Synthesis of ibuprofen
Ibuprofen, 2-(4-isobutylphenyl)propanoic acid, is a non-steroidal anti-inflammatory drug. A simple laboratory preparation starts from methyl 4-isobutylphenylacetate: LDA converts it completely into the enolate at −78 °C, without self-Claisen condensation, and methyl iodide introduces the methyl group at the α carbon. Saponification of the ester gives the acid.
The racemate is obtained: the enolate is planar and CH3I attacks both faces equally. The active enantiomer, (S), can be prepared with a chiral auxiliary (see the example in “Regioselectivity and enantioselectivity”). Industrially, ibuprofen is made by other routes, such as the BHC process, which includes a palladium-catalysed carbonylation.