On oxidizing the mixt. of guaethol, formalin, and caustic soda which was allowed to stand at room temp. 1-3 days with m-nitrobenzenesulfonic acid, we obtained 4-oxy-5-ethoxy isophthalaldehyde. Applying the analogous process to various phenols, namely, guajacol, phenol, o-chlorophenol, p-chlorophenol, p-nitrophenol, salicylic acid, and p-oxybenzoic acid, we obtained 4-oxy-5-methoxyisophthalaldehyde, 4-oxy-isophthaldehyde, 4-oxy-5-chloroisophthalaldehyde and 2-chloro-4-carboxy-6-formyl phenol, 2-oxy-5-chloro isophthalaldehyde and 2-oxy-3-formyl-5-chloro benzoic acid, 2-formyl-4-nitrophenol, 2-oxy-4-formyl benzoic acid, and 4-oxy-3-formyl benzoic acid respectively. o-Nitrophenol gave no condensation product with formalin. α-Naphthol and β-naphthol gave no definite products.
It was found that the condensation reaction with formalin is prevented when the phenol derivative used has negative group such as nitro or carboxyl, and monoaldehyde is obtained generally. The positions to which aldehyde groups are introduced are ortho and para positions to a hydroxyl group as in Reimer-Tieman's reaction.