One-pot synthesis of phenols from aromatic aldehydes by Baeyer–Villiger oxidation with H2O2 using water-tolerant Lewis acids in molecular sieves

Sn-Beta zeolite is employed as catalyst in the Baeyer–Villiger oxidation of aromatic aldehydes. Aldehydes involving alkoxy substituents are oxidized to the corresponding formate ester which are hydrolyzed to the corresponding phenols. Choosing the adequate reaction conditions the main product can be preselected. Dioxane solvent and a hydrogen peroxide deficit give predominantly the ester whereas ethanol solvent or aqueous acetonitrile favor the phenol product. Double bonds in alkyl side chains do not react and the corresponding unsaturated phenols are obtained with very high chemoselectivity. Brønsted sites are active for the Baeyer–Villiger oxidation of aromatic aldehydes with H2O2 provided that the molecule does not contain olefinic groups. In any case, the selectivity of Brønsted acid zeolites is lower than that of Sn-Beta.