Potassium on potassium-graphite as reagent in the paal-knorr synthesis of 2,5-dimethylthiophene.

Abstract

This thesis describes a new principle for the synthesis of thiophene from diketone. Thiophene is a five-membered heterocyclic aromatic compound containing one sulphur atom. The thiophene structure can be found in certain natural products and is also incorporated in several pharmacologically active compounds.

The procedure described in the thesis uses the combination of graphite and metallic potassium. When they are reacted together they form an interesting compound, potassium graphite, in which the metal atoms are intercalated between the sheets of the graphite. If the potassium graphite then is treated with elemental sulphur (flowers of sulphur), potassium sulphide is formed on the surface of the potassium graphite. The thiophene molecule is formed by heating the potassium sulphide with a 1,4-diketone followed by the addition of a dehydrating (water adsorbing) reagent.

Unfortunately, the procedure has so far given only moderate chemical yield, but the results show that the principle works. Further development may give a practically useful method.