Specific dehydrogenation process (I)

A process for the production of a compound of formula (II):

• wherein
• R is —CH═O or —CH2OCOR′, wherein R′ is a —C1-C16 alkyl group,
• wherein
• the process comprises conducting in the presence of at least one oxidative reactant and in the presence of at least one additive compound a selective dehydrogenation of a compound of formula (I):
• wherein
• R has the same meanings as in the compound of formula (II), wherein
• the at least one oxidative reactant is a compound of formula (III):
• wherein
• R1 is —CN, —Cl or —F,
• R2 is —CN, —Cl or —F,
• R3 is —H, —CH3, —Cl or —F, and
• R4 is —H, —CH3, —Cl or —F.