WO2015155153, SYNTHESIS OF VORTIOXETINE VIA (2,4-DIMETHYLPHENYL)(2-IODOPHENYL)SULFANE INTERMEDIATE

WO2015155153,  SYNTHESIS OF VORTIOXETINE VIA (2,4-DIMETHYLPHENYL)(2-IODOPHENYL)SULFANE INTERMEDIATE

LEK PHARMACEUTICALS D.D. [SI/SI]; Verovskova 57 1526 Ljubljana (SI)
Inventors:ZUPANCIC, Borut; (SI)

Vortioxetine is disclosed as Example 1 e in WO 2003/029232 A1 and is described as being prepared analogously to Example 1 . The process used to prepare Example 1 involves the preparation of 1 -(2-((2-(trifluoromethyl)phenyl)thio)phenyl)piperazine on a solid polystyrene support, followed by decomplexation using visible light irradiation, and purification by preparative LC-MS and ion-exchange chromatography. The overall yield for the preparation of vortioxetine is described as 17%.

Several alternative palladium catalyzed processes for the preparation of vortioxetine are described in Examples 17 to 25 of WO 2007/144005 A1 . These processes describe the preparation of vortioxetine from 2,4-dimethylthiophenol and 2-bromoiodobenzene (or 1 ,2-dibromobenzene) starting materials via a 1 -(2-bromo-phenylsulfanyl)-2,4-dimethyl-benzene intermediate. Each of these processes involves the use of a palladium catalyst and a phosphine ligand.

The preparation of vortioxetine is also described by Bang-Andersen et al. in J. Med. Chem. (201 1 ), Vol. 54, 3206-3221 . Here, in a first step, te/t-butyl 4-(2-bromophenyl)piperazine-1 -carboxylate intermediate is prepared from Boc-piperazine and 2-bromoiodobenzene in a palladium catalyzed coupling reaction. te/t-Butyl 4-(2-bromophenyl)piperazine-1 -carboxylate is then reacted with 2,4-dimethylthiophenol, again in the presence of palladium catalyst and a phosphine ligand, to provide Boc-protected vortioxetine. In the final step, vortioxetine is deprotected using hydrochloric acid to give vortioxetine hydrochloride.

WO 2013/102573 A1 describes a reaction between 1 -halogen-2,4-dimethyl-phenyl, 2-halogen-thiophenol and an optionally protected piperazine in the presence of a base and a palladium catalyst consisting of a palladium source and a phosphine ligand.

Each of the above processes has disadvantages. The process described in WO 2003/029232 is low yielding and unsuitable for the large scale production of vortioxetine, whereas the processes described in WO 2007/144005 A1 , WO 2013/102573 A1 and by Bang-Andersen et al. require the use of expensive starting materials, palladium catalyst and phosphine ligand. In addition, the toxicity of palladium is well known, Liu et al. Toxicity of Palladium, Toxicology Letters, 4 (1979) 469-473, and the European Medicines Agency' s Guideline on the Specification for Residues of Metal Catalysts sets clear limits on the permitted daily exposure to palladium arising from palladium residue within drug substances, www.ema.europa.eu. Thus it would be desirable to avoid the use of a palladium catalyst in the synthesis of vortioxetine and the subsequent purification steps required to remove palladium residue from the final pharmaceutical product.

The invention is described below in further detail by embodiments, without being limited thereto.

A general concept of the process of the present invention may be represented in Scheme 1 .

Scheme 1 : General representation of the basic synthetic concept of the present invention.

Scheme 2.

X = NH₂: lb

Scheme 2: Representation of a particular synthetic embodiment of the present invention.

Compound III can also be prepared from 2,4-dimethylbenzenethiol (II) and 1 -fluoro-2-nitrobenzene (l"'a) or 1 -chloro-2-nitrobenzene (l'"b). In the first step (2,4-dimethylphenyl)(2- nitrophenyl)sulfane (III') is formed and in the second reaction step nitro group is reduced to ami

Z = F: l"'a

Z = CI: l"'b

Scheme 3: Representation of a particular synthetic embodiment of the present invention.

Example 7: Preparation of 1 -(2-((2,4-dimethylphenyl)thio)phenyl)piperazine vortioxetine, VII)

Mixture of (2,4-dimethylphenyl)(2-iodophenyl)sulfane V (0.34 g, 1 .0 mmol), piperazine VI (0.13 g, 1 .5 mmol), K₃P0₃ (0.42 g, 2.0 mmol), Cul (19 mg, 0.1 mmol), and 2-phenylphenol (68 mg, 0.4 mmol) in dry and degassed DMSO (2 mL) was heated under nitrogen atmosphere at 120°C for 20 h. Water (10 mL) is then added and product is extracted to EtOAc (3 x 10 mL). Combined organic layers were washed with water (3 x 10 mL) and brine (2 x 10 mL) and dried over Na₂S0₄. After evaporation of the solvent crude product is purified by chromatography to afford title compound: H NMR (CDCI₃, 500 MHz) δ 1 .63 (br s, 1 H), 2.33 (s, 3H), 2.37 (s, 3H), 3.02-

3.09 (m, 8H), 6.52 (m, 1 H), 6.87 (m, 1 H), 7.04 (m, 1 H), 7.06-7.10 (m, 2H), 7.16 (m, 1 H), 7.39 (d, J= 7.8 Hz, 1 H); MS (ESI) m/z: 299 [MH]⁺.

Example 8: Preparation of 1 -(2-((2,4-dimethylphenyl)thio)phenyl)piperazine (vortioxetine, VII)

Mixture of (2,4-dimethylphenyl)(2-iodophenyl)sulfane V (0.34 g, 1 .0 mmol), piperazine VI (0.13 g, 1 .5 mmol), K₃P0₃ (0.42 g, 2.0 mmol), Cul (19 mg, 0.1 mmol), and N,N-diethyl-2-hydroxybenzamide (39 mg, 0.2 mmol) in dry and degassed DMSO (2 mL) was heated under nitrogen atmosphere at 120 ^ for 20 h. Water (10 mL) is then added and product is extracted to EtOAc (3 x 10 mL). Combined organic layers were washed with water (3 x 10 mL) and brine (2 x 10 mL) and dried over Na₂S0₄. After evaporation of the solvent crude product is purified by chromatography to afford title compound: H NMR (CDCI₃, 500 MHz) δ 1 .63 (br s, 1 H), 2.33 (s, 3H), 2.37 (s, 3H), 3.02-3.09 (m, 8H), 6.52 (m, 1 H), 6.87 (m, 1 H), 7.04 (m, 1 H), 7.06-7.10 (m, 2H), 7.16 (m, 1 H), 7.39 (d, J= 7.8 Hz, 1 H); MS (ESI) m/z: 299 [MH]⁺.

Example 9: Preparation of 1 -(2-((2,4-dimethylphenyl)thio)phenyl)piperazine hydrobromide

(vortioxetine HBr, VII.HBr)

To a solution of vortioxetine VII (1 .80 g, 6.03 mmol) in iPrOAc (20 mL) at room temperature 48% HBr (0.68 mL, 6.03 mmol) was slowly added. Obtained mixture was stirred at room temperature for 1 h, white precipitate was then filtered off, washed with acetone (2 x 20 mL), and dried to afford title compound VII.HBr as a white powder (2.15 g, 94% yield): H NMR (DMSO-d₆, 500 MHz) δ 2.23 (s, 3H), 2.32 (s, 3H), 3.15-3.27 (m, 8H), 6.40 (m, 1 H), 6.96 (m, 1 H), 7.08-7.17 (m, 3H), 7.24 (m, 1 H), 7.32 (d, J= 7.8 Hz, 1 H), 8.85 (br, 2H).

Reference Example 1 : Preparation of 1 -(2-((2,4-dimethylphenyl)thio)phenyl)piperazine

(vortioxetine, VII)

Mixture of piperazine (1 .0 g, 1 1 .6 mmol), NaOtBu (1 .37 g, 13.8 mmol), Pddba₂ (40 mg, 0.07 mmol), and 1 ,3-bis(2,6-di-i-propylphenyl)imidazolium chloride (24 mg, 0,07 mmol) in dry and degassed toluene (10 mL) is stirred at room temperature for 1 h. (2,4-Dimethylphenyl)(2-iodophenyl)sulfane V (1 .32 g, 3.86 mmol) is then added, reaction mixture is heated to l OO'C and stirred for 24 h. After cooling to room temperature to the reaction mixture water (5 mL) and Celite (0.4 g) is added. After stirring for 20 min salts are filtered off, organic layer is separated, washed with brine (2 x 10 mL), dried over Na₂S0₄ and solvent is evaporated to afford crude product, which is then purified by chromatography to afford title compound as yellowish crystals: H NMR (CDCI₃, 500 MHz) δ 1 .63 (br s, 1 H), 2.33 (s, 3H), 2.37 (s, 3H),

Reference Example 2: Preparation of 1 -(2-((2,4-dimethylphenyl)thio)phenyl)piperazine

(vortioxetine, VII)

Mixture of piperazine (1 .29 g, 15.0 mmol), NaOtBu (1 .77 g, 17.8 mmol), Pddba2 (52 mg, 0.09 mmol), and rac-BINAP (93 mg, 0,15 mmol) in dry and degassed toluene (10 mL) was stirred at room temperature for 1 h. (2,4-Dimethylphenyl)(2-iodophenyl)sulfane V (1 .70 g, 5.0 mmol) was then added, reaction mixture was heated to 100°C and stirred for 24 h. After cooled to room temperature to the reaction mixture water (5 mL) and Celite (0.4 g) were added. After stirring for 20 min salts were filtered off, organic layer was separated, washed with brine (2 x 10 mL), dried over Na₂S0₄ and solvent was evaporated to afford product as an orange oil (1 .41 g, 95% yield): H NMR (CDCI₃, 500 MHz) δ 1 .63 (br s, 1 H), 2.33 (s, 3H), 2.37 (s, 3H), 3.02-3.09 (m, 8H), 6.52 (m, 1 H), 6.87 (m, 1 H), 7.04 (m, 1 H), 7.06-7.10 (m, 2H), 7.16 (m, 1 H), 7.39 (d, J = 7.8 Hz, 1 H); MS (ESI) m/z: 299 [MH]⁺.

Comparative Example 1 : Preparation of 1 -(2-((2,4-dimethylphenyl)thio)phenyl)piperazine

(vortioxetine, VII)

Mixture of (2,4-dimethylphenyl)(2-bromohenyl)sulfane V" (0.29 g, 1 .0 mmol), piperazine VI (0.13 g, 1 .5 mmol), K₃P0₃ (0.42 g, 2.0 mmol), Cul (19 mg, 0.1 mmol), and 2-phenylphenol (68 mg, 0.4 mmol) in dry and degassed DMSO (2 mL) was heated under nitrogen atmosphere at 120°C for 20 h. Vortioxetine VII was not formed.

Comparative Example 2: Preparation of 1 -(2-((2,4-dimethylphenyl)thio)phenyl)piperazine

(vortioxetine, VII)

Mixture of (2,4-dimethylphenyl)(2-bromophenyl)sulfane V (0.29 g, 1 .0 mmol), piperazine VI (0.13 g, 1 .5 mmol), K₃P0₃ (0.42 g, 2.0 mmol), Cul (19 mg, 0.1 mmol), and N,N-diethyl-2-hydroxybenzamide (39 mg, 0.2 mmol) in dry and degassed DMSO (2 mL) was heated under nitrogen atmosphere at 120 ^ for 20 h. Vortioxetine VII was not formed.


















Vojmir Urlep, President of the Lek Management Board,










//////