The skeletal photorearrangement including 6πelectrocyclization induced by UV light of ortho-halogen-substituted diarylethenes has been studied. It has been found that the reaction pathways leading to bi-or tricyclic frameworks depend on the kind of halogen substituent and solvent. Photocyclization with halogen abstraction leads to bicyclic fused aromatics, while the tricyclic frameworks are formed due to the tandem 6π-electrocyclization/ sigmatropic shift reaction. THF is preferred as the solvent in the former process and chloroform in the latter reaction. It was found for the first time that, owing to the ability of this series of diarylethenes to undergo skeletal photorearrangement with the release of the bromide cation, they can be used both as brominating agents and as Lewis acids for catalyzing electrophilic reactions.

Manipulating the equilibrium between a ketone and an enol by light opens up ample opportunities in material chemistry and photopharmacology. By incorporating β-ketoester into the ethene bridge of a photoactive diarylethene, we achieved reversible light-induced tautomerization to give thermally stable enol. In a pristine state, the tautomeric equilibrium is almost completely shifted toward the ketone. Photocyclization of diarylethene results in a new equilibrium containing a significant fraction of the enol tautomer.

In recent decades there have been significant improvements in the efficiency of synthesis as a result of considerable progress in tandem reactions, cascade transformations and related one‐pot processes. These methodologies are less time‐consuming, more cost‐effective, and produce less waste compared to the classical stepwise protocols. The Nazarov cyclization is an important and versatile method for the synthesis of five‐membered carbocycles which are found in many natural compounds and functional molecules. Current activities in the field of the Nazarov reaction are focused on development of better catalysts, asymmetric options and increasing the efficiency of synthesis. This transformation is suitable for applying to an intensified step‐economy in interrupted versions and one‐pot protocols. Interrupted Nazarov reactions in particular take advantage of the stereospecific nature of the electrocyclization. The universality of these reactions has facilitated an access to a plethora of complex small molecules of high medicinal relevance. In this review, we present a comprehensive summary of recent advances in the interrupted Nazarov‐type cyclization, and classify these reactions according to the structure of the substrate or the reaction mechanism. This is the first review that presents a survey on various types of interrupted Nazarov cyclization and deals with the recent advances, especially using tandem/domino or one‐pot reaction strategies and covers the literature from 2009 to 2019.

It was found that imidazole prevents the side process of diarylethenes photocyclization and the photodegradation of photochromic compounds.

The acid-catalyzed cyclization of benzylidenes based on 16-dehydropregnenolone acetate (16-DPA) was studied. It was found that these compounds readily undergo regioselective interrupted Nazarov cyclization with trapping chloride ion and an efficient method of the synthesis of d-annulated pentacyclic steroids based on this reaction was proposed. The structures of the synthesized pentacyclic steroids were determined by NMR and X-ray diffraction. It was found that the reaction affords a single diastereomer, but the latter can crystallize as two conformers depending on the structure. Antiproliferative activity of synthesized compounds was evaluated against two breast cancer cell lines: MCF-7 and MDA-MB-231. All tested compounds showed relatively high antiproliferative activity. The synthetic potential of the protocol developed was illustrated by the gram-scale experiment.