The use of solid acids to promote the one-pot synthesis of dl-5-(4-hydroxyphenyl)hydantoin Original Research Article

Clays, zeolites and organic polymers bearing sulfonic acid groups are used to promote the direct synthesis of dl-5-(4-hydroxyphenyl)hydantoin from urea, phenol and glyoxylic acid. Only organic polymers lead to good results, in particular a sulfonic polystyrene-divinylbenzene resin with a small particle size, whereas very poor results are obtained when clays or zeolites are used to promote this amidoalkylation reaction. A possible explanation for these rather surprising differences in behavior involves the different hydrophilic/hydrophobic character of the solids, particularly given the aqueous reaction medium. The pre-treatment of the resin and the particle size are important factors that influence the final result. Although the results are no better than those obtained with hydrochloric acid in the homogeneous phase, these resins do represent the only environmentally friendly alternative.