Mannich Reaction

the substitution of hydrogen in organic compounds by an amino methyl group (amino methylation) upon action of formaldehyde and ammonia (as well as amines or their hydrochloride salts). Various compounds containing a mobile hydrogen atom at the carbon atom participate in the Mannich reaction—for example, aldehydes and ketones containing hydrogen at the a-carbon atom; malonic acid derivatives; phenols; heterocyclic compounds; and acetylene hydrocarbons. Equations representing the acetone and indol reactions are given below. Dimethylamine hydrochloride is used in the first case, and piperidine in the second:

The mechanism of the Mannich reaction apparently reduces to the formation of an amino methyl cation that attacks the carbon atom, which has a partially negative charge (electrophilic substitution):

The Mannich reaction is widely used in organic synthesis and in industry, mainly in the preparation of pharmaceuticals. The reaction was discovered in 1917 by the German chemist C. Mannich, who demonstrated its general nature and subsequently carried out studies on the reaction over a period of 30 years.