2,5-Diamidofuran anion receptors

Article abstract of DOI:10.1016/S0040-4039(02)02883-6

3,4-Diphenylfuran-2,5-dicarboxylic acid bis-N-phenylamide 1 and 3,4-biphenyl-furan-2,5-dicarboxylic acid bis-N-butylamide 2 have been synthesised and shown to act as fluoride selective anion receptors in DMSO-d₆/0.5% water solution.

Full text of DOI:10.1016/S0040-4039(02)02883-6

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 1367–1369
2,5-Diamidofuran anion receptors
Salvatore Camiolo, Philip A. Gale,* Michael B. Hursthouse, Mark E. Light and Colin N. Warriner
School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
Received 18 October 2002; revised 12 December 2002; accepted 20 December 2002
Abstract—3,4-Diphenylfuran-2,5-dicarboxylic acid bis-N-phenylamide 1 and 3,4-biphenyl-furan-2,5-dicarboxylic acid bis-N-butyl-
amide 2 have been synthesised and shown to act as fluoride selective anion receptors in DMSO-d6/0.5% water solution. © 2003
Elsevier Science Ltd. All rights reserved.
In 1997, Crabtree and co-workers reported that very
simple isophthalamide type anion receptors form
remarkably strong complexes with fluoride and chloride
in organic solution.1 This discovery has led to the
incorporation of this hydrogen bond donor unit in a
variety of anion2 and ion-pair3 receptors as well as in
self-assembling systems.4 With the aim of enhancing the
anion affinity of this motif, we synthesised analogous
X-Ray quality crystals of 1 were obtained by slow
receptors containing a central pyrrole ring (instead of a
benzene) in order to introduce an additional hydrogen
evaporation of an acetonitrile solution of the receptor.12
The receptor adopts a cleft conformation (Fig. 1). The
molecules form chains along the a axis via NH···O
hydrogen bond linkages (Fig. 2) such that the furan
bond donor group. Our first generation 2,5-diamidopyr-
role receptors were found to be selective for carboxyl-
ates in DMSO-d6/0.5%water solution.5 Second genera-
tion systems employed pendant arms containing amine,
amide or ammonium groups to modulate the affinity of
these systems and we found that amine functionalised
receptors were selective for acidic oxo-anions such as
− 6
HSO4 . Crabtree found that introduction of a central
pyridine ring increased the selectivity for smaller halides
such as fluoride.7 We have found that deprotonation of
the central pyrrole ring in our 2,5-diamidopyrrole sys-
tems allowed the formation of an unusual interlocked
dimer.8 We therefore wished to synthesise a variety of
2,5-diamidofurans and study their anion receptor and
potential self-assembly properties.
3,4-Diphenylfuran-2,5-dicarboxylic acid was synthe-
sised by literature methods.9 This material was con-
verted to the acid chloride and then coupled with
aniline or n-butylamine affording the diamides 110 and
211 in 80 and 53% overall yields, respectively.
Figure 1. The X-ray crystal structure of compound 1 (aceto-
* Corresponding author.
nitrile and certain hydrogen atoms omitted for clarity).
0040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)02883-6

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S. Camiolo et al. / Tetrahedron Letters 44 (2003) 1367–1369
Figure 2. Hydrogen bonding array present in the solid-state (certain atoms have been omitted for clarity).
rings adopt alternating orientations (in contrast to the
2,5-diamidopyrrole anion analogue which has been
shown to form an interlocked dimer in the solid state8).
There are two unique hydrogen bonds operating as
independent pairs; the shorter pair (N2ꢀH2···O1, 2.17
anions so favouring smaller anions such as fluoride
which presumably resides further from the oxygen than
larger bound anions.7 We are continuing to study the
anion-binding and assembly properties of 2,5-diamid-
ofuran containing systems. The reports of these studies
will be reported in due course.
,
A) link the molecules into centrosymmetric dimers and
,
the longer pair (N1ꢀH1···O3, 2.43 A) connect the
dimers into chains.
Acknowledgements
Dilution studies were conducted on both compounds in
DMSO-d6/0.5% water, however, no shifts in the amide
NH resonances were observed. In dichloromethane,
compound 2 appears to dimerise in solution but with a
low dimerisation constant (1.7 M−1).13 Anion binding
studies were conducted in DMSO-d6/0.5% water solu-
P.A.G. would like to thank the Royal Society for a
University Research Fellowship and the EPSRC for a
project studentship (to S.C.), a quota studentship (to
C.N.W.) and for use of the crystallographic facilities at
the University of Southampton. In addition P.A.G.
would like to thank Professor Kristin Bowman-James
(Lawrence, Kansas) for helpful discussions.
1
tion using H NMR titration techniques.14 The results,
summarised in Table 1, reveal that both compounds
show a high selectivity for fluoride under these
conditions.
In contradistinction to the oxo-anion selective 2,5-
diamidopyrroles,5 2,5-diamidofurans show selectivity
for fluoride in DMSO-d6/0.5% water solution. The oxo-
anion selectivity of the former systems is believed to be
due to the ability of the receptor to form three hydro-
gen bonds to the two oxygen atoms in an oxo-anion
such as benzoate.15 The absence of the central NH
hydrogen bond donor group in 1 and 2 and the pres-
ence of an oxygen atom may introduce a repulsive
component to the interaction of these species with
References
1. Kavallieratos, K.; de Gala, S. R.; Austin, D. J.; Crabtree,
R. H. J. Am. Chem. Soc. 1997, 119, 2325–2326.
2. Hossain, M. A.; Llinares, J. M.; Powell, D.; Bowman-
James, K. Inorg. Chem. 2001, 40, 2936–2937.
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Chem., Int. Ed. 2001, 40, 3606–3608.
Table 1. NMR titrations were conducted in DMSO-d6/
0.5% water at 298 K
5. (a) Gale, P. A.; Camiolo, S.; Chapman, C. P.; Light, M.
E.; Hursthouse, M. B. Tetrahedron Lett. 2001, 42, 5095–
5097; (b) Gale, P. A.; Camiolo, S.; Tizzard, G. J.; Chap-
man, C. P.; Light, M. E.; Coles, S. J.; Hursthouse, M. B.
J. Org. Chem. 2001, 68, 7849–7853.
Added aniona
Association constant
(M−1) with
Association constant
(M−1) with compound
2b
compound 1b
6. Navakhun, K.; Gale, P. A.; Camiolo, S.; Light, M. E.;
Hursthouse, M. B. Chem. Commun. 2002, 2084–2085.
7. Kavallieratos, K.; Bertao, C. M.; Crabtree, R. H. J. Org.
Chem. 1999, 64, 1675–1683.
8. (a) Camiolo, S.; Gale, P. A.; Hursthouse, M. B.; Light,
M. E.; Shi, A. J. Chem. Commun. 2002, 758–759; (b)
Gale, P. A.; Navakhun, K.; Camiolo, S.; Light, M. E.;
Hursthouse, M. B. J. Am. Chem. Soc. 2002, 124, 11228–
11229; (c) Camiolo, S.; Gale, P. A.; Hursthouse, M. B.;
Light, M. E. Org. Biomol. Chem., in press.
Fluoridec
Dihydrogen
phosphate
Benzoate
Chloride
1140
78
557
46
49
47
28
14
a Anion added as tetrabutylammonium salt.
b Errors in association constants estimated to be a maximum of
15%.
c Dried under high vacuum without heating. The fluoride was
assumed to be anhydrous when calculating the concentrations used
in the fitting procedure, however, this is unlikely to be the case and
these values must therefore be treated with a certain degree of
caution. However, the titration profiles clearly indicate the selectiv-
ity of these receptors for fluoride.
9. Backer, H. J.; Stevens, W. Recl. Trav. Chim. Pays-Bas
1940, 59, 423–444.
10. 3,4-Diphenylfuran-2,5-dicarboxylic acid bis-N-phenyl-
amide 1

S. Camiolo et al. / Tetrahedron Letters 44 (2003) 1367–1369
1369
3,4-Diphenylfuran-2,5-dicarboxylic acid (2.0 g, 0.0048
mol) was suspended in freshly distilled thionyl chloride
(50 ml) and heated at reflux overnight. The thionyl
chloride was removed in vacuo and the resulting solid
dried under high vacuum for 2 h. The resulting 3,4-
diphenylfuran-2,5-dicarbonyl dichloride was dissolved in
dry dichloromethane (80 mL). Triethylamine (2.0 g,
0.0198 mol), DMAP (catalytic quantity) and aniline (1.27
g, 0.0136 mol) were added whilst the solution was stirred
under a nitrogen atmosphere. The reaction mixture was
stirred overnight and the organic solution was then
washed with water (4×100 ml), dried with magnesium
sulfate and the dichloromethane removed in vacuo. The
product was recrystallised from acetonitrile (200 ml)
affording the final product (1.77 g, 80%) as a white
powder. (Found: C, 75.82; H, 5.11; N, 5.69.
C30H22N2O3+H2O requires C, 75.61; H, 5.08; N, 5.88%).
1H NMR in DMSO-d6 300 MHz, l (ppm): 7.24–7.83 (m,
20H, ArH), 10.49 (s, 2H, NH). 13C NMR in DMSO-d6
400 MHz l (ppm): 121.3, 124.8, 128.0, 128.2, 129.3,
130.5, 130.8, 132.7, 138.3, 141.9, 156.2. ES+ mass spec-
trum, m/z, 560 (M+Et3NH+), 917 (2M+) HRES MS
C60H44N4O6Na calcd 939.3153, found 939.3180, D=2.8
ppm. Mp=278°C.
dichloromethane (80 ml). Triethylamine (2.0 g, 0.0198
mol), DMAP (catalytic quantity) and n-butylamine (1.00
g, 0.0136 mol) were added whilst the solution was stirred
under a nitrogen atmosphere. The reaction mixture was
stirred overnight and the organic solution was then
washed with water (4×100 ml), dried with magnesium
sulfate and the dichloromethane removed in vacuo. The
yellow residue was crystallised from diethyl ether (200 ml)
resulting in a white crystalline material (1.07 g, 53%).
(Found: C, 73.79; H, 7.16; N, 6.51. C26H30N2O3+0.33
MeOH requires C, 73.69; H, 7.36; N, 6.53%). 1H NMR in
CDCl3 300 MHz, l (ppm): 0.88 (t, J=7.3 Hz, 6H, CH3),
1.24 (m, 4H, CH2), 1.43 (m, 4H, CH2), 3.32 (m, 4H,
CH2), 6.28 (t, J=5.5 Hz, 2H, NH), 7.17–7.30 (m, 10H,
ArH). 13C NMR in CDCl3 400 MHz l (ppm): 13.7, 20.0,
31.4, 39.0, 128.3, 128.4, 130.2, 130.3, 131.0, 142.4, 158.2.
ES+ mass spectrum, m/z, 520 (M+Et3NH+), 837 (2M+H+)
HRES MS C52H60N4O6Na calcd 859.4405, found
859.4408, D=0.4 ppm. Mp=144°C.
12. Crystallographic data (excluding structure factors) for the
structure in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplemen-
tary publication number CCDC 195420. Copies of the
data can be obtained free of charge, on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax:
+44 (0)1223-336033 or e-mail: deposit@ccdc.cam.ac.uk].
11. 3,4-Diphenylfuran-2,5-dicarboxylic acid bis-N-butyl-
amide 2
13. NMRDILL Dimer, kindly provided by Professor C.A.
3,4-Diphenylfuran-2,5-dicarboxylic acid (2.0 g, 0.0048
mol) was suspended in freshly distilled thionyl chloride
(50 ml) and heated at reflux overnight. The thionyl
chloride was removed in vacuo and the resulting solid
dried under high vacuum for 2 h. The 3,4-diphenylfuran-
2,5-dicarbonyl dichloride was dissolved in dry
–
Hunter see: Bisson, A. P.; Hunter, C. A.; Morales, J. C.;
Young, K. Chem. Eur. J. 1998, 4, 845–851.
14. Hynes, M. J. J. Chem. Soc., Dalton Trans. 1993, 311–312.
15. Camiolo, S.; Gale, P. A.; Hursthouse, M. B.; Light, M.
E. Tetrahedron Lett. 2002, 43, 6995–6996.