Sommelet reaction

The Sommelet reaction is an organic reaction in which a benzyl halide is converted to an aldehyde by action of hexamine and water.[1][2]

One example, thiophene-2-carboxaldehyde is prepared by the reaction of hexamine with 2-chloromethylthiophene.[3] The reaction is formally an oxidation of the carbon.

Reaction mechanism and scope

The benzyl halide 1 reacts with hexamine to a quaternary ammonium salt 3, each time just alkylating one nitrogen atom. Then the benzylammonium undergoes an acid-catalyzed hydrolysis process.

Depending on the hydrolysis conditions, the hexamine unit might instead break apart, leaving a benzyl amine (the Delépine reaction).

The reaction can also be applied to the oxidation of benzylic amines. In this way, m-xylylenediamine can be converted to isophthalaldehyde.[4]

References
  1. Marcel Sommelet (1913). "Sur un mode de décomposition des halogénoalcoylates d'hexaméthylène – tétramine". Compt. Rend. 157: 852–854.
  2. March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
  3. Kenneth B. Wiberg. "2-Thiophenealdehyde". Org. Synth. 3: 811. doi:10.15227/orgsyn.000.0005.
  4. Ackerman, J. H.; Surrey, A. R. (1967). "Isophthalaldehyde". Organic Syntheses. 47: 76. doi:10.15227/orgsyn.047.0076.
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