AN IMPROVED PROCESS FOR PREPARATION OF TRIENTINE DIHYDROCHLORIDE

Abstract

The present invention provides a process for preparation of trientine dihydrochloride (1) comprising reaction of protected triethylene tetramine with hydrochloric acid in an aqueous system to yield the dihydrochloride salt wherein the formation of inorganic impurities and undesired salts is controlled significantly.

Claims

1. A process for preparation of Trientine dihydrochloride comprising a reaction of tert-butyl-N-(2-aminoethyl)-N-2-[(2-aminoethyl)-(tert-butoxy)carbonyl]amino]ethyl} carbamate in presence of hydrochloric acid to give Trientine dihydrochloride, wherein an amount of the hydrochloric acid present in the reaction is less than a molar equivalent quantity with respect to the tert-butyl-N-(2-aminoethyl)-N-2-[(2-aminoethyl)-(tert-butoxy)carbonyl]amino]ethyl} carbamate of formula.

2. The process as claimed in claim 1, wherein the reaction is carried out in an aqueous medium.

3. The process as claimed in claim 1, wherein a reaction temperature is maintained in a range of 80 to 110 C.

4. The process as claimed in claim 1, wherein the hydrochloric acid is used in a range of 1.6 to 2.1 molar equivalents.

5. The process as claimed in claim 1, wherein a reaction mass is formed after completion of the reaction, thereafter the reaction mass is concentrated, treated with ethanol, cooled and filtered to yield Trientine dihydrochloride.

6. The process as claimed in claim 1, wherein the reaction is a single step reaction.

7. The process as claimed in claim 1, wherein the reaction avoids following steps: preparing a tetrahydrochloride salt from the tert-butyl-N-(2-aminoethyl)-N-2-[(2-aminoethyl)-(tert-butoxy)carbonyl]amino]ethyl} carbamate, converting the tetrahydrochloride salt to a Trientine free base, and re-converting the Trientine free base to the Trientine dihydrochloride by a subsequent reaction with the hydrochloric acid.

8. The process as claimed in claim 1, wherein the reaction avoids the amount of the hydrochloric acid present in the reaction to be multi-molar equivalent quantity with respect to the tert-butyl-N-(2-aminoethyl)-N-2-[(2-aminoethyl)-(tert-butoxy)carbonyl]amino]ethyl} carbamate.

9. The process as claimed in claim 1, wherein there is no formation of sodium chloride during the process.

10. The process as claimed in claim 9, wherein the process contains no unit operation for separation and filtration of the sodium chloride.

11. A process for preparation of Trientine dihydrochloride comprising reacting tert-butyl-N-(2-aminoethyl)-N-2-[(2-amino ethyl)-(tert-butoxy)carbonyl]amino]ethyl} carbamate with about 1.6 moles to 2.1 moles per mole substrate of hydrochloric acid at pH 7-8 to form the Trientine dihydrochloride and isolating the Trientine dihydrochloride.

12. The process as claimed in claim 11, wherein the reaction is carried out in an aqueous medium.

13. The process as claimed in claim 11, wherein a reaction temperature is maintained in a range of 80 to 110 C.

14. The process as claimed in claim 11, wherein the Trientine dihydrochloride is isolated by concentration of a reaction mixture followed by addition of ethanol to form an isolated product.

15. The process as claimed in claim 11, wherein the reaction mixture after addition of ethanol is a clear solution, which is then cooled and filtered.

16. The process as claimed in claim 11, wherein the reaction is carried out in an autoclave or at atmospheric pressure.

17. The process as claimed in claim 11, wherein the reaction avoids following steps: preparing a tetrahydrochloride salt from the tert-butyl-N-(2-aminoethyl)-N-2-[(2-aminoethyl)-(tert-butoxy)carbonyl]amino]ethyl} carbamate, converting the tetrahydrochloride salt to a Trientine free base, and re-converting the Trientine free base to the Trientine dihydrochloride by a subsequent treatment with hydrochloric acid.

18. The process as claimed in claim 11, wherein there is no formation of sodium chloride during the process.

19. The process as claimed in claim 14, wherein the isolated product has sulphated ash below regulatory limits.

20. The process as claimed in claim 1, wherein the process produces the triethylenetetramine dihydrochloride with a yield of around 80% and a purity of greater than equal to 98%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0026] The present inventors, in their pursuit for developing a convenient, commercially viable and economical process for obtaining trientine dihydrochloride conforming to regulatory specifications, carried out extensive experimentation aimed at minimizing the synthetic steps as against the circuitous routes disclosed in prior art. Surprisingly, it was observed that a direct, single-step process for preparation of the dihydrochloride salt was possible when the reaction of tertiary butoxycarbonyl protected amine (6) with hydrochloric acid was carried out in an aqueous system at 80 to 110 C. in the pH range of 7-8. In this reaction, hydrochloric acid which was used in less than molar equivalent quantities with respect to the protected amine reactant, served the dual purpose of deprotection of the protecting group and formation of the salt, providing the selective dihydrochloride formation. It was also observed that the reaction could be carried out either at mild pressure in an autoclave or at atmospheric pressure.

[0027] This novel strategy thus avoids lengthy, time consuming reaction sequence of preparing tetrahydrochloride salt from the protected diamine, its conversion to trientine free base, followed by re-conversion to the dihydrochloride salt by reaction with hydrochloric acid. Consequently, use of multi-molar equivalents of hydrochloric acid, excessive organic solvents and the multiple unit operations at intermediate stages are avoided to give a convenient and robust process for the dihydrochloride salt (1) which conforms to regulatory requirements.

[0028] A noteworthy part of the embodied method was that there was no formation of sodium chloride during the process, due to which the unit operations for separation and filtration of the salt were eliminated and more importantly, problems associated with sulphated ash content, which hampered the purity of the final product; dihydrochloride salt were avoided.

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[0029] In an embodiment, tert-butyl-N-(2-aminoethyl)-N-2-[(2-aminoethyl)-(tert-butoxy)carbonyl] amino]ethyl} carbamate of formula (6) was treated with concentrated hydrochloric acid.

[0030] The amount of hydrochloric acid employed for deprotection of the amine group and subsequent dihydrochloride formation was in the range of 1.6 to 2.1 equivalents with respect to the tertiary butoxycarbonyl-protected diamine (6).

[0031] It was noted that if, during the reaction eventually the pH was excessively higher or lower than the range of 7 to 8, there were problems in isolating the desired dihydrochloride salt resulting in substantial yield loss.

[0032] The reaction mixture was heated in the temperature range of 80-110 C.

[0033] The reaction was carried out at atmospheric pressure or in a pressure vessel (autoclave) wherein the pressure was maintained in the range of 2-10 Kg/cm.sup.2.

[0034] After completion of the reaction as monitored by TLC, the aqueous reaction mixture was concentrated and ethanol was added to the residue. The resultant mixture was heated till a clear solution was obtained. Further cooling of the reaction mixture, filtration and drying yielded the desired compound, triethylenetetramine dihydrochloride (1) with yield around 80% and purity98% (purity within USP limits).

[0035] Compound (6) was prepared following known methods by reaction of ethylene diamine (2) with chloroacetonitrile (3) using potassium carbonate as base and solvent acetonitrile to give 2-({2-[(cyanomethyl)amino]ethyl}amino) acetonitrile (4). Compound (4) was further treated with ditertiarybutyl dicarbonate and the resulting boc-protected dinitrile (5) was hydrogenated using Raney nickel, ammonia and isopropyl alcohol to yield compound (6).

[0036] Alternatively, the preparation of compound (4) and its further reaction with ditertiarybutyl dicarbonate was carried out in-situ.

[0037] The following examples are meant to be illustrative of the present invention. These examples exemplify the invention and are not to be construed as limiting the scope of the invention.

EXAMPLES

Example 1: Preparation of 2-([2-[cyanomethyl]-t-butyloxycarbonylamino]ethyl-t-butyloxy carbonylamino)acetonitrile (5)

[0038] Potassium carbonate (481.9 g) was added to a stirred mixture of ethylenediamine (100.0 g) in acetonitrile (800 ml) and cooled to around 10 C. Chloroacetonitrile (263.8 g) was gradually added at same temperature and stirred at 25-30 C., till completion of the reaction, as monitored by HPLC. The mixture was cooled to 5-15 C. and Boc-anhydride (762.1 g) was added to it, followed by stirring at the same temperature. The temperature was raised to 25-30 C. and the mass was stirred till completion of the reaction, as monitored by HPLC.

[0039] The reaction mass was filtered and the filtrate was concentrated. Toluene was added to the residue, and the mixture was heated to around 70 C. followed by cooling and filtration to give 2-([2-[cyanomethyl)-t-butyloxycarbonylamino]ethyl-t-butyloxycarbonylamino) acetonitrile (5).

[0040] Yield: 506.8 g

[0041] % Yield: 89.9%

Example 2: Preparation of t-butyl(N-2-aminoethyl)N-([2-[(2-aminoethyl)t-butyloxy)carbonylamino] ethyl) carbamate (6)

[0042] Raney nickel (120.0 g) in isopropanol (100 ml) was charged into an autoclave, followed by a mixture of Compound 5 (200 g) in isopropanol (400 ml). Cooled ammonia solution prepared by purging ammonia gas in 1400 ml isopropanol, equivalent to 125 g ammonia was gradually charged to the autoclave and the reaction was carried out around 15-25 C. under hydrogen pressure of 2-5 Kg/cm.sup.2.

[0043] After completion of the reaction, as monitored by HPLC, the mass was filtered, concentrated, and methyl tertiary butyl ether was added to the residue. The mixture was heated to around 50 C., followed by cooling of the mass, stirring, optional seeding with compound 6 and filtration to give tertiary butyl-(N-2-aminoethyl)N-([2-[(2-aminoethyl)-(tert-butyloxy) carbonylamino] ethyl) carbamate.

[0044] Yield: 174 g

[0045] % Yield: 85%

Example 3: Preparation of Triethylenetetramine Dihydrochloride (1)

[0046] Concentrated hydrochloric acid (121.5 g) was gradually added to a stirred mixture of tertiary-butyl-N-(2-aminoethyl)-N-2-[(2-aminoethyl)-(tert-butoxy) carbonyl] amino] ethyl} carbamate (Compound 6, 200.0 g) and water (1400 ml) at 20-30 C. The reaction mixture was heated in the temperature range of 100-105 C. till completion of the reaction, as monitored by HPLC, with optionally distilling out water, if so required.

[0047] The reaction mass was concentrated and ethanol (600 ml) was added to the residue, followed by heating till a clear solution was obtained. The reaction mixture was gradually cooled with stirring, filtered and dried to provide triethylenetetramine dihydrochloride (1).

[0048] Yield: 88.9 g, (70%)

[0049] Purity: 99%