To reduce time, energy, the use of solvents, which are not considered not sustainable, and, possibly, also reduce the formation of side products, we decided to test mechanochemical conditions for the synthesis of these types of photoswitches. As a reference reaction, we chose condensation of 1 and 4a (Table ). The substrates were loaded in a stainless-steel jar containing 10 mm and 4 mm balls of the same material, and ball-milled for 60 min at 500 rpm in a planetary mill Restch PM100. Then, the solids were recovered from the milling jar and neutralized. Further work-up was dependent on the type of base/auxiliary. Finally, the conversion and yields were determined with the help of nuclear magnetic resonance spectroscopy using dibromomethane as an internal standard (see Supporting Information).