A process for the preparation of a N-[2-(2-pyridinyl)ethyl]carboxamide derivative of general formula or a salt thereof in which: - p is an integer equal to 1, 2, or 3; - X is the same or different and is a hydrogen atom, a halogen atom, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms; - Hal 1 represents a halogen atom; - R 1 is a hydrogen atom, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms or a C 1 -C 8 -alkoxycarbonyl; - R 2 is a hydrogen atom or a cyclopropyl group; and - A represents a phenyl group being optionally substituted by one or more substituents chosen independently of each other as being a halogen atom, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms; as to the N-oxides of the 2-pyridine thereof; said process comprising: - a first step according to reaction scheme 1: in which: A and R 2 are as defined above; X and p are defined as above; and Hal 1 or Hal 2 represent independently from each other a halogen atom; R 3 and R 4 represent independently from each other a C 1 -C 6 -alkyl; comprising the reaction of a halogenopyridyl derivative of formula with a malonic dialkyl ester of formula in the presence of a base and a polar solvent to provide a malonic dialkyl ester pyridyl derivative of formula; - a second step according to reaction scheme 2: in which: X, R 1, R 2, R 3, R 4, Hal 1, p and A are as defined above; Ac represents an acetyl group; and Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+; comprising the reaction of a N-acetoxymethylcarboxamide derivative of formula with a malonic dialkyl ester pyridyl derivative of formula or salts thereof in a solvent to provide a 2-pyridylethylcarboxamide derivative of formula; - a third step according to scheme 3: in which: R 1, R 2, R 3 and R 4, Hal 1, A, X, p are defined as above; Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+; comprising the saponification of the 2-pyridylethylcarboxamide derivative of formula obtained in step B according to scheme 2 in the presence of a base into a compound of general formula - a fourth step according to scheme 4 In which R 1, R 2, Hal 1, A, X, p are defined as above; Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+. comprising the decarboxylation of the 2-pyridylethylcarboxamide derivative of general formula obtained in step C according to scheme 4 into a compound of general formula. - p is an integer equal to 1, 2, or 3; - X is the same or different and is a hydrogen atom, a halogen atom, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms; - Hal 1 represents a halogen atom; - R 1 is a hydrogen atom, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms or a C 1 -C 8 -alkoxycarbonyl; - R 2 is a hydrogen atom or a cyclopropyl group; and - A represents a phenyl group being optionally substituted by one or more substituents chosen independently of each other as being a halogen atom, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms; - a first step according to reaction scheme 1: in which: A and R 2 are as defined above; X and p are defined as above; and Hal 1 or Hal 2 represent independently from each other a halogen atom; R 3 and R 4 represent independently from each other a C 1 -C 6 -alkyl; comprising the reaction of a halogenopyridyl derivative of formula with a malonic dialkyl ester of formula in the presence of a base and a polar solvent to provide a malonic dialkyl ester pyridyl derivative of formula; A and R 2 are as defined above; X and p are defined as above; and Hal 1 or Hal 2 represent independently from each other a halogen atom; R 3 and R 4 represent independently from each other a C 1 -C 6 -alkyl; comprising the reaction of a halogenopyridyl derivative of formula with a malonic dialkyl ester of formula in the presence of a base and a polar solvent to provide a malonic dialkyl ester pyridyl derivative of formula; - a second step according to reaction scheme 2: in which: X, R 1, R 2, R 3, R 4, Hal 1, p and A are as defined above; Ac represents an acetyl group; and Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+; comprising the reaction of a N-acetoxymethylcarboxamide derivative of formula with a malonic dialkyl ester pyridyl derivative of formula or salts thereof in a solvent to provide a 2-pyridylethylcarboxamide derivative of formula; X, R 1, R 2, R 3, R 4, Hal 1, p and A are as defined above; Ac represents an acetyl group; and Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+; - a third step according to scheme 3: in which: R 1, R 2, R 3 and R 4, Hal 1, A, X, p are defined as above; Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+; comprising the saponification of the 2-pyridylethylcarboxamide derivative of formula obtained in step B according to scheme 2 in the presence of a base into a compound of general formula R 1, R 2, R 3 and R 4, Hal 1, A, X, p are defined as above; Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+; - a fourth step according to scheme 4 In which R 1, R 2, Hal 1, A, X, p are defined as above; Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+. comprising the decarboxylation of the 2-pyridylethylcarboxamide derivative of general formula obtained in step C according to scheme 4 into a compound of general formula. R 1, R 2, Hal 1, A, X, p are defined as above; Cation + represents Li +, Na +, K +, Mg 2+, Ca 2+, Al 3+.