Cesium extraction chromatography

The debenzylated AT-boc-protected diamine (469 mg, 1 mmol), 3-bromopro-pionic acid (158 mg, 1 mmol), cesium carbonate (652mg, 2mmol) and lOmL of acetone were placed in a 50 mL round-bottomed flask equipped with a magnetic stir bar and a reflux condenser. The mixture was heated under reflux for 24 h. The volatiles were removed on a rotary evaporator and the residue was triturated with dichloromethane. The extracts were filtered and dried over anhydrous sodium sulfate after evaporation of the solvent on a rotary evaporator, a pale yellow foam was obtained which was purified by silica gel chromatography (eluent CH2Cl2/hexane, 1/2, v/v) to yield white crystals (362 mg, 67 %). m.p. 161-163 °C. 

Typical procedure. O-A-PhenylbutYl-O -butyl carbonate 989 [711] To 4-phenyl-l-buta-nol 985 (100 mg, 0.67 mmol) in anhydrous DMF (1.6 mL, 0.4 m) were added cesium carbonate (625 mg, 2.10 mmol, 3 equiv.) and tetrabutylammonium iodide (208 mg, 0.67 mmol, 1 equiv.). CO2 gas (flow rate 25-30 mL min ) was bubbled into the reaction mixture for 2-3 min, and then 1-bromobutane 988 (274 mg, 0.22 mL, 2.0 mmol) was added to the suspension. The reaction proceeded at ambient temperature with CO2 gas bubbling for 3.5 h, after which time the starting material (4-phenyl-l-butanol) had been consumed. The reaction mixture was then poured into water (30 mL) and extracted with hexanes/EtOAc (3 1 v/v, 60 mL). The organic layer was washed with water (2 x 30 mL) and brine (30 mL), and dried over anhydrous sodium sulfate. Evaporation of the solvent followed by flash column chromatography (hexanes/EtOAc, 9 1 v/v) afforded 0-4-phenylbutyl-0 -butyl carbonate 989 (157 mg, 94%) as a colorless oil. 

The use of 13a in the extraction process or in the transport through supported liquid membranes (SLMs) allows to recover more than 98% of the cesium cation present in solution, making this derivative extremely attractive for declassification of nuclear wastes. Ligand 13a was dso used for the selective detection of cesium in ISEs and ISFETs with very high selectivity and low detection limit. Very recently, we anchored calix[4]arene-crown-5 and -crown-6 derivatives on silica-gel via hydrosilanization and we were able to separate by chromatography potassium or cesium fi"om other alkali metal ions with high efficiency. ... 

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