects of Henan Province (C20150011).
We thank Mr. Yuquan Feng for crystal analysis (Nanyang Normal
University). We thank Dr. Hui Zhang and Mr. Shengdian Huang
for their assistance with chiral HPLC (University of Nebraska).
(R)-TS2
47.75
(
S)-TS1
39.52
(
R,S)-DH-1-D
REFERENCES
1. a) Cinar, M. E.; Ozturk, T. Chem. Rev. 2015, 115, 3036–3140. b)
Mishra, A., Ma, C.-Q.; Bäuerle, P. Chem. Rev. 2009, 109, 1141– 1276.
c) Miller, L. L.; Mann, K. R. Acc. Chem. Res. 1996, 29, 417– 423. d)
Bäuerle, P., Segelbacher, U., Maier, A.; Mehring, M. J. Am. Chem.
Soc. 1993, 115, 10217– 10223.
0.00
S,S,S)-DH-1-D
0.00
(R,R,R)-DH-1-D
(
2. a) Facchetti, A.; Deng, Y.; Wang, A.; Koide, Y.; Sirringhaus, H.;
Marks, T. J.; Friend, R. H. Angew. Chem., Int. Ed. 2000, 39,
4547−4551. b) Schoonveld, W. A.; Wildeman, J.; Fichou, D.; Bob-
bertk, P. A.; van Wees, B. J.; Klapwijk, T. M. Nature, 2000, 404,
Figure 9. Potential energy surface for racemization of DH-1-
D at the B3LYP/6-31G(d,p)+ZPVE level of theory
9
77−980. c) Cnops, K.; Rand, B. P.; Cheyns, D.; Verreet, B.; Empl,
M. A.; Heremans, P. Nature Commun.2014, 5, 4406.
. a) Xiao, K.; Liu, Y.; Qi, T.; Zhang, W.; Wang, F.; Gao, J.; Qiu,
3
CONCLUSIONS
W.; Ma, Y.; Cui, G.; Chen, S.; Zhan, X.; Yu, G.; Qin, J.; Hu, W.; Zhu,
D. J. Am. Chem. Soc. 2005, 127, 13281−13286. b) Zhang, X.; Côté, A.
P.; Matzger, A. J. J. Am. Chem. Soc. 2005, 127, 10502−10503. c) Kim,
E.; Coropceanu, V.; Gruhn, N. E.; Sánchez-Carrera, R. S.; Snoeberger,
R.; Matzger, A. J.; Brédas, J. J. Am. Chem. Soc. 2007, 129,
13072−13081.
We demonstrate a facile and efficient “iterative deprotona-
tion/ CC-bond coupling” strategy for the construction of con-
jugated double helical ladder oligomer, starting from the achi-
ral, saddle-shaped ,-COTh building block. The highly regi-
oselective deprotonation of ,-COTh, using n-BuLi, is the
key step in the synthetic strategy. Diastereoselectivity is cru-
cial for the formation of double helices rac-DH-2 and rac-
DH-3 from racemic precursors (rac-3 and rac-DH-1), in
which rac-DH-3 showcases the longest double helix. These
distinctive features provide a possibility to establish a general
guideline for preparation of double helical oligomers with a
defined length. Furthermore, the X-ray crystallographic stud-
ies on the three double helical oligomers clearly show the mo-
lecular structures of π-conjugated double helical ladder oligo-
mers. Resolution of rac-DH-1-D allowed us to establish both
strong chirooptical properties and large barriers for racemiza-
tion of the lowest double helical homologue. Although the
resolution of the higher homologues was not successful, this
work will facilitate the synthetic approaches to enantiopure
double helical ladder oligomers and provide a configurational-
ly stable framework for the construction of organic materials
based upon chiral π-conjugated systems.
4
. a) Chernichenko, K. Y.; Sumerin, V. V.; Shpanchenko, R. V.;
Balenkova, E. S.; Nenajdenko, V. G. Angew. Chem., Int. Ed. 2006, 45,
−4. b) Dadvand, A.; Cicoira, F.; Chernichenko, K. Y.; Balenkova, E.
1
S.; Osuna, R. M.; Rosei, F.; Nenajdenko, V. G.; Perepichka, D. F.
Chem.Commun. 2008, 5354−5356. c) Ivasenko, O.; MacLeod, J. M.;
Chernichenko, K. Y.; Balenkova, E. S.; Shpanchenko, R. V.;
Nenajdenko, V. G.; Rosei, F.; Perepichka, D. F. Chem. Commun.
2009, 1192−1194.
5. a) Rajca, A.; Wang, H.; Pink, M.; Rajca, S. Angew. Chem., Int.
Ed. 2000, 39, 4481-4483. b) Torroba, T.; García-Valverde, M. Angew.
Chem., Int. Ed. 2006, 45, 8092–8096. c) Zak, J. K.; Miyasaka, M.;
Rajca, S.; Lapkowski, M.; Rajca, A. J. Am. Chem. Soc. 2010, 132,
3246−3247. d) Miyasaka, M.; Pink, M.; Rajca, S.; Rajca, A. Angew.
Chem., Int. Ed. 2009, 48, 5954–5957. e) Miyasaka, M.; Rajca, A.;
Pink, M.; Rajca, S. J. Am. Chem. Soc. 2005, 127, 13806–13807.
6. a) Li, C.; Shi, J.; Xu, L.; Wang, Y.; Cheng, Y.; Wang, H. J. Org.
Chem. 2009, 74, 408−411. b) Wang, Z.; Shi, J.; Wang, J.; Li, C.; Tian,
X.; Cheng, Y.; Wang, H. Org. Lett. 2010, 12, 456-459. c) Liu, X.; Yu,
P.; Xu, L.; Yang, J.; Shi, J.; Wang, Z.; Cheng, Y.; Wang, H. J. Org.
Chem. 2013, 78, 6316-6321. d) Li, L.; Zhao, C.; Wang, H. Chem. Rec.
2016, 16, 797−809.
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7. a) Korevaar, P. A.; de Greef, T. F. A.; Weijer, E. W. Chem.
28. Rajca, A.; Miyasaka, M.; Pink, M.; Wang, H.; Rajca, S. J. Am.
Chem. Soc. 2004, 126, 15211–15222.
Mater. 2014, 26, 576–586. b) Schlütter, F.; Nishiuchi, T.; Enkelmann,
V.; Müllen, K. Angew. Chem., Int. Ed. 2014, 53, 1538–1542. c) Khalil,
G. E.; Adawi, A. M.; Robinson, B.; Cadby, A. J.; Tsoi, W. C.; Kim, J-
S.; Charas, A.; Morgado, J.; Lidzey, D. G. J. Phys. Chem.B, 2011,115,
29. Analysis of crude NMR spectrum also reveals that the yield of
rac-DH-3 is about twice to that of meso-DDH-1-Cl
0. Lovinger, A. J.; Nuckolls, C.; Katz, T. J. J. Am. Chem. Soc.
998, 120, 264–268.
31. a) Miyasaka, M.; Pink, M.; Rajca, A.; Rajca, S. Chem. Eur. J.
2
(Figure S29, SI).
3
1
2028–12035. d) Tian, Y.; Park, G.; Kertesz, M.; Chem. Mater. 2008,
20, 3266−3277. e) Anthony, J. E. Chem. Rev. 2006, 106, 5028–5048.
. a) Luh, T-Y. Acc. Chem. Res. 2013, 46, 378–389. b) Sakai, N.;
1
8
Matile, S. J. Am. Chem. Soc. 2011, 133, 18542–18545. c) Lin, N-T.;
Lin, S-Y.; Lee, S-L.; Chen, C-H.; Hsu, C-H.; Hwang, L. P.; Xie, Z-Y.;
Chen, C-H.; Huang, S-L.; Luh, T-Y. Angew.Chem., Int. Ed. 2007, 46,
4481–4485.
2004, 10, 6531–6539. b) Miyasaka, M.; Pink, M.; Olankitwanit, A.;
Rajca, S.; Rajca, A. Org. Lett. 2012, 14, 3076–3079. c) Swager, T. M.;
Gutierrez, G. D. Synfacts, 2012, 8, 964.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
2. rac-DH-1-D was resolved using analytical scale ChiralPak
9
. Rajca, A. Safronov, A. Rajca, S. Shoemaker, R. Angew. Chem.,
AD-H column with n-hexane/isopropanol (90:10, v/v) as eluent and
flow rate of 1.0 mL/min.
Int. Ed. Engl. 1997, 36, 488−491.
10. Marsella, M. J. Acc. Chem. Res. 2002, 35, 944−951.
33. Martin, R. H.; Marchant, M. J. Tetrahedron 1974, 30, 347–349.
34. Bachrach, S. M. J. Org. Chem. 2009, 74, 3609–3611.
11. Chen, J. X.; Han, J. W.; Wong, H. N. C. Org. Lett. 2015, 17,
4296−4299.
12. a) Han, J.-W.; Li, X.; Wong, H. N. C. Chem. Rec. 2015, 15,
07–131. b) Huang, H.; Hau, C.-K.; Law, C. C. M.; Wong, H. N. C.
Org. Biomol. Chem. 2009, 7, 1249–1257. c) Rajca, A.; Rajca, S.;
Pink, M.; Miyasaka, M. Synlett 2007, 1799–1822.
35. Huang, H.; Stewart, T.; Gutmann, M.; Ohhara, T.; Niimura, N.;
Li, Y.-X.; Wen, J.-F.; Bau, R.; Wong, H. N. C. J. Org. Chem. 2009,
74, 359–369.
1
-1
3
6. a) For (+)-DH-1-D, [α]  +176 (c 0.061, cyclohexane) 10
D
1
3. a) Lehn, J.-M.; Rigault, A. Angew. Chem., Int. Ed. 1988, 27,
1095–1097. b) Koert, U.; Harding, M. M.; Lehn, J. M. Nature 1990,
46, 339–342. c) Hasenknopf, B.; Lehn, J. M.; Baum, G.; Fenske, D.
Proc. Natl. Acad. Sci. 1996, 93, 1397–1400.
4. Huc, I.; Lehn, J.-M.; Berl, V.; Khoury, R. G.; Krische, M. J.
2 -1
deg cm g . b) Concentrations of samples used for optical rotation
and CD spectra were determined using molar extinction coefficient,
obtained from linear Lambert-Beer plot for rac-DH-1-D in
cyclohexane (Figure S5, SI). c) CD spectra for DH-1-D in cyclohex-
3
1
-
1
-1
ane, max/nm (max/L mol cm ): (-)-enantiomer, 327 (-11.0), 242
Nature 2000, 407, 720–723.
15. Berl, V.; Huc, I.; Khoury, R. G.; Lehn, J.-M. Chem. Eur. J.
001, 7, 2810–2820.
(
+23.4); (+)-enantiomer, 327 (+11.0), 242 (-24.0).
2
37. Eliel, E. L.; Wilen, S. H. Stereochemistry of Organic
Compounds Wiley: New York, 1994; pp 1013–1019.
1
1
6. Watson, J. D.; Crick, F. H. C. Nature 1953, 171, 737–738.
7. a) Tanaka, Y.; Katagiri, H.; Furusho, Y.; Yashima, E. Angew.
3
8. Rajca, A.; Miyasaka, M. In Functional Organic Materials -
Chem., Int. Ed. 2005, 44, 3867–3870. b) Ikeda, M.; Tanaka, Y.;
Hasegawa, T.; Furusho, Y.; Yashima, E. J. Am. Chem. Soc. 2006, 128,
6806–6807. c) Maeda, T.; Furusho, Y.; Sakurai, S.; Kumaki, J.;
Okoshi, K.; Yashima, E. J. Am. Chem. Soc. 2008, 130, 7938–7945.
Syntheses and Strategies; Mueller, T. J. J.; Bunz, U. H. F., Eds.;
Wiley-VCH: New York, 2007; pp 543−577.
3
9. a) Lin, F.; Peng, H.-Y.; Chen, J.-X.; Chik, D. T. W.; Cai, Z.-W.;
Yam V. W. W.; Wong, H. N. C. J. Am. Chem. Soc. 2010, 132,
16383–16392. b) Rajca, A.; Rajca, S. Angew. Chem., Int. Ed. 2010,
9, 672–674. c) Shibata, T.; Chiba, T.; Hirashima, H.; Ueno, Y.;
Endo, K. Angew. Chem., Int. Ed. 2009, 48, 8066–8069. d) Peng, H.-
Y.; Lam, C.-K.; Mak, T. C. W.; Cai, Z.-W.; Ma, W.-T.; Li, Y.-X.;
Wong, H. N. C. J. Am. Chem. Soc. 2005, 127, 9603–9611. e) Rajca,
A.; Wang, H.; Bolshov, P.; Rajca, S. Tetrahedron 2001, 57, 3725–
3735.
1
8. Marsella, M. J.; Kim, I. T.; Tham, F. J. Am. Chem. Soc. 2000,
22, 974–975.
9. a) Wang, Y.; Song, J.; Xu, L.; Kan, Y.; Shi, J.; Wang, H. J. Org.
1
4
1
Chem. 2014, 79, 2255−2262. b) Wang, Y.; Gao, D.; Shi, J.; Kan, Y.;
Song, J.; Li, C.; Wang, H. Tetrahedron, 2014, 70, 631–636. c) Sun,
H.; Shi, J.; Zhang, Z.; Zhang, S.; Liang, Z.; Wan, S.; Cheng, Y.;
Wang, H. J. Org. Chem., 2013, 78, 6271–6275. d) Wu, T.; Shi, J.; Li,
C.; Song, J.; Xu, L.; Wang, H. Org. Lett., 2013, 15, 354–357.
40. a) Pop, F.; Auban-Senzier, P.; Canadell, E.; Rikken G. L. J. A.;
Avarvari, N. Nature Commun. 2014, 5, 3757. b) Pospíšil, L.;
Bednárová, L.; Štěpánek, P.; Slavíček, P.; Vávra, J.; Hromadová, M.;
Dlouhá, H.; Tarábek, J.; Teplý, F. J. Am. Chem. Soc. 2014, 136,
20. a) Xiao, S.; Pink, M.; Wang, H.; Rajca, S.; Rajca, A. J. Sulfur
Chem. 2008, 29, 425–432. b) Miyasaka, M.; Pink, M.; Rajca, S.
Rajca, A. Org. Lett. 2010, 12, 3230–3233. (c) Swager, T. M.; Batson,
J. Synfacts, 2010, 1136-1136.
1
0826–10829. c) Pop, F.; Auban-Senzier, P.; Frackowiak, A.;
21. Kauffmann, T.; Greving, B.; Kriegesmann, R.; Mitschker, A.;
Ptaszynski, K.; Olejniczak, I.; Wallis, J. D.; Canadell, E.; Avarvari, N.
J. Am. Chem. Soc. 2013, 135, 17176–17186. d) Avarvari, N.; Wallis, J.
D. J. Mater. Chem. 2009, 19, 4061–4076.
Woltermann, A. Chem. Ber. 1978, 111, 1330–1336.
22. Streiwieser, A, Jr. Acc. Chem. Res. 1984, 17, 353–357.
2
3. a) Xi, Z. Acc. Chem. Res. 2010, 43, 1342–1351. b) Liu, L.;
Zhang, W.; Luo, Q.; Li, H.; Xi, Z. Organometallics, 2010, 29, 278–
81.
4. Wang, C.; Luo, Q.; Sun, H.; Guo, X.; Xi, Z. J. Am. Chem. Soc.
2007, 129, 3094–3095.
5. Rajca, A.; Safronov, A.; Rajca, S.; Wongsriratanakul, J. J. Am.
Chem. Soc. 2000, 122, 3351–3357.
6. Kabir, S. M. H.; Miura, M.; Sasaki, S.; Harada, G.; Kuwatani,
Y.; Yoshida, M.; Iyoda, M. Heterocycles 2000, 52, 761–774.
7. Wang, Y.; Wang, Z.; Zhao, D.; Wang, Z.; Cheng, Y.; Wang, H.
Synlett 2007, 2390–2394.
41. Frisch, M. J. et al. Gaussian 09, Revision A.01; Gaussian, Inc.:
Wallingford, CT, 2009.
2
2
2
2
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