Molecular Stacking and Photoreactions of Fluorine-Substituted Benzyl Muconates in the Crystals

The solid-state photoreactions of fluorine-substituted benzyl (Z,Z)- and (E,E)-muconates have been investigated. The reaction of 16 derivatives was carried out under UV- and γ-ray radiations, and the products were characterized by NMR spectroscopy and X-ray diffractions. [2+2] Dimerization, EZ isomerization, and polymerization occurred depending on the monomer structure and provided a highly selective photoproduct during each reaction. The reaction mechanism was discussed based on the monomer packing in the crystals. The single-crystal structure analysis of the monomers has revealed that the reaction pathways and the structure of the products are closely related to the molecular packing formed by intermolecular interactions such as C−H···O and C−H···F interactions. The reactivity and the structure of the dimers as the products of regioselective cyclodimerization are well accounted for by the relative orientation of the reacting monomer molecules in the crystals. The topochemical polymerization of a 2,6-difluorobenzyl ester derivative is also described.