An Assessment of the Causes of the “ Cesium Effect ”
نویسندگان
چکیده
Cesium alkanoates (chiefly the propionate) have been investigated for their solubility, nucleophilic reactivity, and degree of ion pairing in dimethylformamide (DMF) and, in some cases, dimethyl sulfoxide (DMSO) solutions. 133Cs NMR has been used to establish the degree of ion pairing. From the data obtained it is concluded that the cesium ion is virtually completely solvated and that the carboxylates are essentially free and highly reactive. The consequences of this effect on macrocyclization by means of nucleophilic substitution are discussed.
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