Greener route for the synthesis of photo- and thermochromic spiropyrans using a highly efficient, reusable, and biocompatible choline hydroxide in an aqueous medium

Here, we report the synthesis of photo- and thermochromic spiropyrans promoted by a highly efficient, biocompatible, and reusable choline hydroxide (ChOH) in greener solvent water. This procedure provides several advantages such as simple workup, mild reaction conditions, short reaction time, and high yields of the products. Furthermore, the ChOH could be reused at least five times without significantly losing its catalytic activity. The structures of the synthesized spiropyran derivatives were confirmed by several characterization methods such as ¹H NMR, ¹³C NMR, and mass spectra.