Patent Application
20240294458
The invention relates to a novel process for manufacturing an aniline 2,
wherein PG denotes hydrogen or an amino protective group. The process according to the invention is particularly suitable for large-scale manufacturing of aniline 2 under GMP conditions.
Anilines 2 are crucial intermetidates in the synthesis of ralmitaront (Formula IV), a partial agonist of the TAAR1 (PCT application WO2017157873).
For marketing products, it is necessary to produce pharmaceuticals in large quantities and according to good manufacturing practice (“GMP”). Hence, high-yielding, cheap, safe and reproducible syntheses are of utmost importance.
WO2015086495 discloses a process for making anilines 2, which involves catalytic hydrogenation of nitroarenes 1 in protic solvents.
However, it has now been found that using a protic solvent for the hydrogenation, as described in WO2015086495, hampers the subsequent workup and isolation procedure on an industrial scale. Namely, on an industrial scale, it is preferable to crystallize and filter said anilines 2 after the hydrogenation step. The crystallization of anilines 2 has been found to require aprotic solvent systems, such as a mixture of TBME and heptane. Accordingly, if the hydrogenation of nitroarene 1 is performed in a protic solvent, such as methanol, a solvent swap is required for the subsequent crystallization step. A solvent swap generally consumes time and energy (distillation of large amounts of solvent), among other drawbacks.
What is more, the use of protic solvents in the hydrogenation of nitroarenes 1 has been found to produce varying trace amounts of side products, which is highly problematic when working under GMP conditions. Thus, for example, when ethanol was used as a solvent for the catalytic hydrogenation of (S)-tert-butyl 2-(4-nitrophenyl)morpholine-4-carboxylate (II),
(S)-tert-butyl 2-(4-ethylamino)morpholine-4-carboxylate (III) was observed as a side product, among others.
Therefore, there is a need for a new process for manufacturing anilines 2.
It has now been found that nitroarenes 1 can be hydrogenated in an aprotic solvent, greatly facilitating the workup procedure of the resulting anilines 2 on an industrial scale. In addition, the hydrogenation, when performed in an aprotic solvent, surprisingly does not lead to the formation of any side product.
Thus, in a first aspect, the present invention provides a process for manufacturing an aniline 2, wherein PG denotes an amino protective group
comprising:
reacting a nitroarene 1, wherein PG denotes an amino protective group, with hydrogen
In a further aspect, the present invention provides an aniline 2, wherein PG denotes an amino protective group
when manufactured according to the inventive process described herein.
In a further aspect, the present invention provides a process for manufacturing 5-ethyl-4-methyl-N-[4-[(2S) morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide (Formula IV), or a pharmaceutically acceptable salt thereof,
comprising the inventive process described herein.
In a further aspect, the present invention provides the use of the process according to the invention for the manufacture of 5-ethyl-4-methyl-N-[4-[(2S) morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide (Formula IV), or a pharmaceutically acceptable salt thereof.
Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein, unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims and the abstract), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and the abstract), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
The term “elevated pressure” refers to any pressure above ambient (i.e., atmospheric) pressure.
The term “elevated temperature” refers to any temperature above ambient (i.e., room) temperature.
The term “catalyst loading” refers to the amound of catalyst relative to a given reactant, calculated in weight percent (“% wt/wt”). In cases where a catalyst is provided in a wet form, e.g. wet Pd/C, the catalyst loading is calculated based on the amount of dry catalyst.
The term “protective group” (PG) denotes a group which selectively blocks a reactive site in a multifunctional compound such that a chemical reaction can be carried out selectively at another unprotected reactive site in the meaning conventionally associated with it in synthetic chemistry. Protective groups can be removed at the appropriate point. Exemplary amino protective groups are Boc (tert-butoxycarbonyl), benzyl, 4-methoxybenzyl, benzhydryl, Fmoc (fluorenylmethoxycarbonyl), Cbz (benzyloxycarbonyl), Moz (p-methoxybenzyl carbonyl), Troc (2,2,2-trichloroethoxycarbonyl), Teoc (2-(Trimethylsilyl)ethoxycarbonyl), Adoc (adamantoxycarbonyl), formyl, acetyl, and cyclobutoxycarbonyl. Further particular amino protective groups are tert-butoxycarbonyl (Boc) and fluorenylmethoxycarbonyl (Fmoc). A more particular protecting group is tert-butoxycarbonyl (Boc). Exemplary protecting groups and their application in organic synthesis are described, for example, in “Protective Groups in Organic Chemistry” by T. W. Greene and P. G. M. Wutts, 5th Ed., 2014, John Wiley & Sons, N.Y, which is included herein by reference in its entirety.
In a first aspect, the present invention provides a process for manufacturing an aniline 2, wherein PG denotes an amino protective group
In one embodiment, the present invention provides a process for manufacturing an aniline 2, wherein PG denotes hydrogen or an amino protective group
In one embodiment, each amino protective group is independently selected from Boc (t-butoxycarbonyl), benzyl, 4-methoxybenzyl, benzhydryl, Fmoc (fluorenylmethoxycarbonyl), Cbz (benzyloxycarbonyl), Moz (p-methoxybenzyl carbonyl), Troc (2,2,2-trichloroethoxycarbonyl), Teoc (2-(Trimethylsilyl)ethoxycarbonyl), Adoc (adamantoxycarbonyl), formyl, acetyl, and cyclobutoxycarbonyl.
In a preferred embodiment, the amino protective group is Boc (t-butoxycarbonyl).
In one embodiment, said nitroarene 1 is nitroarene 1a, and said aniline 2 is aniline 2a
In one embodiment, said nitroarene 1 is nitroarene 1b, and said aniline 2 is aniline 2b
In a preferred embodiment, said nitroarene 1 is (S)-tert-butyl 2-(4-nitrophenyl)morpholine-4-carboxylate (II)
In a preferred embodiment, said aniline 2 is (S)-tert-butyl 2-(4-aminophenyl)morpholine-4-carboxylate (I)
In one embodiment, said transition metal catalyst is selected from Pt, Pd, Pt—V and Ni, wherein each of said Pt, Pd, Pt—V and Ni is on a solid support. In one embodiment, said solid support is selected from activated carbon, allumina, silica and an aluminium alloy.
In one embodiment, said transition metal catalyst is selected from PtO2, Pd/C, Pt—V/C, Pt/C, and Raney Ni.
In a preferred embodiment, said transition metal catalyst is Pd/C.
In a particularly preferred embodiment, said transition metal catalyst is Pd/C and contains 5% wt/wt of palladium relative to charcoal (5% Pd/C).
In a further particularly preferred embodiment, said transition metal catalyst is Evonik Noblyst® P1093 5% Pd/C.
In one embodiment, the catalyst loading is 0.1% wt/wt to 1% wt/wt relative to nitroarene 1.
In a preferred embodiment, the catalyst loading is 0.4% wt/wt to 0.6% wt/wt relative to nitroarene 1.
In a particularly preferred embodiment, the catalyst loading is 0.5% wt/wt relative to nitroarene 1.
In a further particularly preferred embodiment, the catalyst loading is 0.55% wt/wt relative to nitroarene 1.
In one embodiment, said aprotic solvent is an ether.
In a preferred embodiment, said ether is tert-butyl methyl ether (TBME).
While using an aprotic solvent for the hydrogenation of nitroarene 1 to form aniline 2 solved the problems observed with the process described in WO2015086495, the reaction was found to be slow and require elevated reaction temperatures. Surprisingly, adding trace amounts of water to the reaction mixture resulted in a dramatically increased conversion rate of nitroarene 1 to aniline 2 (
Thus, in one embodiment, said aprotic solvent contains trace amounts of water.
In one embodiment, said trace amounts of water are 0.01% wt/wt to 0.1% wt/wt relative to the aprotic solvent.
In a preferred embodiment, said trace amounts of water are 0.05% wt/wt to 0.5% wt/wt relative to the aprotic solvent.
In a particularly preferred embodiment, said trace amounts of water are 0.25% wt/wt relative to the aprotic solvent.
In one embodiment, the process of the invention is conducted at elevated temperature.
In one embodiment, said elevated temperature is 35° C. to the boiling point of the reaction mixture.
In a preferred embodiment, said elevated temperature is 40° C. to 60° C.
In one embodiment, the process of the invention is conducted at elevated hydrogen pressure.
In one embodiment, said elevated hydrogen pressure is 1 barg to 10 barg.
In a preferred embodiment, said elevated hydrogen pressure is 3 barg.
In one embodiment:
In a preferred embodiment:
In a particularly preferred embodiment, the process according to the invention is:
In one aspect, the present invention provides an aniline 2, wherein PG denotes hydrogen or an amino protective group,
when manufactured according to the process of the invention.
In one aspect, the present invention provides an aniline 2, wherein PG denotes an amino protective group,
when manufactured according to the process of the invention.
In a further aspect, the present invention provides a process for manufacturing 5-ethyl-4-methyl-N-[4-[(2S) morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide (Formula IV), or a pharmaceutically acceptable salt thereof, comprising the process according to the invention.
In a further aspect, the present invention provides the use of the process according to the invention for the manufacture of 5-ethyl-4-methyl-N-[4-[(2S) morpholin-2-yl]phenyl]-1H-pyrazole-3-carboxamide (Formula IV), or a pharmaceutically acceptable salt thereof.
The invention will be more fully understood by reference to the following examples. The claims should not, however, be construed as limited to the scope of the examples.
The following abbreviations are used in the present text:
(S)-tert-butyl 2-(4-nitrophenyl)morpholine-4-carboxylate (II) (50.0 g), TBME (500 mL, containing <5 ppm water) and water (877 μL) are charged into an autoclave reactor and, under inert conditions, wet 5% Pd/C (Evonik Noblyst® P1093, 582 mg-corresponding to 275 mg on dry basis) is added to the mixture. The reactor is sealed and made inert again by washing the gas phase with argon. The gas phase is washed with hydrogen 5 times and the pressure released. The reactor is heated under stirring to Ti=40±2° C. and then pressurized to 3 barg of hydrogen. Stirring is continued for 6 h while maintaining a constant internal temperature (Ti=40±2° C.) and hydrogen pressure (Pi=3 barg) while recording the hydrogen consumption over time as a measure of the reaction conversion. After 6 h, the temperature is increased to Ti=60±2° C. and the reaction is continued at this temperature for 18 h. After this time, the reactor is cooled to Ti=20±5° C., the stirring stopped, the pressure released carefully and the reactor is made inert with argon. The reaction mixture is filtered to remove the heterogeneous catalyst using a total of 180 mL TBME to wash the reactor and the filter cake. The resulting solution is concentrated to ˜140 mL by distilling the solvent at ambient pressure and then cooled to Ti=50±2° C. n-Heptane (75 mL) is added to the concentrated solution within ≥30 min and the resulting solution is seeded with (S)-tert-butyl 2-(4-aminophenyl)morpholine-4-carboxylate (250 mg as a slurry in 5 mL of n-heptane). The resulting mixture is stirred at Ti=50±2° C. for ≥30 min and then more n-heptane (125 mL) is added within 30 min maintaining Ti=50±2° C. The mixture is cooled under stirring to Ti=20±3° C. within 3 h (cooling ramp: 10° C./h) and stirring is continued at this temperature for ≥12 h. The resulting suspension is filtered and the filter cake washed with a mixture of n-heptane (80 mL) and TBME (40 mL). The wet cake is dried under vacuum at 50±3° C. until constant weight is attained to afford the title compound (40.2 g) as a white solid.
(S)-tert-butyl 2-(4-nitrophenyl)morpholine-4-carboxylate (II) (50.0 g) and TBME (100 mL, containing <5 ppm water) are charged in an autoclave reactor and, under inert conditions, wet 5% Pd/C (Evonik Noblyst® P1093, 116 mg-corresponding to 55 mg on dry basis) is added to the mixture. The reactor is sealed and made inert again by washing the gas phase with argon. The gas phase is washed with hydrogen 5 times and the pressure released. The reactor is heated under stirring to Ti=40±2° C. and then pressurized to 3 barg of hydrogen. Stirring is continued for 5 h while maintaining a constant internal temperature (Ti=40±2° C.) and hydrogen pressure (Pi=3 barg) while recording the hydrogen consumption over time as a measure of the reaction conversion. After 5 h, the temperature is increased to Ti=60±2° C. (increasing the temperature determined a faster consumption of hydrogen, that was complete within 6.5 h) and the reaction is continued at this temperature for 18 h. After this time, the reactor is cooled to Ti=20±5° C., the stirring stopped, the pressure released carefully and the reactor is made inert with argon. The reaction mixture is filtered to remove the heterogeneous catalyst using a total of 50 mL TBME to wash the reactor and the filter cake. The resulting solution is concentrated to ˜25 mL by distilling the solvent at ambient pressure and then cooled to Ti=50±2° C. n-Heptane (50 mL) is added to the concentrated solution within ≥1 h. The resulting mixture is cooled under stirring to Ti=0±3° C. within 5 h (cooling ramp: 10° C./h) and stirring is continued at this temperature for ≥12 h. n-Heptane (20 mL) is added at Ti=0±3° C. within 30 min and the mixture is stirred at 0° C. for additional 4 h. The resulting suspension is filtered and the filter cake washed with n-heptane (40 mL). The wet cake is dried under vacuum at 50±3° C. until constant weight is attained to afford the title compound (8.29 g) as a white solid.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21206827.4 | Nov 2021 | EP | regional |
This application is a continuation of International Application No. PCT/EP2022/080899 having an international filing date of Nov. 7, 2022, which claims benefit of priority to European Patent Application No. 21206827.4, filed Nov. 8, 2021, each of which is incorporated herein by reference in its entirety
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2022/080899 | Nov 2022 | WO |
| Child | 18657765 | US |
