Bucherer reaction

The Bucherer reaction is an organic chemical reaction names and named after Hans Theodor Bucherer ( 1869-1949 ). The reaction is also Bucherer Lepetit reaction or falsely Bucherer -Le- Petit- called reaction. Describes the reaction of naphthols to naphthylamines in the presence of ammonia and sodium. The reactant either 1 -naphthol or 2-naphthol stellungsiisomere can be used:

The French chemist Robert Lepetit discovered in 1898 as the first this reaction, but noted Bucherer, regardless of Lepetit, their reversibility and tremendous opportunities for the chemical industry fixed. Bucherer published his results in 1904, with which his name is permanently connected with the reaction.

The Bucherer reaction proceeds in aqueous medium catalyzed by sulfite. This reversible attacks on protonated aromatics to, tautomerizes to hydrogen sulfite and is attacked by ammonia or an amine. After elimination of the sulfite, the corresponding naphthylamine in which the hydroxyl group of the naphthol is substituted by an amino group formally obtained.

Reaction mechanism

The reaction is described here by the example of 1- naphthol and runs via an addition -elimination mechanism from. In the first step is a proton on the carbon atom having the highest electron density, that is preferably attached at the C2 or C4, 1- naphthol (1). This leads to the resonance-stabilized adduct 2 In the next step, supporting the bisulfite anion at the C3 carbon. It is followed by a tautomerization to the energetically more favorable molecule 3 This is nucleophilic amine, in this case ammonia, attacked. With elimination of water, the resonance-stabilized cation 4 deprotonation forms provides the enamine 5 The enamine eliminated the hydrogen sulfite to form 1 -naphthylamine (6).

The reaction is reversible and can be summarized as follows: