The Asinger reaction (sometimes referred to as the Asinger-4 component reaction or A-4CR for short) is a multicomponent reaction for the synthesis of 3-thiazolines and other related heterocycles. It is named after Friedrich Asinger who first reported it in 1956.
An ñ-halogenated carbonyl-component reacts with sodium hydrosulfide (NaSH) and forms a thiol in situ. The thiol reacts directly with another carbonyl component and ammonia to form a thiazoline. The reaction works also by using elemental sulphur, an ñâÂÂsubstituted ketone, another carbonyl component and ammonia; in this case, a mixture of products is formed.
The formation of 3-thiazolines also occurs by using ñ-thioaldehyde or ñ-thioketone and ammonia.
A simplified route of the Asinger-reaction was developed at Degussa. An ñ-halogenated carbonyl compound reacts with sodium hydrosulfide (NaSH) and forms a thiol in situ which reacts directly with aldehydes or ketones and ammonia to 3-thiazolines. The chemical industry developed based on the Asinger-reaction multi stage processes for the production of pharmaceuticals like D-penicillamine and the aminoacid <small>DL</small>-cysteine.