Mannich-type reactions in water using anionic water-soluble calixarenes as recoverable and reusable catalysts

Abstract

Mannich-type reactions in water can be carried out without the need for any added surfactants and organic solvents. The water-soluble calix[4]resorcinarene sulfonic acid, 2,8,14,20-tetramethyl-5,11,17,23-tetrakis(sulfomethyl)calix[4]resorcinarene, which functions as an efficient inverse phase-transfer catalyst, can be recovered as an aqueous solution and recycled after the simple extraction of the water-insoluble products.