Green chemistry: efficient acetalization of aldehydes with alcohols using the acid red 52 photocatalyst

Green chemistry is developing to invent new reactions that are cheaper, cleaner and use less energy. Acetalization is a common strategy for the protection of aldehydes in synthetic chemistry, yet actual protocols of acetals synthesis are limited by difficult workups, the use of high-loading catalyst, harsh reaction conditions, and catalyst tedious preparation. Alternatively, photocatalysis allows to access functional products with minimum synthetic procedures and waste generation. Here we use sodium 4-[6-(diethylamino)-3-(diethyliminio)-3H-xanthen-9-yl]benzene-1,3-disulfonate (acid red 52) as photocatalyst under yellow light irradiation. We obtained a wide array of acyclic and cyclic acetals in 75–93% yields. Results show the efficient acetalization of aldehydes with alcohols at room temperature, the use of abundant and sustainable alcohols as both the solvents and coupling agents, low catalyst loading, short reaction time, and readily available catalyst, which might be applied to green-catalyzed systems.