Rainer Ludwig Claisen

Scientific contributions

• Described the condensation of aromatic aldehydes with aliphatic aldehydes or ketones in 1881. This variation of the now well-known aldol condensation reaction is called the Claisen–Schmidt condensation.
• Discovered (1887) the condensation reaction of an ester with an activated methylene group, now known as the Claisen condensation.
• Synthesis of cinnamates by reacting aromatic aldehydes with esters. The reaction is known as the Claisen reaction and was described by Claisen for the first time in 1890.
• Discovered the thermally induced rearrangement of allyl phenyl ether in 1912. He details its reaction mechanism in his last scientific publication (1925). In his honor, the reaction has been named the Claisen rearrangement.
• Synthesis of isatin via a process known as the Claisen isatin synthesis, described for the first time in 1879.
• Designer of a special distillation flask called the Claisen flask. With the increased modularity of modern glassware this functionality is often achieved with a Claisen adapter, of which there are many types, attached to a normal flask.