The Boots synthesis of ibuprofen is an important example often discussed in the context of green chemistry because it demonstrates a relatively efficient and selective pharmaceutical synthesis. The process begins with isobutylbenzene as the starting material. In the first step, isobutylbenzene undergoes Friedel–Crafts acylation with acetyl chloride in the presence of a Lewis acid catalyst such as aluminium chloride to form p-isobutylacetophenone. This step introduces the acetyl group selectively at the para position, minimizing the formation of unwanted isomers and improving atom economy compared to less selective methods. In the second step, p-isobutylacetophenone is converted into