Practical Approach for Quantitative Green Esterifications

Abstract

Subquantitative synthetic esterification reactions have been transformed into quantitative aqueous reactions. The esterification reactions involve carboxylic acids, alkyl halides or mesylate with granular polytetrafluoroethylene (PTFE), lithium carbonate, tetrabutyl ammonium bromide and were mediated solely by water. Various alkyl donors were employed including α-halo ketones, α-halo esters, α-halo amide, allyl bromide, benzyl chloride, alkyl iodides and alkyl mesylate. The scope of the carboxylic acids ranged from aromatic to aliphatic and from water-soluble to water-insoluble. Among the 58 reaction examples, 54 esterifications were quantitative and the other four had yields above 94%. Six of the reactions were scaled up to more than 10 g. In 30 examples and all the enlarged scale examples, no organic solvents were used at all and the products were collected simply by filtration. The yields for esterification reactions with secondary halides were quantitative compared to previous reported yields of only ...