Process for the preparation of angiotensin receptor blockers and intermediates thereof
A process for the preparation of a biphenyl-containing compound of general formula I: wherein R 1 is a C 3-6 carbonyl containing compound; R 2 is a substituted or unsubstituted, straight or branched C 3-6 alkyl group, or R 1 and R 2 together with the nitrogen atom to which they are bonded are joined together to form a substituted heterocyclic group selected from the group consisting of substituted or unsubstituted imidazoles, substituted or unsubstituted benzimidazoles and substituted or unsubstituted 1,3-diazaspiro[4,4]non-1-en-4-one; and R 3 is a carboxylic acid ester, cyano, a substituted or unsubstituted 1H-tetrazolyl group or a substituted or unsubstituted group which may be converted in vivo into a carboxy group is provided, the process comprising reacting a compound of general formula II: wherein R 1 and R 2 have the aforestated meanings with a compound of general formula III: wherein Z is a leaving group and R 3 has the aforestated meaning in a biphasic solvent system in the presence of a phase transfer catalyst.
1 . A process for the preparation of a biphenyl-containing compound of general formula I:
wherein R 1 is a C 3-6 carbonyl containing compound; R 2 is a substituted or unsubstituted, straight or branched C 3-6 alkyl group, or R 1 and R 2 together with the nitrogen atom to which they are bonded are joined together to form a substituted heterocyclic group selected from the group consisting of substituted or unsubstituted imidazoles, substituted or unsubstituted benzimidazoles and substituted or unsubstituted 1,3-diazaspiro[4,4]non-1-en-4-one; and R 3 is a carboxylic acid ester, cyano, a substituted or unsubstituted 1H-tetrazolyl group or a substituted or unsubstituted group which may be converted in vivo into a carboxy group, the process comprising reacting a compound of general formula II:
wherein R 1 and R 2 have the aforestated meanings with a compound of general formula III:
wherein Z is a leaving group and R 3 has the aforestated meaning in a biphasic solvent system and in the presence of a phase transfer catalyst.
2 . The process of claim 1 , wherein the biphasic solvent system comprises water and a water immiscible solvent.
3 . The process of claim 2 , wherein the water immiscible solvent is selected from the group consisting of a halogenated hydrocarbon, aromatic hydrocarbon, aliphatic hydrocarbon, ketone, ether, and mixtures thereof.
4 . The process of claim 2 , wherein the water immiscible solvent is selected from the group consisting of methylene chloride, toluene, methyl isobutyl ketone, tert-butyl methyl ether, heptane, cyclohexane, n-heptane, hexane, octanol, n-decane, decalene and mixtures thereof.
5 . The process of claim 1 , wherein the phase transfer catalyst is selected from the group consisting of a quaternary ammonium phase transfer catalyst, a phosphonium phase transfer catalyst and a pyridinium phase transfer catalyst.
6 . The process of claim 1 , wherein the phase transfer catalyst is a quaternary ammonium phase transfer catalyst selected from the group consisting of tricaprylylmethylammonium chloride, tetra-n-butylammonium bromide, benzyltriethylammonium chloride, cetyltrimethylammonium bromide, cetylpyridinium bromide, N-benzylquininium chloride, tetra-n-butylammonium chloride, tetra-n-butylammonium hydroxide, tetra-n-butylammonium iodide, tetra-ethylammonium chloride, benzyltributylammonium bromide, benzyltriethylammonium bromide, hexadecyltriethylammonium chloride, tetramethylammonium chloride, hexadecyltrimethyl ammonium chloride, octyltrimethylammonium chloride and mixtures thereof.
7 . The process of claim 1 , wherein the phase transfer catalyst is selected from the group consisting of tetrabutyl ammonium bromide, tetrabutyl ammonium hydroxide, tetramethyl ammonium iodide, tetrabutyl ammonium sulfate and mixtures thereof.
8 . The process of claim 1 , wherein the reaction is carried out in the presence of an acid binding agent.
9 . The process of claim 8 , wherein the acid binding agent is selected from the group consisting of an alkali metal hydroxide, alkali metal carbonate, alkali metal bicarbonate and mixtures thereof.
10 . The process of claim 8 , wherein the acid binding agent is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate and mixtures thereof.
11 . The process of claim 1 , wherein the compound of formula I is methyl 4′-[(1,4′-dimethyl-2′-propyl[2,6′-bi-1H-benzimidazol]-1′-yl)methyl]-[1,1′-biphenyl]-2-carboxylate.
12 . The process of claim 11 , wherein the methyl 4′-[(1,4′-dimethyl-2′-propyl[2,6′-bi-1H-benzimidazol]-1′-yl)methyl]-[1,1′-biphenyl]-2-carboxylate is thereafter converted to telmisartan or a pharmaceutically acceptable salt thereof.
13 . The process of claim 11 , further comprising hydrolyzing the methyl 4′-[(1,4′-dimethyl-2′-propyl[2,6′-bi-1H-benzimidazol]-1′-yl)methyl]-[1,1′-biphenyl]-2-carboxylate to provide telmisartan.
14 . The process of claim 13 , wherein the step of hydrolyzing is carried out in the presence of a base and in a solvent.
15 . The process of claim 14 , wherein the base is selected from the group consisting of sodium hydroxide, potassium hydroxide, potassium carbonate and mixtures thereof.
16 . The process of claim 14 , wherein the solvent is selected from the group consisting of water, methanol, ethanol, isopropanol, and mixtures thereof.
17 . The process of claim 12 , further comprising purifying telmisartan or a pharmaceutically acceptable salt thereof.
18 . The process of claim 17 , wherein the telmisartan is purified in a solvent selected from the group consisting of a halogenated hydrocarbon, alcohol, and mixtures thereof.
19 . Telmisartan prepared in accordance with the process of claim 1 and having a purity of equal to or greater than about 98%.
20 . The process of claim 1 , wherein in the compound of formula I R 1 and R 2 together with the nitrogen to which they are bonded represent a substituted benzimidazole and R 3 is a substituted or unsubstituted 1H-tetrazolyl group.
21 . The process of claim 20 , wherein the compound of formula I is candesartan of the formula
22 . The process of claim 1 , wherein in the compound of formula I R 1 and R 2 together with the nitrogen to which they are bonded represent a substituted imidazole and R 3 is a substituted or unsubstituted 1H-tetrazolyl group.
23 . The process of claim 22 , wherein the compound of formula I is thereafter converted to a pharmaceutically acceptable salt thereof.
24 . The process of claim 22 , wherein the compound of formula I is thereafter converted to a potassium salt.
25 . The process of claim 24 , wherein the compound is of the formula
26 . The process of claim 1 , wherein in the compound of formula I R 1 and R 2 together with the nitrogen to which they are bonded represent a substituted 1,3-diazaspiro[4,4]non-1-en-4-one and R 3 is a substituted or unsuubstituted 1H-tetrazolyl group.
27 . The process of claim 26 , wherein the compound of formula I is irbesartan of the formula
28 . The process of claim 1 , wherein in the compound of formula I R 1 is a C 5 carbonyl containing compound, R 2 is a C 3 -C 6 substituted alkyl group and R 3 is a substituted or unsubstituted 1H-tetrazolyl group.
29 . The process of claim 28 , wherein the compound of formula I is valsartan of the formula
30 . A pharmaceutical composition comprising the compound obtained from the process of claim 1 and at least one pharmaceutically acceptable excipient.
31 . A process for preparing an intermediate of telmisartan, the process comprising reacting a 1,4′-dimethyl-2′-propyl[2,6′-bi-1H-benzimidazole] with a methyl 4′-(bromomethyl)[1,1′-biphenyl]-2-carboxylate in a biphasic solvent system in the presence of an acid binding agent and a phase transfer catalyst to provide methyl 4′-[(1,4′-dimethyl-2′-propyl[2,6′-bi-1H-benzimidazol]-1′-yl)methyl]-[1,1′-biphenyl]-2-carboxylate.
32 . The process of claim 31 , further comprising hydrolyzing the methyl 4′-[(1,4′-dimethyl-2′-propyl[2,6′-bi-1H-benzimidazol]-1′-yl)methyl]-[1,1′-biphenyl]-2-carboxylate to provide telmisartan.
33 . The process of claim 32 , further comprising purifying telmisartan or a pharmaceutically acceptable salt thereof.
34 . The process of claim 33 , wherein the purity of telmisartan is equal to or greater than about 98%.
35 . A process for the purification of telmisartan comprising (a) providing a solution comprising telmisartan and a water-immiscible solvent; (b) treating the solution with at least one base and (c) adding an acid or a mixture of acids to the product of step (b).
36 . The process of claim 35 , wherein the water-immiscible solvent is a lower alcohol, the base is selected from the group consisting of a nitrogen-containing base, alkali metal hydroxide, sodium alcoholate and mixtures thereof and the acid is selected from the group consisting of acetic acid, hydrochloric acid, hydrobromic acid, sulfuric acid and mixtures thereof.
37 . The process of claim 35 , wherein the water-immiscible solvent is selected from the group consisting of methanol, ethanol, 2-propanol, and mixtures thereof, the base is selected from the group consisting of ammonia, triethyl amine, diisopropyl amine, dimethyl amine, monomethyl amine, diisopropyl ethyl amine and mixtures thereof, and the acid is selected from the group consisting of acetic acid, hydrochloric acid, hydrobromic acid, sulfuric acid and mixtures thereof.
38 . The process of claim 37 , wherein the telmisartan has a purity equal to or greater than about 99.5%.