Selective monoalkylation of p-tert-butylcalix-[4]-arene in a methyl carbonate ionic liquid.

Methyl carbonate ionic liquids are shown to readily mono-deprotonate p-tert-butylcalix-[4]-arenes initiating the formation of an organic mono-anionic p-tert-butylcalix-[4]-arate salt, methanol and carbon dioxide. These calix-[4]-arate salts have been successfully used in alkylation reactions with dialkyl sulfates and alkyl halides to form a mono-alkylated single product with high yield. This method avoids the common use of alkali metal bases such as caesium fluoride hence providing a safer and more selective synthetic route.