It was found that glycidyloxystyrenes, including glycidyloxystyrene and substituted glycidyloxystyrene, can be synthesized from hydroxycinnamic acid or substituted hydroxycinnamic acids in a one-pot, two-step process. The substrate can be thermally decarboxylated and then without purification, reacted in the presence of a halomethyl-oxirane and a base. The resulting product can be polymerized or coppolymerized to a fully substituted product.