4-Substituted and 4,5-disubstituted 3,6-di(2-pyridyl)pyridazines: Ligands for supramolecular assemblies

Article abstract of DOI:10.1002/ejoc.200701114

The syntheses by inverse electron demand Diels-Alder reactions and characterization of 28 members of a family of 3,6-di(2-pyridyl)pyridazines, functionalized in the 4- or 4,5-positions are reported. Single crystal structural data are presented for four representative derivatives. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200701114

FULL PAPER
DOI: 10.1002/ejoc.200701114
4-Substituted and 4,5-Disubstituted 3,6-Di(2-pyridyl)pyridazines: Ligands for
Supramolecular Assemblies
Edwin C. Constable,*[a] Catherine E. Housecroft,*[a] Markus Neuburger,[a]
Sébastien Reymann,[a] and Silvia Schaffner[a]
Keywords: Cycloadditions / Diazines / Heterocycles / Pyridazine / Tetrazine
The syntheses by inverse electron demand Diels–Alder reac- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
tions and characterization of 28 members of a family of 3,6-
di(2-pyridyl)pyridazines, functionalized in the 4- or 4,5-posi-
tions are reported. Single crystal structural data are pre-
sented for four representative derivatives.
Germany, 2008)
In this paper, we report the syntheses and characterization
of 28 new 4- and 4,5-substituted 3,6-di(2-pyridyl)pyridazine
derivatives (Scheme 2) and the single crystal structures of
representative examples.
Introduction
The coordination chemistry of 3,6-disubstituted pyrid-
azine and 1,2,4,5-tetrazine ligands has produced a wide
range of structurally diverse complexes including polynu-
clear assemblies.[1–4] One aspect of particular interest is the
assembly of metal–ligand grids, for example [2ϫ2] grids for
combinations of copper(I)[5] or nickel(II)[6] with 3,6-di(2-
pyridyl)pyridazine (1, Scheme 1, a), and silver(I) with 3,6-
bis[2-(6-phenylpyridyl)]pyridazine[7] or 3,6-bis[2-(6-meth-
ylpyridyl)]pyridazine.[8] Despite the realization of such as-
sembly patterns, we have observed that silver(I) also forms
simpler 1:2 or 2:2 metal-to-ligand complexes with both 1
and 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (dptz) in which each
silver(I) centre is close to being square planar.[9–11] In an
effort to understand the factors that control the stoichiome-
try and structure of silver(I) complexes containing 3,6-di(2-
pyridyl)pyridazine ligands, we have initiated a series of
studies in which bulky substituents are introduced into the
4-position of the pyridazine ring (Scheme 1). Our strategy
follows from the fact that molecular modelling[12] indicates
that a sterically demanding substituent R will force ring C
(Scheme 1, b) out of the plane containing ring B, thereby
influencing the coordinating ability of the ligand. With
rings A, B and C lying in, or close to, a common plane,
each 3,6-di(2-pyridyl)pyridazine ligand can bind up to two
silver(I) centres. We have illustrated that the introduction of
a phenyl substituent (ligand 2) perturbs the structure only
slightly.[11] However, when R = SiMe3, ligand 3 (Scheme 1,
a) undergoes significant twisting upon coordination, affect-
ing both the stoichiometry and structure of the complex.[13]
We have now expanded the range of ligands under study.
Scheme 1. (a) 3,6-Di(2-pyridyl)pyridazine (1, R = H), 4-phenyl-3,6-
di(2-pyridyl)pyridazine (2) and 3,6-di(2-pyridyl)-4-(trimethylsilyl)-
pyridazine (3) in the trans,trans-conformation adopted by the free
ligand. (b) Coordination of one metal-binding domain of the li-
gand; coordination to silver(I) may be influenced by sterically de-
manding R substituents (see text).
Results and Discussion
Each of the 4- and 4,5-substituted 3,6-di(2-pyridyl)pyrid-
azines shown in Scheme 2 was synthesized by an inverse
electron demand Diels–Alder reaction between 3,6-di(2-
pyridyl)-1,2,4,5-tetrazine[14] and an appropriate alkyne. The
tetrazine is an electron deficient diene, and reacts most ef-
fectively with dienophiles that possess electron-releasing
substituents.[15] The methodology is well established, dating
back more than 40 years,[14,15] and has more recently been
applied by Warrener[16] and Schubert.[17,18] All the new
compounds, with the exception of 20 and 26–29, were pre-
pared by heating a mixture of 3,6-di(2-pyridyl)-1,2,4,5-
tetrazine and the alkyne in toluene at reflux (Scheme 3).
Toluene proved to be the most useful solvent for the reac-
tions under study, and was chosen in preference to dmso,
[a] Department of Chemistry, University of Basel,
Spitalstrasse 51, 4056 Basel, Switzerland
Fax: +41-61-267-1018
E-mail: edwin.constable@unibas.ch
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E. C. Constable, C. E. Housecroft et al.
FULL PAPER
Scheme 2. Structures of the substituted 3,6-di(2-pyridyl)pyridazines described in this work, and ring labelling for NMR assignments.
Each aryl substituent attached to ring B is labelled ring D. For R = C6H4-4-Ph, the terminal Ph ring is labelled E.
dmf and Ph2O, all of which were investigated during initial
trials. The ratios of reactants and reaction times are given
in the experimental section. The alkynes were prepared by
Sonogashira methodology,[19,20] as previously reported for
most of the reagents.[21–38] The intense purple colour of the
tetrazine is lost upon formation of the substituted 3,6-di(2-
pyridyl)pyridazines, and typically, a colour change from
purple to orange, yellow or brown (depending on the al-
kyne) was observed. Use of spot TLC readily determined
when a reaction had reached completion. Compound 20
was prepared by the acid hydrolysis of 19. Attempts to syn-
thesize derivatives 26–29 under the above conditions were
Scheme 3. General procedure for the formation of 4-substituted
unsuccessful, temperatures higher than the boiling point of
and 4,5-disubstituted 3,6-di(2-pyridyl)pyridazines; toluene was
used for all syntheses except those for 20 and 26–29.
toluene being necessary. For these compounds, the most ef-
ficient route was to use neat reactants, heated to 170 °C for
between 18 h (compound 29) and 10 d (compound 28). The
new 3,6-di(2-pyridyl)pyridazines were purified by chroma-
1
The new compounds were characterized by H and 13C
tographic workup (see Exp. Section) with the exception of NMR spectroscopy (assignments being made by COSY,
5 which was recrystallized from ethanol. NOESY, HMQC and HMBC techniques), mass spectrome-
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Ligands for Supramolecular Assemblies
try and elemental analysis. With the exception of 5, the elec-
trospray mass spectrum of each compound showed a peak
assigned to the parent ion or parent ion plus Na+ or K+.
Samples were injected into the mass spectrometer as aceto-
nitrile or dichloromethane solutions and, in some cases, sol-
vent is detected with the parent ion. For compound 5, facile
loss of a methyl substituent was observed.
1
The symmetrical appearance of the H NMR spectrum
of compound 1[17,39] is clearly lost upon the formation of 4Ј-
substituted derivatives, or in asymmetrical 4,5-disubstituted
derivatives of 1. In the monosubstituted compounds, a
NOESY cross peak between protons H5B and H2D allowed
assignment of the signals for the ring D protons. In com-
pound 28, a combination of 2D techniques allowed rings A
and C to be distinguished. The signals assigned to protons
H5B and H3C exhibit the greatest perturbation as the sub-
stituent in the 4Ј-position changes. Compared to a chemical
shift of δ = 8.70 ppm for H5B in 1 (CDCl3), this proton
appears over a shift range of δ = 9.01 to 8.25 ppm in the
4Ј-substituted compounds listed in Scheme 2. For proton
H3C, a resonance in the range δ = 7.66 to 8.43 ppm is ob-
served in comparison with a chemical shift of δ = 7.91 ppm
in 1 (CDCl3).
The structures of compounds 8, 10, 12 and 20 were deter-
mined by single-crystal X-ray diffraction. X-ray quality
crystals of 8·CHCl3 grew in a period of several days from a
chloroform solution of 8 left to stand at room temperature.
The structure of 8 is shown in Figure 1 (a), with selected
bond parameters listed in the caption. Bond lengths and
angles within the aromatic rings are unexcep-
tional.[16,17,39–42] The angles between the least-squares pla-
nes of the rings containing atoms N1 and N2, and N4 and
N2 are 27.81(9) and 10.66(9)°. These compare with angles
of 7.8 and 14.7° for the parent 3,6-di(2-pyridyl)pyrid-
azine.[39] The plane of the arene substituent is twisted
63.63(9)° out of that of the pyridazine ring (see discussion
for compound 12). The nitro group is essentially coplanar
with the arene ring [angle between the least-squares planes
= 4.2(2)°], and the N5–C18 bond length of 1.468(2) Å is
consistent with delocalization of π-electrons between the
two units. Molecules of 8 pack in chains which are sup-
Figure 1. (a) Molecular structure of compound 8 in 8·CHCl3 with
ellipsoids plotted at the 50% probability level. Selected bond
lengths and angles: N2–N3 1.338(2), C1–N1 1.338(2), C5–N1
1.339(2), C10–N4 1.343(2), C14–N4 1.336(2), C5–C6 1.486(3), C9–
C10 1.484(2), C7–C15 1.498(2), C18–N5 1.468(2), N5–O1 1.223(2),
N5–O2 1.227(2) Å; O1–N5–O2 123.3(2), O1–N5–C18 118.2(2),
O2–N5–C18 118.5(2)°. (b) Packing diagram showing π-stacking of
pairs of pyridine rings containing atoms N1 (dark grey) and N4
(pale grey). Solvent molecules have been omitted.
ported by π-stacking interactions between pairs of pyridine (close to the distances observed in compound 8) and 2.41
rings containing atoms N1 or N4 (Figure 1, b). The dis- and 2.57 Å.[41]
tance between the least-squares planes of pairs of rings con-
X-ray quality crystals of 10 were grown from a chloro-
taining N1 is 3.32 Å, and between those of pairs of rings form solution of the compound at room temperature. The
containing N4 is 3.29 Å. The CHCl3 solvate molecules oc- molecular structure is shown in Figure 2 and selected bond
cupy cavities between the chains. The chloroform C–H unit lengths are given in the caption. Bond lengths and angles
is involved in a non-classical, bifurcated hydrogen-bonded within the aromatic rings are similar to those in 8. The
interaction[43,44] to the pyridazine N2N3 unit of an adjacent angles between the least-squares planes of the rings of the
molecule [C21H211···N2i 2.49 Å, C21···N2i 3.356(3) Å, 3,6-di(2-pyridyl)pyridazine unit are 10.75(8) and 23.29(9)°.
C21–H211···N2i 145°. C21H211···N3i 2.25 Å, C21···N3i The arene ring of the NCC6H4 substituent is twisted
3.205(3) Å, C21–H211···N3i 158°; symmetry code i denotes 55.72(8)° out of the plane of the pyridazine ring (see dis-
x, y – 1, z]. A search of the Cambridge Structural Database cussion for compound 12). In the solid state, molecules of
(v. 5.28)[45] using Conquest v. 1.9[46] for bifurcated hydro- 10 pack in head-to-head pairs with the cyano groups acting
gen-bonded interactions between a C–H group and a as weak hydrogen bond π-acceptors with respect to aro-
six-membered 1,2-diaza heterocyclic ring gave 23 matic C–H hydrogen-bond donors[43] [N5–H171iC17i
hits.[16,41,42,46–62] Of these, two involve chloroform solvent 2.739(3) Å, C15–H171iC17i 2.864(3) Å; symmetry code i
molecules with CH···N distances of 2.41 and 2.20 Å,[60] denotes 1 – x, –y, –z].
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E. C. Constable, C. E. Housecroft et al.
FULL PAPER
Crystals of 20 suitable for X-ray diffraction were grown
by diffusion of diethyl ether into an acetonitrile solution of
20 left standing at room temperature. Figure 4 shows the
molecular structure of the compound. While the bond pa-
rameters within the aromatic rings of the pyridazine unit
are as expected, the deviation from coplanarity of the three
rings differs from that in compounds 8, 10 and 12. The
angles between the least-squares planes of the pyridazine
ring and the rings containing atoms N1 and N4 are 16.06(6)
and 60.52(6)°, respectively. The plane of the arene ring in
the 4-HOC6H4 substituent is twisted through 29.74(6)° with
respect to the plane of the pyridazine ring, and this angle
is smaller than the corresponding twist angle in 8, 10 or 12.
Whereas in 8, 10 and 12, steric congestion is relieved largely
through a twisting of the arene ring, in 20, it is one of the
pyridine rings that undergoes the largest degree of twisting.
This difference could be due to the presence of an electron-
withdrawing substituent on the arene ring in each of com-
pounds 8, 10 and 12, but an electron-donating substituent
in compound 20. In the latter case, a smaller deviation from
coplanarity between the arene and pyridazine rings helps to
minimize the loss in π-conjugation between the electron-
rich arene ring and the pyridazine unit.
Figure 2. Molecular structure of compound 10 with ellipsoids plot-
ted at the 50% probability level. Selected bond lengths: N2–N3
1.342(2), C1–N1 1.337(2), C5–N1 1.343(2), C10–N4 1.343(2), C14–
N4 1.341(3), C5–C6 1.484(2), C9–C10 1.490(2), C8–C19 1.493(2),
C15–C16 1.448(2), C15–N5 1.145(2) Å.
Figure 3 illustrates the molecular structure of 12, X-ray
quality crystals of which were grown by slow evaporation
at room temperature of a chloroform solution of 12. The
bond parameters in the 3,6-di(2-pyridyl)pyridazine unit are
as expected. The angles between the least-squares planes of
the pyridazine ring and the rings containing atoms N1 and
N4 are 27.38(8) and 6.21(8)°, respectively. The plane of the
bromophenyl substituent is twisted 58.98(8)° out of the
plane of the pyridazine ring, thus mimicking the situation
in compounds 8 and 10. Ring twisting is necessary to relieve
steric congestion, and is achieved by rotation of the arene
ring when an electron withdrawing substituent (Br, CN or
NO2) is present. A contrasting situation is observed in com-
pound 20 (see below). The molecular packing in the crystal
lattice features head-to-head pairs of molecules with Br···Br
contacts [Br···Brii 3.8343(6) Å; symmetry code ii denotes
1
–1/2 + x, /2 – y, z] which are comparable with the sum of
the van der Waals radius of bromine (3.90 Å). A recent
study by Boyd and co-workers concludes that, although the
Cambridge Structural Database (v. 5.27)[45] contains several
structures with particular short Br···Br contacts, most sepa-
rations are consistent with normal van der Waals con-
tacts.[63]
Figure 4. Molecular structure of compound 20 with ellipsoids plot-
ted at the 50% probability level. Selected bond lengths: N2–N3
1.344(2), C1–N1 1.339(2), C5–N1 1.348(2), C10–N4 1.345(2), C14–
N4 1.340(2), C5–C6 1.489(2), C9–C10 1.495(2), C8–C15 1.480(2),
C18–O1 1.358(2) Å.
The packing of molecules of 20 is dictated primarily by
hydrogen-bonded interactions which leads to the assembly
of chains. Within each chain, these contacts involve the OH
group and the two nitrogen atoms of the pyridazine ring,
supplemented by non-classical C–H···N hydrogen bonds
[Figure 5, O1···N2i 2.780(2) Å, O1–H1···N2i 172°; O1···N3i
3.545(2) Å, O1–H1···N3i 156°; C19···N3i 3.417(2) Å, C19–
1
H191···N3i 149°; symmetry code i denotes 1 – x, /2 + y,
3/2 – z]. Weak hydrogen bonds involving aromatic C–H do-
nors operate between the chains [C12···N4ii 3.419(2) Å,
C12–H121···N4ii 169°; C13···O1iii 3.458(2) Å, C13–
H131···O1iii 159°; symmetry code ii denotes –1 + x, y, z; iii
Figure 3. Molecular structure of compound 12 with ellipsoids plot-
ted at the 50% probability level. Selected bond lengths: N2–N3
1.3336(2), C1–N1 1.336(2), C5–N1 1.349(2), C10–N4 1.340(2),
C14–N4 1.334(2), C5–C6 1.488(2), C9–C10 1.485(2), C7–C15
1.485(2), C18–Br 1.894(2) Å.
1
stands for –1 + x, /2 – y, –1/2 + z].
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Ligands for Supramolecular Assemblies
149.5 (C6A), 147.9 (C6C), 137.1 (C4A/4C), 136.9 (C4B), 136.7
(C4A/4C), 133.9 (C5B), 124.5 (C3C/5A/5C), 124.0 (C3C/5A/5C), 123.8
(C3C/5A/5C), 121.7 (C3A), 19.2 (CMe), 13.0 (CHPr) ppm. ES MS: m/z
= 347 [M – iPr]+. C23H30N4Si (390.60): calcd. C 70.72, H 7.74, N
14.34; found C 70.71, H 7.50, N 14.30.
Compound 5: A solution of dptz (500 mg, 2.11 mmol) and Me-
OCH2CϵCH (280 mg, 3.99 mmol) in toluene (80 mL) was heated
at reflux for 24 h. After removal of the solvent, 5 was purified by
recrystallization from ethanol. Compound 5 was isolated as a beige
powder (0.46 g, 1.7 mmol, 81%); m.p. 129.7 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.87 (s, 1 H, H5B), 8.68 (m, 2 H, H6A+3A),
8.63 (d, J = 4.6 Hz, 1 H, H6C), 8.37 (d, J = 8.0 Hz, 1 H, H3C), 7.82
(m, 2 H, H4A+4C), 7.31 (m, 2 H, H5A+5C), 4.96 (s, 2 H, CH2), 3.47
(s, 3 H, Me) ppm. 13C NMR (100 MHz, CDCl3): δ = 157.5
(C3B/6B), 155.9 (C3B/6B), 155.6 (C6A), 153.5 (C2A), 149.4 (C6A), 148.2
(C6C), 139.6 (C4B), 136.8 (C4A/4C), 136.7 (C4A/4C), 124.4 (C5A),
124.1 (C3C), 123.6 (C5C), 122.6 (C5B), 121.5 (C3A), 70.8 (CCH2), 58.8
(CMe) ppm. ES MS (MeCN): m/z = 328 [M – CH3 + Na +
MeCN]+. C16H14N4O: calcd. C 69.05, H 5.07, N 20.13; found
68.25, H 5.36, N 19.79.
Figure 5. Part of two of the hydrogen-bonded chains of moecules
in the solid-state structure of 20. Symmetry code i denotes 1 – x,
3
1/2 + y, /2 – z. See text for bonding parameters.
Conclusions
We have reported the synthesis by inverse electron de-
mand Diels–Alder reactions and characterization of a large
series of 3,6-di(2-pyridyl)pyridazines which are function-
alized in the 4- or 4,5-positions. The compounds have been
fully characterized by spectroscopic and mass spectrometric
methods, and the single-crystal structures of four represen-
tative compounds have been described. We will shortly pres-
ent results of investigations of the coordination behaviour
of these new ligands, to gain insight into the effects that
varying the electronic and steric effects of the 4- or 4,5-
substituents have upon the nature, including nuclearity, of
their silver(I) complexes.
Compound 6: A solution of dptz (0.94 g, 4.0 mmol) and dodecyne
(1.0 g, 6.0 mmol) in toluene (70 mL) was heated at reflux for 50 h.
The solvent was removed and the product was purified by column
chromatography (alumina, hexane/EtOAc, 4:1), second band.
Compound 6 was isolated as a pale yellow oil that crystallized on
standing (1.0 g, 2.7 mmol, 68%); m.p. 101.5 °C. 1H NMR
(500 MHz, CDCl3): δ = 8.72 (d, J = 8.1 Hz, 1 H, H3A), 8.70 (m, 2
H, H6A+6C), 8.47 (s, 1 H, H5B), 8.07 (d, J = 7.6 Hz, 1 H, H3C), 7.86
(m, 2 H, H4A+4C), 7.36 (m, 2 H, H5A+5C), 3.05 (t, J = 7.6 Hz, 2 H,
HringCH2), 1.57 (quintet, J = 7.6 Hz, 2 H, HringCH2CH2), 1.25 (m, 2
H, HringCH2CH2CH2), 1.19 [m, 12 H, (CH2)6], 0.84 (t, J = 7.2 Hz, 3
H, Me) ppm. 13C NMR (125 MHz, CDCl3): δ = 159.1 (C3B), 157.2
(C6B), 156.4 (C2C), 153.6 (C2A), 149.3 (C6A/6C), 148.4 (C6A/6C),
142.8 (C4B), 137.1 (C4A/4C), 136.7 (C4A/4C), 125.5 (C5B), 124.7
(C5A), 124.5 (C3C), 123.4 (C5C), 121.7 (C3A), 32.2 (CringCH2), 31.8
(Calkyl), 29.7 (Calkyl), 29.45 (Calkyl), 29.4 (Calkyl), 29.3 (Calkyl), 29.2
(Calkyl), 29.1 (Calkyl), 22.6 (Calkyl), 14.0 (CMe) ppm. ES MS
(CH2Cl2): m/z = 496 [M + K + CH2Cl2]+. C24H30N4: calcd. C
76.97, H 8.07, N 14.96; found C 76.55, H 8.09, N 14.82.
Experimental Section
General: 1H and 13C NMR spectra were recorded with Bruker
Avance DRX 400 or 500 spectrometers; the numbering scheme
adopted for the 3,6-di(2-pyridyl)pyridazines is shown in Scheme 2.
Chemical shifts for 1H and 13C NMR spectra are referenced to
residual solvent peaks with respect to TMS (δ = 0 ppm); all spectra
were recorded at about 298 K. Electrospray (ES) and MALDI-
TOF mass spectra were recorded using Finnigan MAT LCQ and
PerSeptive Biosystems Voyager mass spectrometers, respectively.
High resolution mass spectra (CHCl3/MeOH solutions) were re-
corded with a Bruker FTMS 4.7T BioApex II mass spectrometer
at the University of Fribourg. Melting points were recorded using
a Stuart Scientific SMP3 melting point apparatus, starting at 90 °C
with a heating rate of 3 °Cmin–1. iPr3SiCϵCH (Acros), Me-
OCH2CϵCH (Sigma–Aldrich), HOCH2CϵCH (Sigma–Aldrich),
diphenylethyne (Fluka), dodec-1-yne (Alfa Aesar), 1-ethynyl-
cyclohexan-1-ol (Acros), 1-iodo-4-methoxybenzene (Acros) and
1,3,5-tribromobenzene (Acros) were used as received.
Compound 7: 4-Ethynylaniline[21] (0.40 g, 3.4 mmol) and dptz
(0.81 g, 3.4 mmol) were dissolved in toluene (120 mL). The solution
was heated at reflux for 5 d. The solvent was removed under re-
duced pressure, and the product was purified by column
chromatography (alumina, CHCl3, third band). Compound 7 was
isolated as a dark brown powder (0.99 g, 3.0 mmol, 88%); m.p.
1
213.4 °C. H NMR (400 MHz, CDCl3): δ = 8.76 (d, J = 7.5 Hz, 1
H, H3A), 8.72 (d, J = 5.5 Hz, 1 H, H6A), 8.59 (s, 1 H, H5B), 8.55
(d, J = 5.5 Hz, 1 H, H6C), 7.88 (td, J = 7.5, 1.6 Hz, 1 H, H4A), 7.77
(m, 2 H, H4C+3C), 7.38 (dd, J = 7.6, 4.8 Hz, 1 H, H5A), 7.26 (m, 1
H, H5C), 7.04 (d, J = 8.5 Hz, 2 H, H2D), 6.56 (d, J = 8.5 Hz, 2 H,
H3D) ppm. 13C NMR (100 MHz, CDCl3): δ = 158.3 (C6B/3B), 157.5
(C6B/3B), 156.4 (C2A/2C), 153.6 (C2A/2C), 149.3 (C6A), 149.1 (C6C),
147.0 (C4D), 140.3 (C4B), 137.1 (C4C), 136.4 (C4A), 130.3 (C2D),
126.0 (C1D), 124.8 (C5B/3A), 124.7 (C5B/3A), 124.6 (C5C), 123.1
(C5A), 121.8 (C3C), 114.8 (C3D) ppm. ES MS (CH2Cl2): m/z = 326
[M]+, 447 [M + K + 2MeCN]+. C20H15N5·H2O: calcd. C 71.84, H
4.82, N 20.94; found C 72.03, H 4.64, N 21.19.
Compound 4: iPr3SiCϵCH (0.53 g, 2.9 mmol) and dptz (0.69 g,
2.9 mmol) were dissolved in toluene (100 mL). The solution was
heated at reflux for 10 d. After evaporation of the solvent, the prod-
uct was purified by column chromatography [alumina, hexane/
CH2Cl2/EtOAc (1:1:1), third band]. 4 was isolated as a white solid
(135 mg, 0.346 mmol, 11.7%); m.p. 151.6 °C. 1H NMR (500 MHz,
CDCl3): δ = 9.01 (s, 1 H, H5B), 8.76 (m, 2 H, H3A+6A), 8.65 (d, J Compound 8: 1-Ethynyl-4-nitrobenzene[21] (0.30 g, 2.1 mmol) and
= 4.7 Hz, 1 H, H6C), 8.38 (d, J = 7.8 Hz, 1 H, H3C), 7.88 (m, 2 H,
H4A+4C), 7.39 (m, 2 H, H5A+5C), 1.50 (septet, J = 7.5 Hz, 3 H,
CHPr), 1.07 (d, J = 7.5 Hz, 18 H, Me) ppm. 13C NMR (125 MHz,
CDCl3): δ = 163.9 (C3B), 157.2 (C2C), 155.3 (C6B), 153.6 (C2A),
dptz (0.40 g, 1.7 mmol) were dissolved in toluene (80 mL), and the
reaction mixture was heated at reflux for 5 d. The solvent was re-
moved and 8 was purified by column chromatography (alumina,
hexane/EtOAc, 1:2, second band). Compound 8 was isolated as a
Eur. J. Org. Chem. 2008, 1597–1607
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1601

E. C. Constable, C. E. Housecroft et al.
FULL PAPER
brown powder (0.51 g, 1.4 mmol, 83%); m.p. 177.3 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.77 (d, J = 8.1 Hz, 1 H, H3A), 8.70 (d, J
= 4.1 Hz, 1 H, H6A), 8.63 (s, 1 H, H5B), 8.32 (d, J = 5.0 Hz, 1 H,
H2D+4E), 7.28 (dd, J = 7.6, 4.8 Hz, 1 H, H5C) ppm. 13C NMR
(100 MHz, CDCl3): δ = 158.2 (C3B/6B), 157.6 (C3B/6B), 155.8 (C2C),
153.3 (C2A), 149.4 (C6A), 149.0 (C6C), 141.0 (C4B/4D/1E), 140.1
H6C), 8.15 (m, 3 H, H3C+3D), 7.90 (td, J = 7.5, 1.6 Hz, 1 H, H4A), (C4B/4D/1E), 140.0 (C4B/4D/1E), 137.1 (C4A), 136.5 (C4C), 135.7 (C1D),
7.85 (td, J = 7.5, 1.6 Hz, 1 H, H4C), 7.41 (m, 3 H, H5A+2D), 7.27
129.3 (C2D), 128.7 (C3E), 127.6 (C4E), 127.0 (C3D/2E), 126.9
(dd, J = 7.6, 4.8 Hz, 1 H, H5C) ppm. 13C NMR (100 MHz, CDCl3): (C3D/2E), 125.4 (C5B), 124.8 (C5A/3C), 124.7 (C5A/3C), 123.3 (C5C),
δ = 157.7 (C6B/3B), 157.4 (C6B/3B), 154.6 (C2A/2C), 152.7 (C2A/2C),
121.8 (C3A) ppm. ES MS (CH2Cl2): m/z = 508 [M + K +
149.4 (C6A), 148.7 (C6C), 147.4 (C4D), 144.2 (C4B), 138.4 (C1D),
CH2Cl2]+, 893 [2M + K + CH2Cl2]+. C26H18N4 (386.46): calcd. C
137.3 (C4A), 136.9 (C4C), 129.6 (C3D), 125.5 (C5B), 125.0 (C5A), 80.81, H 4.69, N 14.50; found C 80.79, H 4.70, N 14.33.
124.6 (C5C), 123.8 (C3C), 123.4 (C2D), 121.8 (C3A) ppm. ES MS
Compound 12: A solution of dptz (0.26 g, 1.1 mmol) and 1-bromo-
(CHCl3): m/z
= + M +
356 [M]+, 477 [Na CHCl3]+.
4-ethynylbenzene[23,24] (0.21 g, 1.1 mmol) in toluene (50 mL) was
heated at reflux for 11 d. The solvent was then removed and the
product purified by column chromatography (alumina, EtOAc,
third fraction). Compound 12 was isolated as an orange powder
(0.39 g, 1.0 mmol, 91%); m.p. 134.6 °C. 1H NMR (500 MHz,
CD3CN): δ = 8.78 (d, J = 7.5 Hz, 1 H, H3A), 8.72 (d, J = 4.5 Hz,
1 H, H6A), 8.62 (s, 1 H, H5B), 8.45 (d, J = 4.5 Hz, 1 H, H6C), 7.97
(d, J = 8.0 Hz, 1 H, H3C), 7.92 (td, J = 7.5, 1.5 Hz, 1 H, H4A), 7.82
(td, J = 7.8, 1.6 Hz, 1 H, H4C), 7.43 (d, J = 8.5 Hz, 2 H, H3D), 7.41
C20H13N5O2·0.5H2O: calcd. C 65.93, H 3.87, N 19.22; found C
65.96, H 3.58, N 19.58.
Compound 9: 1-Ethynyl-4-methylbenzene[22] (0.39 g, 3.4 mmol) and
dptz (0.78 g, 3.3 mmol) were dissolved in toluene (90 mL), and the
reaction mixture was heated at reflux for 6 d. The solvent was re-
moved under reduced pressure, and 9 was purified by column
chromatography (alumina, hexane/EtOAc, 1:2, second band).
Compound 9 was isolated as an orange powder (0.97 g, 3.0 mmol,
1
91%); m.p. 149.9 °C. H NMR (500 MHz, CDCl3): δ = 8.79 (d, J (dd, J = 7.4, 4.8 Hz, 1 H, H5A), 7.28 (dd, J = 7.4, 4.8 Hz, 1 H,
= 7.8 Hz, 1 H, H3A), 8.71 (d, J = 4.8 Hz, 1 H, H6A), 8.65 (s, 1 H,
H5C), 7.13 (d, J = 8.5 Hz, 2 H, H2D) ppm. 13C NMR (125 MHz,
H5B), 8.50 (d, J = 4.8 Hz, 1 H, H6C), 7.90 (t, J = 7.8 Hz, 1 H, H4A), CD3CN): δ = 158.0 (C3B/6B), 157.7 (C3B/6B), 155.4 (C2C), 153.1
7.83 (d, J = 7.8 Hz, 1 H, H3C), 7.78 (t, J = 7.8 Hz, 1 H, H4C), 7.40
(dd, J = 7.6, 4.8 Hz, 1 H, H5A), 7.27 (dd, J = 7.6, 4.8 Hz, 1 H,
H5C), 7.16 (d, J = 6.8 Hz, 2 H, H2D), 7.09 (d, J = 6.8 Hz, 2 H,
H3D), 2.33 (s, 3 H, Me) ppm. 13C NMR (125 MHz, CDCl3): δ =
(C2A), 149.4 (C6A), 149.0 (C6C), 139.4 (C4B), 137.2 (C4A), 136.7
(C4C), 136.0 (C1D), 131.6 (C3D), 130.4 (C2D), 125.4 (C5B), 124.9
(C3C/5A), 124.8 (C3C/5A), 123.5 (C5C), 122.9 (C4D), 121.8 (C3A) ppm.
ES MS (CD3CN): m/z = 391 [M]+, 494 [M + Na + 2MeCN]+, 841
158.3 (C3B/6B), 157.6 (C3B/6B), 155.8 (C2C), 153.3 (C2A), 149.3 (C6A), [2M + Na + MeCN]+. C20H13BrN4 (389.25): calcd. C 61.71, H
148.9 (C6C), 140.4 (C4B/4D), 138.5 (C4B/4D), 137.3 (C4A), 136.7 3.37, N 14.39; found C 61.90, H 3.41, N 14.33.
(C4C), 133.7 (C1D), 129.2 (C3D), 128.9 (C2D), 125.5 (C5B), 125.0
Compound 13: A solution of dptz (414 mg, 1.75 mmol) and 1-eth-
(C3C), 124.8 (C5A), 123.4 (C5C), 121.9 (C3A), 21.3 (CMe) ppm. FAB
ynyl-4-iodobenzene[25] (400 mg, 1.75 mmol) in toluene (120 mL)
MS: m/z = 323 [M]+. C21H16N4 (324.38): calcd. C 77.76, H 4.97,
was heated at reflux for 74 h. After removal of solvent, 13 was
purified by column chromatography (alumina, EtOAc/hexane, 1:1,
N 17.27; found C 77.64, H 5.09, N 17.31.
Compound 10: 4-Ethynylbenzonitrile[21] (0.50 g, 3.9 mmol) and dptz
(0.83 g, 3.5 mmol) were dissolved in toluene (140 mL), and the
solution was heated at reflux for 6 d. After removal of solvent,
crude 10 was purified by column chromatography (alumina, hex-
ane/EtOAc, 1:1, second fraction). Compound 10 was isolated as a
second band). Compound 13 was isolated as a pink solid (0.70 g,
1.6 mmol, 92%); m.p. 137.6 °C. H NMR (400 MHz, CDCl3): δ =
1
8.76 (d, J = 8.0 Hz, 1 H, H3A), 8.69 (d, J = 4.4 Hz, 1 H, H6A), 8.59
(s, 1 H, H5B), 8.43 (d, J = 4.4 Hz, 1 H, H6C), 7.94 (d, J = 8.0 Hz,
1 H, H3C), 7.88 (td, J = 8.0, 1.6 Hz, 1 H, H4A), 7.80 (td, J = 8.0,
1.6 Hz, 1 H, H4C), 7.62 (d, J = 8.8 Hz, 2 H, H3D), 7.38 (dd, J =
7.6, 4.8 Hz, 1 H, H5A), 7.26 (dd, J = 7.6, 4.8 Hz, 1 H, H5C), 6.98
(d, J = 8.4 Hz, 2 H, H2D) ppm. 13C NMR (100 MHz, CDCl3): δ =
157.9 (C3B), 157.7 (C6B), 155.4 (C2C), 153.1 (C2A), 149.4 (C6A),
148.9 (C6C), 139.4 (C4D), 137.4 (C3D), 137.1 (C4A), 136.6 (C4C),
1
pale yellow powder (1.03 g, 3.07 mmol, 87.7%); m.p. 163.5 °C. H
NMR (400 MHz, CDCl3): δ = 8.79 (d, J = 8.0 Hz, 1 H, H3A), 8.71
(d, J = 4.8 Hz, 1 H, H6A), 8.62 (s, 1 H, H5B), 8.35 (d, J = 4.4 Hz,
1 H, H6C), 8.13 (d, J = 7.8 Hz, 1 H, H3C), 7.92 (td, J = 7.8, 1.6 Hz,
1 H, H4A), 7.86 (td, J = 7.8, 1.6 Hz, 1 H, H4C), 7.61 (d, J = 8.0 Hz,
2 H, H3D), 7.42 (dd, J = 7.6, 4.8 Hz, 1 H, H5A), 7.36 (d, J = 8.0 Hz, 136.5 (C1D), 130.5 (C2D), 125.3 (C5B), 124.8 (C5A), 124.7 (C3C),
2 H, H2D), 7.28 (dd, J = 7.6, 4.8 Hz, 1 H, H5C) ppm. 13C NMR
(100 MHz, CDCl3): δ = 157.7 (C3B/6B), 157.5 (C3B/6B), 154.7
(C2C/2A), 152.7 (C2C/2A), 149.4 (C6A), 148.7 (C6C), 142.3 (C1D),
138.7 (C4B), 137.2 (C4A), 136.9 (C4C), 132.0 (C3D), 129.4 (C2D),
125.5 (C5B), 125.0 (C5A), 124.7 (C3C), 123.8 (C5C), 121.8 (C3A),
118.4 (C4D), 111.9 (CCN) ppm. ES MS (MeCN): m/z = 439 [M +
Na + 2MeCN]+. C21H13N5 (335.37): calcd. C 75.21, H 3.91, N
20.88; found C 75.03, H 3.95, N 20.73.
123.5 (C5C), 121.8 (C3A), 94.6 (C4D) ppm. ES MS (MeCN): m/z =
437 [M]+, 499 [M + Na + MeCN]+, 935 [2M + Na + MeCN]+.
C20H13IN4 (436.25): calcd. C 55.06, H 3.00, N 12.84; found C
55.00, H 3.01, N 12.64
Compound 14: A solution of dptz (0.13 g, 0.53 mmol) and 1-eth-
ynyl-4-(trifluoromethyl)benzene[26] (90 mg, 0.53 mmol) in toluene
(50 mL) was heated at reflux for 4 d. The solvent was removed and
then 14 was purified by column chromatography (alumina, EtOAc/
hexane, 1:1, second fraction). Compound 14 was isolated as a deep
red powder (0.15 g, 0.39 mmol, 74%). 1H NMR (500 MHz,
[D6]DMSO): δ = 8.81 (d, J = 5.5 Hz, 1 H, H6A), 8.69 (d, J = 8.0 Hz,
1 H, H3A), 8.55 (s, 1 H, H5B), 8.38 (d, J = 7.6 Hz, 1 H, H6C), 8.10
(td, J = 7.6, 1.6 Hz, 1 H, H4A), 8.05 (d, J = 5.5 Hz, 1 H, H3C), 8.01
Compound 11: 4-Ethynylbiphenyl[21] (400 mg, 2.25 mmol) and dptz
(300 mg, 1.27 mmol) were dissolved in toluene (70 mL), and the
solution was heated at reflux for 66 h. Solvent was then removed
and crude 11 was purified by column chromatography (alumina,
hexane/EtOAc, 1:1, second fraction), to give 11 as a violet powder
(0.42 g, 1.1 mmol, 85%); m.p. 167.5 °C. 1H NMR (400 MHz, (td, J = 7.5, 1.6 Hz, 1 H, H4C), 7.72 (d, J = 8.5 Hz, 2 H, H2D), 7.61
CDCl3): δ = 8.81 (d, J = 8.0 Hz, 1 H, H3A), 8.73 (d, J = 5.6 Hz, 1
H, H6A), 8.71 (s, 1 H, H5B), 8.49 (d, J = 5.0 Hz, 1 H, H6C), 7.95
(d, J = 7.5 Hz, 1 H, H3C), 7.90 (td, J = 7.5, 1.6 Hz, 1 H, H4A), 7.81
(td, J = 7.5, 1.6 Hz, 1 H, H4C), 7.60 (d, J = 8.3 Hz, 2 H, H2E), 7.55
(d, J = 8.3 Hz, 2 H, H3D), 7.41 (m, 3 H, H5A+3E), 7.35 (m, 3 H,
(dd, J = 7.6, 4.8 Hz, 1 H, H5A), 7.52 (d, J = 8.5 Hz, 2 H, H3D),
7.44 (dd, J = 7.6, 4.8 Hz, 1 H, H5C) ppm. 13C NMR (125 MHz,
[D6]DMSO): δ = 157.9 (C3B/6B), 157.3 (C3B/6B), 154.7 (C2A/2C),
152.3 (C2A/2C), 149.8 (C6A), 148.6 (C6C), 141.2 (q, JCF = 1.4 Hz,
C1D), 138.5 (C4B), 137.6 (C4A), 137.1 (C4C), 129.5 (C2D), 128.5 (q,
1602
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1597–1607

Ligands for Supramolecular Assemblies
JCF = 32 Hz, C4D), 125.4 (C5B), 125.3 (C5C), 125.1 (q, JCF = 3.8 Hz, (d, J = 8.0 Hz, 2 H, H2), 7.14 (d, J = 8.0 Hz, 2 H, H3), 3.04 (s,
C3D), 124.8 (C5A+3C), 124.0 (C5C), 122.0 (q, JCF = 240 Hz, CF3),
121.3 (C3A) ppm. ES MS (MeCN): m/z = 379 [M]+, 442 [L + Na
+ MeCN]+. C21H13F3N4·0.25H2O: calcd. C 65.88, H 3.55, N 14.63;
found C 65.92, H 3.57, N 14.63.
1 H, CϵCH), 2.61 (t, J = 7.6 Hz, 2 H, HringCH2), 1.61 (m, 2 H,
HringCH2CH2), 1.30 (m, 10 H, Halkyl), 0.90 (t, J = 7.5 Hz, 3 H, HMe
)
ppm. 13C NMR (125 MHz, CDCl3): δ = 144.4 (C4), 132.3 (C2),
128.6 (C3), 119.7 (C1), 93.7 (CCϵCH), 84.1 (CCϵCH), 36.2 (CringCH2),
32.1 (Calkyl), 31.5 (Calkyl), 29.7 (Calkyl), 29.6 (Calkyl), 22.9 (Calkyl),
14.4 (CMe) ppm. ES MS: m/z = 214 [M]+. C16H22·0.5H2O: calcd.
C 86.04, H 10.38; found C 85.67, H 10.39.
Compound 15: 1-tert-Butyl-4-ethynylbenzene[27] (0.28 g, 1.8 mmol)
and dptz (0.20 g, 1.3 mmol) were dissolved in toluene (30 mL). The
reaction mixture was heated at reflux for 42 h, after which time
solvent was removed. Crude 15 was purified by column chromatog-
raphy (alumina, hexane/EtOAc, 2:1, second band), and 15 was iso-
lated as a beige powder (0.42 g, 1.1 mmol, 87%); m.p. 180.0 °C. 1H
NMR (500 MHz, CDCl3): δ = 8.78 (d, J = 7.8 Hz, 1 H, H3A), 8.71
(d, J = 4.8 Hz, 1 H, H6A), 8.66 (s, 1 H, H5B), 8.49 (d, J = 4.8 Hz,
1 H, H6C), 7.89 (td, J = 7.5, 1.6 Hz, 1 H, H4A), 7.85 (d, J = 7.8 Hz,
1 H, H3C), 7.78 (dt, J = 7.6, 1.2 Hz, 1 H, H4C), 7.38 (dd, J = 7.4,
4.8 Hz, 1 H, H5A), 7.31 (d, J = 8.3 Hz, 2 H, H3D), 7.27 (dd, J =
Compound 17: 1-Ethynyl-4-octylbenzene (0.40 g, 1.9 mmol) and
dptz (0.35 g, 1.5 mmol) were dissolved in toluene (75 mL), and the
solution was heated at reflux for 7 d. Solvent was removed and
then crude 17 was purified by column chromatography (alumina,
hexane/EtOAc, 3:2, second fraction). Compound 17 was isolated
as a brown oil which slowly crystallized on standing (0.60 g,
1.4 mmol, 93%); m.p. 95.9 °C. 1H NMR (500 MHz, CDCl3): δ =
8.78 (d, J = 8.1 Hz, 1 H, H3A), 8.71 (d, J = 4.5 Hz, 1 H, H6A), 8.65
7.6, 4.8 Hz, 1 H, H5C), 7.19 (d, J = 8.2 Hz, 2 H, H2D), 1.29 (s, 9 (s, 1 H, H5B), 8.49 (d, J = 4.5 Hz, 1 H, H6C), 7.89 (td, J = 7.5,
H, Me) ppm. 13C NMR (125 MHz, CDCl3): δ = 158.3 (C6B), 157.6 1.6 Hz, 1 H, H4A), 7.85 (d, J = 8.1 Hz, 1 H, H3C), 7.77 (td, J =
(C3B), 156.0 (C2C), 153.4 (C2A), 151.6 (C4D), 149.4 (C6A), 149.0 7.5, 1.6 Hz, 1 H, H4C), 7.39 (dd, J = 7.6, 4.8 Hz, 1 H, H5A), 7.26
(C6C), 140.3 (C4B), 137.1 (C4A), 136.4 (C4C), 133.7 (C1D), 128.6 (dd, J = 7.6, 4.8 Hz, 1 H, H5C), 7.16 (d, J = 8.0 Hz, 2 H, H2D),
(C2D), 125.5 (C5B), 125.3 (C3D), 124.8 (C3C/5A), 124.6 (C3C/5A),
123.2 (C5C), 121.8 (C3A), 34.6 (CCMe3), 31.2 (CMe) ppm. ES MS
7.10 (d, J = 8.0 Hz, 2 H, H3D), 2.58 (t, J = 7.6 Hz, 2 H, HringCH2),
1.58 (m, 2 H, HringCH2CH2), 1.27 [m, 10 H, (CH2)5], 0.86 (t, J =
(CH2Cl2): m/z = 488 [M + K + CH2Cl2]+. C22H18N4O2 (370.41): 7.5 Hz, 3 H, Me) ppm. 13C NMR (125 MHz, CDCl3): δ = 158.3
calcd. C 78.66, H 6.05, N 15.29; found C 78.45, H 6.17, N 15.10,
(C3B/6B), 157.6 (C3B/6B), 155.9 (C2C), 153.4 (C2A), 149.3 (C6A), 148.9
(C6C), 143.4 (C4D/4B), 140.4 (C4D/4B), 137.1 (C4A), 136.4 (C4C),
133.9 (C1D), 128.7 (C2D), 128.4 (C3D), 125.4 (C5B), 124.8 (C3C),
124.7 (C5A), 123.2 (C5C), 121.8 (C3A), 35.51 (CD–CH2), 31.7 (Calkyl),
31.1 (CD–CH2CH2), 29.4 (Calkyl), 29.2 (Calkyl), 29.15 (Calkyl), 22.6
(Calkyl), 14.0 (CMe) ppm. ES MS (CH2Cl2): m/z (%) = 544 [M + K
+ CH2Cl2]+, 910 [2M + K + CH2Cl2]+.C28H30N4 (422.57): calcd.
C 79.59, H 7.16, N 13.26; found C 78.85, H 7.34, N 13.12.
Compound 16: 1-Butyl-4-ethynylbenzene[27] (0.40 g, 2.5 mmol) and
dptz (0.52 g, 2.2 mmol) were dissolved in toluene (120 mL), and
the reaction mixture was heated at reflux for 88 h. Ths solvent was
removed and then the crude product was purified by column
chromatography (alumina, hexane/EtOAc, 1:1, second fraction).
Compound 16 was isolated as a brown oil which slowly crystallized
on standing (0.62 g, 1.7 mmol, 78%); m.p. 108.2 °C. 1H NMR
(500 MHz, CDCl3): δ = 8.78 (d, J = 7.6 Hz, 1 H, H3A), 8.71 (d, J
= 5.0 Hz, 1 H, H6A), 8.64 (s, 1 H, H5B), 8.48 (d, J = 5.0 Hz, 1 H,
1-Decyl-4-ethynylbenzene: The method was as for 1-ethynyl-4-octyl-
benzene, starting from 1-iodo-4-octylbenzene (2.0 g, 5.8 mmol),
H6C), 7.89 (td, J = 7.5, 1.6 Hz, 1 H, H4A), 7.84 (d, J = 7.6 Hz, 1 CuCl (57 mg, 0.58 mmol), and PdCl2(PPh3)2 (0.41 g, 0.58 mmol).
H, H3C), 7.77 (td, J = 7.5, 1.6 Hz, 1 H, H4C), 7.38 (dd, J = 7.6,
4.8 Hz, 1 H, H5A), 7.25 (dd, J = 7.6, 4.8 Hz, 1 H, H5C), 7.16 (d, J
= 8.5 Hz, 2 H, H2D), 7.10 (d, J = 8.1 Hz, 2 H, H3D), 2.58 (t, J =
7.5 Hz, 2 H, HringCH2), 1.57 (m, 2 H, HringCH2CH2), 1.32 (m, 2 H,
HCH2Me), 0.90 (t, J = 7.1 Hz, 3 H, HMe) ppm. 13C NMR (125 MHz,
CDCl3): δ = 158.3 (C3B/6B), 157.6 (C3B/6B), 155.9 (C2C), 153.4 (C2A),
1-Decyl-4-ethynylbenzene was isolated as a yellow oil (1.3 g,
5.4 mmol, 93%). 1H NMR (500 MHz, CDCl3): δ = 7.42 (d, J =
8.0 Hz, 2 H, H2), 7.14 (d, J = 8.0 Hz, 2 H, H3), 3.04 (s, 1 H,
CϵCH), 2.61 (t, J = 7.6 Hz, 2 H, HringCH2), 1.62 (m, 2 H,
HringCH2CH2), 1.29 [m, 14 H, (CH2)7], 0.91 (t, J = 7.5 Hz, 3 H, Me)
ppm. 13C NMR (125 MHz, CDCl3): δ = 144.0 (C4), 132.1 (C2),
149.3 (C6A), 148.9 (C6C), 143.3 (C4D), 140.4 (C4B), 137.1 (C4A), 128.4 (C3), 119.2 (C1), 83.9 (CHCϵC), 76.4 (CHCϵC), 36.2 (CringCH2),
136.4 (C4C), 133.9 (C1D), 128.7 (C2D), 128.4 (C3D), 125.4 (C5B),
124.8 (C3C), 124.7 (C5A), 123.2 (C5C), 121.7 (C3A), 35.2 (CringCH2),
33.2 (CringCH2CH2), 22.2 (CCH2CH3), 13.8 (CMe) ppm. ES MS
32.2 (Calkyl), 31.5 (CringCH2CH2), 29.8 (Calkyl), 29.6 (Calkyl), 29.4
(Calkyl), 29.3 (Calkyl), 22.9 (Calkyl), 14.4 (CMe) ppm. ES MS: m/z =
[M]+ 242. C18H26 (242.40): calcd. C 89.19, H 10.81; found C 89.08,
(CH2Cl2): m/z = 488 [M + K + CH2Cl2]+, 855 [2M + K + H 10.75.
CH2Cl2]+. C24H22N4 (366.46): calcd. C 78.66, H 6.05, N 15.29;
Compound 18: 1-Decyl-4-ethynylbenzene (0.80 g, 3.3 mmol) and
found C 78.64, H 6.17, 15.35.
dptz (0.71 g, 3.0 mmol) were dissolved in toluene (70 mL) and the
solution was heated at reflux for 3 d. Solvent was then removed
and crude 18 was purified by column chromatography (alumina,
hexane/EtOAc, 1:1, second fraction). Compound 18 was obtained
as a beige solid (1.2 g, 2.7 mmol, 90%); m.p. 100.6 °C. 1H NMR
(500 MHz, CDCl3): δ = 8.78 (d, J = 7.9 Hz, 1 H, H3A), 8.69 (d, J
= 4.5 Hz, 1 H, H6A), 8.64 (s, 1 H, H5B), 8.47 (d, J = 4.5 Hz, 1 H,
H6C), 7.87 (td, J = 7.7, 1.6 Hz, 1 H, H4A), 7.83 (d, J = 8.1 Hz, 1
H, H3C), 7.75 (td, J = 7.7, 1.6 Hz, 1 H, H4C), 7.37 (dd, J = 7.6,
4.8 Hz, 1 H, H5A), 7.24 (dd, J = 7.6, 4.8 Hz, 1 H, H5C), 7.15 (d, J
= 8.0 Hz, 2 H, H2D), 7.09 (d, J = 8.0 Hz, 2 H, H3D), 2.59 (t, J =
7.6 Hz, 2 H, HringCH2), 1.59 (m, 2 H, HringCH2CH2), 1.28 [m, 14 H,
(CH2)7], 0.88 (t, J = 7.5 Hz, 3 H, HMe) ppm. 13C NMR (125 MHz,
CDCl3): δ = 158.3 (C3B/6B), 157.6 (C3B/6B), 155.9 (C2C), 153.3 (C2A),
149.3 (C6A), 148.9 (C6C), 143.3 (C4D/4B), 140.4 (C4D/4B), 137.0
1-Ethynyl-4-octylbenzene:
1-Iodo-4-octylbenzene[28]
(1.0 g,
3.2 mmol), CuCl (32 mg, 0.32 mmol) and PdCl2(PPh3)2 (0.23 g,
0.32 mmol) were suspended in dry, argon degassed, Et3N (100 mL).
Then Me3SiCϵCH (0.9 mL, 6 mmol) was added and the mixture
was stirred at 60 °C for 18 h. Solvent was removed and the residue
was extracted with hexane (100 mL). The solution was filtered and
the filtrate was evaporated to dryness. The residue was purified by
column chromatography (alumina, hexane, second fraction). The
product was dissolved in THF (100 mL) and an aqueous solution
of 1  NaOH added (120 mL). The mixture was stirred at room
temperature overnight and then diluted with water until a precipi-
tate formed. 1-Ethynyl-4-octylbenzene was extracted with CH2Cl2
and the combined organic phases were dried with MgSO4. The
solvent was removed to give 1-ethynyl-4-octylbenzene as an orange
oil (0.60 g, 2.8 mmol, 88%). 1H NMR (500 MHz, CDCl3): δ = 7.42 (C4A), 136.3 (C4C), 133.9 (C1D), 128.7 (C2D), 128.4 (C3D), 125.4
Eur. J. Org. Chem. 2008, 1597–1607
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1603

E. C. Constable, C. E. Housecroft et al.
(C5B), 124.8 (C3C), 124.6 (C5A), 123.2 (C5C), 121.7 (C3A), 35.6 Compound 22: 1-Bromo-3-ethynylbenzene (prepared by base depro-
FULL PAPER
(CringCH2), 31.8 (Calkyl), 31.2 (CringCH2CH2), 29.5 (2Calkyl), 29.4
tection of the trimethylsilyl analog[31]) (0.35 g, 1.9 mmol) and dptz
(Calkyl), 29.2 (Calkyl), 29.1 (Calkyl), 22.6 (Calkyl), 14.1 (CMe) ppm. ES (0.46 g, 1.9 mmol) were dissolved in toluene (60 mL) and the solu-
MS (CH2Cl2): m/z = 572 [M + K + CH2Cl2]+. C30H34N4 (450.63): tion was heated at reflux for 9 d. Solvent was then removed and
calcd. C 79.96, H 7.61, N 12.43; found C 79.87, H 7.56, N 12.39.
crude 22 was purified by column chromatography (alumina,
CHCl3, third fraction). Compound 22 was isolated as a beige pow-
der (0.61 g, 1.6 mmol, 83%); m.p. 154.2 °C. H NMR (500 MHz,
Compound 19: 1-Ethynyl-4-methoxybenzene[22,29,30] (0.33 g,
2.5 mmol) and dptz (0.60 g, 2.5 mmol) and were dissolved in tolu-
ene (50 mL) and the reaction mixture was heated at reflux for 70 h.
Solvent was then removed and crude 19 was purified by column
chromatography (alumina, CHCl3, third band). Compound 19 was
isolated as a beige powder (591 mg, 1.73 mmol, 69.5%); m.p.
1
CDCl3): δ = 8.78 (d, J = 7.5 Hz, 1 H, H3A), 8.72 (d, J = 4.8 Hz, 1
H, H6A), 8.61 (s, 1 H, H5B), 8.44 (d, J = 4.8 Hz, 1 H, H6C), 7.99
(d, J = 7.8 Hz, 1 H, H3C), 7.90 (td, J = 7.8, 1.6 Hz, 1 H, H4A), 7.82
(td, J = 7.8, 1.6 Hz, 1 H, H4C), 7.47 (t, J = 1.5 Hz, 1 H, H2D), 7.45
(d, J = 7.5 Hz, 1 H, H4D), 7.40 (dd, J = 7.6, 4.8 Hz, 1 H, H5A),
7.28 (dd, J = 7.6, 4.8 Hz, 1 H, H5C), 7.12 (m, 2 H, H6D+5D) ppm.
13C NMR (125 MHz, CDCl3): δ = 157.9 (C3B/6B), 157.7 (C3B/6B),
155.2 (C2C), 153.0 (C2A), 149.4 (C2A), 148.8 (C2C), 139.1 (C4B/1D),
139.0 (C4B/1D), 137.2 (C4A), 136.7 (C4C), 131.6 (C2D/4D), 131.3
(C2D/4D), 129.7 (C5D), 127.5 (C6D), 125.5 (C5B), 124.9 (C5A), 124.8
(C3C), 123.5 (C5C), 122.4 (C3D), 121.8 (C3A) ppm. ES MS (CH2Cl2):
m/z = 512 [M + K + CH2Cl2]+. C20H13BrN4 (389.25): calcd. C
61.71, H 3.37, N 14.39; found C 61.82, H 3.43, N 14.21.
1
125.1 °C. H NMR (400 MHz, CDCl3): δ = 8.80 (d, J = 7.9 Hz, 1
H, H3A), 8.74 (d, J = 4.8 Hz, 1 H, H6A), 8.65 (s, 1 H, H5B), 8.54
(d, J = 4.8 Hz, 1 H, H6C), 7.92 (td, J = 7.7, 1.6 Hz, 1 H, H4A), 7.85
(d, J = 7.6 Hz, 1 H, H3C), 7.81 (td, J = 7.4, 1.6 Hz, 1 H, H4C), 7.42
(dd, J = 7.6, 4.8 Hz, 1 H, H5A), 7.30 (dd, J = 7.6, 4.8 Hz, 1 H,
H5C), 7.21 (d, J = 8.8 Hz, 2 H, H2D), 6.84 (d, J = 8.9 Hz, 2 H,
H3D), 3.81 (s, 3 H, OMe) ppm. 13C NMR (400 MHz, CDCl3): δ =
159.8 (C4D), 158.3 (C3B/6B), 157.6 (C3B/6B), 156.0 (C2C), 153.4 (C2A),
149.3 (C6A), 149.0 (C6C), 140.1 (C4B), 137.3 (C4A), 136.7 (C4C),
130.4 (C2D), 128.8 (C1D), 125.2 (C5B/3C/5A), 124.9 (C5B/3C/5A), 124.8 1,3-Dibromo-5-ethynylbenzene: 1,3-Dibromo-5-iodobenzene (0.50 g,
(C5B/3C/5A), 123.3 (C5C), 121.9 (C3A), 114.0 (C3D), 55.3 (Me) ppm.
MALDI MS: m/z = 342 [M]+. C21H16N4O (340.38): calcd. C 74.10,
H 4.74, N 16.46; found C 73.76, H 4.85, N 16.52.
1.4 mmol), CuCl (30 mg, 0.30 mmol), and PdCl2(PPh3)2 (0.20 g,
0.30 mmol) were suspended in dry Et3N (50 mL) under dry argon.
Me3SiCϵCH (0.25 mL, 1.8 mmol) was added and the mixture
stirred at 60 °C for 20 h. Solvent was then removed and the residue
extracted with hexane (120 mL). The solution was filtered and the
filtrate evaporated to dryness. The residue was purified by column
chromatography (alumina, hexane/CH2Cl2, 9:1, second fraction).
The silyl-protected product was dissolved in THF (50 mL) and
aqueous NaOH (1 , 100 mL) was added. The mixture was stirred
at room temperature overnight and then diluted with water until a
precipitate formed. The compound was extracted with CH2Cl2 and
the combined organic phases were dried with MgSO4. Solvent was
removed to give 1,3-dibromo-5-ethynylbenzene as a pale brown
powder (0.35 g, 1.4 mmol, 97%); m.p. 109.4 °C (ref.[24] 107.0–
108.0 °C). Spectroscopic and mass spectrometric properties were
consistent with those previously reported.[24]
Compound 20: Compound 19 (230 mg, 0.676 mmol) was dissolved
in acetic acid (10 mL), the solution was cooled to 0 °C and then
HBr (48% aqueous, 10 mL) was added. After being maintained at
0 °C for 20 min, the reaction mixture was heated under reflux for
3 h. The solution was then cooled and adjusted to pH 14 with
NaOH (aqueous, 20%). The orange-yellow solution was then ex-
tracted with CH2Cl2, unreacted 19 being removed into the aqueous
phase (adjusted to pH 5–6 and appearing pink). Compound 20 was
purified by column chromatography (silica, CH2Cl2/MeOH, 5:1,
second fraction) and was isolated as a pink-purple powder (137 mg,
1
63%); m.p. 239.3 °C. H (500 MHz, CDCl3): δ = ppm 8.76 (m, 1
H, H6A), 8.70 (d, J = 7.6 Hz, 1 H, H3A), 8.56 (s, 1 H, H5B), 8.46
(m, 1 H, H6C), 8.00 (t, J = 7.5 Hz, 1 H, H4A), 7.89 (t, J = 7.5 Hz,
1 H, H4C), 7.80 (d, J = 7.6 Hz, 1 H, H3C), 7.51 (m, 1 H, H5A), 7.38
(m, 1 H, H5C), 7.10 (d, J = 8.5 Hz, 2 H, H2D), 6.75 (d, J = 8.5 Hz,
2 H, H3D). Poor solubility of 20 prevented recording of a well-
resolved 13C NMR spectrum. MALDI MS: m/z = 327 [M + H]+.
High resolution MS: m/z = 327.12412; calcd. for [M + H]+
C20H15N4O 327.12460.
Compound 23: A solution of 1,3-dibromo-5-ethynylbenzene (0.21 g,
0.77 mmol) and dptz (0.18 g, 0.77 mmol) in toluene (50 mL) was
heated under reflux for 6 d. Solvent was then removed and the
crude product was purified by column chromatography (alumina,
EtOAc/hexane, 3:1, third fraction). Compound 23 was obtained as
1
a beige powder (0.21 g, 0.45 mmol, 58%); m.p. 231.2 °C. H NMR
(500 MHz, CDCl3): δ = 8.80 (d, J = 8.0 Hz, 1 H, H3A), 8.75 (d, J
= 5.5 Hz, 1 H, H6A), 8.61 (s, 1 H, H5B), 8.46 (d, J = 4.5 Hz, 1 H,
H6C), 8.11 (d, J = 7.6 Hz, 1 H, H3C), 7.93 (td, J = 7.5, 1.6 Hz, 1
H, H4A), 7.89 (td, J = 7.5, 1.6 Hz, 1 H, H4C), 7.64 (t, J = 1.5 Hz,
1 H, H4D), 7.44 (dd, J = 7.6, 4.8 Hz, 1 H, H5A), 7.34 (m, 3 H,
H5C+2D) ppm. 13C NMR (125 MHz, CDCl3): δ = 157.9 (C3B/6B),
157.6 (C3B/6B), 154.8 (C2C), 152.9 (C2A), 149.6 (C6A), 149.0 (C6C),
140.8 (C4B), 137.9 (C1D), 137.4 (C4A), 137.0 (C4C), 133.9 (C4D),
130.6 (C2D), 125.6 (C5B), 125.2 (C5A), 124.9 (C3C), 123.9 (C5C),
122.8 (C3D), 122.0 (C3A) ppm. ES MS (CH2Cl2): m/z = 593 [M +
K + CH2Cl2]+. C20H12Br2N4 (468.15): calcd. C 51.31, H 2.58, N
11.97; found C 51.73, H 2.67, N 12.02.
Compound 21: 1-Acetyl-4-ethynylbenzene[21] (0.31 g, 2.2 mmol) and
dptz (0.50 g, 2.1 mmol) were dissolved in toluene (80 mL), and the
solution was heated under reflux for 72 h. After removal of the
solvent, the crude product was purified by column chromatography
(alumina, CH2Cl2/EtOAc, 5:1, second fraction). Compound 21 was
isolated as a beige solid (0.58 g, 1.6 mmol, 75%); m.p. 156.4 °C. 1H
NMR (500 MHz, CDCl3): δ = 8.78 (d, J = 8.0 Hz, 1 H, H3A), 8.71
(d, J = 4.7 Hz, 1 H, H6A), 8.65 (s, 1 H, H5B), 8.38 (d, J = 4.7 Hz,
1 H, H6C), 8.02 (d, J = 7.8 Hz, 1 H, H3C), 7.90 (dt, J = 7.6, 1.7 Hz,
1 H, H4A), 7.89 (d, J = 8.1 Hz, 2 H, H3D), 7.82 (td, J = 7.5, 1.6 Hz,
1 H, H4C), 7.41 (dd, J = 7.5, 4.4 Hz, 1 H, H5A), 7.35 (d, J = 8.1 Hz,
2 H, H2D), 7.27 (dt, J = 7.5, 4.4 Hz, 1 H, H5C), 2.59 (s, 3 H, Me)
ppm. 1H NMR (125 MHz, CDCl3): δ = 197.6 (CCO), 158.0
Compound 24: 1,3-Dimethoxy-5-ethynylbenzene[32] (0.20 g,
(C3B/6B), 157.8 (C3B/6B), 155.3 (C2C), 153.1 (C2A), 149.6 (C6A), 149.0 1.2 mmol) and dptz (0.26 g, 1.1 mmol) were dissolved in toluene
(C6C), 142.1 (C1D), 139.6 (C4B), 137.4 (C4A), 136.9 (C4C), 136.6 (35 mL), and the solution was heated at reflux for 7 d. Solvent was
(C4D), 129.2 (C2D), 128.4 (C3D), 125.7 (C5B), 125.1 (C5A), 124.9
(C3C), 123.7 (C5C), 122.0 (C3A), 26.7 (CMe) ppm. ES MS (MeCN):
then removed and crude 24 was purified by column chromatog-
raphy (alumina, hexane/EtOAc, 1:2, second fraction). Compound
m/z = 456 [M + Na + 2MeCN]+. C22H16N4O (352.39): calcd. C 24 was isolated as a pale orange powder (0.36 g, 0.97 mmol, 88%);
74.98, H 4.58, N 15.90; found C 75.20, H 4.70, N 15.68.
m.p. 147.2 °C. 1H NMR (400 MHz, CDCl3): δ = 8.78 (d, J =
1604
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1597–1607

Ligands for Supramolecular Assemblies
8.4 Hz, 1 H, H3A), 8.71 (d, J = 5.0 Hz, 1 H, H6A), 8.66 (s, 1 H,
H5B), 8.55 (d, J = 5.0 Hz, 1 H, H6C), 7.90 (td, J = 8.0, 1.6 Hz, 1
H, H4A), 7.80 (m, 2 H, H3C+4C), 7.40 (dd, J = 7.6, 4.8 Hz, 1 H,
1,3-Dibromo-5-[(4-methoxyphenyl)ethynyl]benzene:
thoxybenzene (0.54 g, 2.3 mmol), 1,3-dibromo-5-ethynylbenzene
(0.60 g, 2.3 mmol), CuCl (23 mg, 0.23 mmol), and PdCl2(PPh3)2
1-Iodo-4-me-
H5A), 7.28 (dd, J = 7.6, 4.8 Hz, 1 H, H5C), 6.41 (t, J = 2.5 Hz, 1 (0.17 g, 0.23 mmol) were suspended in dry, argon degassed, Et3N
H, H4D), 6.39 (d, J = 2.5 Hz, 2 H, H2D), 3.64 (s, 6 H, Me) ppm. (60 mL) under argon. The reaction mixture stirred at 60 °C for
13C NMR (100 MHz, CDCl3): δ = 160.6, 158.3, 157.7, 155.8, 153.3, 18 h, after which time, solvent was removed and the residue ex-
149.3, 149.1, 140.3, 138.6, 137.1, 136.4, 125.2, 124.7, 123.2, 121.8,
107.0, 100.9, 55.3 ppm. ES MS (CH2Cl2): m/z = 492 [M + K +
CH2Cl2]+. C22H18N4O2 (370.41): calcd. C 71.34, H 4.90, N 15.13;
found C 71.30, H 4.80, N 14.95.
tracted with hexane (100 mL). The solution was filtered and filtrate
evaporated to dryness. The residue was purified by column
chromatography (alumina, hexane, second fraction) and 1,3-di-
bromo-5-[(4-methoxyphenyl)ethynyl]benzene was isolated as a be-
ige solid (0.56 g, 1.5 mmol, 65%); m.p. 101.2 °C. 1H NMR
(500 MHz, CDCl3, ring labelling as in 28): δ = 7.59 (t, J = 1.6 Hz,
1 H, H4D), 7.58 (d, J = 1.6 Hz, 2 H, H2D), 7.45 (d, J = 8.8 Hz, 2
H, H2E), 6.89 (d, J = 8.8 Hz, 2 H, H3E), 3.83 (s, 3 H, Me) ppm.
13C NMR (125 MHz, CDCl3): δ = 160.1 (C4E), 133.5 (C4D), 133.2
(C2D), 132.7 (C2E), 127.1 (C1D/1E), 122.5 (C3D), 114.3 (C1D/1E),
Compound 25: 1-Ethynylcyclohexan-1-ol (0.19 g, 1.5 mmol) and
dptz (0.30 g, 1.3 mmol) were dissolved in toluene (70 mL) and the
reaction mixture was heated under reflux for 15 d. After removal
of solvent, crude 25 was purified by column chromatography (alu-
mina, hexane/EtOAc, 1:1, second fraction). Compound 25 was ob-
tained as a pale pink powder (0.30 g, 0.90 mmol, 71%); m.p.
141.2 °C. 1H NMR (400 MHz, CDCl3): δ = 8.77 (s, 1 H, H5B), 8.75
(m, 2 H, H6A+3A), 8.66 (ddd, J = 4.8, 2.0, 1.2 Hz, 1 H, H6C), 8.37
(dt, J = 7.6, 1.2 Hz, 1 H, H3C), 8.02 (td, J = 7.6, 1.6 Hz, 1 H, H4A),
7.90 (td, J = 7.6, 1.6 Hz, 1 H, H4C), 7.49 (ddd, J = 7.6, 4.8, 1.2 Hz,
1 H, H5A), 7.42 (ddd, J = 7.6, 4.8, 1.2 Hz, 1 H, H5C), 1.96 (m, 2
H, H2Dax), 1.85 (m, 2 H, H3Dax), 1.65 (m, 3 H, H4Deq+2Deq), 1.49
114.1 (C3E), 92.1 [C(ring D)CϵC], 85.3 [CCϵC(ring E)], 55.3 (COMe
)
ppm. ES MS: m/z (%) = 365 [M]+. C15H11Br2O (367.06): calcd. C
49.22, H 2.75; found C 49.25, H 2.85.
Compound 28: 1,3-Dibromo-5-(4-methoxyphenylethynyl)benzene
(0.20 g, 0.55 mmol) and dptz (0.13 g, 0.55 mmol) were heated with-
out solvent at 170 °C for 10 d. The product was purified by column
(m, 2 H, H3Deq), 1.20 (m, 1 H, H4Dax) ppm. 13C NMR (100 MHz, chromatography (alumina, EtOAc, third fraction) and 28 was iso-
CDCl3): δ = 158.0 (C6B/2A/2C), 157.6 (C6B/2A/2C), 157.3 (C6B/2A/2C),
153.2 (C3B), 149.5 (C6A), 147.7 (C4B), 146.5 (C6C), 138.5 (C4C), 1H NMR (500 MHz, CDCl3): δ = 8.45 (ddd, J = 4.8, 1.6, 1.2 Hz,
137.2 (C4A), 126.5 (C3C), 124.8 (C5A), 124.3 (C5C), 121.9 (C5B/3A), 1 H, H6C), 8.40 (d, J = 4.8, 1.6, 1.2 Hz, 1 H, H6A), 7.87 (dt, J =
lated as a beige powder (0.23 g, 0.40 mmol, 73%); m.p. 189.2 °C.
121.8 (C5B/3A), 70.9 (C1D), 36.3 (C2D), 25.6 (C4D), 21.9 (C3D) ppm. 8.0, 1.2 Hz, 1 H, H3A), 7.77 (td, J = 7.5, 1.6 Hz, 1 H, H4A), 7.67
ES MS (CHCl3): m/z = 454 [M + CHCl3]+. C20H20N4O·0.25H2O:
(td, J = 7.5, 1.6 Hz, 1 H, H4C), 7.60 (dt, J = 8.0, 1.2 Hz, 1 H, H3C),
7.39 (t, J = 1.5 Hz, 1 H, H4D), 7.25 (dd, J = 7.5, 4.8 Hz, 1 H, H5A),
7.21 (dd, J = 7.5, 4.8 Hz, 1 H, H5C), 6.98 (d, J = 1.5 Hz, 2 H, H2D),
6.77 (d, J = 8.7 Hz, 2 H, H2E), 6.63 (d, J = 8.7 Hz, 2 H, H3E), 3.69
(s, 3 H, Me) ppm. 13C NMR (125 MHz, CDCl3): δ = 159.1
(C3B/6B), 158.9 (C4E), 157.8 (C3B/6B), 155.8 (C2C), 155.2 (C2A), 149.0
(C6C), 148.8 (C6A), 139.1 (C4B/5B), 138.7 (C4B/5B), 136.6 (C4A), 136.2
(C4C), 132.8 (C4D), 131.9 (C2D), 131.3 (C2E), 125.9 (C1E), 125.0
(C3A+3C), 123.4 (C5A), 123.0 (C5C), 121.7 (C3D), 113.5 (C3E), 55.0
(CMe) ppm. ES-MS (CH2Cl2): m/z = [M + K + CH2Cl2]+ 696.
C27H19Br2N4O (575.28): calcd. C 56.37, H 3.33, N 9.74; found C
56.24, H 3.20, N 9.68.
calcd. C 71.30, H 6.13, N 16.63; found C 71.88, H 6.07, N 16.69.
Compound 26: Diphenylethyne (214 mg, 1.20 mmol) and dptz
(200 mg, 0.85 mmol) were heated together without solvent at
170 °C for 66 h. The crude product was subjected to column
chromatography (alumina, CHCl3) and 26 was collected as the
third fraction. Compound 26 was isolated as a red powder (258 mg,
0.66 mmol, 77.6%); m.p. 190.8 °C. 1H NMR (400 MHz, CDCl3): δ
= 8.43 (d, J = 4.7 Hz, 2 H, H6A), 7.69 (dt, J = 7.8, 2.0 Hz, 2 H,
H4A), 7.66 (dt, J = 7.2, 1.6 Hz, 2 H, H3A), 7.18 (ddd, J = 7.2, 4.7,
1.6 Hz, 2 H, H5A), 7.00 (m, 6 H, H4D+3D), 6.87 (m, 4 H, H2D) ppm.
13C NMR (100 MHz, CDCl3): δ = 158.9 (C3B), 156.1 (C2A), 148.8
(C6A), 139.2 (C4B/1D), 136.1 (C4A), 134.7 (C4B/1D), 130.1 (C2D/3D),
Compound 29: 1,2-Bis(4-ethynylphenyl)ethyne[34,35] (0.15 g,
127.5 (C2D/3D), 127.2 (C4D), 125.0 (C5A), 122.8 (C3A) ppm. ES MS 0.66 mmol) and dptz (625 mg, 2.65 mmol) were heated without sol-
(MeCN): m/z
C26H18N4·0.25H2O: calcd. C 79.88, H 4.77, N 14.33; found C chromatography (silica, CH2Cl2/MeOH, 9:1, second fraction).
= + Na +
385 [M]+, 477 [M MeCN]+. vent at 170 °C for 18 h. The product was purified by column
79.67, H 4.80, N 14.33.
Compound 29 was isolated as a pale brown powder (0.34 g,
0.53 mmol, 80%). Dec. Ͼ 300 °C. H NMR (400 MHz, CDCl3): δ
1
Compound 27: 1-Bromo-4-[(4-methoxyphenyl)ethynyl]benzene[33]
(0.30 g, 1.1 mmol) and dptz (0.25 g, 1.1 mmol) were heated without
solvent at 170 °C for 5 d. The product was purified twice by column
chromatography (alumina, hexane/EtOAc, 1:1 followed by alu-
mina, CHCl3, third fraction). Compound 27 was isolated as a pur-
ple powder (0.23 g, 0.47 mmol, 45%); m.p. 198.8 °C. 1H NMR
(500 MHz, CDCl3): δ = 8.46 (d, J = 4.5 Hz, 1 H, H6A/6C), 8.40 (d,
J = 4.5 Hz, 1 H, H6A/6C), 7.72 (m, 2 H, H3A+4A), 7.67 (td, J = 7.6,
1.8 Hz, 1 H, H4C), 7.60 (dt, J = 8.0, 1.2 Hz, 1 H, H3C), 7.19 (m, 4
H, H5A+5C+3D), 6.74 (d, J = 8.4 Hz, 4 H, H2D+2E), 6.58 (d, J =
8.4 Hz, 2 H, H3E), 3.69 (s, 3 H, Me) ppm. 13C NMR (125 MHz,
CDCl3): δ = 159.0 (C4E), 158.5 (C3B/6B), 158.3 (C3B/6B), 155.9
(C2A/2C), 155.6 (C2A/2C), 148.7 (C6A/6C), 148.6 (C6A/6C), 138.6
(C4B/5B), 137.8 (C4B/5B), 136.1 (C4A/4C), 135.9 (C4A/4C), 133.8 (C1D),
= 8.80 (d, J = 7.5 Hz, 2 H, H3A), 8.74 (d, J = 4.8 Hz, 2 H, H6A),
8.66 (s, 2 H, H5B), 8.46 (d, J = 4.8 Hz, 2 H, H6C), 7.98 (d, J =
7.5 Hz, 2 H, H3C), 7.92 (td, J = 7.5, 1.6 Hz, 2 H, H4A), 7.83 (td, J
= 7.5, 1.6 Hz, 2 H, H4C), 7.47 (d, J = 8.4 Hz, 4 H, H3D), 7.42 (dd,
J = 7.6, 4.8 Hz, 2 H, H5A), 7.29 (dd, J = 7.6, 4.8 Hz, 2 H, H5C),
7.26 (d, J = 8.4 Hz, 4 H, H2D) ppm. 13C NMR (100 MHz, CDCl3):
δ = 158.0 (C3B/6B), 157.7 (C3B/6B), 155.5 (C2C), 153.2 (C2A), 149.4
(C6A), 149.0 (C6C), 139.8 (C1D), 137.2 (C4A), 137.1 (C4B), 136.7
(C4C), 131.6 (C3D), 128.9 (C2D), 125.4 (C5B), 124.9 (C5A/3C), 124.8
(C5A/3C), 123.5 (C5C), 123.1 (C4D), 121.9 (C3A), 90.2 (CCϵC) ppm.
MALDI-MS: m/z (%) = 643 [M]+. C42H26N8·CH3OH: calcd. C
76.54, H 4.48, N 16.61; found C 76.57, H 4.41, N 15.96.
1-Bromo-3,5-diethynylbenzene: 1-Bromo-3,5-diethynylbenzene was
131.5 (C2D/2E), 131.2 (C2D/2E), 130.6 (C3D), 126.1 (C1E), 124.7 formed as side-product from the synthesis of 1,3-dibromo-5-ethyn-
(C3A+3C), 122.7 (C5A/5C), 122.6 (C5A/5C), 121.3 (C4D), 113.0 (C3E), ylbenzene (see above). 1,3-dibromo-5-iodobenzene was isolated as
54.8 (CMe) ppm. ES MS (CH2Cl2): m/z = 618 [M + K +
CH2Cl2]+.C27H19BrN4O (495.38): calcd. C 65.46, H 3.87, N 11.31;
found C 64.99, H 3.80, N 11.29.
an orange powder (0.14 g, 0.68 mmol, 5.7%); m.p. 110.2 °C (lit.[24]
108.5–109.0 °C). Spectroscopic and mass spectrometric properties
were consistent with those previously reported.[24]
Eur. J. Org. Chem. 2008, 1597–1607
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1605

E. C. Constable, C. E. Housecroft et al.
FULL PAPER
Compound 30: A solution of dptz (0.16 g, 0.68 mmol) and 1-bromo-
3,5-diethynylbenzene (25) (64 mg, 0.31 mmol) in toluene (60 mL)
was refluxed for 14 d at 120 °C. After evaporation of the solvent
under reduced pressure, the crude product was purified by column
chromatography [alumina, EtOAc/hexane (2:1), the second band
was collected]. The product was obtained as a deep pink solid
(0.16 g, 0.26 mmol, 87%, C34H21BrN8, 621.5 g/mol); m.p. 236.9 °C.
1H NMR (500 MHz, CDCl3): δ = 8.77 (m, 4 H, H3A+6A), 8.51 (ddd,
J = 4.8, 1.7, 0.9 Hz, 2 H, H6C), 8.43 (s, 2 H, H5B), 8.02 (dt, J =
7.8, 0.8 Hz, 2 H, H3C), 7.92 (td, J = 7.6, 1.6 Hz, 2 H, H4A), 7.87
(td, J = 7.6, 1.6 Hz, 2 H, H4C), 7.44 (ddd, J = 7.6, 4.8, 1.2 Hz, 2
H, H5A), 7.36 (d, J = 1.6 Hz, 2 H, H2D), 7.34 (ddd, J = 7.6, 4.8,
1.2 Hz, 2 H, H5C), 7.11 (t, J = 1.6 Hz, 1 H, H4D) ppm. 13C NMR
(125 MHz, CDCl3): δ = 157.8 (C3B/6B), 157.7 (C3B/6B), 154.9 (C2C),
152.9 (C2A), 149.3 (C6A), 148.9 (C6C), 139.1 (C3D), 138.4 (C4B),
137.2 (C4A), 136.8 (C4C), 131.5 (C2D), 128.1 (C4D), 125.4 (C5B),
finement of 2944 reflections (279 parameters) with IϾ3.0σ (I) con-
verged at final R1 = 0.0248 (R1 all data = 0.0500), wR2 = 0.0259
(wR2 all data = 0.0341), gof = 1.113.
Crystal Data for Compound 20: C20H14N4O, M = 326.36, mono-
clinic, space group P21/c, a = 6.1956(1), b = 18.1993(3), c =
14.0703(2) Å, β = 96.416(1)°, U = 1576.57(4) Å3, Z = 4, Dcalcd.
=
1.375 Mgm–3, µ(Mo-Kα) = 0.089 mm–1, T = 173 K, 3595 reflections
collected. Refinement of 2402 reflections (226 parameters) with
IϾ3.0σ (I) converged at final R1 = 0.0330 (R1 all data = 0.0521),
wR2 = 0.0408 (wR2 all data = 0.0459), gof = 0.979.
CCDC-668674 (for 8), -668673 (for 10), -668671 (for 12) and
-668672 (for 20) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
124.9 (C5A), 124.8 (C3C), 123.8 (C5C), 122.0 (C1D), 121.8 (C3A
)
ppm. ES-MS (CH2Cl2): m/z = 744 [M + K + CH2Cl2]+, 1366 [2M
+ K + CH2Cl2]+. High resolution MS: m/z = 621.11490 and Acknowledgments
623.11291; calcd. for [M + H]+ C34H22BrN8 621.11508 and
623.11303.
We thank the Swiss National Science Foundation and the Univer-
sity of Basel for financial support. Valérie Jullien, Azad Mahmood,
Hoi Shan Chow, Kate Harris and Ana Hernandez are acknowl-
edged for recording the 500-MHz NMR spectra. We also thank
Fredy Nydegger (University of Fribourg) for recording high resolu-
tion mass spectra.
Compound 31: 1,3,5-Triethynylbenzene[36–38] (0.15 g, 0.99 mmol)
and dptz (700 mg, 2.97 mmol) were dissolved in toluene (50 mL).
The mixture was heated under reflux at 120 °C for 6 d. The solvent
was removed by evaporation and the product purified by chromato-
graphic work-up [silica, dichloromethane/MeOH (9:1), the second
band was collected], to give a 31 as a pink powder (0.54 g,
0.69 mmol, 69%); m.p. 165.9 °C. 1H NMR (500 MHz, CDCl3): δ
= 8.77 (m, 6 H, H3A+6A), 8.56 (d, J = 5.0 Hz, 3 H, H6C), 8.25 (s, 3
H, H5B), 7.90 (m, 6 H, H4A+3C), 7.86 (td, J = 7.5, 1.6 Hz, 3 H,
H4C), 7.44 (dd, J = 7.6, 4.8 Hz, 3 H, H5A), 7.35 (dd, J = 7.6, 4.8 Hz,
3 H, H5C), 7.14 (s, 3 H, H2D) ppm. 13C NMR (125 MHz, CDCl3):
δ = 158.0 (C3B/6B), 157.8 (C3B/6B), 155.3 (C2C), 153.1 (C2A), 149.4
(C6A), 149.0 (C6C), 139.3 (C4B), 137.6 (C1D), 137.3 (C4A), 136.8
(C4C), 129.5 (C2D), 125.6 (C5B), 125.1 (C3C/5A), 125.0 (C3C/5A),
123.9 (C5C), 121.9 (C3A) ppm. ES-MS: m/z = 775 [M + H]+. High
resolution MS: m/z = 775.27831; calcd. for [M + H]+ C48H31N12
775.27947.
[1] W. Kaim, Coord. Chem. Rev. 2002, 230, 127–139.
[2] Z. Xu, L. K. Thompson in Comprehensive Coordination Chem-
istry II (Eds: J. A. McCleverty, T. J. Meyer), Elsevier, Oxford,
2004, vol. 1, pp. 63–95.
[3] L. K. Thompson, Coord. Chem. Rev. 2002, 233–234, 193–206.
[4] P. N. W. Baxter in Comprehensive Supramolecular Chemistry
(Eds: J. L. Atwood, J. E. D. Davies, D. D. Macnicol, F. Vögtle),
Pergamon, Oxford, 1996, vol. 9, pp. 165–211.
[5] M.-T. Youinou, N. Rahmouni, J. Fischer, J. A. Osborn, Angew.
Chem. Int. Ed. Engl. 1992, 6, 733–735.
[6] N.-D. Sung, K.-S. Yun, T.-Y. Kim, K.-Y. Choi, M. Suh, J.-G.
Kim, I.-H. Suh, J. Chin, Inorg. Chem. Commun. 2001, 4, 377–
380.
Crystal Structure Determinations. General: Data were collected
with an Enraf Nonius Kappa CCD instrument; data reduction,
solution and refinement used the progams COLLECT,[64] SIR92,[65]
DENZO/SCALEPACK[66] and CRYSTALS.[67] Structures have
been analysed using Mercury v. 1.4.2.[46]
[7] I. Weissbuch, P. N. W. Baxter, I. Kuzmenko, H. Cohen, S. Co-
hen, K. Kjaer, P. B. Howes, J. Als-Nielsen, J.-M. Lehn, L. Lei-
serowitz, M. Lahav, Chem. Eur. J. 2000, 6, 725–734.
[8] P. N. W. Baxter, J.-M. Lehn, B. O. Kneisel, D. Fenske, Angew.
Chem. Int. Ed. Engl. 1997, 36, 1978–1981.
[9] E. C. Constable, C. E. Housecroft, B. M. Kariuki, N. Kelly,
C. B. Smith, C. R. Chim. 2002, 5, 425–430.
Crystal Data for Compound 8: C21H14Cl3N5O2, M = 474.73, tri-
clinic, space group P-1, a = 6.0955(1), b = 12.3860(2), c =
15.2362(4) Å, α = 108.742(1), β = 91.078(1), γ = 100.147(1)°, U =
[10] E. C. Constable, C. E. Housecroft, B. M. Kariuki, N. Kelly,
C. B. Smith, Inorg. Chem. Commun. 2002, 5, 199–202.
[11] E. C. Constable, C. E. Housecroft, B. M. Kariuki, M. Neu-
burger, C. B. Smith, Aust. J. Chem. 2003, 56, 653–655.
[12] Calculations were carried out at the PM3 level using Spartan
2004, Wavefunction Inc.
[13] E. C. Constable, C. E. Housecroft, M. Neuburger, S. Reymann,
S. Schaffner, Chem. Commun. 2004, 1056–1057.
[14] W. A. Butte, F. H. Case, J. Org. Chem. 1961, 26, 4690–4692.
[15] R. A. Carboni, R. V. Lindsey, J. Am. Chem. Soc. 1959, 81,
4342–4346.
[16] R. A. Russell, D. E. Marsden, M. Sterns, R. N. Warrener, Aust.
J. Chem. 1981, 34, 1223–1234.
[17] R. Hoogenboom, G. Kickelbick, U. S. Schubert, Eur. J. Org.
Chem. 2003, 24, 4887–4896.
[18] R. Hoogenboom, B. C. Moore, U. S. Schubert, J. Org. Chem.
2006, 71, 4903–4909.
1068.77(4) Å3,
Z = 2, Dcalcd. = =
1.475 Mgm–3, µ(Mo-Kα)
0.458 mm–1, T = 173 K, 5091 reflections collected. Refinement of
3058 reflections (280 parameters) with I Ͼ3.05σ (I) converged at
final R1 = 0.0372 (R1 all data = 0.0657), wR2 = 0.0421 (wR2 all
data = 0.0735), gof = 1.119.
Crystal Data for Compound 10: C21H13N5, M = 335.37, monoclinic,
space group P21/c, a = 14.5427(3), b = 6.4822(1), c = 17.991(1) Å,
β = 105.991(1)°, U = 1624.71(6) Å3, Z = 4, Dcalcd. = 1.371 Mgm–3,
µ(Mo-Kα) = 0.086 mm–1, T = 173 K, 3724 reflections collected. Re-
finement of 2138 reflections (235 parameters) with IϾ1.5σ (I) con-
verged at final R1 = 0.0398 (R1 all data = 0.0821), wR2 = 0.0432
(wR2 all data = 0.1082), gof = 1.098.
Crystal Data for Compound 12: C20H13BrN4, M = 389.25, ortho-
rhombic, space group Pcab, a = 6.2688(3), b = 21.845(3), c =
24.209(3) Å, U = 3315.4(5) Å3, Z = 8, Dcalcd. = 1.560 Mgm–3,
µ(Mo-Kα) = 2.489 mm–1, T = 173 K, 4828 reflections collected. Re-
[19] K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett.
1975, 16, 4467–4470.
[20] K. Sonogashira, J. Organomet. Chem. 2002, 653, 46–49.
1606
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1597–1607

Ligands for Supramolecular Assemblies
[21] S. Takahashi, Y. Kuroyama, K. Sonogashira, N. Hagihara,
Synthesis 1980, 627–630.
[22] A. Elangovan, S.-W. Yang, J.-H. Lin, K.-M. Kao, T.-I. Ho,
Org. Biomol. Chem. 2004, 2, 1597–1602.
[23] R. P. Hsung, C. E. D. Chidsey, L. R. Sita, Organometallics
1995, 14, 4808–4815.
[24] J. M. A. Robinson, B. M. Kariuki, K. D. M. Harris, D. Philp,
J. Chem. Soc. Perkin Trans. 2 1998, 2459–2470.
[25] O. Livastre, S. Cabioch, P. H. Dixneuf, J. Vohlidal, Tetrahedron
1997, 53, 7595–7604.
[26] E. L. Bruner, A. R. Span, S. L. Bernasek, J. Schwartz, Lang-
muir 2001, 17, 5696–5702.
[27] Y. Fujita, Y. Misumi, M. Tabata, T. Masuda, J. Polym. Sci., A
1998, 36, 3157–3163.
[28] T. Abe, T. Yamaji, T. Kitamura, Bull. Chem. Soc. Jpn. 2003,
76, 2175–2178.
[44]
[45]
[46]
T. Steiner, Angew. Chem. Int. Ed. 2002, 41, 48–76.
F. H. Allen, Acta Crystallogr., Sect. B 2002, 58, 380–388.
I. J. Bruno, J. C. Cole, P. R. Edgington, M. K. Kessler, C. F.
Macrae, P. McCabe, J. Pearson, R. Taylor, Acta Crystallogr.,
Sect. B 2002, 58, 389–397.
[47]
S-Q. Zhang, Sichuan Shifan Daxue Xuebao, Ziran Kexueban
2001, 24, 384–387.
[48]
[49]
H. van der Meer, Acta Crystallogr., Sect. B 1972, 28, 367–370.
H.-K. Fun, S.-F. Zhang, Z.-F. Chen, H. Liang, S. Chantrap-
romma, Acta Crystallogr., Sect. E 2006, 62, o2178–o2180.
T. Hokelek, E. Kilic, S. Aktan, Acta Crystallogr., Sect. C 1999,
55, 383–385.
T. F. Knopfel, P. Zarotti, T. Ichikawa, E. M. Carreira, J. Am.
Chem. Soc. 2005, 127, 9682–9683.
U. Groselj, S. Recnik, J. Svete, A. Meden, B. Stanovnik, Tetra-
hedron: Asymmetry 2002, 13, 821–833.
V. J. Catalano, M. A. Malwitz, S. J. Horner, J. Vasquez, Inorg.
Chem. 2003, 42, 2141–2148.
G. D. Andreetti, G. Bocelli, P. Sgarabotto, Acta Crystallogr.,
Sect. B 1980, 36, 1839–1846.
F. Abraham, B. Mernari, M. Lagrenee, S. Sueur, Acta Crys-
tallogr., Sect. C 1989, 45, 1327–1329.
[50]
[51]
[52]
[53]
[54]
[55]
[29] A. Elangovan, Y.-H. Wang, T.-I. Ho, Org. Lett. 2003, 5, 1841–
1844.
[30] J. G. Rodríguez, A. Lafuente, R. Martín-Villamil, J. Polym.
Sci., A 2005, 43, 5987–5997.
[31] M. J. Mio, L. C. Kopel, J. B. Braun, T. L. Gadzikwa, K. L.
Hull, R. G. Brisbois, C. J. Markworth, P. A. Grieco, Org. Lett.
2002, 4, 3199–3202.
[56]
[57]
[58]
T. Hokelek, Acta Crystallogr., Sect. C 1991, 47, 1432–1434.
Y. J. L e e, Y. J. P a r k , J. Korean Chem. Soc. 1981, 25, 219–227.
T. Mathew, M. Keller, D. Hunkler, H. Prinzbach, Tetrahedron
Lett. 1996, 37, 4491–4494.
[32] L. Gehringer, C. Bourgogne, D. Guillon, B. Donnio, J. Am.
Chem. Soc. 2004, 126, 3856–3867.
[33] K. Kondo, T. Fujitani, N. Ohnishi, J. Mater. Chem. 1997, 7,
429–433.
[34] E. C. Constable, D. Gusmeroli, C. E. Housecroft, M. Neu-
burger, S. Schaffner, Polyhedron 2006, 25, 421–428.
[35] C. D. Simpson, J. D. Brand, A. J. Berresheim, L. Przybilla,
H. J. Räder, K. Müllen, Chem. Eur. J. 2002, 8, 1424–1429.
[36] F. Effenberger, W. Kurtz, Chem. Ber. 1973, 106, 511–524.
[37] E. Weber, M. Hecker, E. Koepp, W. Orlia, M. Czugler, I.
Csöregh, J. Chem. Soc. Perkin Trans. 2 1988, 1251–1257.
[38] S. Leininger, P. J. Stang, S. Huang, Organometallics 1998, 17,
3981–3987.
[39] S. Ghumaan, B. Sarker, S. Patra, K. Parimal, J. van Slageren,
J. Fiedler, W. Kaim, G. K. Lahiri, Dalton Trans. 2005, 706–712.
[40] M. Balogh, P. Laszlo, K. Simon, J. Org. Chem. 1987, 52, 2026–
2029.
[41] M. J. Haddadin, Y. Wang, S. Frenkel, S. G. Bott, L. Yang, P. S.
Braterman, C. Carvallo, A. P. Marchand, W. H. Watson, R. P.
Kashyap, M. Krawiec, S. A. Borne, Heterocycles 1994, 37, 869–
882.
[42] W. H. Watson, R. P. Kashyap, M. Krawiec, D. Sun, T. F. Carl-
son, A. P. Marchand, Y. Wang, J. Chem. Crystallogr. 1994, 24,
259–266.
[59]
[60]
[61]
[62]
[63]
T. Yasuda, Y. Sakai, S. Aramaki, T. Yamamoto, Chem. Mater.
2005, 17, 6060–6068.
F. Thebault, A. J. Blake, C. Wilson, N. R. Champness, M.
Schröder, New J. Chem. 2006, 30, 1498–1508.
U. J. Scheele, S. Dechert, F. Meyer, Inorg. Chim. Acta 2006,
359, 4891–4900.
Y. V. Tomilov, D. N. Platonov, D. V. Dorokhov, O. M. Nefedov,
Tetrahedron Lett. 2007, 48, 883–886.
G. Atwell, P. D. W. Boyd, W. A. Denny, S. Yang, Acta Crys-
tallogr., Sect. E 2006, 62, o5080–o5082.
COLLECT Software, Nonius BV, 1997–2001.
A. Altomare, G. Cascarano, G. Giacovazzo, A. Guagliardi,
M. C. Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr.
1994, 27, 435–435.
Z. Otwinowski, W. Minor, Methods in Enzymology, vol. 276
(Eds.: C. W. Carter, R. M. Sweet Jr), 1997, Academic Press,
New York, pp. 307.
P. W. Betteridge, J. R. Carruthers, R. I. Cooper, K. Prout, D. J.
Watkin, J. Appl. Crystallogr. 2003, 36, 1487–1487.
Received: November 26, 2007
[64]
[65]
[66]
[67]
[43] G. R. Desiraju, T. Steiner, The Weak Hydrogen Bond, Oxford
University Press, 1999.
Published Online: January 31, 2008
Eur. J. Org. Chem. 2008, 1597–1607
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1607