A. M. Costero et al. / Tetrahedron 60 (2004) 4683–4691
4689
Perkin–Elmer 1750 FT-IR and a Bruker Equinox 55 FT-IR.
NMR spectra were recorded with Bruker Avance 300/500
and Varian Unity-300/400 spectrometers. Chemical shifts
are reported in parts per million downfield from TMS.
Spectra were referenced to residual undeuterated solvent.
High-resolution mass spectra were taken with a Fisons
VG-AUTOSPEC. UV spectra were run at 20 8C (thermo-
stated) on a Shimadzu UV-2102 PC.
(d), 131.19 (d), 123.25 (d, s, 2 signals), 71.18 (t), 70.67–
70.19 (t, several signals), 68.73 (t), 49.98 (t, CH2N–), 44.96
(t, CH2-N–); UV (CH3CN): 1¼17398, lmax¼293 nm.
4.1.4. Synthesis of 2. 2-(2-Methyloxycarbonyl-4-nitro-
phenyl)-5-nitrobenzoic acid (0.509 g, 1.47 mmol) was
converted into its acid chloride, as described for the
synthesis of 1. Benzene (30 ml) was added and evaporated
to yield 2-(2-methyloxycarbonyl-4-nitrophenyl)-5-nitro-
benzoic acid chloride as a solid (0.536 g, 1.47 mmol). It
was dissolved in dry CH2Cl2 (25 ml) and used in the
following step.
4.1.1. Synthesis of 4,40-dinitro-2,20-diphenic anhydride
acid (3). 4,40-Dinitro-2,20-diphenic acid (0.197 g,
0.594 mmol) was stirred at 90 8C in acetic anhydride
(40 ml) for 24 h. After removal of the solvent under
vacuum, a clear brown oil was obtained. This oil was
washed with Et2O, allowing separation of the soluble
starting acid (0.078 g) and its anhydride as a brown powder
that was dried under vacuum. (0.119 g, 0.38 mmol, 64%
yield). Mp 230–233 8C. HRMS (EI): found Mþ 314.0181,
C14H6N2O7 requires 314.0175; nmax 1815 (CvO), 1733
(CvO), 1525, 1350 cm21; dH (CDCl3) 8.92 (2H, d,
J¼2.3 Hz, Ar-H), 8.53 (2H, dd, J1¼8.5 Hz, J2¼2.3 Hz,
Ar-H), 7.46 (2H, d, J¼8.5 Hz, Ar-H); dC (CD3COCD3)
166.1 (COOCO), 148.5, 147.0, 131.6, 126.4, 125.3, 124.8
(12 CAr).
To a stirred mixture of 1-aza-18-crown-6 (95%) (0.408 g,
1.47 mmol) and dry triethylamine (99%) (0.150 g,
1.47 mmol) in dry CH2Cl2 (20 ml) at 0 8C, the above
solution was added dropwise under Ar atmosphere. Then,
the mixture was stirred at room temperature and monitored
by TLC. After completion of the reaction (12 h), the
solution was concentrated under reduced pressure and the
crude reaction product was purified by chromatography
through a neutral alumina column using CH2Cl2/EtOAc
(8:2) as eluents to give 2 as a brown oil (0.530 g,
0.887 mmol). (60% yield). HRMS (EI): found Mþ
591.2073. C27H33N3O12 requires 591.2064. nmax 1731
(OCvO), 1634 (NCvO), 1608, 1524 (NvO, asym.),
1349 (NvO, sym.), 1123 cm21; dH (CDCl3) 8.85 (1H, d,
J¼2.4 Hz, Ar-H), 8.39–8.36 (2H, m, Ar-H), 8.27 (1H, dd,
J1¼8.5 Hz, J2¼2.4 Hz, Ar-H), 7.63 (1H, d, J¼8.5 Hz, Ar-
H), 7.40 (1H, d, J¼8.5 Hz, Ar-H), 3.79 (3H, s, OCH3),
3.65–3.54 (20H, m, –OCH2–), 3.42 (2H, m, –NCH2–),
3.36 (2H, m, –NCH2–); dC (CDCl3) 168.20 (CON), 165.23
(–COO), 148.07, 147.66, 145.52, 143.65, 137.35, 133.02,
131.59, 130.78, 126.44, 125.93, 123.50 and 123.11 (12 CAr),
71.49, 70.95, 70.90, 69.50, 69.00 (10 –OCH2–), 53.29
(–OCH3), 49.91 (–NCH2), 45.19 (–NCH2); UV (CH3CN):
1¼1470, lmax¼284 nm.
4.1.2. Synthesis of 2-(2-methyloxycarbonyl-4-nitro-
phenyl)-5-nitrobenzoic acid (4). 4,40-Dinitro-2,20-diphenic
anhydride acid (0.119 g, 0.38 mmol) was stirred for 5 h in
refluxing MeOH (40 ml). Then, the solvent was evaporated
under vacuum, to give a dark brown solid. This solid was
dissolved in boiling CHCl3 and the hot solution filtered.
After evaporation of the solvent under reduced pressure, a
white powder (0.132 g, 0.38 mmol) was obtained. Mp 176–
180 8C. nmax 2956 (OH), 1728, 1698, 1525, 1350,
1265 cm21; dH (CDCl3) 8.97 (1H, d, J¼2.4 Hz, Ar-H),
8.92 (1H, d, J¼2.4 Hz, Ar-H), 8.46 (1H, dd, J1¼8.5 Hz,
J2¼2.4 Hz, Ar-H), 8.43 (1H, dd, J1¼8.5 Hz, J2¼2.4 Hz, Ar-
H), 7.37 (2H, d, J¼8.5 Hz, Ar-H), 3.75 (3H, s, OCH3); dC
(CD3COCD3) 166.13 (COO), 165.83 (COO), 149.54,
149.42, 148.77, 143.70, 132.81, 132.79, 132.08, 131.76,
127.4, 127.45, 126.14 and 125.82 (12 CAr), 53.25 (OCH3);
MS (EI): Mþ (346, 65%); Mþ21 (345, 100%).
4.2. Transport experiments
Experiments of transport were carried out across an organic
liquid bulky membrane consisting in 15 ml of ethanol-free
CHCl3 confined in a 12 mm of diameter U-shaped tube. A
known amount of carrier was dissolved in this membrane
(see Table 3). Picrate salts were synthesised from picric acid
and the corresponding hydroxide of each metal, and most of
them were purified by recrystallisation in ethanol/water.
Initial solutions of picrate salts in water were prepared: Liþ
(0.02 M), Naþ (0.02 M), Naþ (0.005 M), Kþ (0.005 M),
Csþ (0.005 M), Mg2þ (0.02 M) and Ba2þ (0.005 M).
4.1.3. Synthesis of 1. 4,40-Dinitro-2,20-diphenic acid
(0.063 g, 0.19 mmol) was added to an excess of thionyl
chloride (30 ml) and the stirred suspension was heated under
reflux until disappearance of the precipitate (ca. 2 h). The
resulting solution was concentrated under reduced pressure
until all the SOCl2 had been removed. It was dissolved in
benzene (30 ml) and dropped over a stirred solution of
1-aza-18-crown-6 (0.105 g, 0.38 mmol) and triethylamine
(0.039 g, 0.38 mmol) in benzene (30 ml) under an argon
atmosphere. The resulting solution was stirred overnight at
room temperature, the reaction mixture filtered and the
filtrate then washed with water (3£2 ml), dried over
anhydrous Na2SO4 and concentrated to yield 1 as a brown
oil (0.099 g, 63%). HRMS (EI): found (Mþþ1) 823.3643;
C38H55N4O16 requires 823.3613; nmax: 2867, 1633 (CvO),
Solution of carrier in CHCl3 (15 ml) was transferred to a
U-shaped tube, provided with a magnetic stirring bar. Initial
solutions of the picrate salts (5 ml) were added to one of the
branches of the tube (source phase). 5 ml of pure water was
allocated in the other (receiving phase). In addition, one
blank experiment for each initial solution was carried out, so
as to determine the passive transport, by replacing the 15 ml
of carrier solution with 15 ml of pure ethanol-free CHCl3.
After 48 h stirring (350 rpm) at 293^1 K, aqueous
receiving phase was homogenised and a convenient aliquot
was transferred to a 1 cm pathlength quarz UV cell.
Distilled water was added to the cell till complete 3 ml of
1523 (NvO, asym.), 1349 (NvO, sym.), 1113 (CO) cm21
;
dH (CDCl3) 8.33 (2H, d, J2¼2.7 Hz, Ar-H), 8.29 (2H, dd,
J1¼8.4 Hz, J2¼2.7 Hz, Ar-H), 7.74 (2H, dd, J1¼8.4 Hz, Ar-
H), 3.7–3.5 (48H, m broad band, –CH2– linked to O and
N); dC (CDCl3) 168.24 (s), 147.28 (s), 141.31 (s), 138.17