Synthesis and X-ray crystallographic analysis of chiral pyridyl substituted carbocyclic molecular clefts

Article abstract of DOI:10.1016/j.tet.2006.03.014

Ditopic symmetrical bis(pyridyl) ligands incorporating the chiral dibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-dione cleft have been synthesised and characterised by NMR spectroscopy, mass spectrometry and X-ray crystallography. The ligands, which inco

Full text of DOI:10.1016/j.tet.2006.03.014

Tetrahedron 62 (2006) 4870–4878
Synthesis and X-ray crystallographic analysis of chiral
pyridyl substituted carbocyclic molecular clefts
a
Connie K. Y. Lee, Jennifer L. Groneman, Peter Turner, Louis M. Rendina
a
a
a,*
b,
*
and Margaret M. Harding
a
School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia
School of Chemistry, The University of New South Wales, Sydney, New South Wales 2052, Australia
b
Received 21 December 2005; revised 10 February 2006; accepted 2 March 2006
Available online 31 March 2006
Abstract—Ditopic symmetrical bis(pyridyl) ligands incorporating the chiral dibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-dione cleft
have been synthesised and characterised by NMR spectroscopy, mass spectrometry and X-ray crystallography. The ligands, which incorporate
pyridyl groups directly connected to the carbocyclic cleft core or via alkyne or phenyl linkers were accessed from palladium-catalysed
coupling reactions of 2,8-dibromodibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-dione. X-ray crystal analyses show the interplanar angles
ꢀ
between the two cleft aromatic rings in these molecules, which range from 97.80(3) to 109.80(4) .
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
groups. A key feature of the dibenzobicyclo[b,f][3.3.1]-
1
4
nona-5a,6a-diene-6,12-dione 1 is its angular or cleft-like
framework that is imposed by the bicyclononane skeleton.
Apart from its well-defined geometry, the cleft possesses
an element of chirality as well as functional handles that
allow access to new structural motifs with the potential for
chiral molecular recognition processes. Thus, the carbonyl
groups can be transformed to hydroxyls or oximes by re-
action with lithium aluminium hydride and hydroxylamine,
Oligopyridines are widely studied as ligands and building
blocks in coordination and supramolecular chemistries to-
day. Most prevalent are those where the heteroaromatic
1
units are directly connected to each other via a carbon–
carbon single bond, examples include bipyridines, terpyri-
dines and phenanthrolines. Oligopyridines of the types
described are characterised by their rigid structure. In recent
years, the incorporation of semi-rigid and flexible oligopyr-
idines in supramolecular systems has also been the subject of
intensive study. Typically, their structures contain a flexible
1
0,12,14
respectively.
The ready access to the bisarylbromide
derivative 2 also allows entry into aryl and alkynyl-
substituted clefts through metal catalysed cross-coupling
reactions.
2
11
alkyl bridging unit between the pyridyl groups. The versa-
tility of oligopyridines as ligands is reflected in many elegant
syntheses of architecturally fascinating supramolecular
structures, ranging from discrete species such as polygons,
O
3
R
O
4
5
6
7
catenanes, rotaxanes, single and double-stranded helices
to extended systems, which include grids and wires.
8
9
R
O
R
R
O
9
1-105°
Recently, the dibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-
6,12-dione framework has been identified as a versatile su-
pramolecular building block,
1
2
R = H
R = Br
1
0–12
and the applications and
potential of this system in supramolecular chemistry have
1
3
In the course of our studies towards the assembly of chiral
metallomacrocycles of nanoscale dimensions, we required
the efficient synthesis of bispyridyl derivatives of the clefts
L1, L2 and L3 in which the distance between the pyridyl
units was systematically varied. In addition, given that sub-
been reviewed recently. These molecular clefts can be con-
sidered as analogues of Tr o¨ ger’s base but contain a carbo-
cyclic core that may be elaborated to introduce additional
molecular recognition groups via the ketone functional
1
1,12
stituents may influence the size of the cleft angle,
X-ray
Keywords: Molecular clefts; Supramolecular chemistry; Metal complexa-
tion; Suzuki cross-coupling; Sonogashira cross-coupling; X-ray analysis.
crystallographic analyses were undertaken to provide mea-
surements of the cleft angle in order to gauge the likely out-
come of metal complexation and self-assembly studies.
*
Corresponding authors. Tel.: +61293855638; fax: +61293855949; e-mail
addresses: rendina@chem.usyd.edu.au; harding@unsw.edu.au
0
040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.03.014

C. K. Y. Lee et al. / Tetrahedron 62 (2006) 4870–4878
4871
O
Ligand L3 contains two new biaryl bonds and hence is acces-
sible via a number of different routes (Scheme 2). The first
route investigated used Suzuki coupling of the diaryl
boronic ester 5 to the dibromo cleft 2. The synthesis of the di-
aryl boronic ester 5 has not been reported previously, and re-
quired initial preparation of the corresponding aryliodide 11
R
R
O
1
8
(
Scheme 3). Aniline 10, was converted to the iodide 11 ac-
L1 R =
L2 R =
N
1
9
cording to the literature report. However, in our hands, the
literature yields could not be reproduced, and careful temper-
ature control and the use of sodium nitrite/HBF were re-
N
4
quired to furnish the diaryliodide 11 in only moderate yield
of 44%. The diazotization step required slow addition of an
L3 R =
N
aqueous solution of NaNO (over 1.5 h) with the internal
2
temperature of the reaction mixture being maintained at no
ꢀ
higher than ꢁ40 C. Iodination was effected with addition
ꢀ
2
. Results and discussion
of KI also at ꢁ40 C and allowing the reaction mixture to
warm slowly to rt. Purification of the crude diaryliodide 11
according to the literature procedure by recrystallisation
from hot toluene was unsuccessful due to the apparent insol-
ubility of 11. All attempts to convert the crude diaryliodide
11 to the boronic ester 5 were unsuccessful upon treatment
with PdCl (dppf)$CH Cl , bis(pinacolato)diborane and
2
.1. Synthesis
The target ligands L1, L2 and L3 are pyridyl, acetylenyl-
pyridyl and p-(4 -pyridyl)phenyl derivatives of the parent
0
molecular cleft 1. While there have been numerous recent re-
2
2
2
2
0
ports and reviews on catalysts and conditions to effect metal
catalysed couplings,
KOAc in dioxane or DMSO (Scheme 3).
1
5,16
the application of these methods to
heterocycles is frequently limited and deactivation of the
metal catalyst by heterocycles requires careful optimisation
of reaction conditions.
The alternative strategy to ligand L3 involved initial attach-
ment of a para-substituted boronic ester to the cleft followed
by introduction of the pyridyl groups (Scheme 2). The first
key step involved the coupling of the dibromo cleft 2 with
4-nitrophenylboronic acid. The nitro groups serve as func-
tional handles enabling conversion of adduct 6 to the di-
iodide 7, the latter being a suitable coupling partner for the
subsequent Suzuki reaction with (4-pyridyl)boronic acid
pinacol ester. This route failed as reaction of cleft 2 with
4-nitrophenylboronic acid under PdCl (PPh ) catalysis re-
1
7
Ligand L1 was prepared by the direct coupling of the
dibromo cleft 2 with (4-pyridyl)boronic acid pinacol ester
under the catalysis of PdCl (PPh ) (Scheme 1). The synthe-
2
3 2
sis of the ligand L2 from the dibromo cleft 2 and 4-ethynyl-
pyridine was first attempted using the protocol developed
for appending alkynyl units to the peripheral arms of the
2
3 2
1
1
cleft (Scheme 1). Thus, dibromo cleft 2 was treated with
-ethynylpyridine hydrochloride, PdCl (PPh ) and CuI in
neat triethylamine, that is, the standard Sonogashira condi-
sulted predominantly in the monocoupled product 13 under
forcing conditions and long reaction times. Hence the corre-
sponding iodide 12 was prepared via the Sandmeyer reaction
4
2
3 2
1
6
11
tions. However, these conditions afforded only the homo-
0
of the diamino cleft 15 (Scheme 4). While the rate of the
coupled product, (4,4 -dipyridyl)butadiene 3. Use of the
more active Pd(PPh ) catalyst under similar conditions
reaction improved by the use of the iodide 12 in place of
the bromide 2, the monocoupled product 14 was the major
product due to its poor solubility, which resulted in precipi-
tation during the reaction (Scheme 5). Changing the solvent
and conditions was unsuccessful, and while minor amounts
of the bisnitro product 6 were formed, the extremely low
solubility of this product in all common organic solvents
precluded efficient purification.
3
4
led to the same result. Further optimisation of the reaction
by the use of Pd(PPh ) –CuI as the catalytic system and
3
4
the use of organic solvents showed that in contrast to most
successful Sonogashira reactions that are performed using
an amine base, the choice of solvent was critical to the suc-
cess of the reaction. While the use of THF and MeCN re-
sulted in formation of the monocoupled cleft 4 in 30% and
43% yield, respectively, the desired ligand L2 was obtained
in 83% yield with the use of DMF (Scheme 1).
To avoid these problems, the alternative approach involved
preparation of the more soluble bisphenol 8 via Suzuki
L1
2
i
N
O
ii
iv
or v
N
N
or iii
Br
3
vi
O
4
L2
Scheme 1. Reagents and conditions: i. PdCl
)
2
(PPh
3
)
2
, Na
N, MeCN; v. Pd(PPh
2
CO
3
, (4-pyridyl)boronic acid pinacol ester, DME–H
, CuI, Et N, DMF.
3
2 2 3 2 3 3 4
O; ii. PdCl (PPh ) , CuI, Et N; iii. Pd(PPh ) ,
CuI, Et
3
N, THF; iv. Pd(PPh
3
4
, CuI, Et
3
3
)
4

4872
C. K. Y. Lee et al. / Tetrahedron 62 (2006) 4870–4878
NO2
I
O
O
iii, iv
O
O
O2N
I
6
7
O
ii
v
N
B
O
5
2
L3
i
vi
viii
OH
OTf
O
O
vii
O
O
HO
TfO
8
9
Scheme 2. Reagents and conditions: i. PdCl
CH CO H; iv. NaNO , H SO
PdCl (PPh , Na CO
2
(PPh
3
)
2
, Na
2
CO
3
, DME–H O; ii. 4-nitrophenylboronic acid, PdCl
2
2 3 2 2 3 2
(PPh ) , Na CO , DME–H O; iii. Fe/
3
2
2
2
4
, KI; v. (4-pyridyl)boronic acid pinacol ester, PdCl
2
(PPh , Na CO , DME–H O; vi. 4-(hydroxy)boronic acid pinacol ester,
2
3
)
2
2
3
2
3
)
2
2
3
, DME–H
2
O; vii. Tf
2
O, pyridine, CH
2
Cl ; viii. (4-pyridyl)boronic acid pinacol ester, Pd(PPh
2
3
)
4
2 3 2
, Na CO , DME–H O.
O
B
i, ii
iii
N
NH2
N
I
N
O
10
11
5
Scheme 3. Reagents and conditions: i. NaNO
dioxane or DMSO.
2
, 40% aq HBF
4
, EtOH, ꢁ40 ꢀC; ii. KI, ꢁ40 ꢀC to rt; iii. bis(pinacolato)diborane, PdCl
2 2 2
(dppf)$CH Cl , KOAc,
2
1
O
O
dard Suzuki reaction conditions, treatment of (4-pyridyl)-
boronic acid pinacol ester with bistriflate 9 in the presence of
PdCl (dppf)$CH Cl (2.5 mol %), K PO and KBr in di-
NH2
i
I
2
2
2
3
4
H2N
I
oxane gave no reaction. The use of more forcing conditions
(increased catalyst loading, use of the more active Pd(PPh3)4
catalyst and prolonged reaction time) also resulted in no re-
action. The failure of this reaction is most likely because of
the precipitation of palladium black at the reaction onset,
which results from the side reaction of the triflate with the
O
O
15
12
Scheme 4. Reagents and conditions: i. H
2
SO
4
2
, NaNO , KI.
2
1,22
triphenylphosphine ligand to afford phosphonium salts.
Accordingly, application of the methodology of Fu et al.
2
3
NO2
O
O
for coupling of aryl triflates and boronic acids was investi-
gated. Following the reported optimal conditions, there
was no reaction at rt using Pd(OAc) and PCy in DMF,
R
i
R
R
2
3
O
O
and the successful synthesis of ligand L3 required the use
of Pd(PPh ) and sodium carbonate in DME–H O with heat-
ing. Purification of L3 required chromatography, followed
2
R = Br
3 4
2
1
1
3 R = Br
4 R = I
1
2 R = I
by recrystallisation from MeOH and trifluoroacetic acid.
Scheme 5. Reagents and conditions: i. PdCl
4-nitrophenylboromic acid, DME–H O.
2 3 2 3 4 2 3
(PPh ) or Pd(PPh ) , Na CO ,
2
2
.2. X-ray crystallography
reaction of the dibromo cleft 2 and (4-hydroxyphenyl)bor-
onic acid pinacol ester, catalysed by PdCl (PPh ) (Scheme
Single crystals of racemic L1, L2 and L3 suitable for X-ray
diffraction analysis were obtained by recrystallisation from
MeOH. Crystallographic details and pertinent metric details
are summarised in Tables 1–3, and ORTEP depictions are
provided in Figures 1 and 2. The crystal structure of ligand
L1 includes a water solvate molecule that forms a hydrogen
bond with L1. The crystal structure of L2 contains a disor-
dered methanol solvate molecule, whilst the solid state
2
3 2
2
). In contrast to attempted preparation of 6, the bisphenol 8
was formed in good yield and exhibited good solubility thus
avoiding the problems encountered with the nitro com-
pound. Bisphenol 8 was treated with triflic anhydride and
pyridine to afford the corresponding bistriflate 9 as a suitable
coupling partner for Suzuki reactions. However, under stan-

C. K. Y. Lee et al. / Tetrahedron 62 (2006) 4870–4878
Table 1. Single crystal X-ray diffraction details for ligands L1, L2 and L3
4873
Compound
L1
L2
L3
Formula
C
27
H
20
N
2
O
3
C
32
H
22
N
2
O
3
39 26 2 2
C H N O
Crystal system
Molecular weight
Size (mm )
Orthorhombic
420.45
Monoclinic
482.52
Triclinic
554.62
3
0.31ꢂ0.27ꢂ0.26
Pccn(#56)
17.3760(6)
10.6974(4)
10.8602(3)
—
0.33ꢂ0.17ꢂ0.15
0.31ꢂ0.26ꢂ0.10
Space group
˚
P2 /c(#14)
1
P1ð#2Þ
a (A)
˚
7.499(6)
27.08(2)
12.224(10)
—
104.336(13)
—
2405(3)
1.333
11.7599(10)
15.3672(14)
16.5565(14)
95.6950(10)
107.2570(10)
97.1050(10)
2806.1(4)
1.313
b (A)
˚
c (A)
ꢀ
a ( )
ꢀ
b ( )
ꢀ
—
—
g ( )
3
V (A )
˚
2018.67(12)
1.383
4
0.091
ꢁ3
D
Z
calcd (g cm
)
4
0.086
4
0.081
ꢁ1
m(Mo Ka) (mm
)
T(SADABS)min,max
0.891, 0.977
70.00
0.733, 1.000
57
—
61
ꢀ
2qmax ( )
hkl range
N
ꢁ28 28, ꢁ17 17, ꢁ14 17
ꢁ10 9, ꢁ34 34, ꢁ16 16
ꢁ16 16, ꢁ22 21, ꢁ23 23
40,515
22,452
48,618
N
N
N
ind (Rmerge)
obs [I>2s(I)]
4405(0.025)
3505
150
0.0428, 0.1055
1.270
5603(0.078)
3339
354
0.0560, 0.1287
1.401
17,155(0.070)
10,392
775
0.0446, 0.0903
1.148
var
2
R1(F),wR2(F )
GoF (all)
ꢁ3
˚
rmax (e A
)
ꢁ0.199, 0.463
ꢁ0.311, 0.306
ꢁ0.267, 0.385
˚
Table 2. Selected bond lengths (A) and angles ( ) for ligands L1, L2 and L3
ꢀ
Ligand L1
O(1)–C(7)
C(1)–C(8)–C(7)
1.2164(10)
108.78(7)
C(5)–C(4)–C(10)–C(14)
C(3)–C(4)–C(10)–C(11)
25.88(12)
24.59(12)
Ligand L2
O(1)–C(7)
C(7)–C(8)–C(9)
1.228(2)
107.51(16)
O(2)–C(15)
C(1)–C(16)–C(15)
1.224(3)
108.01(16)
Ligand L3
O(1)–C(7)
O(2)–C(15)
C(7)–C(8)–C(9)
1.2167(13)
1.2174(14)
108.75(9)
O(3)–C(46)
O(4)–C(54)
C(46)–C(47)–C(48)
1.2148(13)
1.2173(14)
108.84(9)
C(1)–C(16)–C(15)
107.28(10)
ꢁ142.45(12)
34.17(17)
C(40)–C(55)–C(54)
108.02(10)
ꢁ141.28(12)
144.00(12)
50.40(17)
C(5)–C(4)–C(18)–C(23)
C(11)–C(12)–C(29)–C(34)
C(22)–C(21)–C(24)–C(25)
C(33)–C(32)–C(35)–C(39)
C(44)–C(43)–C(57)–C(62)
C(50)–C(51)–C(68)–C(69)
C(61)–C(60)–C(63)–C(64)
C(70)–C(71)–C(74)–C(78)
46.43(17)
38.33(18)
ꢁ34.18(17)
Table 3. Cleft angle q and nitrogen–nitrogen separations for L1, L2 and L3
bridgehead superstructure, provides a simple measure of
the intramolecular cleft angle. Previous analyses of 2,8-
disubstituted dibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-
O
6,12-dione clefts have suggested substituent effects on cleft
angles, with angles of 100–104 observed for clefts
ꢀ
substituted with electron-donating aryl groups. The cleft
O
R
R
1
1
θ
angles for L1, L2 and L3 (two independent molecules) are
ꢀ
ꢀ
97.80(3), 102.47(8), 103.30(4) and 109.80(4) , respectively
Compound
Interplanar ‘cleft’ angle q ( )
Distance between
˚
nitrogen atoms (A)
(Table 3). The single crystal structures indicate that the
linker units of L1, L2 and L3 affect the overall shape of
the oligopyridine clefts, though it is not clear if this reflects
packing influences or electronic effects. The significantly
different cleft angles found in the two independent mole-
cules of L3 suggest that packing influences are most likely
to be the cause of the cleft angle variation, though we have
not yet identified any particular causal contacts. The cleft an-
L1
L2
L3
97.80(3)
102.47(8)
103.30(4), 109.80(4)
13.57(1)
17.55(1)
21.35(1), 21.40(1)
a
a
The asymmetric unit contains two independent molecules.
structure of ligand L3 contains two crystallographically
independent molecules.
ꢀ
gle of 109.80(4) observed in the second molecule of L3 is
much like that which would be expected of an sp carbon
3
The dihedral angle formed by the least square planes of the
two opposing phenyl rings immediately attached to the
based geometry, suggesting perhaps that this molecule is ac-
tually least affected by packing influences. Paradoxically,

4874
C. K. Y. Lee et al. / Tetrahedron 62 (2006) 4870–4878
Figure 1. ORTEP depiction of structures of L1 showing 50% displacement ellipsoids and the hydrogen bonding interaction with the solvate water molecule.
the L3 intramolecular nitrogen–nitrogen distances are much
˚
the same at 21.35(1) and 21.40(1) (A) (Table 3), and there is
of subtle differences in packing and electronic influences,
with no reliable systematic trend yet evident.
no obvious explanation for this contrast to the differing cleft
angles found in the two molecules of L3.
2.3. Metal complexation studies
The molecules of L1 and L3 pack with the apex of one mol-
ecule effectively nestling into the cleft of another, as sug-
gested in Figure 2. In contrast, the stacking of molecules
in the structure of L2 is interleaved with the terminal residue
of neighbouring molecules, as shown in Figure 3. The cleft
angle of L2 is between those of L1 and L3, suggesting, in
contrast to early observations that this packing difference
does seem to influence the cleft angle. The solid state cleft
angle of any particular molecule appears to be the outcome
Preliminary metal complexation studies of the racemic
ligand L1 with palladium(II) have been performed. Thus, a
solution of [Pd(ONO ) (en)] in H O (16.7 mM) was treated
2
2
2
with a solution of racemic ligand L1 in MeOH (16.7 mM) at
ambient temperature. ESI–MS analysis of the crude reaction
mixture was consistent with the formation of the [2+2]
2
+
metallomacrocycle and peaks at 631 [Mꢁ2NO ] , 508
3
4
+
4+
[Mꢁ4NO +7MeOH] , 380 [Mꢁ4NO +3MeOH]
and
284 [Mꢁ4NO ] were detected. Due to the chirality of
3
3
4
+
3
Figure 2. ORTEP depiction of structures of L3 showing 50% displacement ellipsoids.

C. K. Y. Lee et al. / Tetrahedron 62 (2006) 4870–4878
4875
Figure 3. Ball and stick depiction of L2 showing the interleaving of the molecules.
the ligand L1, the formation of stereoisomers is possible. In
contrast to studies with bipyridyl clefts and zinc(II)
have confirmed that under appropriate conditions the ditopic
symmetrical bis(pyridyl) ligands can be used in the assembly
of chiral [2+2] metallomacrocycles. The incorporation of
these ligands into the design of chiral metallomacrocycles
of nanoscale dimensions is currently under investigation in
these laboratories.
[
Zn(OTf) ] where enantiomeric ligand–ligand recognition
2
2
4
1
occurred, the H NMR spectrum of L1 and Pd contained
multiple signals consistent with formation of several com-
plexes. Full characterisation of these complexes therefore
requires studies with the pure enantiomers, which are acces-
1
1
sible from optically pure 2.
4. Experimental
Analogous results were obtained upon treatment of ligands
L2 and L3 with [Pd(ONO ) en]. These reactions were per-
4.1. General experimental procedures
2
2
formed at more dilute concentrations due to the poor solubil-
ity of ligands L2 and L3 relative to L1 in MeOH. ESI-MS
analysis of the reaction mixtures was consistent with the
formation of the corresponding [2+2] metallomacrocycles.
In the case of L2, peaks were detected at m/z 616
Melting points were measured on a Reichardt hot-stage and
1
13
are uncorrected. H and C NMR spectra were recorded at
300 K on Bruker DPX200 and Bruker DPX300 NMR spec-
trometers. Low and high resolution mass spectra (EI) were
obtained on a Kratos MS902 spectrometer at 70 eV. Values
of m/z are quoted with intensities expressed as percentages
of the base peak in parentheses. Infrared spectra were
recorded on a Shimadzu FTIR-8400S spectrometer. Single
crystal X-ray analyses were performed on either an
APEXII-FR591 diffractometer or a Bruker SMART 1000
CCD diffractometer. PdCl (PPh ) and 4-ethynylpyridine
4
+
[
5
Mꢁ4NO +4MeOH+10H O]
and 557 [Mꢁ4NO +
3
2
3
4
+
MeOH+5H O]
2
while for L3 peaks at m/z 833
2
+
4+
[
Mꢁ2NO +MeOH+H O] , 720 {2[Mꢁ4NO ] }, 660
3
2
3
4
+
[
Mꢁ4NO +6MeOH+6H O] .
3
2
2
3 2
3
. Conclusions
hydrochloride were purchased from Sigma-Aldrich. (4-Pyr-
idine)boronic acid pinacol ester and (4-hydroxyphenyl)bor-
onic acid pinacol ester were sourced from Boron Molecular
The new dibenzobicyclo[b,f][3.3.1]nona-5a,6a-diene-6,12-
dione molecular clefts incorporating pyridyl, ethynylpyridyl
and p-(4 -pyridyl)phenyl groups were prepared via Pd and
Pd–CuI catalysed cross-coupling methodologies. The choice
of solvent was critical in mediating the cross-coupling re-
actions, with polar solvents such as DME–H O and DMF
Pty Ltd. 4-Pyridylboronic acid was purchased from Alfa
0
25
Asar. Pd(PPh3)4
[b,f][3.3.1]nona-5a,6a-diene-6,12-dione were synthesised
and (ꢃ)-2,8-dibromodibenzobicyclo
1
1
according to literature procedures.
2
being required to facilitate these reactions. X-ray crystallo-
graphic analyses of the clefts confirm previous studies,
which have shown that the substituents on the aryl rings
affect the dimensions, and packing motifs, of the cleft in
the solid state. Preliminary metal complexation studies
4.1.1. (± ±-2ꢀ8-ꢁipyridyldibenzobicyclo[bꢀ f][3.3.1]nona-
5aꢀ6a-diene-6ꢀ12-dione L1. To a mixture of dibromo dione
2 (200 mg, 0.492 mmol), (4-pyridine)boronic acid pinacol
ester (202 mg, 0.986 mmol), Na CO (312 mg, 2.96 mmol)
2
3
and PdCl (PPh ) (70 mg, 20 mol %) at rt were added
2 3 2

4876
C. K. Y. Lee et al. / Tetrahedron 62 (2006) 4870–4878
ꢁ
3
DME (10 mL) and H O (2 mL). The mixture was degassed
2
(1.0 mL, 7.25ꢂ10 mol) was added to a mixture of the
ꢁ5
and purged with nitrogen (six cycles), then heated at
ꢀ
dibromo cleft 2 (20.0 mg, 4.83ꢂ10 mol) and 4-ethynyl-
ꢁ4
8
5 C under an atmosphere of nitrogen for three days. After
pyridine hydrochloride (40.0 mg, 2.90ꢂ10 mol) in dry
cooling to rt, the solvents were removed in vacuo. The result-
ing residue was taken up in EtOAc (30 mL) and washed with
H O (20 mL). The aqueous phase was separated and
DMF (5 mL) at rt. Under a steady stream of nitrogen,
Pd(PPh3)4 (3 mg, 5 mol %) and CuI (0.5 mg, 5 mol %)
were quickly added. The dark brown reaction mixture was
evacuated and purged with nitrogen (3ꢂ freeze-pump-thaw
2
extracted with EtOAc (3ꢂ30 mL). The organic solutions
ꢀ
were combined and washed with brine (30 mL), then dried
(Na SO ) and concentrated to dryness. Flash chromatogra-
phy of the tan residue on silica, eluting with MeOH/hexane
cycles) then heated at 80 C in the dark under an atmosphere
of nitrogen for three days. After the cooling to rt, the reaction
mixture was taken up in EtOAc (30 mL) and washed with
H O (30 mL). The layers were separated and the aqueous
2
4
(1:99 to 1.5:98.5) afforded L1 as a off-white solid [R 0.13;
MeOH/hexane (1:99)] (154 mg, 78%); mp 114–116 C; IR
f
2
ꢀ
KBr) 1688, 1682 cm ; dH (200 MHz, CDCl ) 3.08 (t,
solution was extracted with EtOAc (5ꢂ20 mL). The organic
ꢁ
1
(
solutions were combined and washed with H O (4ꢂ30 mL)
3
2
J¼3.0 Hz, 2H), 4.15 (t, J¼3.0 Hz, 2H), 7.47 (d, J¼5.4 Hz,
and brine (30 mL), then dried (Na SO ) and evaporated un-
4
2
2
H), 7.63 (d, J¼8.1 Hz, 2H), 7.82 (d, J¼8.1, 2.0 Hz, 2H),
der reduced pressure. Flash column chromatography of the
resulting brown residue on silica, eluting with a gradient of
MeOH/CH Cl (1.5:98.5 to 4:96) afforded ligand L2 (18 mg,
8
CDCl ) 31.9, 48.5, 121.5, 126.8, 129.5, 129.9, 132.8,
.27 (d, J¼2.0 Hz, 2H), 8.67 (br s, 2H); d (300 MHz,
C
3
2
2
1
40.4, 149.4, 193.5; UV lmax (MeOH) 374 (sh) (481), 356
sh) (1307), 338 (1782), 324 (1883), 306 (2241), 274
83%) as a white solid [R 0.31; MeOH/CH Cl (4:96)];
f 2 2
mp>300 C; IR (KBr) 2231, 2210, 1686, 1589 cm ; dH
ꢀ
ꢁ1
(
(
+
3123), 270 (3126); m/z (EI, %) 402 (M , 100), 385 (24),
(300 MHz, CDCl ) d 3.04 (t, J¼2.8 Hz, 2H), 4.10 (t,
3
3
74 (28), 357 (13), 332 (9), 331 (2), 296 (6), 280 (2), 266
5), 239 (2), 207 (1), 201 (4), 167 (3), 152 (2), 132 (1), 89
J¼2.8 Hz, 2H), 7.45 (d, J¼6.2 Hz, 4H), 7.52 (d, J¼8.0 Hz,
2H), 7.79 (dd, J¼8.0, 1.9 Hz, 2H), 8.17 (s, 2H), 8.62 (d, J¼
6.2 Hz, 4H); d (300 MHz, CDCl ) 31.7, 48.6, 88.4, 92.1,
(
(
ꢄ
1), 79 (1), 52 (2). Found: M , 402.1369. C H N O re-
+
2
7
18
2
2
C
3
ꢄ
+
quires M , 402.1368. Crystals suitable for X-ray diffraction
were obtained by recrystallisation from MeOH.
123.3, 125.6, 129.0, 129.3, 130.8, 131.9, 137.2, 140.2,
149.9, 192.8; m/z (EI, %) 450 (M , 100), 422 (29), 421 (25),
ꢄ
+
ꢄ
+
4
05 (19), 380 (10); Found: M 450.1360. C H N O re-
31 18 2 2
ꢄ
0
bicyclo[bꢀf][3.3.1]nona-5aꢀ6a-diene-6ꢀ12-dione 4. Trie-
+
4
.1.2. (± ±-2ꢀ8-(4-ꢂromo-4 -ethynylpyridyl±dibenzo-
quires M , 450.1368. Crystals suitable for X-ray diffraction
were obtained by recrystallisation from MeOH.
ꢁ3
thylamine (1.0 mL, 7.25ꢂ10 mol) was added to
ꢁ
5
a mixture of the dibromo cleft 2 (20.0 mg, 4.83ꢂ10 mol)
and 4-ethynylpyridine hydrochloride (101 mg,
.25ꢂ10 mol) in dry THF (4 mL) at rt. Under a steady
stream of nitrogen, Pd(PPh ) (3 mg, 5 mol %) and CuI
4.1.4. (± ±-2ꢀ8-ꢁi(4-hydroxyphenyl±dibenzobicyclo[bꢀ f]
[3.3.1]nona-5aꢀ6a-diene-6ꢀ12-dione 8. To a mixture of
dibromo cleft 2 (100 mg, 0.249 mmol), (4-hydroxyphenol)
boronic acid pinacol ester (110 mg, 0.500 mmol), Na CO
3
ꢁ
4
7
3
4
2
(
0.5 mg, 5 mol %) were quickly added. The dark reaction
(80.0 mg, 0.755 mmol) and PdCl (PPh )
(3.5 mg,
20 mol %) were added DME (5 mL) and H O (1 mL). The
2
3 2
mixture was evacuated and purged with nitrogen (3ꢂ
2
ꢀ
freeze-pump-thaw cycles), then heated at 50 C in the dark
mixture was degassed and purged with nitrogen (six cycles),
ꢀ
under an atmosphere of nitrogen for 50 h. After cooling to
rt, the dark mixture was filtered, the solids washed with
EtOAc (15 mL) and MeOH (15 mL). The filtrate was evapo-
rated in vacuo and the resulting residue was taken up in
then heated at 85 C under an atmosphere of nitrogen for
24 h. After cooling to rt and evaporation of solvent, the resi-
due was taken up in EtOAc (30 mL) and washed with 3 M
HCl (30 mL). The layers were separated and the aqueous
phase was extracted with EtOAc (3ꢂ30 mL). The organic
solutions were combined and washed with brine (30 mL),
then dried (Na SO ) and evaporated in vacuo. The resulting
EtOAc (30 mL). After washing with aq NaHCO (30 mL),
3
the layers were separated and the aqueous solution was ex-
tracted with EtOAc (3ꢂ30 mL). The organic solutions
2
4
were combined and washed with aq NaHCO (2ꢂ30 mL)
off-white solid was washed with cold Et O (30 mL) then
2
3
and brine (30 mL), then dried (Na SO ) and evaporated un-
2
dried under high vacuum to afford bisphenol 8 as an off-
white solid (60 mg, 58%) [R 0.34; MeOH/hexane (1:9)];
4
der reduced pressure. Flash column chromatography of the
resultant brown residue on silica, eluting with MeOH/
CH Cl (1.5:98.5) afforded the cleft 4 (5.5 mg, 20%) as
a white solid [Rf 0.31; MeOH/CH Cl (1.5:98.5)];
2
mp>300 C; IR (KBr) 1688, 1645, 1589, 1454,
1
2
8
1
2
8
(
(
(
f
ꢀ
ꢁ1
mp>300 C; IR (KBr) 3219 (br), 1670 cm
;
dH
(200 MHz, d-DMSO) 3.02 (br m, 2H), 4.07 (br m, 2H),
6.83 (d, J¼8.6 Hz, 2H), 7.46 (d, J¼8.6 Hz, 2H), 7.51 (d,
J¼8.1 Hz, 2H), 7.83 (dd, J¼8.1, 2.0 Hz, 2H), 7.97 (d,
2
2
2
ꢀ
ꢁ
1
+
402 cm
;
dH (300 MHz, CDCl3)
d
3.01 (t, J¼
J¼2.0 Hz, 2H), 9.66 (br s, 2H); m/z (EI, %) 432 (M , 100),
.9 Hz, 2H), 4.04 (br m, 1H), 4.09 (br m, 1H), 7.37 (d, J¼
.2 Hz, 1H), 7.57 (dd, J¼8.0, 2.2 Hz, 1H), 7.67 (dd, J¼7.9,
.8 Hz, 1H), 7.73 (d, J¼8.2 Hz, 1H), 7.88 (d, J¼6.5 Hz,
H), 8.10 (dd, J¼1.8 Hz, 1H), 8.21 (dd, J¼2.1 Hz 1H),
419 (73), 404 (33), 388 (10), 362 (9), 327(8), 312 (10),
299 (14), 294 (15), 265 (22), 263 (11), 240 (11), 211 (43),
209 (34), 191 (9), 189 (12), 185 (22), 183 (15), 155 (21),
149 (41), 125 (18), 121 (23), 107 (23), 105 (95), 81 (48),
ꢄ
+
ꢄ
+
.71 (d, J¼6.4 Hz, 2H); m/z (EI, %) 429 (M , 100), 399
79 (64), 77 (69), 67 (48), 55 (54). Found: M , 432.1366.
ꢄ
+
33), 385 (26), 358 (45), 348 (41), 320 (62), 291 (36), 263
28), 261 (9), 213 (12), 163 (11), 149 (29), 131 (18), 126
C H O requires M , 432.1362.
29 20 4
ꢄ
+
14), 85 (18), 71 (28); Found: M 427.0213. C H BrN O
1 2
4.1.5. (± ±-2ꢀ8-ꢁi(phenyl-4-trifluoromethanesulfonate±
dibenzobicyclo[bꢀ f][3.3.1]nona-5aꢀ6a-diene-6ꢀ12-dione 9.
2
4
14
ꢄ
+
requires M , 427.0208.
ꢁ
3
Pyridine (0.10 mL, 1.28ꢂ10 mol) was added to bisphenol
ꢁ
4
4
[
.1.3. (± ±-2ꢀ8-ꢂis(4-ethynylpyridyl±dibenzobicyclo[bꢀ f]
3.3.1]nona-5aꢀ6a-diene-6ꢀ12-dione L2. Triethylamine
8 (115 mg, 2.66ꢂ10 mol) suspended in dry CH Cl
2
2
(17 mL) at rt under an atmosphere of nitrogen. The resultant

C. K. Y. Lee et al. / Tetrahedron 62 (2006) 4870–4878
4877
ꢀ
solution was cooled to 0 C (ice bath) followed by addition
sodium nitrite (23 mg, 0.33 mmol) was added over 2 h to
a stirred solution of cleft 15 (34 mg, 0.12 mmol) in water
ꢁ
4
of triflic anhydride (0.15 mL, 8.81ꢂ10 mol). After stir-
ꢀ
ring at rt for 2 h, the reaction was quenched with aq NaHCO
(1.5 mL) and concd H SO (four drops) at 0 C. After
2
3
4
(
organic solution was washed with satd aq CuSO
1 mL) and the mixture extracted into Et O (3ꢂ15 mL). The
30 min, an aqueous solution (1.5 mL) of KI (79.5 mg,
0.48 mmol) was slowly added. The reaction mixture was
warmed to rt and left to stand for 40 min. The mixture was
poured onto water (40 mL) and extracted with EtOAc
(3ꢂ30 mL). The combined organic extracts were washed
with 10% aq Na S O (100 mL) and brine (100 mL), then
2
4
(
(
3ꢂ15 mL), H O (1ꢂ15 mL), and brine (1ꢂ15 mL), dried
2
Na SO ) and concentrated in vacuo to afford crude bistri-
2
4
flate 9 as a yellow oil (183 mg, 99%) [R 0.93; MeOH/
f
CHCl (1:9)], which was used in the next reaction without
3
2 2 7
further purification; dH (200 MHz, CDCl ) 3.07 (t, J¼
dried (Na SO ) and concentrated in vacuo. Flash chromato-
2 4
3
2
.6 Hz, 2H), 4.13 (t, J¼2.6 Hz, 2H), 7.33 (d, J¼8.8 Hz,
H), 7.59 (d, J¼8.0 Hz, 2H), 7.60 (d, J¼8.8 Hz, 2H), 7.74
graphy of the orange residue on silica, eluting with EtOAc/
hexane (1:5) afforded the diiodide 12 as an off-white col-
oured solid (42.5 mg, 70%) [R 0.81 (CH Cl )]; mp 243.5–
2
(
dd, J¼8.0, 2.2 Hz, 2H), 8.18 (d, J¼2.2 Hz, 2H).
f
2
2
ꢀ
ꢁ1
2
45.5 C; IR (NaCl) 1683 cm ; dH (200 MHz) 2.96 (t,
4
[
.1.6. (± ±-2ꢀ8-ꢂis(4-phenylpyridyl±dibenzobicyclo[bꢀ f]
3.3.1]nona-5aꢀ6a-diene-6ꢀ12-dione L3. To a mixture of
J¼3.0 Hz, 2H), 3.96 (t, J¼3.0 Hz, 2H), 7.19 (d, J¼8.1 Hz,
2H), 7.83 (dd, J¼8.1, 2.0 Hz, 2H), 8.27 (d, J¼2.0 Hz, 2H);
ꢁ
4
+
+
+
the bistriflate 9 (183 mg, 2.63ꢂ10 mol), 4-pyridinylbor-
m/z (ES , %) 500.8 (M+H , 18%), 499.8 (M , 100), 218.2
(41), 189.2 (36). Anal. Calcd for C H I O : (%) C 40.83,
H 2.02. Found: C 41.07, H 2.12.
ꢁ
4
onic acid (100 mg, 8.13ꢂ10 mol) and sodium carbonate
1
7 10 2 2
ꢁ3
(
H O (6 mL). The mixture was evacuated and purged with ni-
140 mg, 1.32ꢂ10 mol) were added DME (20 mL) and
2
ꢀ
trogen (3ꢂ freeze-pump-thaw cycles) and heated at 85 C in
4.2. Metal complexation
the dark under an atmosphere of nitrogen for 46 h. After
cooling to rt, the mixture was taken up in CH Cl
ꢁ5
A solution of ligand L1 (10 mg, 2.49ꢂ10 mol) in MeOH
2
2
(250 mL) and washed with H O (120 mL). The layers
were separated and the organic layer was washed with aq
(1.5 mL) was added dropwise to a solution of [Pd(ONO )
(en)] (7.25 mg, 2.49ꢂ10 mol) in H O (1.5 mL) at
2
2 2
ꢁ5
2
ꢀ
ꢀ
Na CO (2ꢂ50 mL). The aqueous solution was extracted
20 C. The homogeneous solution was stirred at 20 C for
four days. The residue was redissolved in CD OD/D O
(1:1) and analysed by H NMR spectroscopy. The H
2
3
with CH Cl (100 mL); the organic solutions were com-
2
2
3
2
1
1
bined then dried (Na SO ) and evaporated in vacuo. Flash
2
4
column chromatography of the residue on silica, eluting
with MeOH/CH Cl (3:97), followed by recrystallisation
of the resulting white solid from MeOH and trifluoroacetic
NMR spectrum contained multiple peaks consistent with
the formation of a mixture of stereoisomers. Analysis by
ESI mass spectrometry showed peaks consistent with the
2
2
2
+
acid afforded ligand L3 as colourless crystals (100 mg,
6
formation of the [2+2] macrocycle, m/z 631 [Mꢁ2NO ] ,
3
ꢀ
KBr) 1683, 1653, 1558 cm ; d (200 MHz, CDCl ) 3.10
4+
3 3
4+
4+
8%) [R 0.27; MeOH/CH Cl (4:96)]; mp>300 C; IR
f
508 [Mꢁ4NO +7MeOH] , 380 [Mꢁ4NO +3MeOH]
2
ꢁ
2
1
(
and 284 [Mꢁ4NO ] .
H
3
3
(
m, 2H), 4.15 (m, 2H), 7.55 (d, J¼5.9 Hz, 4H), 7.63 (d,
J¼8.0 Hz, 2H), 7.72 (s, 8H), 7.83 (dd, J¼8.0, 2.0 Hz, 2H),
.29 (d, J¼2.0 Hz, 2H), 8.69 (d, J¼5.9 Hz, 4H); m/z (EI,
In an analogous fashion, methanolic solutions of ligand L2
(4.49 mg, 1ꢂ10 mol; 1.2 mL) and ligand L3 (5.54 mg,
ꢁ
5
8
%
2
+
ꢁ5
) 554 (M , 40), 553 (100), 526 (77), 277 (15), 242 (9),
28 (8), 165 (9), 156 (23), 149 (19), 105 (11), 95 (15), 91
1ꢂ10 mol; 3.3 mL) were independently treated with
ꢁ
5
[Pd(ONO ) (en)] (2.91 mg, 1ꢂ10 mol) in H O (1.2 mL).
2
2
2
ꢄ
+
ꢀ
(
20), 77 (69), 79 (27), 67 (28), 55 (37). Found: M ,
After stirring at 20 C for 6 h, the crude reaction mixtures
were analysed by ESI mass spectrometry. Peaks consistent
with the formation of the [2+2] metallomacrocycles were
observed as follows: for L2-containing macrocycle, m/z
ꢄ
+
5
44.1991. C H N O requires M , 554.1994. Crystals
39 26 2 2
suitable for X-ray diffraction were obtained by recrystallisa-
tion from MeOH and trifluoroacetic acid.
2
+
4+
8
33 [Mꢁ2NO +MeOH+H O] , 720 [Mꢁ4NO ] , 661
3
2
4
3
+
4
.1.7. Attempted preparation of (± ±-2ꢀ8-bis(4-nitro-
[Mꢁ4NO +6MeOH+6H O] ; for L3-containing macro-
3 2
4
3 3
+
phenyl±dibenzobicyclo[bꢀf][3.3.1]nona-5aꢀ6a-diene-6ꢀ12-
dione 6. Using the same protocol for the synthesis of cleft L1,
the reaction of the dibromo cleft 2 (78 mg, 0.19 mmol),
Na CO (123 mg, 1.16 mmol), 4-nitrophenylboronic acid
cycle, m/z 616 [Mꢁ4(NO )]
and 557 [Mꢁ4NO +
4
+
5MeOH+5H O] .
2
4.3. X-ray diffraction
2
3
(
74 mg, 0.44 mmol) and PdCl (PPh ) (30 mg, 43 mmol) fol-
2 3 2
lowed by flash chromatography, eluting with EtOAc/hexane
3:1) afforded the crude monocoupled product 13 as a cream
solid (55 mg, 64%) [R 0.65; EtOAc/hexane (2:1)]; dH
Data collections were undertaken at 150(2) K, graphite
˚
monochromated Mo Ka radiation (0.71073 A). For L1 and
(
L3, an APEXII-Kappa-FR591 rotating anode diffractometer
was used for the data collection, while for L2, a Bruker
SMART 1000 sealed tube diffractometer was used. The dif-
fraction data integration and reduction for L1, L2 and L3
f
(
7
200 MHz) 3.05–3.02 (2H, m), 4.11–4.05 (2H, m), 7.81–
.58 (6H, m), 8.31–8.10 (4H, m); m/z (EI, %) 448.9 (MH ,
7%), 446.9 (M , 100), 419.0 (33), 263.2 (32). Crude 13
+
+
9
was treated further with Na CO (123 mg, 1.16 mmol), 4-ni-
2
6
were undertaken with SAINT and XPREP, subsequent
computations were carried out with the XTAL and
WinGX graphical user interfaces. A multi-scan correction
2
3
2
7
trophenylboronic acid (74 mg, 0.44 mmol) and PdCl (PPh )
2
3 2
1
28
(30 mg, 43 mmol). H NMR analysis of the resulting product
indicated a complex mixture of products.
2
9
determined with SADABS was applied to the data of L1
and L2. There was no crystal decay during the data collec-
tions. The structures were solved by direct methods with
4
6
.1.8. (± ±-2ꢀ8-ꢁiiododibenzobicyclo[bꢀ f][3.3.1]nona-5aꢀ
a-diene-6ꢀ12-dione 12. An aqueous solution (1 mL) of
3
0
31
SIR97 and extended and refined with SHELXL97.

4878
C. K. Y. Lee et al. / Tetrahedron 62 (2006) 4870–4878
Anisotropic displacement parameters were refined for the
non-hydrogen atoms. The asymmetric unit for L1 contains
half of the molecule located on a two fold axis passing
through the bridgehead carbon site C(9), and there is also
a water molecule residing on a two fold axis. In addition
to the cleft molecule, the asymmetric unit for L2 contains
a methanol solvate disordered over two sites with occupan-
cies refined and then fixed at 0.5. The asymmetric unit for L3
contains two crystallographically independent molecules.
H. D.; Arana, C. Inorg. Chem. 1993, 32, 4436; (h) Constable, E.
C.; Hannon, M. J.; Tocher, D. A. J. Chem. Soc., Dalton Trans.
1993, 12, 1883; (i) Constable, E. C.; Elder, S. M.; Healy, J.;
Ward, M. D.; Tocher, D. A. J. Am. Chem. Soc. 1990, 112, 4590.
8. (a) Bassami, D. M.; Lehn, J.-M.; Fromme, K.; Fenske, D.
Angew. Chem., Int. Ed. 1998, 37, 2364; (b) Baxter, P. N. W.;
Lehn, J.-M.; Fischer, J.; Youinou, M.-T. Angew. Chem., Int.
Ed. Engl. 1994, 33, 2284; (c) Baxter, P. N. W. J. Org. Chem.
2000, 65, 1257.
9. (a) Ziessel, R. Synthesis 1999, 11, 1839; (b) Harriman, A.; Zies-
sel, R. Coord. Chem. Rev. 1998, 171, 331; (c) Harriman, A.;
Ziessel, R. Chem. Commun. 1996, 1707.
10. Try, A. C.; Painter, L.; Harding, M. M. Tetrahedron Lett. 1998,
39, 9809.
3
2
ORTEP depictions are provided in Figures 1 and 2.
Crystallographic data (excluding structure factors) for
the structures in this paper have been deposited to the Cam-
bridge Crystallographic Data Centre as supplementary pub-
lication numbers CCDC 293459, 29360 and 293461. Copies
of the data can be obtained, free of charge, on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: +44
11. Kimber, M. C.; Try, A. C.; Painter, L.; Harding, M. M.; Turner,
P. J. Org. Chem. 2000, 65, 3042.
12. Field, J. D.; Turner, P.; Harding, M. M.; Hatzikominos, T.; Kim,
L. New J. Chem. 2002, 26, 720.
1
223 336033 or email: deposit@ccdc.cam.ac.uk].
1
3. Turner, J. J.; Harding, M. M. Supramol. Chem. 2005, 17, 369.
Acknowledgements
14. Tatemitsu, H.; Ogura, F.; Nakagawa, Y.; Nakagawa, M.;
Naemura, K.; Nakagawa, M. Bull. Chem. Soc. Jpn. 1975, 48,
2473.
15. (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457;
(b) Suzuki, A. J. Organomet. Chem. 1999, 576, 147.
Financial support from Australian Research Council Discov-
ery Grant Scheme is gratefully acknowledged (L.M.R and
M.M.H).
1
6. (a) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
1975, 4467; (b) Rossi, R.; Carpita, A.; Bellina, F. Org. Prep.
Proced. Int. 1995, 27, 129.
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