Process for the preparation of a 2-pyridylethylcarboxamide derivative

1. A process for the preparation of a N-[2-(2-pyridinyl)ethyl]carboxamide derivative of formula (I) or a salt thereof

in which:

p is an integer equal to 1, 2, 3 or 4;

X is the same or different and is a hydrogen atom, a halogen atom, a nitro group, a cyano group, a hydroxy group, an amino group, a sulfanyl group, a pentafluoro-λ 6 -sulfanyl group, a formyl group, a formyloxy group, a formylamino group, a carboxy group, a carbamoyl group, a N-hydroxycarbamoyl group, a carbamate group, a (hydroxyimino)-C 1 -C 6 -alkyl group, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms, a C 2 -C 8 -alkenyl, a C 2 -C 8 -alkynyl, a C 1 -C 8 -alkylamino, a di-C 1 -C 8 -alkylamino, a C 1 -C 8 -alkoxy, a C 1 -C 8 -halogenoalkoxy having 1 to 5 halogen atoms, a C 1 -C 8 -alkylsulfanyl, a C 1 -C 8 -halogenoalkylsulfanyl having 1 to 5 halogen atoms, a C 2 -C 8 -alkenyloxy, a C 2 -C 8 -halogenoalkenyloxy having 1 to 5 halogen atoms, a C 3 -C 8 -alkynyloxy, a C 3 -C 8 -halogenoalkynyloxy having 1 to 5 halogen atoms, a C 3 -C 8 -cycloalkyl, a C 3 -C 8 -halogenocycloalkyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkylcarbonyl, a C 1 -C 8 -halogenoalkylcarbonyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkylcarbamoyl, a di-C 1 -C 8 -alkylcarbamoyl, a (N—C 1 -C 8 -alkyl)oxycarbamoyl, a C 1 -C 8 -alkoxycarbamoyl, a (N—C 1 -C 8 -alkyl)-C 1 -C 8 -alkoxycarbamoyl, a C 1 -C 8 -alkoxycarbonyl, a C 1 -C 8 -halogenoalkoxycarbonyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkylcarbonyloxy, a C 1 -C 8 -halogenoalkylcarbonyloxy having 1 to 5 halogen atoms, a C 1 -C 8 -alkylcarbonylamino, a C 1 -C 8 -halogenoalkylcarbonylamino having 1 to 5 halogen atoms, a C 1 -C 8 -alkylaminocarbonyloxy, a di-C 1 -C 8 -alkylaminocarbonyloxy, a C 1 -C 8 -alkyloxycarbonyloxy, a C 1 -C 8 -alkylsulphenyl, a C 1 -C 8 -halogenoalkylsulphenyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkylsulphinyl, a C 1 -C 8 -halogenoalkylsulphinyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkylsulphonyl, a C 1 -C 8 -halogenoalkyl-sulphonyl having 1 to 5 halogen atoms, a (C 1 -C 6 -alkoxyimino)-C 1 -C 6 -alkyl, a (C 1 -C 6 -alkenyloxyimino)-C 1 -C 6 -alkyl, a (C 1 -C 6 -alkynyloxyimino)-C 1 -C 6 -alkyl, a (benzyloxyimino)-C 1 -C 6 -alkyl, a benzyloxy, a benzylsulfanyl, a benzylamino, a phenoxy, a phenylsulfanyl or a phenylamino;

R 1 is selected from the group consisting of a hydrogen atom, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms and a C 1 -C 8 -alkoxycarbonyl;

R 2 is selected from the group consisting of a hydrogen atom and a cyclopropyl group; and

A represents a phenyl group or a 5-, 6- or 7-membered non-fused heterocycle with one, two or three heteroatoms which may be the same or different, the heterocycle being linked by a carbon atom; each of this group being optionally substituted by one or more substituents independently selected from the group consisting of a halogen atom, a nitro group, a cyano group, a hydroxy group, an amino group, a sulfanyl group, a pentafluoro-λ 6 -sulfanyl group, a formyl group, a formyloxy group, a formylamino group, a carboxy group, a C 1 -C 8 -alkyl, a C 1 -C 8 -halogenoalkyl having 1 to 5 halogen atoms, a C 2 -C 8 -alkenyl, a C 2 -C 8 -alkynyl, a C 1 -C 8 -alkylamino, a di-C 1 -C 8 -alkylamino, a C 1 -C 9 -alkoxy, a C 1 -C 8 -halogenoalkoxy having 1 to 5 halogen atoms, a C 1 -C 8 -alkoxy-C 2 -C 8 -alkenyl, a C 1 -C 8 -alkylsulfanyl, a C 1 -C 8 -halogenoalkylsulfanyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkoxycarbonyl, a C 1 -C 8 -halogenoalkoxycarbonyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkylcarbonyloxy, a C 1 -C 8 -halogenoalkylcarbonyloxy having 1 to 5 halogen atoms, a C 1 -C 8 -alkylsulphenyl, a C 1 -C 8 -halogenoalkylsulphenyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkylsulphinyl, a C 1 -C 8 -halogenoalkylsulphinyl having 1 to 5 halogen atoms, a C 1 -C 8 -alkylsulphonyl, a C 1 -C 8 -halogenoalkylsulphonyl having 1 to 5 halogen atoms and a C 1 -C 8 -alkylsulfonamide;

and the N-oxide of the 2-pyridine thereof;

said process comprising:

(A)-a first step according to reaction scheme 1:

in which:

A and R 2 are as defined above; and

Hal represents a halogen atom;

comprising the reaction of a halogenobenzoyl derivative with aqueous R 2 NH 2 , in a R 2 NH 2 aq./halogenobenzoyl derivative molar ratio of from 1 to 10, to provide a carboxamide derivative;

(B)-a second step according to reaction scheme 2:

in which:

R 1 , R 2 and A are as defined above;

comprising the reaction of a carboxamide derivative obtained in step one with an aldehyde group in an aldehyde group/carboxamide derivative molar ratio of from 1 to 10, in a polar solvent, at a temperature of from 20° C. to reflux, to provide a N-hydroxymethylcarboxamide derivative;

(C)-a third step according to reaction scheme 3:

in which:

R 1 , R 2 and A are as defined above; and

Ac represents an acetyl group;

comprising the reaction of a N-hydroxymethylcarboxamide derivative obtained in step two with acetic anhydride (Ac 2 O) or acetyl chloride (AcCl) in an Ac 2 O or AcCl/N-hydroxymethylcarboxamide derivative molar ratio of from 1 to 10, in an organic solvent, in the presence of a mineral or organic base, to provide a N-acetoxymethylcarboxamide derivative;

(D)-a fourth step according to reaction scheme 4:

in which:

X, R 1 , R 2 , p and A are as defined above;

Ac represents an acetyl group;

R 3 represents a hydrogen atom or CO 2 Alk; and

Alk represents a C 1 -C 8 -alkyl group;

comprising the reaction of a N-acetoxymethylcarboxamide derivative obtained in step three with a 2-pyridyl acetate derivative in a N-acetoxymethylcarboxamide derivative/2-pyridyl acetate derivative molar ratio of from 1 to 5, in an organic solvent, in the presence of a base; to provide a 2-pyridylethylcarboxamide derivative; and

(E)-a fifth step comprising the decarboxylation of the 2-pyridylethylcarboxamide derivative obtained in step four into a compound of formula (I).

2. The process of claim 1 wherein p is 2.

3. The process of claim 1 wherein X is independently selected from the group consisting of chlorine and CF 3 .

4. The process of claim 1 wherein the 2-pyridyl moiety is substituted by X in the 3- and/or in the 5-position.

5. The process of claim 1 wherein R 1 is selected from the group consisting of a hydrogen atom, a methyl group, CF 3 , CHF 2 , CClF 2 and CCl 3 .

6. The process of claim 1 wherein R 2 is a hydrogen atom.

7. The process of claim 1 wherein A is a phenyl group.

8. The process of claim 7 wherein A is substituted by one or two substituents.

9. The process of claim 8 wherein each substituent of A is independently selected from the group consisting of chlorine and CF 3 .

10. The process of claim 7 wherein the A is substituted in ortho position.

11. The process of claim 1 wherein the compound of formula (I) is selected from the group consisting of:

N-{2-[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethyl}-2-trifluoromethylbenzamide;

N-{2-[3-chloro-5-(trifluoromethyl)-2-pyridinyl]ethyl}-2-iodobenzamide; and

N-{2-[3,5-dichloro-2-pyridinyl]ethyl}-2-trifluoromethylbenzamide.

12. The process of claim 1 wherein step A is conducted in the presence of a mixture of water and an organic solvent.

13. The process of claim 1 wherein step A is conducted at a temperature of from 0° C. to reflux.

14. The process of claim 1 wherein step B is conducted in the presence of a mineral base in catalytic quantity.

15. The process of claim 1 wherein step C is conducted at a temperature of from 0° C. to 50° C.

16. The process of claim 1 wherein, in step C, the base is introduced in catalytic quantity.

17. The process according to claim 1 wherein step D is conducted at a temperature of from 0° C. to 80° C.