Leuckart reaction

History

The Leuckart reaction is named in honor of its developer, the German chemist Rudolf Leuckart (1854–1899). He discovered that heating benzaldehyde with formamide does not produce benzylidenediformamide as anticipated, but benzylamine. In 1891, a colleague of Leuckart at the University of Göttingen, Otto Wallach, performed further reactions using alicyclic and terpenoid ketones as well as aldehydes, demonstrating the general application. Over the course of the past century, chemists have discovered several methods to improve the yield of the reaction and carry it out under less strenuous conditions. Pollard and Young summarized various ways in which amines can be formed: using either formamide or ammonium formate, or both, or adding formic acid to formamide. However, using just ammonium formate as the reagent produces the best yields. Using formamide produces low yields compared to ammonium formate but yields can be increased by using large amount of formamide, or using ammonium formate, ammonium sulfate, and magnesium chloride as catalysts.