Sommelet–Hauser rearrangement
The Sommelet–Hauser rearrangement is a rearrangement reaction of certain benzyl quaternary ammonium salts. The reagent is sodium amide or another alkali metal amide and the reaction product a N,N-dialkylbenzylamine with a new alkyl group in the aromatic ortho position. For example, benzyltrimethylammonium iodide, I, rearranges in the presence of sodium amide to yield the o-methyl derivative of N,N-dimethylbenzylamine.Mechanism
The benzylic methylene proton is acidic and deprotonation takes place to produce the benzylic ylide. This ylide is in equilibrium with a second ylide that is formed by deprotonation of one of the ammonium methyl groups. Though the second ylide is present in much smaller amounts, it undergoes a 2,3-sigmatropic rearrangement and subsequent aromatization to form the final product.
The Stevens rearrangement is a competing reaction.
