Cesium salts; such cesium carbonate, cesium acetate, cesium hydroxide, cesium formate, cesium propionate, cesium chloride, cesium sulfate, cesium trifluoroacetate, cerium fluoride; are frequently used in organic synthesis. Among these, cesium carboxylates such as cesium formate, cesium acetate, propionate, cesium butyrate, or cesium levulinate are also utilized in nucleophilic substitution reactions replacing the standard cesium salts. Exemplary advantages of cesium carboxylates are summarized as follows:
· Cesium carboxylates can serve as a reliable cesium precursor with added benefits such as easy manipulation and more compatibility with low-temperature conditions that permit the use of low boiling point reactants.
· Cesium carboxylates such as cesium formate and cesium acetate are more soluble (easier to work with) in reaction mixtures than the commonly used cesium carbonate or cesium fluoride owing to its greater solubility in the reaction mixture at a broader temperature range.
In most of the reactions using cesium carboxylates, the higher solubility of cesium carboxylates facilitates the chemistries to proceed at much lower reaction temperatures. Reduced reaction temperatures widen the reaction scope and accommodate the use volatile and unstable reactants.
In reaction chemistry, cesium carboxylates are preferred over their lithium, sodium, and potassium salt counterparts. The higher cost of cesium carboxylates is offset by clear ‘Cesium Effect’ advantages such as higher yields, shorter reaction times, smaller amounts of reagents required, milder reaction conditions and easier work-up procedures.