A Two-Step Synthesis of Avobenzone.

Avobenzone is an important agent in sunscreen that reacts with the full spectrum of UVA/UVB light. In fact, avobenzone has one of the largest UV light absorbance ranges of all sunscreen agents. The wide absorbance range of avobenzone helps the sunscreen better protect the skin. This project involved two steps to synthesize avobenzone. Starting with 4-tert-butylbenzaldehyde, 4-methoxyacetophenone, and a base, an Aldol reaction was used to create a ketol intermediate. This step involved experimentation with several bases, including sodium hydroxide and potassium-tert-butoxide, to attempt to stop the product at this intermediate ketol form. Two different mixing methods were also compared in the synthesis of this ketol intermediate. The second step involved conversion of the ketol to the diketone avobenzone product after combination with an oxidizing agent. To make this synthesis more green, a one-step synthesis relying on a Claisen reaction was also attempted.