The Claisen rearrangement is a commonly used organic chemical reaction that involves the rearrangement of vinyl or allyl groups. Synonyms for the Claisen rearrangement include Claisen-Yaldane rearrangement, Claisen-Schmidt reaction, Claisen-Schmidt condensation, and Claisen ester condensation. The reaction is named after the German chemist Ludwig Claisen who first described it in 1912. The Claisen rearrangement is a useful tool in organic synthesis, as it enables the conversion of a simple starting compound into a variety of more complex molecules. It is widely used in the pharmaceutical industry for the synthesis of drugs and medicinal compounds. The various synonyms for the Claisen rearrangement refer to specific variations of the reaction, each with their own unique set of parameters and conditions.