Methyl benzoate (p-tolylsulfonyl)hydrazone (I) was prepared from the reaction between (p-tolylsulfonyl)hydrazide and either methyl benzimidate hydrochloride or methyl orthobenzoate. When the potassium or sodium salt of this hydrazone was decomposed, thermally or photochemically, in the presence of alcohols, benzaldehyde mixed acetals could be isolated in good yields and of high purity. When the decomposition was carried out in the presence of piperidine, there was produced 1(α-methoxybenzyl) piperidine (II) and α,α-dipiperidinotoluene (III). The reaction products can be explained by assuming the initial formation of phenylmethoxydiazomethane.