The Sommelet reaction is an organic reaction in which a benzyl halide is converted to an aldehyde by action of hexamine and water. It is named after the French chemist Marcel Sommelet, who first reported the reaction in 1913.
One example, thiophene-2-carboxaldehyde is prepared by the reaction of hexamine with 2-chloromethylthiophene.  The reaction is formally an oxidation of the carbon.