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The irradiation of β‐enaminones, generated in situ from cyclic 1,3‐diketones and activated alkenes leads to polyheterocyclic skeletons. The photoproduct chemoselectivity depends on the type of cyclic 1,3‐diketones employed viz., 2‐acetylcyclopentanone and 2‐acetylcyclohexanone. The observed chemoselectivity was rationalized based on the Dieckmann‐Kon rule.

 

The study evaluates compatibility of stabilizers with dye doped liquid crystal (LC) scaffolds that are used in electronically dimmable materials. The photodegradation of the materials was investigated and suitable stabilizers were evaluated to slow the degradation process. Various types of benzotriazole-based stabilizers were evaluated for stabilizing the liquid crystals. Based on spin trapping experiments, radicals generated upon UV exposure is likely responsible for the degradation of the system. The radical generation is competitively inhibited by the addition of stabilizers. 

Hydrogen bonding mediated control of photochemical reactions is highlighted with an eye towards the development of Brønsted acid mediated photocatalysis. 

This account highlights the role of restricted bond rotations to influence excited state reactivity of organic molecules. It highlights photochemical reactivity of various organic molecules and the design strategies that could be exploited by chemists to utilize restricted bond rotations to uncover new excited state reactivity and achieve selectivity. 

Aryl‐maleimides undergo a novel [2+4]‐photodimerization instead of the expected [2+2]‐photodimerization under both direct irradiation with visible light and under sensitized energy transfer conditions. This new excited state reactivity in aryl‐maleimides is deciphered through photochemical, photophysical, and spectroscopic studies. The stereochemistry of the photodimer depends on the type of non‐bonding interactions prevalent during photodimerization which is in turn dictated by the substituents on the maleimide ring. More importantly, the stereochemistry of the photodimer formed is complementary to the product observed under thermal conditions.