ИСТИНА

Stilbenes and azobenzenes as structural units are both widely used in modern organic and material chemistry to construct light-tunable (supra)molecular systems. Their well-studied photochemical properties enable the rational design of molecular switches, light-controlled ion channels and receptors, while certain stilbenes and the recently discovered red- and NIR absorbing azobenzenes show a potential in biochemical and biomedical applications. Over the years various methods to construct these photosensitive cores have been developed, most notable being Wittig/Horner-Wadsworth-Emmons and Heck reactions in the case of stilbenes; while azo-coupling, Mills reaction, oxidation of anilines and reductive coupling of aromatic nitro derivatives are the most convenient routes toward azobenzenes. Despite the abundance of methods, many of them feature drastic reaction conditions in certain synthetic steps, so a unique synthetic strategy is commonly developed for each targeted compound, hindering the design of new stilbene- or azobenzene-containing structures. In this work we synthesized a series of stilbenes and azobenzenes bearing two different functional groups in p-position to the double bond, which can be orthogonally modified in CuAAC, nucleophilic substitution or cross-coupling reactions. Haloalkyl, azido, ethynyl and iodo groups were chosen so that after the first functional group is used, the second one can be used directly or transformed to another reactive unit in one or two steps. This enables the facile bridging of various molecular blocks required for a specific task with a photosensitive linker, as the conditions of both coupling and a second group modification are tolerant to a wide range of functionalities. To assess the synthetic capabilities of the approach a number of calix[4]arene semitubes comprising two calixarene and two photosensitive fragments of different structures were synthesized. Notably, most of these new macrocycles can hardly be obtained in a direct azobenzene or stilbene synthesis or require more complicated synthetic procedures to be applied and/or uncommon precursors, which need to be obtained beforehand. Lastly, developed procedures allow for the presence of other functionalities and different substitution patterns in stilbene/azobenzene cores so the list of linkers showed in this study can easily be extended given that required precursors are available.