The Asinger-reaction (sometimes referred to as the Asinger-4 component reaction or A-4CR for short) is a

multicomponent reaction In chemistry, a multi-component reaction (or MCR), sometimes referred to as a "Multi-component Assembly Process" (or MCAP), is a chemical reaction where three or more compounds react to form a single product. By definition, multicomponent reaction ...

for the synthesis of 3-

thiazoline Thiazolines (or dihydrothiazoles) are a group of isomeric 5-membered heterocyclic compounds containing both sulfur and nitrogen in the ring. Although unsubstituted thiazolines are rarely encountered themselves, their derivatives are more common a ...

s and other related heterocycles. It is named after

Friedrich Asinger Friedrich Asinger (26 June 1907 in Freiland/Niederdonau (Austria); – 7 March 1999 in Aachen) was an Austrian chemist and professor for Technical Chemistry. He is well known for his development of a multi-component reaction, the Asinger reaction ...

who first reported it in 1956. Asinger Reaction 1

Process

An α-halogenated carbonyl-component reacts with sodium hydrosulfide (NaSH) and forms a

Thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl gro ...

''in situ''. The thiol reacts directly with another carbonyl component and

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

to form a thiazoline. The reaction works also by using elemental sulphur, an α–substituted

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...

, another carbonyl component and ammonia; in this case, a mixture of products is formed. The formation of 3-thiazolines also occurs by using α-

thioaldehyde In organic chemistry, a thial or thioaldehyde is a functional group which is similar to an aldehyde, , in which a sulfur (S) atom replaces the oxygen (O) atom of the aldehyde (R represents an alkyl or aryl group). Thioaldehydes are even more re ...

or α-

thioketone In organic chemistry, thioketones (; also known as thiones or thiocarbonyls) are organosulfur compounds related to conventional ketones in which the oxygen has been replaced by a sulfur. Instead of a structure of , thioketones have the structure ...

and ammonia. A simplified route of the Asinger-reaction was developed at Degussa. An α-halogenated carbonyl compound reacts with sodium hydrosulfide (NaSH) and forms a

''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 Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

DL-

cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometime ...

References

Literature

* * * {{DEFAULTSORT:Asinger Reaction Multiple component reactions Name reactions