Dihetarylethene photocyclization as a synthetic route to fluorescent compounds

Synthesis of Benzocarbazole Derivatives by Photocyclization

“…It should be noted that compounds 9 and 10 contain a β‐dicarbonyl moiety completely in the enol form as one of the cyclic substituents at the ethene bridge. Earlier, we have demonstrated for the first time that the 1,3,5‐triene moiety generated in such a way can undergo photocyclization …”

“…Previously, we applied this approach to develop a simple and convenient method for the synthesis of polycyclic products VI by photocyclization of imidazol‐2‐ones IV, which were prepared by the condensation of N , N′ ‐dimethylurea with aryl glyoxals and enols. (Scheme ) …”

Multicomponent Assembly of Trisubstituted Imidazoles and Their Photochemical Cyclization into Fused Polyheterocyclic Scaffolds

“…Once we obtained a diverse set of trisubstituted imidazole derivatives 13 , we proceeded to explore the photochemical annulation of these compounds that would presumably involve electrocyclization of the enol tautomeric form of 13a and subsequent elimination of water . The protocol was tuned utilizing imidazole 13a as the model substrate (Table ).…”

“…In 2014, Peshkov, Gorobets and co-workers reported a comprehensive study on the microwave-assisted multicomponent condensation of 2-aminoazines 7 , 2-oxoaldehydes 5 , and cyclic 1,3-dicarbonyl compounds 8 providing a general access to imidazo­[1,2- a ]­azine derivatives 9 and 10 (Scheme a, conditions A–C) . In 2019, Mityanov, Krayushkin and co-workers took the above advancements further by utilizing imidazo­[1,2- a ]­pyridines 10 obtained under a modified conventional heating protocol (conditions D) in the photochemical cyclization process affording polyheteroaromatic scaffolds 11 (Scheme a). , In the present work we aim to expand the scope of this chemistry to the use of a broad range of previously uncovered acyclic nitrogen bis-nucleophiles 12 (Scheme b). This involves the exploration of a three-component Biginelli-like reaction of 12 with 2-oxoaldehydes 5 and cyclic 1,3-dicarbonyl compounds 8 as well as a subsequent photocyclization of resulting trisubstituted imidazoles 13 into imidazole-fused polycyclic scaffolds 14 .…”

Multicomponent one‐pot synthesis of novel imidazole‐2‐thione derivatives containing allomaltol fragment

“…The efficient preparative method for the synthesis of various polyheterocyclic systems is based on this type of photocyclization. [ 9–14 ] Thus, the development of new approaches to the synthesis of 1,3,5‐hexatriene systems containing an enol fragment is an actual task. A convenient approach to the synthesis of hydroxyl‐containing terarylenes is based on the application of the multicomponent reactions (MCRs) methodology.…”