Photoisomerization of fluorinated 1,3-dimethyl-5-propenyl uracils as a cycle of sequential reactions: Electrocyclization in its use in light-fueled nanomotors

Research in the last ten years has demonstrated that light energy can be used to power artificial nanomotors by exploiting photochemical processes in appropriately designed systems. The photochemical properties of fluorinated derivatives of 1,3-dimethyl-5-propenyl uracils were studied assuming that the electrocyclization of the diene would be a dominant reaction. The primarily formed intermediate, a cyclobutene derivative was expected to undergo further electrocyclic conrotatory ring-opening leading to corresponding E or Z isomer. Keeping in mind the Woodward–Hoffmann and torquoselectivity rules, this photoisomerization is the stereospecific reaction, where the isomerization of each of isomers processes through a different trans–cis cyclobutene-intermediates. This is a cycle of a sequent reactions capable to provide the selective 360° clockwork rotation, which can be used as a model to design a light-fueled nanomotor.