New three- and four-armed flexible bridging ligands for use in metallosupramolecular chemistry: syntheses and X-ray structures

Article abstract of DOI:10.1016/j.tet.2009.07.068

Preparations are described of twelve new tritopic and tetratopic ligands by coupling of two phenolic precursors with a range of heterocyclic units. X-ray crystal structures of four representative examples revealed the conformations in the solid state with

Full text of DOI:10.1016/j.tet.2009.07.068

Tetrahedron 65 (2009) 7948–7953
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
New three- and four-armed flexible bridging ligands for use in
metallosupramolecular chemistry: syntheses and X-ray structures
*
Justine R.A. Cottam, Peter J. Steel
Chemistry Department, University of Canterbury, Christchurch, New Zealand
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 17 April 2009
Received in revised form 23 June 2009
Accepted 23 July 2009
Available online 29 July 2009
Preparations are described of twelve new tritopic and tetratopic ligands by coupling of two phenolic
precursors with a range of heterocyclic units. X-ray crystal structures of four representative examples
revealed the conformations in the solid state with the nitrogen donor atoms separated by distances
ranging from 10.9 to 18.2 Å.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
We now extend this design strategy to a range of three- and
four-armed ligands derived from two commercially available phe-
The term metallosupramolecular chemistry1,2 is used to describe
the use of combinations of bridging organic ligands and metallic
reagents for the construction of both discrete and polymeric as-
semblies with diverse architectures.3–10 Originally, rigid bridging
ligands were used for the rational construction of symmetrical
polygons (squares, hexagons, etc.) and polyhedra (cubes, octahedra,
dodecahedra, etc.). For some time, we have employed many flexible
ligands that provide access to other less symmetrical topologies
(helicates, rectangles, boxes, cages, etc.) that are not available to the
more rigid ligands.10 Recently11 we reported the synthesis of a family
of ditopic ligands by coupling commercially available bisphenols
with various nitrogen heterocycles. For example, ligands 1 and 2
weremade by reactions of bisphenols A and P with 2-bromopyridine
and 2-chloromethylpyridine, respectively. By varying the starting
bisphenol, the nature of the heterocycle and the presence or other-
wise of additional methylenespacer groups, wewere able to prepare
a range of ligands that hold two metal centres apart by varying
distances and use these for the preparation of a range of novel
metallosupramolecular assemblies.12
nolic precursors. These new ligands are potentially capable of
bridging three or four metal centres. The syntheses of twelve such
ligands are described along with the crystal structures of four
representative examples.
2. Results and discussion
All the ligands were prepared by nucleophilic substitution re-
actions. Seven three-armed ligands were prepared from precursor
3 by substitutions of appropriate heterocyclic halides (4). Thus,
compounds 5–6 were prepared by nucleophilic aromatic sub-
stitution reactions with 2-bromopyridine (4a), 2-chloropyrazine
(4b), 2-chloroquinoline (4c) and 2-chloroquinoxaline (4d), re-
spectively, (Scheme 1). These reactions were carried out in
a refluxing sulpholane/toluene mixture, reaction conditions we
have found to be particularly effective for the preparation of related
ligands.11,13 The methylene-expanded ligands 9–11 were prepared
by phase-transfer-catalysed triple alkylation of 3 using 2-, 3- and
4-chloromethylpyridines (4e–g). Once again we have used these
reaction conditions to prepare many structurally related ligands.14,15
The products were isolated by standard procedures and purified
by recrystallisation. Isolated yields were generally good and are
shown in Scheme 1. The compounds were all characterised by ele-
mental analysis, mass spectrometry, melting point and by 1H and
13C NMR (see Experimental section). Full assignments of the 1H
NMR spectra were relatively straightforward, being aided by the
symmetrical nature of the compounds. The separate spin systems of
the various aromatic rings were readily identified by their integrals
and cross-couplings and the individual protons of the heterocycles
were assigned from their characteristic chemical shifts, spin–spin
coupling and by comparison with the spectra from our own library
of structurally related ligands containing these heterocycles.10
N
N
O
O
1
N
O
O
N
2
* Corresponding author. Tel.: þ64 3 3642432; fax: þ64 3 3642110.
E-mail address: peter.steel@canterbury.ac.nz (P.J. Steel).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.07.068

J.R.A. Cottam, P.J. Steel / Tetrahedron 65 (2009) 7948–7953
7949
X
N
O
O
N
OH
X
O
N
X
K2CO3
HO
4a-d
sulpholane/toluene
reflux 48 hr
5
X = CH (59%)
X = N (96%)
6
3
X
N
OH
Figure 1. X-ray crystal structure of ligand 5.
O
atoms within the ligand is 10.9 Å. In the extended structure there
are edge-to-face interactions between aromatic rings as well as
C–H/N interactions involving the pyridine rings.
4e-g
The methylene-expanded 4-pyridyl compound 11 crystallises in
the triclinic space group P-1 (Fig. 2). Unlike 5 the asymmetric unit
contains one whole ligand molecule and a disordered solvent
molecule. The overall structure of ligand 11 is quite similar to that of
5 with the three benzene rings splayed in a propeller-like fashion
about the central quaternary carbon atom core. However, each of
the binding arms in the ligand adopts a different conformation. In
two of the ligand arms, the pyridine rings lie almost perpendicular
to the meanplanes of their adjacent benzene ring, whereas in the
third ligand arm the pyridine and benzene ring lie approximately
coplanar with one another. This destroys any potential higher in-
ternal symmetry. The two-atom methyleneoxy spacer groups all
adopt a trans-periplanar arrangement, which is reflected in the
C–C–O–C torsional angles of 165.6, 176.4 and 178.4ꢀ. Due to
the incorporation of a 4-pyridyl group rather than 2-pyridyl, and
the additional methylene spacer groups, the distances between
the potentially coordinating nitrogen atoms are expanded to 16.8,
17.2 and 18.2 Å.
O
N
40% NaOH
NMe4OH
benzene
X
reflux 48 hr
O
N
X
7 X = CH (98%)
8 X = N (40%)
N
O
N
O
O
N
9
2-pyridyl (13%)
10 3-pyridyl (66%)
11 4-pyridyl (57%)
Scheme 1. Preparations of 5–11.
Single crystal X-ray structure determinations were carried out
on 5 and 11 to confirm their structures and to determine their
conformations in the solid state, in order to gain some insight into
the possible mode by which they might act as bridging ligands in
supramolecular assemblies.
The X-ray structure of the 2-pyridyl ligand 5 is shown in Figure 1.
It crystallises in the hexagonal space group P63 about a crystallo-
graphic threefold rotation axis with one third of the tripodal ligand
in the asymmetric unit. The central quaternary carbon, the phenyl
ring and the oxygen atom of the ligand are disordered over two sites,
with the major component having 75% occupancy. In Figure 1 the
minor component having 25% occupancy is not shown.
Figure 2. X-ray crystal structure of 11.
In the solid state the three benzene rings twist around the tet-
rahedral quaternary carbon atom in a propeller-like fashion with
the methyl substituent pointing outwards. The three pyridine rings
are tilted almost perpendicular to the meanplane of the closest
benzene ring, with the internal nitrogen donor atoms all pointing
inwards towards the centre of the adjacent benzene ring and the
centre of the ligand. The distance between the pyridine nitrogen
We next turned our attention to the synthesis of new four-
armed ligands and for this purpose employed the commercially
available 3,3,30,30-tetramethyl-1,10-spirobisindane-5,50,6,60-tetrol
(12) as the phenolic component. This was reacted with the seven
halides 4 in the hope of making seven new four-armed ligands. In
the event, only five of these reactions were successful (Scheme 2).
The three potential ligands 13–15 have a single oxygen atom spacer

7950
J.R.A. Cottam, P.J. Steel / Tetrahedron 65 (2009) 7948–7953
between the two components, whereas ligands 16 and 17 have
two-atom spacer units. Curiously, reactions of 4 with 2-chloro-
pyrazine (4b) and 2-chloromethylpyridine (4e) returned only the
starting materials and failed to produce the desired products.
meanplane of their adjacent catechol rings. The orientations of the
pyridyl groups are such as to preserve a twofold rotation axis, al-
though this is not crystallographically imposed. There is an in-
triguing alignment of two of the pyridine rings on opposite halves
of the molecules that appears to result from an attractive
stacking interaction.
p–p
N
N
O
O
O
O
N
N
4a
13 (46%)
HO
HO
OH
OH
K2CO3
sulpholane/toluene
reflux 48 hr
12
Figure 3. X-ray crystal structure of 13.
X
N
N
X
4c,d
The 2-quinolinyl analogue 14 crystallises in the orthorhombic
space group Pnn2 with half a molecule in the asymmetric unit
(Fig. 4). Thus, in this case the twofold symmetry is crystallographi-
callyimposed. As a consequence thepairs ofnitrogendonorspoint in
opposite directions, which may have important consequences for
the way in which this ligand would bridge metal centres. In this
structure the two quinoline rings within each half of the molecule
X
N
N
X
O
O
O
O
are
p–p stacked. In the solid state the two most distant nitrogen
donors in 13 and 14 are separated by 11.1 and 11.7 Å, respectively.
14 X = CH (64%)
15 X = N (54%)
4f,g
40% NaOH
NMe4OH
benzene
reflux 48 hr
N
N
O
N
O
O
O
N
Figure 4. X-ray crystal structure of 14.
16 3-pyridyl (33%)
17 4-pyridyl (34%)
3. Conclusion
Scheme 2. Preparations of 13–17.
The preparations of twelve new bridging ligands from two
commercially available phenolic precursors, by coupling each with
heterocyclic units, have been described. X-ray crystal structures of
four representative examples revealed different conformations in
the solid state with the terminal nitrogen donors being separated
by distances ranging from 10.9 to 18.2 Å. Due to the flexible nature
of these ligands, it is reasonable to speculate that they will adopt
different conformations when bound to metals in their transition
metal complexes. Nevertheless, the distances spanned by their
bridging cores should remain constant. Metallosupramolecular
assemblies derived from some of these ligands will be described
elsewhere.
These new ligands differ from the others in the series in two
respects. Firstly, these ligands are inherently chiral, although we
have prepared racemic mixtures of the ligands. Secondly, the li-
gands have reduced symmetry relative to the other ligands we have
used. Although they all have twofold rotation axes that relate the
two halves of the ligand, the two heterocyclic rings within each half
are not symmetry related and are therefore in different environ-
ments. We have previously discussed the problems associated with
using such ligands in supramolecular chemistry10 and this is
probably why we have found that these ligands are less useful as
bridging ligands.12
Once again the crystal structures of two representative exam-
ples were determined. The 2-pyridyl ligand 13 crystallises in the
monoclinic space group P21/c with a full molecule in the asym-
metric unit (Fig. 3). The two catechol ring systems are oriented
orthogonal to one another by virtue of the spiro ring junction. The
four pyridyl ether arms are all oriented almost perpendicular to the
We believe that these compounds represent useful new addi-
tions to the library of multi-armed ligands that are presently
available. Their inherent flexibility could conceivably provide access
to topological assemblies not accessible to more established
bridging ligands. Conventional three-armed ligands tend to be ei-
ther planar, such as 2,4,6-tri(4-pyridyl)triazine, used to great effect

J.R.A. Cottam, P.J. Steel / Tetrahedron 65 (2009) 7948–7953
7951
by Fujita and co-workers,16 or tripodal, such as the tren-based li-
gands recently reviewed by Blackman.17 Similarly, four-armed
bridging ligands are usually classified as tetrahedral, such as tetra-
(4-pyridyl)methane,18 planar, such as tetra(4-pyridyl)porphyrins,19
or based on rigid scaffolds such as calixarenes and cavitands.20
129.94, 120.05, 118.49, 111.64, 51.43, 30.76. ESI-MS: Found
MHþ¼538.2141; C35H28N3O3 requires MHþ¼538.2131.
4.3.2. Compound 6. Method A from 3 and 4b. White crystalline
solid. Yield 96%. Mp 178.5 ꢀC. Anal. Found: C, 71.16; H, 4.51; N,15.36.
Calcd for C32H24N6O3: C, 71.10; H, 4.47; N, 15.55. 1H NMR (300 MHz,
CHCl3):
d
8.42 (3H, s, H30), 8.28 (3H, s, H60), 8.27 (3H, s, H50), 7.21
(6H, d, H3, H5), 7.10 (6H, d, H2, H6), 2.24 (3H, s, H8). 13C NMR
4. Experimental
(75 MHz, CDCl3):
d 159.92, 151.25, 145.51, 141.04, 138.48, 135.89,
129.99, 120.33, 51.54, 30.74. ESI-MS: Found MHþ¼541.1966;
4.1. General experimental
C32H25N3O3 requires MHþ¼541.1988.
1H NMR spectra were recorded on Varian Unity 300 or Varian
500 spectrometers at 23 ꢀC with a 3 mm probe operating at
300 MHz or 500 MHz. Spectra were recorded in CDCl3 and refer-
enced relative to the internal standard Me4Si. 13C NMR spectra were
recorded on a Varian Unity 300 spectrometer operating at 75 MHz
and referenced against the solvent signal at 77.10 ppm. Electrospray
(ES) mass spectra were recorded using a Micromass LCT-TOF mass
spectrometer, with a probe operating at 3200 V and a cone voltage
of 30 V. Samples were dissolved in 1:1 acetonitrile/water, and
spectra acquired using source and desolvation temperatures of
80 ꢀC and 150 ꢀC, respectively. Melting points were recorded on an
Electrothermal melting point apparatus and are uncorrected. Ele-
mental analyses were performed by the Campbell microanalytical
laboratory, University of Otago, Dunedin.
4.3.3. Compound 7. Method A from 3 and 4c. Yellow crystalline
solid. Yield 98%. Mp 170 ꢀC. Anal. Found: C, 80.03; H, 5.26; N, 5.72.
Calcd for C47H33N3O3$H2O: C, 79.98; H, 5.00; N, 5.95. 1H NMR
(300 MHz, CHCl3):
d
8.12 (3H, d, H40), 7.83 (3H, d, H80), 7.74 (3H, d,
H50), 7.61 (3H, t, H70), 7.43 (3H, t, H60), 7.26 (12H, m, H2, H3, H5, H6),
7.08 (3H, d, H30), 2.28 (3H, s, H8). 13C NMR (75 MHz, CDCl3):
d
161.49, 152.00, 146.35, 145.23, 139.82, 129.88, 129.80, 127.85,
127.33, 125.66, 124.86, 120.45, 112.73, 51.59, 30.91. ESI-MS: Found
MHþ¼688.2609; C47H34N3O3 requires MHþ¼688.2600.
4.3.4. Compound 8. Method A from 3 and 4d. Yellow solid. Yield
40%. Mp 160 ꢀC. Anal. Found: C, 73.60; H, 4.64; N, 11.13. Calcd for
C44H30N6O3$11⁄2 H2O: C, 73.63; H, 4.63; N, 11.71. 1H NMR (500 MHz,
Unless otherwise stated, reagents were obtained from com-
mercial sources and used as supplied. Solvents were purified by
standard literature procedures and freshly distilled as required. 2-
Chloroquinoxaline 6d was prepared by a literature procedure.21
CHCl3):
m, H60, H7’), 7.28 (12H, m, H2, H3, H5, H6), 2.33 (3H, s, H8). 13C NMR
(75 MHz, CDCl3): 156.75, 151.05, 145.74, 139.95, 139.58, 139.23,
d
8.70 (3H, s, H30), 8.06 (3H, d, H80), 7.81 (3H, d, H50), 7.65 (6H,
d
130.41, 129.96, 128.90, 127.72, 127.50, 120.60, 51.73, 30.92. ESI-MS:
Found MHþ¼691.2489; C44H31N6O3 requires MHþ¼691.2458.
4.2. General reaction procedures
4.3.5. Compound 9. Method B from 3 and 4e. White crystalline solid.
Yield 13%. Mp 92 ꢀC. Anal. Found: C, 78.91; H, 5.73; N, 7.15. Calcd for
C38H33N3O3: C, 78.73; H, 5.74; N, 7.25. 1H NMR (300 MHz, CHCl3):
4.2.1. Method A. A mixture of 3 or 12 (1 equiv) and potassium
carbonate (7 equiv) was stirred in a solution of sulpholane/toluene
(10 ml:5 ml) at room temperature under argon for 45 min. The
haloazine 4a–d (3 or 4 equiv) was added and the mixture was
heated to reflux at w180 ꢀC under argon for 48 h. The resulting
mixture was poured into a solution of 7% aqueous sodium hy-
droxide solution (w30 ml). This was then extracted with chloro-
form and the extracts were combined and reduced in vacuo to give
the crude product in a sulpholane solution. This was added to ac-
etone, heated, treated with decolourising charcoal and filtered. The
acetone was removed in vacuo to give the product in a saturated
sulpholane solution. Just enough water was added to precipitate
the crude product, which was then recrystallised from acetone/
water solution to give the pure product. Typically, these reactions
were carried out on a scale that delivered 1–2 g of purified ligand.
d
8.58 (3H, d, H60), 7.72 (3H, t, H40), 7.68 (3H, d, H30), 7.23 (3H, m, H50),
6.99 (6H, d, H3, H5), 6.89 (6H, d, H2, H6), 5.17 (6H, s, CH2), 2.10 (3H, s,
H8). 13C NMR (75 MHz, CDCl3):
d
157.29, 156.36, 149.05, 142.07,
136.74, 129.59, 122.49, 121.17, 113.89, 70.49, 50.55, 30.64. ESI-MS:
Found MHþ¼580.2596; C38H34N3O3 requires MHþ¼580.2600.
4.3.6. Compound 10. Method B from 3 and 4f. Orange solid. Yield
66%. Mp 133 ꢀC. Anal. Found: C, 78.46; H, 5.78; N, 7.20. Calcd for
C38H33N3O3: C, 78.73; H, 5.74; N, 7.25. 1H NMR (300 MHz, CHCl3):
d
8.67 (3H, s, H20), 8.58 (3H, d, H60), 7.77 (3H, d, H40), 7.32 (3H, m,
H50), 7.02 (6H, d, H3, H5), 6.87 (6H, d, H2, H6), 5.05 (6H, s, CH2), 2.11
(3H, s, H8). 13C NMR (75 MHz, CDCl3):
d
156.41, 149.32, 148.90,
142.24, 135.30, 132.57, 129.66, 123.48, 113.93, 67.45, 50.64, 30.71.
ESI-MS:
Found
MHþ¼580.2591;
C38H34N3O3
requires
MHþ¼580.2600.
4.2.2. Method B. A mixture of 3 or 12 (1 equiv), the appropriate
chloromethylpyridine/HCl 4e–g (3 or 4 equiv), 40% aqueous tetra-
butylammonium hydroxide (6 drops), 40% aqueous sodium hy-
droxide (7 ml) and benzene (25 ml) was refluxed (~80 ꢀC) for 48 h.
The organic layer was then separated, dried over Na2SO4 and
concentrated in vacuo to give a crude solid or oil, which was then
purified by recrystallisation. Again, reaction scales were such as to
furnish 1–2 g of purified ligand.
4.3.7. Compound 11. Method B from 3 and 4g. Orange solid. Yield
57%. Mp 135 ꢀC. Anal. Found: C, 78.47; H, 5.85; N, 7.39. Calcd for
C38H33N3O3: C, 78.73; H, 5.74; N, 7.25. 1H NMR (500 MHz, CHCl3):
d
8.60 (6H, d, H20, H6’), 7.33 (6H, m, H30, H5’), 7.00 (6H, d, H3, H5),
6.84 (6H, d, H2, H6), 5.04 (6H, s, CH2), 2.10 (3H, s, H8). 13C NMR
(75 MHz, CDCl3):
d 156.22, 149.88, 146.31, 142.30, 129.68, 121.48,
113.95, 68.08, 50.64, 30.69. ESI-MS: Found MHþ¼580.2592;
C38H34N3O3 requires MHþ¼580.2600.
4.3. Physical and spectral properties
4.3.8. Compound 13. Method A from 12 and 4a. White crystalline
solid. Yield 46%. Mp 169–171 ꢀC. Anal. Found: C, 75.75; H, 5.47; N,
8.63. Calcd for C41H36N4O4: C, 75.91; H, 5.59; N, 8.64. 1H NMR
4.3.1. Compound 5. Method A from 3 and 4a. Pale yellow solid.
Yield 59%. Mp 152–155 ꢀC. Anal. Found: C, 78.14; H, 5.21; N, 7.70.
Calcd for C35H27N3O3: C, 78.19; H, 5.06; N, 7.82. 1H NMR (300 MHz,
(500 MHz, CHCl3):
d
8.08, 8.00 (4H, d, H60, H600), 7.53, 7.02 (4H, t,
CHCl3):
(6H, d, H2, H6), 6.96 (3H, t, H50), 6.89 (3H, d, H30), 2.19 (3H, s, H8).
13C NMR (75 MHz, CDCl3):
163.47, 152.30, 147.68, 144.93, 139.43,
d
8.19 (3H, d, H60), 7.64 (3H, t, H40), 7.17 (6H, d, H3, H5), 7.05
H40, H400), 7.02 (2H, s, H4), 6.87, 6.83 (4H, t, H50, H500), 6.81 (2H, s,
H7), 6.68, 6.62 (4H, d, H30, H300), 2.44 (2H, d, H2a), 2.38 (2H, d, H2b),
d
1.38 (6H, s, H8), 1.37 (6H, s, H9). 13C NMR (75 MHz, CDCl3):
d 163.19,

7952
J.R.A. Cottam, P.J. Steel / Tetrahedron 65 (2009) 7948–7953
Table 1
Crystal data and X-ray experimental details
Compound
5
11
13
14
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
a (Å)
C35H27N3O3
537.60
93(2)
Hexagonal
P63
C39H33N3O3
591.68
93(2)
Triclinic
P-1
C41H36N4O4
648.74
93(2)
Monoclinic
P21/c
C57H44N4O4
848.96
93(2)
Orthorhombic
Pnn2
14.0521(3)
14.0521(3)
8.1827(5)
90
90
120
6.7134(4)
13.0108(9)
19.2362(16)
109.752(2)
94.467(3)
96.779(2)
16.6512(5)
10.3247(3)
21.1705(5)
90
112.797(1)
90
11.1349(3)
18.1266(4)
11.1145(2)
90
90
90
b (Å)
c (Å)
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
Volume (Å3)
Z
1399.3(1)
2
1.276
0.082
564
1557.8(2)
2
1.261
0.080
624
3355.3(2)
4
1.284
0.084
1368
2243.33(9)
2
1.257
0.079
892
Density (calculated) (mg/m3)
Absorption coefficient (mmꢁ1
F(000)
)
Crystal size (mm3)
Theta range
0.70ꢂ0.25ꢂ0.05
0.62ꢂ0.17ꢂ0.04
0.45ꢂ0.35ꢂ0.10
0.45ꢂ0.43ꢂ0.08
2.90–27.45
1.13–25.05
2.38–25.05
2.59–25.05
for data collection (ꢀ)
Reflections collected
20,714
14,729
51,569
23,598
Independent reflections [R(int)]
Data/restraints/parameters
Goodness-of-fit on F2
1141 [0.0845]
1141/1/167
1.028
5491 [0.0426]
5491/0/417
1.114
5942 [0.0414]
5942/0/442
1.043
2106 [0.0491]
2106/1/294
1.048
R1 [I>2
s(I)]
0.0430
0.0553
0.0447
0.0261
wR2 (all data)
0.1168
0.1517
0.1163
0.0683
163.13, 149.51, 147.35, 147.31, 147.24, 144.97, 144.64, 138.98, 138.89,
119.09, 118.05, 117.91, 116.49, 110.72, 110.47, 59.39, 57.37, 43.40,
31.54, 30.18. ESI-MS: Found MHþ¼649.2793; C41H37N4O4 requires
MHþ¼649.2815.
123.47, 123.35, 110.88, 108.78, 69.27, 69.15, 59.37, 57.40, 43.25,
31.50, 30.35. ESI-MS: Found MHþ¼705.3446; C45H45N4O4 requires
MHþ¼705.3441.
4.3.12. Compound 17. Method B from 12 and 4g. Yellow solid. Yield
34%. Mp 98 ꢀC. Anal. Found: C, 74.99; H, 6.66; N, 6.47. Calcd for
C45H44N4O2$1⁄2 EtOAc: C, 75.38; H, 6.46; N, 7.48. 1H NMR (500 MHz,
4.3.9. Compound 14. Method A from 12 and 4c. Yellow solid. Yield
64%. Mp 196–197 ꢀC. Anal. Found: C, 79.82; H, 5.37; N, 6.49. Calcd
for C57H44N4O4$1⁄2 H2O: C, 79.79; H, 5.29; N, 6.53. 1H NMR
CHCl3): d
8.61, 8.54 (8H, d, H20, H200, H60, H600), 7.42, 7.32 (8H, d, H30,
(500 MHz, CHCl3):
d
8.12, 8.04 (4H, d, H40, 4H00), 7.91, 7.82 (4H, d,
H300, H50, H500), 6.75 (2H, s, H4), 6.33 (2H, s, H7), 5.18, 4.97 (8H, s, H70,
H700), 2.30 (2H, d, H2a), 2.04 (2H, d, H2b),1.31 (6H, s, H8),1.29 (6H, s,
H80, H800), 7.62, 7.54 (4H, d, H50, H500), 7.47, 7.42 (4H, t, H70, H700),
7.32, 7.27 (4H, t, H60, H600), 7.18 (2H, s, H4), 7.05 (2H, s, H7), 6.92, 6.87
(4H, d, H30, H300), 2.56 (2H, d, H2a), 2.49 (2H, d, H2b), 1.46 (6H, s,
H9). 13C NMR (75 MHz, CDCl3):
d 149.66, 149.54, 148.20, 148.03,
146.69, 146.55, 145.66, 143.16, 121.56, 110.39, 108.32, 69.67, 69.56,
59.32, 57.41, 43.24, 31.55, 31.43, 30.32. ESI-MS: Found
MHþ¼705.3471; C45H45N4O4 requires MHþ¼705.3441.
H8), 1.44 (6H, s, H9). 13C NMR (75 MHz, CDCl3):
d 161.88, 161.18,
149.47, 147.30, 146.11, 146.06, 144.90, 144.58, 139.28, 139.18, 129.36,
127.61, 127.58, 127.06, 127.02, 125.47, 125.41, 124.43, 124.31, 119.54,
116.76, 112.12, 111.88, 59.50, 57.49, 51.08, 43.51, 31.59, 30.26. ESI-
MS: Found MHþ¼849.3450; C57H45N4O4 requires MHþ¼849.3441.
4.4. Crystallography
Crystal data and experimental details of the data collections and
structure refinements are listed in Table 1. Data were collected with
4.3.10. Compound 15. Method A from 12 and 4d. Yellow solid. Yield
54%. Mp 244–245 ꢀC. Anal. Found: C, 72.84; H, 4.68; N, 12.69. Calcd
for C53H40N8O4.H2O: C, 73.09; H, 4.86; N, 12.87. 1H NMR (500 MHz,
a APEX CCD area detector, using graphite monochromatised Mo K
a
radiation (l¼0.71073 Å). Almost complete spheres of data were
CHCl3):
d
8.46, 8.38 (4H, s, H30, H300), 7.94, 7.86 (4H, d, H80, H800),
collected. The structures were solved by direct methods using
SHELXS,22 and refined on F2 using all data by full-matrix least-
squares procedures with SHELXL-97.23 Hydrogen atoms were
included in calculated positions with isotropic displacement
parameters 1.3 times the isotropic equivalent of their carrier atoms.
Crystallographic data, as CIF files, have been deposited with the
Cambridge Crystallographic Data Centre (CCDC Nos 728092–
728095). Copies can be obtained free of charge from: The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (e-mail:
deposit@ccdc.cam.ac.uk).
7.52, 7.50 (4H, d, H50, H500), 7.45, 7.38 (6H, m, H60, H600, H70, H700),
7.23 (2H, s, H4), 7.13 (2H, s, H7), 2.60 (2H, d, H2a), 2.53 (2H, d, H2b),
1.50 (6H, s, H8), 1.48 (6H, s, H9). 13C NMR (75 MHz, CDCl3):
d 156.17,
150.30, 147.87, 143.81, 143.44, 139.71, 139.64, 139.49, 139.42, 138.31,
138.14, 130.15, 130.08, 128.74, 128.63, 127.38, 127.35, 127.20, 119.64,
116.83, 104.68, 59.37, 57.57, 51.10, 43.68, 31.55, 30.19. ESI-MS: Found
MHþ¼853.3275; C53H41N8O4 requires MHþ¼853.3251.
4.3.11. Compound 16. Method B from 12 and 4f. White solid. Yield
33%. Mp 104–105 ꢀC. Anal. Found: C, 74.44; H, 6.27; N, 7.44. Calcd
for C45H44N4O4$H2O: C, 74.44; H, 6.41; N, 7.75. 1H NMR (500 MHz,
CHCl3):
d
8.68, 8.58 (4H, d, H20, H200), 8.56, 8.50 (4H, d, H60, H600),
Acknowledgements
7.80, 7.70 (4H, d, H40, H400), 6.78 (2H, s, H4), 6.37 (2H, s, H7), 5.15,
4.96 (8H, s, H70, H700), 2.31 (2H, d, H2a), 2.15 (2H, d, H2b), 1.33 (6H, s,
We thank the Royal Society of New Zealand for funding through
the Marsden Fund and a James Cook Research Fellowship and the
University of Canterbury for Erskine leave.
H8), 1.30 (6H, s, H9). 13C NMR (75 MHz, CDCl3):
d
149.33, 149.22,
148.93, 148.46, 148.31, 145.63, 143.28, 135.34, 135.33, 132.81, 132.68,

J.R.A. Cottam, P.J. Steel / Tetrahedron 65 (2009) 7948–7953
12. Cottam, J. R. A.; Steel, P. J. Unpublished results, 2006.
7953
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