The encapsulation of substrates within micellar structures gives rise to a multitude of effects beyond simple solubilization in water. When incorporated in photochemical reaction design micellar media may offer possibilities to control both reactivity and selectivity. Herein, we describe various important micellar phenomena such as encapsulation, polarity differences, electro-static interactions and hydrogen bonding, and discuss the various resulting mechanisms by which reaction outcomes can be greatly influenced. In this concept article, we showcase selected photochemical reactions to demonstrate how micellar effects can be selectively applied in reaction design.

Micellar photocatalysis has been used to overcome oxygen quenching and enable a [2 + 2] photocycloaddition through triplet-energy transfer in water under aerobic conditions. The cheap and commercially available self-assembling sodium dodecyl sulfate (SDS) micelles were found to increase the oxygen tolerance of a typically oxygen-sensitive reaction. Furthermore, the use of the micellar solution was found to activate α,β-unsaturated carbonyl compounds to energy transfer and allow [2 + 2] photocycloadditions to take place. Our preliminary studies of micellar effects on energytransfer-based reactions demonstrate the reaction between α,β-unsaturated carbonyl compounds and activated alkenes in a mixture of SDS, water and [Ru(bpy) 3 ](PF 6 ) 2 .[a] J.

Micellar photocatalysis allows for a simple and benign reaction set‐up using water as the solvent without the need for oxygen‐removing protocols. Blue light (456 nm) is absorbed by the photocatalyst and allows the [2+2] photocycloaddition to occur between α,β‐unsaturated carbonyl compounds and activated alkenes. The observed reactivity for α,β‐unsaturated aldehydes is completely turned on by the use of a micellar solution as opposed to organic solvents. More information can be found in the Research Article by L. Næsborg and co‐workers (DOI: 10.1002/chem.202300627).