2,5-Dihydroxyterephthalates, 2,5-dichloro-1,4-benzoquinone-3,6- dicarboxylates, and polymorphic 2,5-dichloro-3,6-dihydroxyterephthalates

Reaction of 2,5-dihydroxycyclohexa-1,4-diene-1,4-dicarboxylates with one equivalent of N-chlorosuccinimide cleanly gives 2,5-dihydroxyterephthalates; reaction with four equivalents of N-chlorosuccinimide gives 2,5-dichloro-l,4- benzoquinone-3,6-dicarboxylates instead. The latter compounds react with sodium dithionite to give 2,5-dichloro-3,6-dihydroxyterephthalates, which will find use in the study of polymorphic phase changes.