The article comprises synthesis of calyx[4]-oxa-crown, and calix[4]-thia-crown compounds containing nitrile groups ( 3a, 3b) and amino groups ( 4a, 4b) and their corresponding oxime derivatives ( 5a, 5b) and liquid-liquid extraction studies of these compounds. The oxime derivatives of compounds ( 5a, 5b) have been synthesized by reacting of di-n-butylamino derivatives of calix[4]-oxa-crown, and calix[4]-thia-crown compounds ( 4a, 4b) with amphi-chloroglyoxime in methanol-THF. Their cation and anion transfer studies were performed by using liquid-liquid extraction procedure. It has been concluded from the observations that the compound 3a shows a good extraction behavior toward Na + ion in the presence of other metal cations. Whereas, its oxime derivatives transfers all of the metal cations used in the liquid-liquid extraction studies.
With the development of technology, environmental pollution has become an important problem today. In order to solve this problem, supramolecular chemistry develops new synthetic methods and separation techniques [
These compounds form complexes with alkali metals [
The main aim of this study is to synthesize oxime derivatives of calix-crown compounds and to study their ion transport properties. Because the studies which related oxime derivatized calixarenes are restricted numbers [
Melting points were determined on a Barnsted/Electro thermal apparatus in a sealed capillary and were uncorrected. 1H NMR spectra were recorded on a Bruke Avance DPX 400 spectrometer in CDCl3 with TMS as an internal standard. IR spectra were recorded on a Perkin-Elmer 1605 FTIR System Spectrum BX spectrometer as KBr pellets. UV-vis spectra were obtained on a Shimadzu UV-1700 Pharma visible recording spectrophotometer. Elemental Analysis was recorded on an Elemental CHNS.
Analytical TLC were performed on precoated silica gel plates (SiO2, Merck PF254), while silica gel 60 (Merck, particle, size 0.040 - 0.063 mm, 230 - 240 mesh) was used for preparative column chromatography. The drying agent employed was anhydrous sodium sulfate. All aqueous solutions were prepared with deionized water that had been passed through a Milli-Q Plus water purification system.
Compounds 1, 2a and 2b were synthesized according to the procedures described in the literature [
Scheme 1. Synthesis of compound 5a-5b.
A mixture of compound 2a (4.00 g, 5.10 mmol), K2CO3 (2.81 g, 20.30 mmol), sodium iodide (3.00 g, 20.0 mmol) and 4-chlorobutyronitrile (4.0 g, 20.40 mmol) in dry acetonitrile (200 mL) was stirred and heated under reflux for 24 hr. The solvent was removed in vacuo and 50 ml 2N HCl and 50 ml CH2Cl2 were added and the phases were separated. The aqueous phase was extracted two times with 30 ml CH2Cl2, the organic phases were combined dried with Na2SO4 and the solvent removed in vacuo. The crude product was recrystallized from methanol/CH2Cl2 (5:1). Yield: 44%, mp: 187˚C, IR (KBr) cm−1: 2248 cm−1 (CN). 1H NMR (CDCl3), 1.02 - 1.40 (brs, 36H, But), 1.87 - 2.01 (m, 4H, C-CH2-C), 2.23 (t, 4H, J = 7 Hz, OCH2CH2), 3.28 (t, 4H, J = 7 Hz, CH2CN), 3.37 (d, 4H, J = 13 Hz, ArCH2Ar ), 3.71 - 4.2 (brm, 12H, CH2O), 4.28 (d, 4H, J = 12 Hz, ArCH2Ar), 6.90 - 7.15 (m, 8H, ArH). Calculated for C58H76N2O6, C, 77.67; H, 8.53; N, 3.12. Found: C, 77.50; H, 8.48; N, 3.07.
A mixture of compound 2b (3.5 g, 4.40 mmol), K2CO3 (5.73 g, 17.6 mmol), sodium iodide (2.63, 17.6 mmol) and 4-chlorobutyronitrile (1.82 g, 17.6 mmol) in dry acetonitrile (175 mL) was stirred and heated under reflux for 24 hr. The reaction procedure was then proceeded according to the above described method. Usual work up afforded 3b. Yield: 54%, mp: 147˚C. IR (KBr) cm−1: 2225 cm−1 (CN). 1H NMR (CDCl3), 1.00 - 1.41 (brs, 36H, But), 1.90 - 1.99 (m, 4H, CH2CH2-CH2), 2.34 (t, 8H, J = 6 Hz, OCH2CH2), 3.21 (t, 4H, J = 7 Hz, CH2CN), 3.27 (d, 4H, J = 8 Hz, ArCH2Ar), 3.34 - 3.39 (m, 8H, CH2S), 4.17 (d, 4H, J = 13 Hz, Ar-CH2Ar), 6.82 - 7.30 (m, 8H, ArH), Calculated for C58H76N2O4S2, C, 74.95; H, 8.24; N, 3.01; S, 6.90. Found: C, 74.63; H, 8.16; N, 2.98.
Dry THF (50 mL) was added in a two necked glass flask then LiAlH4 (0.27 g, 7.26 mmol 1:2 equation) was added carefully. The reaction mixture was heated until the boiling point of the solvent. A mixture of compound 3a (3.84 g, 3.63 mmol) in the warm dry THF (100 mL) was added dropwise over a period of 1.5 h. and reflux was continued for an additional 7 h. At the end of this time in order to removing the LiAlH4 remaining from the reaction, distilled water (approximately 5 mL) was added slowly little by little in the ice cold bath until the hydrogen gas emission ended. After the removal of most of the solvent it was taken in the separated funnel with CHCl3 then pH was regulated at 4 - 5 with solution of H2SO4 (20 %), and extracted several times with CHCl3. The combined organic layers were finally washed with distilled water, dried over MgSO4, then evaporated to dryness. The residue was recrystallization was performed in ethanol. Yield: 66%, mp: 152˚C. IR (KBr) cm−1: 3400 cm−1 (NH2), 1H NMR (CDC13), δ 1.02 - 1.40 (brs, 36H, But), 1.78 - 2.10 (m, 8H, CH2CH2), 2.49 (t, 4H, J = 8 Hz, OCH2CH2), 2.98 (t, 4H, J = 8 Hz, CH2N), 3.36 (d, 4H, J = 7 Hz, ArCH2Ar), 3.68 - 4.17 (brm, 12H, CH2O), 4.32 (d, 4H, J = 12 Hz, ArCH2Ar ), 5.01 (s, 4H, NH2 ), 6.87 - 7.12 (m, 8H, ArH). Calculated for: C58H84N2O6, C, 76.99; H, 9.35; N, 3.09. Found: C, 76.58; H, 9.02; N, 3.05.
Dry THF (50 mL) was added in a two necked glass flask then LiAlH4 (0.28 g, 7.30 mmol 1:2 equation) was added carefully. The reaction mixture was heated until the boiling point of the solvent. A mixture of compound 3b (3.95 g, 3.65 mmol) in the warm dry THF (100 mL) was added dropwise over a period of 1.5 h. and reflux was continued for an additional 7 h. The reaction procedure was then proceeded according to the described above. Usual work up afforded 4b. Yield: 64%, mp: 148˚C. IR (KBr ) cm−1: 3412 cm−1 (NH2), 1H NMR (CDC13), δ 1.19 - 1.32 (brs, 36H, But), 1.8 - 2.17 (m, 8H, CH2CH2), 2.49 (t, 4H, J = 7 Hz, OCH2CH2), 3.01 (t, 4H, J = 7 Hz, CH2N), 3.39 (d, 4H, J = 7 Hz, Ar-CH2-Ar), 3.54 - 3.60 (m, 8H, CH2S, CH2O), 3.72 (t, 4H, J = 7 Hz, CH2S), 4.34 (d, 4H, J = 13 Hz, Ar-CH2-Ar), 4.89 (s, 4H, NH2), 6.92 - 7.11 (m, 8H, ArH). Calculated for: C58H84O4N2S2, C, 74.31; H, 9.03; N, 2.98; S, 6.82. Found: C, 74.27; H, 8.92; N, 2.85; S, 6.70.
Synthesis of oxime derivative of compound 4a (5a)
To a solution of compound 4a (4.20 g, 5.0 mmol) in methanol-THF (1:4, 50 mL) was added a solution of amphi-monochloro glyoxime (0.12 g, 10.0 mmol) in MeOH. Then a solution of KOH (% 1 MeOH) was added until pH of the reaction medium is 5. The reaction mixture was stirred at room temperature for 12 h and the solvent was evaporated in vacuo and extracted several times with diethyl ether and dried over Na2SO4. Evaporation of the solvent in vacuo gave the crude product (5a) after recrystallization from EtOH. Yield: 49%, mp: 137˚C. IR (KBr) cm−1, 3200 (OH); 1650 (CN). 1H NMR (CDC13): δ 0.72 - 0.99 (brs, 36H, But), 1.2 - 1.45 (m, 8H, CH2CH2), 2.83 (t, 16H, OCH2CH2), 3.20 (d, 4H, J = 12 Hz, Ar-CH2-Ar), 3.8 - 4.4 (brm, 10H, CH2N, Ar-CH2-Ar, CH=N), 6.37 - 6.41 (m, 10H, ArH, NH), 9.0 (s, 4H, OH). Calculated for: C62H88O10N6 , C, 69.11; H, 8.23; N, 7.80. Found: C, 68.05, H, 8.14; N, 7.75.
Synthesis of oxime derivative of compound 4b (5b)
To a solution of compound 4b (3.5 g, 3.73 mmol) in methanol-THF (1:4, 50 mL) was added a solution of amphi-monochloroglyoxime (0.92 g, 7.46 mmol) in MeOH. Then a solution of KOH (1% MeOH) was added until pH of the reaction medium is 5. The reaction mixture was stirred at room temperature for 12 h. The reaction procedure was then proceeded according to the above described method. Usual work up afforded 5b. Yield: 52%, mp: 151˚C, IR (KBr ) cm−1, 3310 (OH); 1656 (CN). 1H NMR (CDC13): δ 0.91 - 1.41 (brs, 36H, But), 2.71 - 4.38 (brm, 36H, CH2CH2, OCH2CH2, CH2N, Ar-CH2-Ar, CH2S, Ar-CH2-Ar, CH2S, CH2O), 6.94 - 7.20 (m, 12H, ArH, NH, CH=N), 8.95 (s, 4H, OH). Calculated for: C62H88O8N6S2, C, 67.11; H, 7.99; N, 7.58; S, 5.78. Found: C, 67.07, H, 7.84; N, 7.50; S, 5.69.
Picrate extraction experiments were performed following Pedersen’s procedure [
The alkali picrates were prepared as described elsewhere [
The percent extraction (E%) has been calculated as:
E % = ( C 0 − C ) / C 0 × 100 (1)
where C0 and C are the initial and final concentrations of the metal picrate before and after the extraction, respectively.
The properties of calixarenes have been increased in the host-quest chemistry. Because these compounds transport cations, anions and neutral quests selectively. This selectivity is enhanced by functionalizing these compounds with some functional groups. Especially the selectivity is shown when the calix-crown compounds are used. As we know, oxime compounds are complex with metal cations. In this study, our aim is to enhance this present selectivity, so we have joined oxime groups with the calixcrown skeleton. To achieve the desired goal, we have synthesized p-tert-butylcalix[
Synthesis of the compounds 4a and 4b were fulfilled in 66% and 64% yield respectively by the reduction of nitrile groups of 3a and 3b with LiAlH4 in dry THF. Completion of this reaction was followed by the IR spectroscopy indicating the disappearance of the band due to the nitrile groups at 2248 and 2225 cm−1 for 3a and 3b respectively and the appearance of a new band at 3400 and 3412 cm−1 for the primary amine groups. The oxime derivatives of calix-crown (5a and 5b) bearing butyl amine on the lower rim were synthesized by mixing compound 4a and 4b amphi-monochloro glyoxime in the presence of KOH in MeOH-THF then recrystallization from MeOH-CHCl3 in 49%, 52% respectively. The IR spectra of compound 5a and 5b shows a C=N-bands at 1650 cm−1, 1656 cm−1, respectively. 1H NMR spectroscopy is a versatile tool for the identification of calix[
In our previous work, we stated that oxacrown ethers are regarded as hard ionophores, on the other hand, thiacrown ethers soft ionophores [
From the extraction data shown in
metals. It has been thought that this high selectivity of 2a for Na+ against K+ is due to the appropriate size of 2a, which have a cavity size adjusted to that between Li+ and Na+. It is in agreement with our previously reported study [
It is seen from the extractions results that the composition of p-tert-butylcalix [
We thank the Scientific and Technical Research Council of Turkey (TUBITAK-Number TBAG 105T433) for financial support of this work.
Akkuş, G.U. and Aslan, S. (2017) Synthesis and Extraction Studies of Calix[