Chalcon Formation of Different Substituted Acetophenones and p-Hydroxy-benzaldehyde

Abstract

WE have already reported attempts to carry out the chalcon-forming condensation reaction of three isomeric nitro- and several nitro-hydroxy-acetophenones (2-nitro 3-hydroxy-, 3-nitro-4-hydroxy-, 4-nitro-2-hydroxy-, 4-nitro-3-hydroxy-, 5-nitro-2-hydroxy and 6-nitro-3-hydroxy-acetophenone) and p-hydroxy-benzaldehyde in presence of sodium hydroxide and hydrochloric acid catalysts1–3. It was shown that in absolute ethanol saturated with hydrochloric acid gas, p-hydroxy-benzaldehyde readily reacts at room temperature with three isomeric acetophenones. It also reacts with several nitro-hydroxy-acetophenones (3-nitro-4-hydroxy-, 4-nitro-2-hydroxy-, 4-nitro-3-hydroxy-, 6-nitro-3-hydroxy-acetophenone and with 5-nitro-2-hydroxy-acetophenone at high temperatures) as well as with 4-hydroxy-acetophenone. The same substituted acetophenones in the presence of sodium hydroxide as catalyst do not react with p-hydroxy-benzaldehyde at room temperature; moreover, on heating, condensation occurs only with 3-nitro-4-hydroxy-acetophenone. According to the reactions the greater reactivity of p-hydroxy-benzaldehyde in acidic medium can be interpreted as follows.