Solvent Free Synthesis of Chalcones

Solvent Free synthesis of Chalcones

Avobenzone is a common ingredient in sunscreen and chapstick that is utilized to absorb harmful UV rays. The synthesis reported here aims to make it in three steps using a green synthetic route. First 4-methoxyphenone and benzaldehyde are subjected to a solvent-free Aldol dehydration reaction. The starting materials are ground in a mortar dish in the presence of NaOH pellets to produce crude product that was purified by recrystallization. The alkene produced in this reaction is converted to an alcohol using H₂SO₄ and water. The resulting alcohol is then oxidized using oxone or bleach to make avobenzone. These oxidation conditions are considered much more green than those that rely on the use of heavy metal oxidants. All products were analyzed by NMR and IR.