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.本研究针对氟取代（Z,Z）型与（E,E）型粘康酸苄酯的固态光化学反应展开了系统探究。针对16种该类衍生物，我们分别采用紫外光与γ射线进行辐照反应，并通过核磁共振（Nuclear Magnetic Resonance, NMR）波谱法及X射线衍射法对所得产物进行了表征。反应路径取决于单体分子结构，涵盖[2+2]二聚反应、EZ异构化与聚合反应，且各反应均可生成高选择性的光产物。本研究基于晶体内部的单体堆积方式，对反应机理进行了探讨。单体的单晶结构分析结果表明，反应路径与产物结构，与晶体中由C−H···O、C−H···F等分子间相互作用所构建的分子堆积模式密切相关。区域选择性环二聚反应所得二聚体的反应活性与结构，可通过晶体中反应单体分子的相对取向得到充分合理解释。本研究同时还阐述了2,6-二氟苄基酯衍生物的拓扑化学聚合反应。