Process for obtaining 3, 3-diphenylpropylamines

1. A process for obtaining a compound of general formula (I)

wherein

R 1 is C 1 -C 8 alkyl; and

R 3 and R 4 , independently of one another, are selected from H and C 1 -C 8 alkyl, or together form a ring of 3 to 7 members with the nitrogen to which they are bound;

its enantiomers, solvates or salts, comprising subjecting a compound of general formula (V)

wherein

R 1 , R 3 and R 4 have the previously indicated meaning, to a chemoselective reduction.

2. The process according to claim 1 , wherein the chemoselective reduction is carried out with a reducing agent selected from a hydride, borane, a borane derivative or a borane precursor.

3. The process according to claim 2 , wherein said reducing agent is selected from the group consisting of AlH 3 , BH 3 .THF, BH 3 .Me 2 S, NaBH 4 /I 2 , NaBH 4 /BF 3 (OEt) 2 and NaBH 4 /HCl.

4. The process according to claim 1 , additionally comprising subjecting a compound of general formula (IV′)

wherein

R 3 and R 4 , independently of one another, are selected from H and C 1 -C 8 alkyl, or together form a ring of 3 to 7 members with the nitrogen to which they are bound;

to an esterification reaction of the hydroxyl group with a carboxylic acid, an ester, an acid chloride, an anhydride or any other suitable carboxylated derivative, to obtain a compound of general formula (V)

wherein

R 3 and R 4 have the previously indicated meaning.

5. The process according to claim 4 , wherein the esterification reaction is carried out in a reaction medium comprising a basic medium.

6. The process according to claim 5 , wherein the basic medium comprises triethylamine, diisopropylethylamine or pyridine.

7. The process according to claim 5 , wherein the esterification reaction is carried out in a reaction medium comprising triethylamine, an acid chloride and dichloromethane.

8. The process according to claim 4 , additionally comprising subjecting a compound of general formula (IV)

wherein

R 2 is selected from CN, COOR 5 and CONR 6 R 7 ; wherein

R 5 is selected from H, Cl and C 1 -C 8 alkyl; and

R 6 and R 7 , independently of one another, are selected from H and C 1 -C 8 alkyl; and

R 3 and R 4 , independently of one another, are selected from H and C 1 -C 8 alkyl, or together form a ring of 3 to 7 members with the nitrogen to which they are bound;

to a hydrolysis reaction, to obtain a compound of general formula (IV′)

wherein

R 3 and R 4 have the previously indicated meaning.

9. The process according to claim 8 , additionally comprising reacting a compound of general formula (II)

wherein

R 3 and R 4 , independently of one another, are selected from H and C 1 -C 8 alkyl, or together form a ring of 3 to 7 members with the nitrogen to which they are bound;

with a compound of general formula (III)

wherein

R 2 is selected from CN, COOR 5 and CONR 6 R 7 ; wherein

R 5 is selected from H, Cl and C 1 -C 8 alkyl; and

R 6 and R 7 , independently of one another, are selected from H and C 1 -C 8 alkyl;

to give a compound of general formula (IV)

wherein

R 2 has the previously indicated meaning; and

R 3 and R 4 , independently of one another, are selected from H and C 1 -C 8 alkyl, or together form a ring of 3 to 7 members with the nitrogen to which they are bound.

10. The process according to claim 1 , additionally comprising the separation of an enantiomer of the compound of general formula (I).

11. The process according to claim 10 , wherein said enantiomer is the (R) enantiomer.

12. A process for obtaining Fesoterodine

its solvates, or salts, comprising:

a) reacting a compound of formula (IIa)

with a compound of general formula (III)

wherein

R 2 is selected from CN, COOR 5 and CONR 6 R 7 ; wherein

R 5 is selected from H, Cl and C 1 -C 8 alkyl; and

R 6 and R 7 , independently of one another, are selected from H and C 1 -C 8 alkyl;

to give the compound of formula (IVa)

wherein R 2 has the previously indicated meaning;

b) if desired, separating the (R) enantiomer from the mixture of enantiomers of the compound of general formula (IVa);

c) if R 2 is different from COOH in the compound of general formula (IVa), subjecting said compound of formula (IVa) to a hydrolysis to give rise to the compound of formula (IV′a)

d) if desired, separating the (R) enantiomer from the mixture of enantiomers of the compound of general formula (IV′a);

e) subjecting the compound obtained in the previous step to an esterification of the hydroxyl group to give rise to the compound (Va)

f) if desired, separating the (R) enantiomer from the mixture of enantiomers of the compound of general formula (Va);

g) subjecting said compound of formula (Va) to a chemoselective reduction to give the compound of formula (Ia);

and

h) if desired, separating the (R) enantiomer from the mixture of enantiomers of Fesoterodine and converting Fesoterodine into a salt or solvate thereof.

13. A compound of general formula (V)

wherein

R 1 is C 1 -C 8 alkyl;

R 3 and R 4 , independently of one another, are selected from H and C 1 -C 8 alkyl, or together form a ring of 3 to 7 members with the nitrogen to which they are bound;

its enantiomers, solvates or salts.

14. The compound according to claim 13 of formula (Va)

its enantiomers, solvates or salts.

15. The process according to claim 4 , additionally comprising the separation of an enantiomer of the compound of general formula (V).

16. The process according to claim 15 , wherein said enantiomer is the (R) enantiomer.

17. The process according to claim 8 , additionally comprising the separation of an enantiomer of the compound of general formula (IV′).

18. The process according to claim 16 , wherein said enantiomer is the (R) enantiomer.

19. The process according to claim 9 , additionally comprising the separation of an enantiomer of the compound of general formula (IV).

20. The process according to claim 19 , wherein said enantiomer is the (R) enantiomer.