Post-Cycloaddition-retroelectrocyclization transformations of polycyanobutadienes

Article abstract of DOI:10.1002/ejoc.201201371

The thermal [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction between a range of alkynes, activated by electron-donating anilino (p-H ₂NC₆H₄-) substituents, and the electron-deficient olefins tetracyanoethene (T

Full text of DOI:10.1002/ejoc.201201371

FULL PAPER
DOI: 10.1002/ejoc.201201371
Post-Cycloaddition–Retroelectrocyclization Transformations of
Polycyanobutadienes
Adam R. Lacy,[a] Anna Vogt,[a] Corinne Boudon,[b] Jean-Paul Gisselbrecht,[b]
W. Bernd Schweizer,[a] and François Diederich*[a]
Keywords: Cycloaddition / Electrochemistry / Electron acceptors / Charge transfer / Chromophores / Electrocyclic reations
The thermal [2+2] cycloaddition–retroelectrocyclization (CA-
RE) reaction between a range of alkynes, activated by elec-
tron-donating anilino (p-H2NC6H4-) substituents, and the
electron-deficient olefins tetracyanoethene (TCNE) and
7,7,8,8-tetracyano-p-quinodimethane (TCNQ) delivered an-
ilino-substituted polycyanobutadienes (PCBDs). The aniline
NH2 groups provide a convenient handle for further transfor-
mations, yielding a new series of PCBDs without an electron-
donating group. Electrochemical investigations by rotating
disk voltammetry and cyclic voltammetry revealed large an-
odic shifts in both the first and second reduction potentials
as a result of the removal of the electron-donating function-
ality. This methodology allows for PCBD-containing sub-
strates to be further elaborated, generating a new family of
chromophores previously inaccessible by alternative syn-
thetic methods.
Introduction
potential application in optoelectronic devices such as or-
ganic light-emitting diodes and solar cells.[7]
The click-type cycloaddition–retroelectrocyclization
(CA-RE) reaction between electron-rich alkynes[1] and
tetra-,[2] tri-,[3] and dicyanoethenes[3a,4] has been employed
Previous reports on the chemical modification of the
extensively in the rapid, high-yielding formation of polycy- PCBD units resulting from the CA-RE reaction were lim-
anobutadienes (PCBDs; Scheme 1).[5] In addition to intense ited to the spontaneous rearrangement of the cyanovinyl
intramolecular charge-transfer bands and high third-order moiety,[8] and no systematic studies into the chemical reac-
nonlinear optical susceptibilities,[6] members of this family tivity of this class of substrates have been carried out. As we
of molecules possess exceptional, strongly anodically have previously shown that PCBDs bearing weaker electron
shifted electrochemical reduction potentials, despite the donors possess anodically shifted reduction potentials,[2b]
presence of the electron-donating group required to facili- we became interested in developing a methodology by
tate the CA-RE reaction. Such properties rank these easily which the electron-donating group could be transformed
assembled, thermally stable, cyano-based acceptors along- into other functionalities after the CA-RE reaction. Such a
side state-of-the-art p-type dopants, and highlight their strategy would enable us to systematically study the effect
Scheme 1. CA-RE reaction (EDG = electron-donating group).
of substituents on the properties of PCBDs and hence facil-
[a] Laboratorium für Organische Chemie, ETH Zürich,
itate the rational design of novel, strong electron acceptors.
Herein, we report that the use of anilines 1–3 (see
Table 1) as donors in the CA-RE reaction yields PCBDs 4–
7 in which the anilino moiety is a platform for subsequent
derivatization. For the first time, we have been able to syn-
thesize a range of PCBDs 8–16 that lack an electron-donat-
ing group and investigate their physical properties. Further-
Wolfgang-Pauli-Strasse 10, HCI, 8093 Zürich, Switzerland
Fax: +41-44-632-1109
E-mail: diederich@org.chem.ethz.ch
Homepage: http://www.diederich.chem.ethz.ch/
[b] Laboratoire d’Electrochimie et de Chimie Physique du Corps
Solide UMR 7177, Université de Strasbourg, CNRS,
4, rue Blaise Pascal, CS 90032, 67081 Strasbourg Cedex, France
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201201371.
Eur. J. Org. Chem. 2013, 869–879
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F. Diederich et al.
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more, we demonstrate that the new, strongly electron-ac- allowing the construction of previously inaccessible chro-
cepting PCBDs are stable to a range of reaction conditions, mophores.
Table 1. Summary of the synthesis and post-CA-RE reactivity of 4–7.
[a] In MeCN, 25 °C, 1 h. [b] In MeCN, 80 °C, 5 h. [c] 50% H2SO4, NaNO2, 1 h, 0 °C, then H2PO3, 25 °C, 18 h. [d] 50% H2SO4, NaNO2,
1 h, 0 °C, then urea, KI, 3 h. [e] NaBO3·4H2O, AcOH, 60 °C, 10 h. [f] tBuONO, THF, 60 °C, 1 h. [g] tBuONO, I2, MeCN, 25 °C, 3 h. [h]
p-Toluenesulfonic acid monohydrate, NaNO2, H2O, KI, MeCN, 10–15 °C, 30 min.
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Transformations of Polycyanobutadienes
The PCBD derivatives resulting from the CA-RE reac-
tions are susceptible to nucleophilic attack due to the elec-
trophilicity of the dicyanovinyl units. We expected that the
reactivity of this new class of PCBD derivatives towards
nucleophiles would be heightened as they no longer have
electron-donating groups to attenuate their electrophilicity.
This was supported by DFT calculations in which the sub-
strates lacking electron donors were predicted to have
lower-energy LUMOs (see the Supporting Information).
Results and Discussion
Synthesis
We have previously reported the use of unsubstituted an-
ilino groups (p-H2NC6H4-) as activators in the CA-RE re-
action of acetylenes with tetracyanoethene (TCNE) in the
synthesis of PCBD 6.[2c] Accordingly, anilines 1 and 2 were
treated with TCNE in acetonitrile at 25 °C for 1 h to deliver
CA-RE products 4 and 5 in yields of 78 and 62%, respec-
tively (Table 1). Meanwhile, the addition of 7,7,8,8-tetra-
1
Our hypothesis was also confirmed experimentally by H
NMR studies, which showed complete decomposition of 9
after just 1 h in CD3CN in the presence of n-butylamine,
whereas 4 only decomposed slowly under these conditions,
even upon heating at 60 °C (see the Supporting Infor-
mation).
cyanoquinodimethane (TCNQ) to aniline
heating at 80 °C for 5 h to furnish 7 in 85% yield.
1 required
We then submitted tetracyanobutadiene (TCBD) 4 to di-
azotization followed by Sandmeyer-type reaction in 50%
aqueous H2SO4 to access phenyl and iodophenyl derivatives
8 and 9 in yields of 48 and 74%, respectively.[9] The ni-
trophenyl analogue 10 was prepared in moderate yield by
oxidation of 4 with NaBO3 in acetic acid at 60 °C.[10]
In contrast, submission of 5 and 6 to these aqueous di-
azotization conditions led only to decomposition,[11] and
poor solubility prevented the application of this meth-
odology to TCNQ adduct 7. As a result, we sought alterna-
tive conditions: It was found that heating substrates 5–7 at
60 °C with tert-butyl nitrite in THF transformed the aniline
group into phenyl derivatives 11, 13, and 15, respectively,
in yields of 42–55%.[12] Meanwhile, the corresponding aryl
iodides 12, 14, and 16 were formed in yields of 31–62%
upon iodination in acetonitrile.[13] Unfortunately, none of
anilines 5–7 could be oxidized by using the conditions out-
lined above, presumably because of the competing aceto-
lysis of electrophilic substrates 5 and 6,[14] and low oxidation
chemoselectivity in the case of expanded TCNQ derivative 7.
Despite their relative chemical instability, we realized
that the aryl iodide substrates gave us an excellent opportu-
nity to explore the derivatization of molecules bearing the
1,1,4,4-tetracyanobuta-1,3-dienyl (TCBD) core. We found
that 9 readily undergoes Suzuki and Sonogashira cross-cou-
pling reactions to deliver the novel push–pull chromophores
18 and 20 in yields of 69 and 80%, respectively
(Scheme 2).[15] A subsequent second CA-RE reaction of the
electron-rich alkyne 20 with TCNQ delivered the new chro-
mophore 21 featuring both TCBD and expanded TCNQ
electron-accepting moieties.[16] These reactions are notable,
because they significantly broaden the scope of substrates
accessible in the CA-RE reaction to chromophores that are
impossible to access by using the standard CA-RE protocol
and furthermore pave the way for the incorporation of
this versatile motif into more complex molecular architec-
tures.
Scheme 2. Post-CA-RE transformations of aryl iodide 9.
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F. Diederich et al.
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X-ray Crystal Structures
formation), whereas 8 and 13 crystallized from CH2Cl2 and
benzene, respectively (Figure 1). The PCBD units in each
Crystals of 4, 9, 15, and 20 suitable for X-ray diffraction case are highly nonplanar, as previously reported,[2a,2b] with
studies were prepared by slow diffusion of diethyl ether or a torsional angle θ between the two dicyanovinyl planes in
pentane into MeCN, THF, and CHCl3 (see Supporting In- the range 73–127° (Table 2). The corresponding torsional
Figure 1. ORTEP plots of 4, 8, 9, 13, 15, and 20 with vibrational ellipsoids shown at the 50% probability level (T = 100 K). Arbitrary
numbering. Selected bond lengths [Å] and torsional angles [°]: 4: C16–C21 1.407(2), C16–C17 1.407(2), C17–C18 1.368(2), C18–C19
1.400(3), C19–C20 1.399(3), C20–C21 1.371(2), C2–C3–C4–C5 116.5(2); 8: C3–C4 1.402(2), C3–C8 1.409(2), C4–C5 1.384(2), C5–C6
1.389(2), C6–C7 1.392(2), C7–C8 1.382(2), C2–C1–C1–C2 106.4(2); 9: C9–C10 1.404(2), C9–C14, 1.400(2), C10–C11 1.391(2), C11–C12
1.396(2), C12–C13 1.388(2), C13–C14 1.385(2), C1–C2–C3–C4 –121.3(2); 13: C11–C16 1.400(2), C11–C12 1.401(2), C12–C13 1.381(2),
C13–C14 1.386(2), C14–C15 1.386(2), C15–C16 1.384(2), C1–C2–C3–C4 127.2(1); 15, for one of the two different molecules in the unit
cell: C12–C26 1.393(3), C26–C27 1.397(3), C27–C58 1.387(3), C47–C58 1.387(3), C47–C56 1.384(3), C12–C56 1.383(3), C14–C18
1.451(3), C11–C18 1.349(3), C1–C11 1.438(3), C1–C9 1.439(3), C9–C13 1.351(3), C13–C14 1.445(3), C14–C39–C44–C41 71.9(3); 20: C4–
C5 1.400(2), C5–C6 1.371(2), C6–C7 1.399(2), C9–C4 1.396(2), C4–C9 1.396(2), C8–C9 1.374(2), C12–C13 1.399(2), C12–C17 1.400(2),
C13–C14 1.373(2), C14–C15 1.413(2), C15–C16 1.413(2), C16–C17 1.370(2), C1–C2–C3–C31 73.1(2). δr is the quinoid character of the
ring, δr is 0 for benzene and 0.08–0.1 for fully quinoidal rings: δr = {[(a + aЈ) – (b + bЈ)]/2 + [(c + cЈ) – (b + bЈ)]/2}/2.
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Transformations of Polycyanobutadienes
angle in the TCNQ adduct 15 is 72°, in accord with the those of the corresponding N,N-dimethylanilino substrates
value of 57° for the corresponding N,N-dimethylaniline de- 22–25 (Table 3), which reflects the lower donating ability of
rivative.[4a]
the anilino relative to the N,N-dimethylanilino moiety.
Transformation of the anilino into phenyl, p-iodoaryl, or
p-nitroaryl groups uniformly led to the disappearance of the
ICT absorptions, leaving λmax in the range 322–338 nm for
TCNE adducts 8–10 (Figure 2) and 445–448 nm for TCNQ
adducts 15 and 16, respectively (see the Supporting Infor-
mation).
Table 2. X-ray data analysis.
θ [°][a]
δr [Å][b]
4
116.5(2)
106.4(2)
121.3(2)
127.2(1)
71.9(3)
0.034(2)
0.014(2)
0.009(2)
8
9
13
15
20
0.011(2)
0.005(3) [0.097(3) for quinoid ring]
0.035(2) (for both rings in spacer)
73.1(2)
[a] θ = torsional angle between the two dicyanovinyl planes. [b] For
definition, see caption to Figure 1.
We assessed the quinoidal character δr of the aromatic
rings in each crystal structure (see caption to Figure 1 for
definition) to analyze the extent of the ground-state donor–
acceptor interactions for each substrate.[17] Aniline-substi-
tuted intramolecular charge-transfer (ICT) adduct 4 has a
δr value of 0.034(2), which is within the range of values
previously reported for the corresponding dimethylaniline
derivatives.[2b] The expanded push–pull chromophore 20
also exhibits a δr value of 0.035(2) in both rings connecting
the Me2N donor to the TCBD acceptor, indicative of a
ground-state charge-transfer interaction between the donor
and acceptor moieties. Substrates 8, 9, 13, and 15, which
lack electron-donating groups, have δr values of 0.01, which
confirms that they have, as expected, no quinoidal character.
Figure 2. UV/Vis spectra of 4 and 8–10 in CH2Cl2 at 25 °C. See
the Supporting Information for the spectra of other novel PCBDs.
The novel chromophores 18 and 20, which result from
the Sonogashira and Suzuki coupling reactions of aryl iod-
ide 9, were compared with TCBD 22 to investigate how
UV/Vis Spectroscopy
The UV/Vis spectra of the anilino-substituted PCBDs 4– the introduction of the aryl and alkynyl linkers between the
7 feature intramolecular charge-transfer (ICT) absorptions donor and acceptor affects the UV/Vis spectra. The intro-
in CH2Cl2 that are hypsochromically shifted relative to duction of the two different spacers has broadly the same
Table 3. UV/Vis data for ICT compounds in CH2Cl2 at a concentration of 10–5 m.
λmax [nm] (E [eV])
ε [m–1 cm–1]
4
422 (2.94)
519 (2.39)
542 (2.28)
575 (2.16)
508 (2.44)
486 (2.55)
630 (1.97)
470 (2.64)
570 (2.18)
643 (1.93)
676 (1.84)
19500
–
[a]
5
6[2c]
7
3200
26400
13500
13000
19600
23100
9500
18
20
21
22
23[2b]
24[2c]
25[4a]
3200
36300
[a] Low solubility in CH2Cl2 prevented accurate determination of ε.
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F. Diederich et al.
FULL PAPER
effect on the ICT absorption, λmax is bathochromically Table 4. Cyclic voltammetry and rotating disk voltammetry data
recorded in CH2Cl2 + 0.1 m nBu4NPF6.[a]
shifted from 470 nm in 22 to 508 nm in 18 and 486 nm in
20, whereas the molar extinction coefficient ε is reduced
from 23100 to 13500 and 13000 m–1 cm–1, respectively. The
CV
RDV
shift to lower-energy and lower-intensity CT bands upon
incorporation of additional linkers between the electron do-
nor (D) and acceptor (A) in push–pull chromophores is in-
dicative of weaker D–A coupling and has been observed
previously.[18] The UV/Vis spectrum of the double TCNE–
TCNQ adduct 21 features λmax at 630 nm, which is similar
to the position of the CT band in the previously reported
chromophore 25 (λmax = 676 nm),[4a] which indicates that
the main ICT interaction is not significantly affected by the
additional TCBD unit in the molecule.
In line with push–pull chromophores resulting previously
from the CA-RE reaction, the longest-wavelength absorp-
tions originating from ICT disappear completely on pro-
tonation with TFA, to be regenerated upon treatment with
Et3N.[2b] Furthermore, these ICT substrates also exhibit
positive solvatochromism in hexane/CH2Cl2 mixtures.[2b,19]
The most pronounced effect was observed with TCNQ ad-
duct 7, which changed from λmax = 525 nm in 95:5 hexane/
CH2Cl2 to λmax = 575 nm in CH2Cl2, whereas the TCNE
adducts 4, 5, 18, 20, and 22 exhibited shifts in λmax in the
range of 11–31 nm in the same solvents (see the Supporting
Information).
E° [V][b] ΔEp [mV][c] Ep [V][d] E1/2 [V][e] Slope [mV][f]
4
+1.09 +1.05 (1e–)
–0.87 (1e–)
–1.27 (1e–)
+1.05 +1.03 (1e–)
–0.64 (1e–)
–1.32 (1e–)
+1.14
60
90
80
60
60
–0.85
–1.20
100
100
5
–0.64
–1.25
100
110
100
6[g]
–0.27
–0.86
100
100
–0.27 (1e–)
–0.86 (1e–)
+0.50 +0.52 (1e–)
–0.66 (1e–)
–0.81 (1e–)
–0.76 (1e–)
–1.22 (1e–)
–0.67 (1e–)
–1.12 (1e–)
–0.55 (1e–)
–1.01 (1e–)
–1.76 (1e–)
–0.49 (1e–)
–1.26 (1e–)
–0.49 (1e–)
–1.18 (1e–)
–0.16 (1e–)
–0.85 (1e–)
–0.07 (1e–)
–0.75 (1e–)
–0.56 (1e–)
–0.70 (1e–)
–0.55 (1e–)
–0.69 (1e–)
+0.50 (1e–)
–0.77 (1e–)
–1.15 (1e–)
+0.50 +0.48 (1e–)
–0.67 (1e–)
–1.10 (1e–)
+0.45 +0.46 (1e–)
–0.54 (1e–)
–0.68 (1e–)
–0.84 (1e–)
–1.20 (1e–)
+0.91 (1e–)
–0.90 (1e–)
–1.19 (1e–)
+0.87 (1e–)
–0.70 (1e–)
–1.38 (1e–)
+1.00 (1e–)
–0.30 (1e–)
–0.85 (1e–)
+0.42 +0.42 (1e–)
–0.67 (1e–)
–0.81 (1e–)
60
65
60
65
70
70
75
60
60
60
70
65
60
100
60
70
60
75
60
70
60
70
60
60
60
65
60
50
60
60
50
60
60
60
100
60
60
65
70
70
140
65
65
100
50
60
60
7
–0.65
–0.78
–0.74
–1.18
–0.65
–1.10
–0.55
–0.99
–1.71
–0.51
–1.20
–0.47
–1.14
–0.16
–0.81
–0.07
–0.74
–0.54
–0.68
–0.53
–0.67
+0.48
–0.75
–1.15
80
80
125
140
70
70
60
75
70
60
100
80
90
80
95
60
70
70
65
70
70
60
65
60
8
9
10
11
12
13
14
15
16
18
Electrochemistry
The redox potentials of substrates 4–16, 18, and 20–22
were measured by cyclic voltammetry (CV) and rotating
disk voltammetry (RDV) against the ferricinium/ferrocene
couple in CH2Cl2 with 0.1 m nBu4NPF6 as the electrolyte
(Table 4). All of the substrates studied gave well-resolved,
reversible, one-electron reductions for each dicyanovinyl
moiety, and 10 also exhibited a reversible reduction cen-
tered on the nitro group. For the first time, we were able to
systematically assess the influence of the electronic charac-
ter of the substituents on the reduction potentials of aryl-
ated PCBDs (Figure 3) and, as expected, there is a strong
positive correlation between the first reduction potential
and the Hammett value of the para substituent σp.[20] This
delivers a 0.34 V anodic shift in the first reduction potential
on moving from N,N-dimethylaniline-substituted TCBD 22
to nitro derivative 10. There is also a weaker positive corre-
lation for the second reduction potentials (see the Support-
ing Information).
20
21
–0.67
–1.09
70
80
–0.55
–0.69
–0.85
–1.20
+0.92
–0.89
–1.22
60
60
60
70
70
70
80
80
80
80
90
90
100
22
23[h] +0.86
–0.69
–1.26
24[g] +1.00
–0.30
–0.85
25[i]
However, it is clear that the identity of the alkyne, and
the cyanoolefin with which it reacts, is also of great impor-
tance in determining the reduction potentials of the result-
ant PCBDs. In line with previous observations, the first re-
–0.68
–0.82
70
70
[a] CV scan rate, ν = 0.1 Vs–1. All potentials are given vs. the fer-
ductions of all the TCBD derivatives were shifted to more ricinium/ferrocene couple used as an internal standard. [b] E° =
(Epc + Epa)/2, in which Epc and Epa correspond to the cathodic and
anodic peak potentials, respectively. [c] ΔEp = Eox – Ered. [d] Ep =
irreversible peak potential. [e] E1/2 = half-wave potential. [f] Loga-
positive potentials by 0.18–0.23 V when the starting mate-
rial for their synthesis was varied from internal diarylalkyne
1 to terminal alkyne 2.[2b] The anodic shift of penta-
rithmic analysis of the wave obtained by plotting E vs. log[I/(Ilim
–
I)]. [g] Data taken from ref.[2c] [h] Data taken from ref.[2b] [i] Data
cyanobutadienes 6, 13, and 14, which result from the CA-
RE of cyanoalkyne 3 and subsequent derivatization, was
taken from ref.[4a]
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Transformations of Polycyanobutadienes
Figure 3. Relationship between the first reduction potential and the Hammett constant of the para substituent for different classes of
PCBDs. The lines given are lines of best fit as calculated by Microsoft Excel. σp(NMe2) = –0.83, σp(NH2) = –0.66, σp(H) = 0.00, σp(I) =
0.17, and σp(NO2) = 0.78.
uniformly shifted by 0.6 V relative to the corresponding
Conclusions
TCBDs arising from the reactions of internal alkyne 1.[2c]
We have developed protocols that allow, for the first time,
the systematic chemical modification of the products of the
Furthermore, changing from the TCNE to TCNQ adducts
(compare 4, 8, 9, and 22 with 7, 15, 16, and 25), also leads
CA-RE reaction. We then applied this methodology to the
to a shift to more positive potentials of 0.12–0.21 V for the
synthesis of a series of PCBDs not substituted with elec-
tron-donating groups. The properties of this novel class of
substrates were investigated by X-ray diffraction, UV/Vis
spectroscopy, and electrochemical methods. We observed an
inverse correlation between the strength of the donor sub-
stituent and the reduction potentials of the substrates,
which points the way towards the future design of even
more powerful electron acceptors.
Furthermore, we have been able to demonstrate that aryl
iodide derivatives provide a flexible platform for the further
derivatization of PCBDs, allowing the synthesis of pre-
viously inaccessible push–pull chromophores. The current
focus of our research is the development of further reaction
conditions compatible with the PCBD cores, and the appli-
cation of these in the synthesis of complex molecular archi-
tectures.
first reduction.[4a] Different trends are apparent in the sec-
ond reduction potentials, in which the substrates derived
from terminal alkynes 5, 11, and 12 exhibit the cathodically
most shifted reduction potentials in the range –1.14 to
–1.25 V, whereas the TCNQ adducts 7, 15, and 16, which
are able to more effectively separate the two charges, are
the anodically most shifted in the range –0.67 to –0.78 V.
In the series 18 and 20–22, the first reduction potentials
are shifted from –0.89 V in the parent compound 22, to
–0.75 and –0.67 upon insertion of the aryl (18) and aryl-
ethynyl (20) spacers, respectively. This anodic shift corrobo-
rates earlier findings in suggesting that the extra linkers act
to insulate the donor moiety from the acceptor, leading to
a more electron-deficient, easily reduced acceptor.[2b,18]
Only the aniline or dimethylaniline derivatives exhibit
oxidations: aniline TCNE adducts 4–6 give single-electron
irreversible oxidations in the range +1.14 to +1.05 V,
whereas the TCNQ adducts 7 and 21 are oxidized irrevers-
ibly at +0.50 and +0.45 V, respectively. In the series of novel
chromophores assembled with cross-coupling chemistry,
parent dimethylaniline 22 undergoes a reversible single-elec-
tron transfer at +0.92 V, whereas oxidation occurs at +0.48
and +0.50 V for homologated derivatives 18 and 20, respec-
tively. These observations reinforce the previous conclusions
that weaker donor–acceptor coupling accompanies the in-
corporation of the aryl and arylethynyl linkers into the mo-
lecules.[18]
Experimental Section
General: The procedures for the synthesis of 4, 5, and 7–22 are
reported herein. 4-Ethynylaniline 2 is commercially available, and
4-(phenylethynyl)aniline (1),[21] 3-(4-aminophenyl)buta-1,3-diene-
1,1,2,4,4-pentacarbonitrile (6),[2c] and N,N-dimethyl-4-(phenyl-
ethynyl)aniline[22] were prepared according to literature procedures.
All other details can be found in the Supporting Information.
General Procedure (GP A) for the CA-RE Reaction with TCNE:
Alkynylaniline and TCNE (1 equiv.) were dissolved in MeCN
Eur. J. Org. Chem. 2013, 869–879
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875

F. Diederich et al.
FULL PAPER
(30 mL/mmol), and the resulting dark-red solution was stirred at
25 °C under Ar until TLC analysis indicated complete consump-
tion of the starting material. The solvent was removed in a rotary
evaporator under reduced pressure (in vacuo) and the residue puri-
fied by flash column chromatography (FC) on SiO2.
(400 MHz, CD2Cl2): δ = 4.44 (s, 2 H), 6.70 (d, J = 8.8 Hz, 2 H),
7.07 (dd, J = 9.7, 2.0 Hz, 1 H), 7.15–7.24 (m, 3 H), 7.28 (dd, J =
9.7, 2.0 Hz, 1 H), 7.45–7.52 (m, 3 H), 7.53–7.61 (m, 1 H), 7.60–
7.68 (m, 2 H) ppm. 13C NMR (101 MHz, CD2Cl2): δ = 74.18,
87.68, 112.34, 112.91, 114.12, 114.16, 114.88, 124.82, 125.43,
125.72, 129.49, 129.56, 132.95, 133.37, 134.23, 134.41, 134.60,
General Procedure (GP B) for the CA-RE Reaction with TCNQ:
Alkynylaniline and TCNQ (1 equiv.) were dissolved in MeCN
(30 mL/mmol), and the resulting dark-green solution was stirred at
the given temperature under Ar. Workup was carried out as in Ge-
neral Procedure A.
135.67, 150.97, 151.52, 154.11, 172.11 ppm. IR (neat): ν = 3353
˜
(w), 2200 (m), 1619 (w), 1580 (s), 1523 (m), 1445 (m), 1375 (m),
1323 (s), 1294 (s), 1255 (m), 1170 (s), 878 (m), 832 (s), 812 (s) cm–1.
UV/Vis (CH2Cl2): λmax (ε) = 317 (19600), 422 (13000), 575 nm
(26400 m–1 cm–1). HRMS (ESI): calcd. for C26H16N5+ 398.1400; m/z
(%) = 398.1406 (100) [MH]+. C26H15N5·CH2Cl2 (482.09): calcd. C
67.23, H 3.55, N 14.52; found C 67.33, H 3.73, N 14.27.
General Procedure (GP C) for the Transformation of Aniline Moie-
ties into Phenyl Derivatives: A solution of the aniline derivative and
tert-butyl nitrite (2 equiv.) in THF (10 mL/mmol) was heated at
60 °C under Ar. TLC analysis indicated that the reaction is nor-
mally complete within 1 h. The reaction was quenched by addition
of 1 m Na2S2O3 solution (10 mL/mmol) and the mixture extracted
with CH2Cl2 (3ϫ10 mL/mmol). The combined organic layers were
dried with Na2SO4, filtered, and the solvents removed in vacuo,
before purification by FC on SiO2.
8: A 2 m solution of sodium nitrite (0.64 mL, 1.28 mmol) was
added dropwise to a solution of 4 (200 mg, 0.624 mmol) in 50%
aqueous H2SO4 (44 mL), while maintaining the temperature at
0 °C. After stirring at 0 °C for 1 h, a 50% aqueous solution of
H3PO2 (0.572 mL, 5.93 mmol) was added dropwise, and the re-
sulting yellow solution was warmed to 25 °C and stirred for 18 h,
before being neutralized by the dropwise addition of a saturated
solution of NaHCO3. The resulting brown, heterogeneous mixture
was extracted with CH2Cl2 (3ϫ30 mL), and the combined organic
layers were separated, dried with Na2SO4, and filtered. The solvent
was removed in vacuo and FC (SiO2; hexane/CH2Cl2, 1:1 Ǟ
CH2Cl2) provided 8 as a cream solid (91 mg, 0.297 mmol, 48%).[9a]
Rf = 0.2 (SiO2, CH2Cl2). M.p. 232–235 °C. 1H NMR (400 MHz,
CDCl3): δ = 7.54–7.62 (m, 4 H), 7.64–7.72 (m, 6 H) ppm. 13C NMR
(101 MHz, CDCl3): δ = 87.86, 111.02, 111.46, 129.27, 130.14,
General Procedure (GP D) for the Transformation of Anilines into
Iodoaryl Derivatives: A solution of the aniline derivative in MeCN
(5 mL/mmol) was added to
a solution of tert-butyl nitrite
(1.5 equiv.) and iodine (3 equiv.) in MeCN (10 mL/mmol), and the
mixture was stirred at 25 °C under Ar. TLC analysis indicated that
the reaction was normally complete within 3 h. The reaction was
quenched by addition of a 1 m Na2S2O3 solution (10 mL/mmol)
and the mixture extracted with CH2Cl2 (3ϫ10 mL/mmol). The
combined organic layers were dried with Na2SO4, filtered, and the
solvents removed in vacuo before purification by FC on SiO2.
131.01, 134.69, 167.13 ppm. IR (neat): ν = 3057 (w), 2207 (s), 1602
˜
(m), 1539 (m), 1480 (w), 1420 (s), 1348 (w), 1312 (m), 1280 (m),
1247 (m), 1181 (s), 1093 (w), 1079 (m), 1027 (w), 998 (m), 914
(w), 835 (s), 808 (m) cm–1. UV/Vis (CH2Cl2): λmax (ε) = 322 nm
(13200 m–1 cm–1). HRMS (MALDI-TOF, 3-HPA): calcd. for
4: 4-(Phenylethynyl)aniline (1;[21] 1.11 g, 5.73 mmol) was treated ac-
cording to GP A. Purification by FC (SiO2; CH2Cl2 Ǟ CH2Cl2/
MeCN, 97:3) gave 4 as a red solid (1.44 g, 4.48 mmol, 78%). Rf =
0.2 (SiO2, CH2Cl2). M.p. 219–222 °C. 1H NMR (400 MHz,
CD3CN): δ = 5.64 (s, 2 H), 6.76 (d, J = 9.0 Hz, 2 H), 7.64–7.57
(m, 2 H), 7.73–7.67 (m, 1 H), 7.74 (d, J = 9.0 Hz, 2 H), 7.84–7.78
(m, 2 H) ppm. 13C NMR (101 MHz, CD3CN): δ = 75.92, 88.28,
111.77, 112.28, 113.60, 114.19, 114.28, 118.31, 129.45, 129.68,
+
C20H10N4 306.0900; m/z (%) = 306.0899 (1) [M]+, 233.0557 (100).
9: A 2 m solution of sodium nitrite (3.31 mL, 6.62 mmol) was
added dropwise to a solution of 4 (1.00 g, 3.12 mmol) in 50% aque-
ous H2SO4 (218 mL), while maintaining the temperature at 0 °C.
The resulting solution was stirred at 0 °C for 1 h before the addition
of urea (210 mg, 3.50 mmol) in a single portion. The yellow solu-
tion was added dropwise, through a cannula, to a solution of KI
(2.63 g, 15.8 mmol) in H2O (218 mL), while maintaining the tem-
perature of both solutions at 0 °C. The resulting brown, hetero-
geneous mixture was stirred at 0 °C for 3 h before extraction with
CH2Cl2 (3ϫ150 mL). A 1 m solution of Na2S2O3 (30 mL) was
added to the combined organic layers, which were subsequently
separated, dried with Na2SO4, and filtered. The solvent was re-
moved in vacuo, and FC (SiO2; hexane/CH2Cl2, 1:1 Ǟ CH2Cl2)
gave 9 as a yellow solid (990 mg, 2.30 mmol, 74%).[9b] Rf = 0.76
131.94, 133.14, 134.22, 155.43, 163.96, 168.66 ppm. IR (neat): ν =
˜
3482 (w), 3380 (m), 2219 (s), 1626 (s), 1602 (s), 1543 (m), 1525 (w),
1488 (s), 1451 (s), 1337 (s), 1301 (m), 1259 (s), 1198 (m), 1182 (s),
1028 (w), 999 (m), 965 (m), 882 (m), 834 (s) cm–1. UV/Vis (CH2Cl2):
λmax (ε) = 328 (13400), 422 nm (19500 m–1 cm–1). HRMS (ESI):
+
calcd. for C20H12N5 322.1087; m/z (%) = 322.1089 (2) [MH]+,
217.1190 (100). C20H11N5 (321.1014): calcd. C 74.76, H 3.45, N
21.79; found C 74.80, H 3.60, N 21.63.
5: Compound 2 (109 mg, 0.85 mmol) was treated according to
GP A. FC (SiO2; CH2Cl2 Ǟ CH2Cl2/MeCN, 97:3) gave 5 as a dark-
purple solid (130 mg, 0.53 mmol, 62%). Rf = 0.17 (SiO2, CH2Cl2).
M.p. 185–189 °C. 1H NMR (400 MHz, CD3CN): δ = 5.41 (s, 2 H),
6.78 (d, J = 8.9 Hz, 2 H), 7.49 (d, J = 8.9 Hz, 2 H), 8.25 (s, 1 H)
ppm. 13C NMR (101 MHz, CD3CN): δ = 80.42, 96.86, 109.76,
112.08, 112.97, 113.85, 114.04, 119.00, 132.69, 154.59, 157.29,
1
(SiO2, CH2Cl2). M.p. 195–198 °C. H NMR (400 MHz, CD3CN):
δ = 7.51 (d, J = 8.8 Hz, 2 H), 7.57–7.64 (m, 2 H), 7.66–7.73 (m, 1
H), 7.74–7.80 (m, 2 H), 7.98 (d, J = 8.8 Hz, 2 H) ppm. 13C NMR
(101 MHz, CD3CN): δ = 89.59, 89.67, 101.70, 111.46, 111.51,
111.85, 111.95, 129.58, 129.81, 130.78, 130.86, 131.28, 134.33,
139.07, 165.41, 165.88 ppm. IR (neat): ν = 2230 (m), 1594 (w), 1577
˜
160.99 ppm. IR (neat): ν = 3473 (w), 3353 (m), 3028 (m), 2214 (s),
˜
(s), 1557 (m), 1482 (m), 1445 (m), 1397 (m), 1328 (w), 1305 (w),
1270 (w), 1247 (m), 1183 (m), 1062 (m), 1003 (s), 956 (w), 932 (w),
881 (w), 831 (s), 824 (m) cm–1. UV/Vis (CH2Cl2); λmax (ε) = 338 nm
1623 (s), 1607 (s), 1484 (s), 1452 (s), 1354 (s), 1338 (s), 1289 (s),
1179 (s), 993 (w), 826 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε) = 308
(15800), 435 (5280), 519 nm (5700 m–1 cm–1).[23] HRMS (EI): calcd.
(13700 m–1 cm–1). HRMS (ESI): calcd. for C20H10IN4 432.9945;
+
+
for C14H7N5 245.0701; m/z (%) = 245.0696 (100) [M]+.
m/z (%) = 432.9949 (100) [MH]+. C20H9IN4 (431.99): calcd. C
55.58, H 2.10, N 12.96, I 29.36; found C 55.82, H 2.29, N 12.86, I
29.12.
7: 4-(Phenylethynyl)aniline (1; 300 mg, 1.55 mmol) was treated ac-
cording to GP B at 80 °C for 5 h. FC (SiO2; CH2Cl2 Ǟ CH2Cl2/
MeCN 97:3) afforded 7 as a blue-black solid (521 mg, 1.31 mmol,
10: NaBO3·4H2O (120 mg, 0.78 mmol) was added in a single por-
85%). Rf = 0.1 (SiO2, CH2Cl2). M.p. 130–132 °C. 1H NMR tion to a suspension of 4 (50 mg, 0.156 mmol) in glacial acetic acid
876
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 869–879

Transformations of Polycyanobutadienes
(2 mL). The mixture was heated at 60 °C under Ar for 5 h before
cooling to 25 °C. A further loading of NaBO3·4H2O (120 mg,
0.78 mmol) was added and the mixture heated at 60 °C under Ar
for 5 h, by which time the solution had become light-yellow. The
reaction was quenched by the addition of a 1 m Na2S2O3 solution
(2 mL), and the resulting mixture was extracted with CH2Cl2
(3ϫ10 mL). The combined organic layers were dried with Na2SO4
and filtered. The solvents were removed in vacuo, and FC (SiO2;
hexane/CH2Cl2, 1:1 Ǟ CH2Cl2) afforded 10 as a cream solid
(25 mg, 0.071 mmol, 46%).[10] Rf = 0.83 (SiO2, CH2Cl2). M.p. 168–
170 °C. 1H NMR (400 MHz, C6D6): δ = 6.72 (d, J = 8.9 Hz, 2 H),
6.78–6.85 (m, 2 H), 6.85–6.91 (m, 1 H), 6.97–7.02 (m, 2 H), 7.39
(d, J = 8.9 Hz, 2 H) ppm. 13C NMR (101 MHz, C6D6): δ = 88.82,
91.43, 110.47, 110.64, 111.00, 111.21, 124.23, 128.74, 129.40,
129.61, 130.49, 133.98, 135.44, 149.62, 164.04, 164.95 ppm. IR
(CH2Cl2); λmax (ε) = 376 nm (3820 m–1 cm–1). HRMS (EI): calcd.
for C15H5N5 255.0545; m/z (%) = 255.0540 (100) [M]+.
+
14: Compound 6 (100 mg, 0.37 mmol) was treated according to
GP D using 0.5 equiv. of I2. Instead of being subjected to an aque-
ous workup, the solvent was removed in a stream of N2. Purifica-
tion by preparative recycling GPC using a JAIGEL-1H column
(Japan Analytics Industries Co. Ltd.), eluting with CHCl3 at
4 mLmin–1, gave 14 as a yellow foam (44 mg, 0.12 mmol, 31%). Rf
not determined due to rapid decomposition on silica and alumina.
1H NMR (400 MHz, CDCl3): δ = 7.33 (d, J = 8.8 Hz, 2 H), 8.04
(d, J = 8.8 Hz, 2 H) ppm. 13C NMR (101 MHz, CDCl3): δ = 90.85,
104.67, 105.63, 107.85, 108.58, 110.10, 110.27, 110.31, 128.22,
130.04, 135.81, 140.06, 156.89 ppm. IR (neat): ν = 2924 (w), 2232
˜
(w), 1577 (s), 1536 (m), 1482 (m), 1397 (s), 1322 (m), 1299 (m),
1262 (w), 1187 (m), 1138 (w), 1062 (s), 1005 (s), 895 (w), 830 (s)
cm–1. UV/Vis (CH2Cl2): λmax (ε) = 374 nm (3840 m–1 cm–1). HRMS
(neat): ν = 3109 (w), 2924 (w), 2231 (m), 1602 (m), 1523 (s), 1445
˜
(m), 1406 (w), 1348 (s), 1327 (s), 1254 (m), 1181 (s), 1108 (m), 1012
+
(EI): calcd. for C15H4IN4 380.9511; m/z (%) = 380.9506 (92)
(m), 1000 (m), 861 (s), 846 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε)
[M]+, 254.0464 (100).
+
= 338 nm (12500 m–1 cm–1). HRMS (ESI): calcd. for C20H10N5O2
352.0829; m/z (%) = 352.0838 (100) [MH]+.
15: Compound 7 (40 mg, 0.100 mmol) was treated according to
GP C and purified by FC (SiO2; hexane/CH2Cl2, 1:1 Ǟ CH2Cl2)
to give 15 as a dark-red solid (18 mg, 0.046 mmol, 47%). Rf = 0.51
11: Compound 5 (100 mg, 0.408 mmol) was treated according to
GP C, and FC (SiO2; hexane/CH2Cl2, 1:1 Ǟ CH2Cl2) delivered 11
as a pale-yellow solid (40 mg, 0.173 mmol, 42%). Rf = 0.55 (SiO2,
CH2Cl2). M.p. 141–143 °C. 1H NMR (400 MHz, CDCl3): δ = 7.42
(d, J = 7.0 Hz, 2 H), 7.59–7.66 (m, 2 H), 7.72 (ddt, J = 8.4, 7.0,
1.3 Hz, 1 H), 8.02 (s, 1 H) ppm. 13C NMR (101 MHz, CDCl3): δ =
93.31, 98.14, 108.12, 110.51, 110.98, 111.73, 128.79, 129.77, 130.24,
1
(SiO2, CH2Cl2). M.p. 115–117 °C. H NMR (400 MHz, CD2Cl2):
δ = 7.19 (dd, J = 10.0, 1.9 Hz, 1 H), 7.26–7.33 (m, 4 H), 7.33–7.38
(m, 1 H), 7.40–7.51 (m, 5 H), 7.53–7.62 (m, 3 H) ppm. 13C NMR
(101 MHz, CD2Cl2): δ = 78.66, 87.33, 112.40, 112.58, 113.22,
126.84, 126.93, 129.24, 129.49, 129.56, 131.00, 131.24, 133.50,
133.59, 133.88, 134.63, 134.84, 134.89, 149.77, 153.81, 171.09 ppm
(one carbon signal missing as a signal of two CN groups is present
133.92, 151.45, 162.33 ppm. IR (neat): ν = 3046 (m), 2922 (w), 2233
˜
(m), 1574 (w), 1542 (s), 1487 (m), 1445 (s), 1351 (m), 1330 (w),
1317 (w), 1179 (w), 1160 (w), 1074 (w), 1027 (w), 939 (w), 921 (s),
888 (w) cm–1. UV/Vis (CH2Cl2): λmax (ε) = 357 nm (4290 m–1 cm–1).
at δ = 113.22). IR (neat): ν = 2922 (w), 2213 (s), 1979 (s), 1605 (m),
˜
1573 (m), 1535 (m), 1482 (s), 1443 (s), 1387 (m), 1345 (m), 1321
(m), 1273 (m), 1187 (s), 1073 (m), 1059 (m), 1029 (s), 1003 (m), 905
+
HRMS (EI): calcd. for C14H6N4 230.0592; m/z (%) = 230.0587
(s), 834 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε)
= 445 nm
(100) [M]+.
(23500 m–1 cm–1). HRMS (MALDI-TOF, 3-HPA): calcd. for
C26H14N4 382.1213; m/z (%) = 382.1214 (1) [M]+, 242.0754 (100).
+
12: Compound 5 (100 mg, 0.408 mmol) was treated according to
GP D, and FC (SiO2; hexane/CH2Cl2, 1:1 Ǟ CH2Cl2) gave 12 as a
pale-yellow solid (62 mg, 0.175 mmol, 43%). Rf = 0.56 (SiO2,
CH2Cl2). M.p. 195–199 °C. 1H NMR (400 MHz, CDCl3): δ = 7.14
(d, J = 8.5 Hz, 2 H), 7.98 (s, 1 H), 7.99 (d, J = 8.5 Hz, 2 H) ppm.
13C NMR (101 MHz, CDCl3): δ = 93.35, 98.25, 101.73, 108.24,
110.39, 110.88, 111.55, 128.93, 129.89, 139.60, 150.98, 161.30 ppm.
16: Compound 7 (62 mg, 0.156 mmol) was added to a solution of
p-toluenesulfonic acid monohydrate (88 mg, 0.468 mmol) in MeCN
(1 mL), and the resulting suspension of amine salt was cooled to
10 °C. A solution of NaNO2 (22 mg, 0.312 mmol) and KI (65 mg,
0.39 mmol) in H2O (0.3 mL) was gradually added. The mixture was
stirred at this temperature for 10 min, allowed to warm to 25 °C,
and stirred for a further 30 min. A 1 m Na2S2O3 solution (5 mL)
was added and the resulting mixture extracted with CH2Cl2
(3ϫ10 mL). The combined organic layers were dried with Na2SO4
and filtered. The solvents were removed in vacuo, and FC (SiO2;
hexane/CH2Cl2, 1:1 Ǟ CH2Cl2) gave 16 as a dark-red film (49 mg,
0.096 mmol, 62%).[13b] Rf = 0.49 (SiO2, CH2Cl2). 1H NMR
(400 MHz, CDCl3): δ = 6.98 (d, J = 8.5 Hz, 2 H), 7.13 (d, J =
10.4 Hz, 1 H), 7.29–7.37 (m, 3 H), 7.45–7.54 (m, 2 H), 7.55–7.64
(m, 3 H), 7.78 (d, J = 8.5 Hz, 2 H) ppm. 13C NMR (101 MHz,
CDCl3): δ = 79.59, 87.29, 98.68, 112.20, 112.30, 112.99, 113.02,
127.29, 127.33, 129.42, 129.89, 132.06, 133.22, 133.51, 133.92,
133.96, 134.21, 134.85, 138.72, 148.23, 153.54, 170.57 ppm. IR
IR (neat): ν = 3046 (m), 2922 (w), 2853 (w), 2233 (m), 1918 (w),
˜
1660 (w), 1584 (s), 1540 (s), 1481 (m), 1392 (s), 1360 (w), 1335 (w),
1304 (w), 1263 (w), 1185 (w), 1153 (w), 1112 (s), 1059 (m), 1007
(s), 935 (s), 838 (w), 823 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε) =
+
374 nm (4590 m–1 cm–1). HRMS (EI): calcd. for C14H5IN4
355.9559; m/z (%) = 355.9554 (100) [M]+. C14H5IN4 (355.96): calcd.
C 47.22, H 1.42, N 15.73, I 35.63; found C 47.07, H 1.61, N 15.51,
I 35.58.
13: Compound 6 (25 mg, 0.093 mmol) was treated according to
GP C. Instead of being subjected to an aqueous workup, the sol-
vent was removed in a stream of N2. Purification by preparative
recycling GPC using a JAIGEL-1H column (Japan Analytics In-
dustries Co. Ltd.), eluting with CHCl3 at 4 mLmin–1, gave 13 as a
yellow solid (13 mg, 0.051 mmol, 55%). Rf not determined due to
rapid decomposition on silica and alumina. M.p. 130–132 °C. 1H
NMR (400 MHz, CDCl3): δ = 7.60–7.65 (m, 2 H), 7.65–7.73 (m, 2
H), 7.76–7.83 (m, 1 H) ppm. 13C NMR (101 MHz, CDCl3): δ =
90.80, 105.36, 107.86, 108.68, 110.17, 110.35, 110.39, 129.13,
(neat): ν = 3057 (w), 2207 (s), 1602 (m), 1532 (m), 1480 (w), 1420
˜
(s), 1348 (w), 1265 (w), 1229 (w), 1181 (s), 1093 (w), 1079 (m), 1026
(m), 999 (m), 976 (w), 913 (w), 835 (m), 808 (m) cm–1. UV/Vis
(CH2Cl2): λmax (ε) = 309 (13300), 449 nm (24000 m–1 cm–1). HRMS
–
(MALDI-TOF, 3-HPA): calcd. for C26H13IN4 508.0190; m/z (%)
= 508.0185 (100) [M]–.
129.35, 130.64, 135.78, 136.38, 157.85 ppm. IR (neat): ν = 2235
18: A 1:1 mixture of benzene/water (10 mL) was deoxygenated by
bubbling Ar through the solution for 20 min, and the air in a two-
necked flask fitted with a condenser containing 9 (125 mg,
0.290 mmol), [4-(dimethylamino)phenyl]boronic acid (17; 96 mg,
˜
(m), 1593 (w), 1577 (m), 1562 (m), 1541 (s), 1490 (w), 1445 (s),
1327 (m), 1314 (m), 1235 (w), 1189 (s), 1139 (m), 1105 (w), 1080
(w), 999 (m), 933 (w), 897 (w), 846 (w), 801 (w) cm–1. UV/Vis
Eur. J. Org. Chem. 2013, 869–879
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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877

F. Diederich et al.
FULL PAPER
0.58 mmol), Na2CO3 (62 mg, 0.58 mmol), and [Pd(PPh3)4] (10 mg,
0.009 mmol) was exchanged with Ar by performing three evacua-
tion/refilling cycles. The purged benzene/water mixture was trans-
ferred, through a syringe, to the two-necked flask, and the resulting
mixture was heated at 90 °C for 12 h. The mixture was extracted
with CH2Cl2 (3ϫ10 mL/mmol), and the combined organic layers
were dried with Na2SO4 and filtered. The solvents were removed
in vacuo, and FC (SiO2; hexane/CH2Cl2, 1:1 Ǟ CH2Cl2) gave 18
as a dark-red solid (85 mg, 0.20 mmol, 69%).[15a] Rf = 0.39 (SiO2,
(38300), 630 nm (19600 m–1 cm–1). HRMS (MALDI-TOF, DCTB):
calcd. for C42H23N9 653.2071; m/z (%) = 653.2073 (100) [M]+.
+
22:
N,N-Dimethyl-4-(phenylethynyl)aniline[22]
(150 mg,
0.679 mmol) was treated according to GP A, and FC (SiO2; hex-
ane/CH2Cl2, 1:1 Ǟ CH2Cl2) gave 22 as a dark-red solid (220 mg,
0.630 mmol, 93%). Rf = 0.46 (SiO2, CH2Cl2). M.p. 214–217 °C. 1H
NMR (400 MHz, CDCl3): δ = 3.17 (s, 6 H), 6.74 (d, J = 9.4 Hz, 2
H), 7.54 (d, J = 8.0 Hz, 2 H), 7.62 (m, 1 H), 7.70–7.76 (m, 2 H),
7.79 (d, J = 9.4 Hz, 2 H) ppm. 13C NMR (101 MHz, CDCl3): δ =
40.20, 74.28, 87.21, 111.31, 112.05, 112.28, 113.38, 114.30, 117.93,
129.48, 129.76, 131.94, 132.53, 134.29, 154.46, 163.22, 169.34 ppm.
1
hexanes/ethyl acetate, 7:3). M.p. 171–175 °C. H NMR (400 MHz,
CDCl3): δ = 3.05 (s, 6 H), 6.79 (d, J = 9.0 Hz, 2 H), 7.54–7.62 (m,
4 H), 7.64–7.70 (m, 1 H), 7.70–7.78 (m, 4 H), 7.79 (d, J = 8.8 Hz,
2 H) ppm. 13C NMR (101 MHz, CDCl3): δ = 40.24, 83.65, 87.66,
111.16, 111.72, 111.83, 112.41, 112.45, 125.06, 126.67, 127.66,
128.18, 129.39, 130.04, 130.29, 131.40, 134.61, 147.95, 151.28,
IR (neat): ν = 2925 (w), 2229 (w), 2209 (s), 1605 (s), 1577 (w), 1550
˜
(m), 1477 (s), 1434 (s), 1387 (s), 1353 (s), 1304 (m), 1290 (m), 1265
(m), 1232 (w), 1212 (s), 1174 (s), 1062 (m), 1031 (m), 999 (m), 942
(m), 904 (m), 842 (w), 819 (s), 804 (m) cm–1. UV/Vis (CH2Cl2):
λmax (ε) = 312 (13000), 420 (13600, sh), 470 nm (23100 m–1 cm–1).
165.79, 167.89 ppm. IR (neat): ν = 2920 (w), 2224 (m), 1615 (w),
˜
1590 (s), 1538 (s), 1520 (s), 1500 (s), 1444 (s), 1367 (s), 1294 (s),
1255 (m), 1234 (m), 1212 (s), 1170 (s), 1060 (m), 999 (m), 946 (m),
906 (w), 848 (m), 812 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε) = 508 nm
(13500 m–1 cm–1). HRMS (ESI): calcd. for C28H20N5+ 426.1713; m/z
(%) = 426.1075 (100) [MH]+.
+
HRMS (ESI): calcd. for C22H16N5 350.1400; m/z (%) = 350.1406
(100) [MH]+. C22H15N5 (349.13): calcd. C 75.63, H 4.33, N 20.04;
found C 75.50, H 4.47, N 19.92.
Supporting Information (see footnote on the first page of this arti-
cle): Materials and general methods, UV/Vis, electrochemical, com-
putational, and X-ray diffraction data, and 1H and 13C NMR spec-
tra for all new compounds.
20: Toluene (15 mL) was deoxygenated by bubbling Ar through the
solution for 20 min, and the air in a Schlenk tube containing 9
(125 mg, 0.289 mmol), 4-ethynyl-N,N-dimethylaniline (19; 43.6 mg,
0.301 mmol), P(2-furyl)3 (8.1 mg, 0.035 mmol), CuI (3.3 mg,
0.017 mmol), and PdCl2 (3.0 mg, 0.017 mmol) was exchanged with
Ar by performing three evacuation/refilling cycles. The toluene was
transferred, through a syringe, to the Schlenk tube, and diisoprop-
ylamine (34.2 μL, 0.347 mmol) was added. The solution was heated
at 50 °C for 3 h (TLC analysis) and the mixture extracted with
CH2Cl2 (3ϫ20 mL/mmol). The combined organic layers were
dried with Na2SO4, filtered, and the solvents removed in vacuo
before FC (SiO2; hexane/CH2Cl2, 1:1 Ǟ CH2Cl2) delivered 20 as a
dark-green solid (104 mg, 0.231 mmol, 80%).[15b] Rf = 0.47 (SiO2,
Acknowledgments
The work at the Eidgenössische Technische Hochschule (ETH) was
supported by the European Commission through an ERC Ad-
vanced Grant (No. 246637; OPTELOMAC). The authors are grate-
ful for access to the Brutus computer cluster (ETH).
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1
hexanes/ethyl acetate, 7:3). M.p. 189–191 °C. H NMR (400 MHz,
CDCl3): δ = 3.03 (s, 6 H), 6.66 (d, J = 8.9 Hz, 2 H), 7.43 (d, J =
8.9 Hz, 2 H), 7.54–7.63 (m, 4 H), 7.64–7.71 (m, 5 H) ppm. 13C
NMR (101 MHz, CDCl3): δ = 40.13, 85.72, 87.33, 87.90, 99.01,
108.23, 111.03, 111.41, 111.55, 111.70, 111.87, 128.83, 129.31,
129.41, 130.11, 131.20, 131.89, 132.27, 133.44, 134.69, 150.85,
165.72, 167.31 ppm. IR (neat): ν = 3061 (w), 2202 (s), 2164 (w),
˜
1592 (s), 1531 (m), 1510 (m), 1480 (m), 1413 (s), 1370 (w), 1348
(w), 1324 (m), 1263 (m), 1230 (w), 1181 (s), 1131 (m), 1093 (m),
1069 (m), 1026 (m), 999 (m), 977 (w), 945 (w), 910 (w), 834 (s),
806 (s) cm–1. UV/Vis (CH2Cl2): λmax (ε) = 486 nm (13000 m–1 cm–1).
+
HRMS (ESI): calcd. for C30H20N5 450.1713; m/z (%) = 450.1722
(100) [MH]+.
21: Compound 20 (16 mg, 0.036 mmol) was treated according to
GP B for 1 h, and FC (SiO2; hexane/CH2Cl2, 1:1 Ǟ CH2Cl2) gave
21 as a dark-blue solid (21 mg, 0.032 mmol, 91%). Rf = 0.17 (SiO2,
CH2Cl2). M.p. 215–217 °C. 1H NMR (600 MHz, CDCl3): δ = 3.15
(s, 6 H), 6.72 (d, J = 9.1 Hz, 2 H), 6.91 (dd, J = 9.5, 2.0 Hz, 1 H),
7.17 (dd, J = 9.5, 2.0 Hz, 1 H), 7.22 (d, J = 9.1 Hz, 2 H), 7.29 (dd,
J = 9.6, 2.0 Hz, 1 H), 7.47 (dd, J = 9.6, 2.0 Hz, 1 H), 7.59–7.63
(m, 2 H), 7.65–7.68 (m, 2 H), 7.68–7.74 (m, 3 H), 7.77 (d, J =
8.9 Hz, 2 H) ppm. 13C NMR (151 MHz, CDCl3): δ = 40.35, 73.09,
88.21, 90.51, 90.58, 110.56, 110.93, 111.11, 111.26, 111.66, 112.33,
112.92, 114.58, 114.61, 122.78, 125.63, 125.97, 129.33, 130.10,
130.46, 130.56, 130.82, 132.33, 133.73, 134.45, 134.53, 135.36,
135.67, 139.76, 149.69, 153.19, 153.83, 164.91, 165.92, 169.92 ppm.
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Received: October 16, 2012
Published Online: December 17, 2012
Eur. J. Org. Chem. 2013, 869–879
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
879