The Sommelet–Hauser rearrangement (named after M. Sommelet and Charles R. Hauser''Rearrangements of Benzyltrimethylammonium Ion and Related Quaternary Ammonium Ions by Sodium Amide Involving Migration into the Ring'' Simon W. Kantor, Charles R. Hauser

J. Am. Chem. Soc. The ''Journal of the American Chemical Society'' is a weekly peer-reviewed scientific journal that was established in 1879 by the American Chemical Society. The journal has absorbed two other publications in its history, the ''Journal of Analytic ...

, 1951, 73 (9), pp 4122–4131 ) is a

rearrangement reaction In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another ...

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 Arene substitution patterns are part of organic chemistry IUPAC nomenclature and pinpoint the position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon. ''Ortho'', ''meta'', and ''para'' substitution * I ...

. For example, benzyltrimethylammonium iodide, C₆H₅CH₂)N(CH₃)₃, rearranges in the presence of sodium amide to yield the ''o''-methyl derivative of ''N'',''N''-dimethylbenzylamine. : SommeletHauserReaction

Mechanism

The benzylic methylene proton is acidic and deprotonation takes place to produce the benzylic

ylide An ylide or ylid () is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both atoms h ...

(1). This ylide is in equilibrium with a second ylide that is formed by deprotonation of one of the ammonium methyl groups (2). Though the second ylide is present in much smaller amounts, it undergoes a

2,3-sigmatropic rearrangement 2,3-Sigmatropic rearrangements are a type of sigmatropic rearrangements and can be classified into two types. Rearrangements of allylic sulfoxides, amine oxides, selenoxides are neutral. Rearrangements of carbanions of allyl ethers are anionic. ...

because it is more reactive than the first one and subsequent aromatization to form the final product (3).Ahluwalia, V. K., and R. K. Parashar. Organic Reaction Mechanisms. Harrow, U.K.: Alpha Science International, 2005. Print. :

Sommelet-Hauser Rearrangement Mechanism V

The Stevens rearrangement is a competing reaction.

References

{{DEFAULTSORT:Sommelet-Hauser rearrangement Rearrangement reactions Name reactions