Sandmeyer Reaction
The substitution of an aromatic amino group is possible via preparation of its diazonium salt and subsequent displacement with a nucleophile (Cl-, I-, CN-, RS-, HO-). Many Sandmeyer Reactions proceed under copper(I) catalysis, while the Sandmeyer-type reactions with thiols, water and potassium iodide don't require catalysis.
The Sandmeyer Reaction is a very important transformation in aromatic chemistry, because it can result in some substitution patterns that are not achievable by direct substitution.
Mechanism of the Sandmeyer Reaction
Schmidt Reaction
The acid-catalysed reaction of hydrogen azide with electrophiles, such as carbonyl compounds, tertiary alcohols or alkenes. After a rearrangement and extrusion of N2, amines, nitriles, amides or imines are produced.
Mechanism of the Schmidt Reaction
Reaction of carboxylic acids gives acyl azides, which rearrange to isocyanates, and these may be hydrolyzed to carbamic acid or solvolysed to carbamates. Decarboxylation leads to amines.
The reaction with a ketone gives an azidohydrin intermediate, which rearranges to form an amide:
Alkenes are able to undergo addition of HN3 as with any HX reagent, and the resulting alkyl azide can rearrange to form an imine:
Tertiary alcohols give substitution by azide via a carbenium ion, and the resulting alkyl azide can rearrange to form an imine.
Schotten-Baumann Reaction
The use of added base to drive the equilibrium in the formation of amides from amines and acid chlorides.
The acylation of amines with carboxylic acid chlorides leads to the production of one equivalent acid, which will form a salt with unreacted amine and diminish the yield. The addition of an additional equivalent of base to neutralise this acid is a way to optimise the conditions. Normally, aqueous base is slowly added to the reaction mixture.
In general, the use of biphasic aqueous basic conditions is often named "Schotten-Baumann conditions".
Mechanism of the Schotten-Baumann Reaction
