Process Development for Scale-Up of a Novel 3,5-Substituted

Jan 18, 2014 - The development of a reproducible process for multihundred gram production of (Z)-5-((1-(4-chloro-2-(trifluoromethyl)benzyl)-1H-indazol...
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Process Development for Scale-Up of a Novel 3,5-Substituted Thiazolidine-2,4-dione Compound as a Potent Inhibitor for EstrogenRelated Receptor 1 Xun Li,* Ronald K. Russell, Jan Spink, Scott Ballentine, Christopher Teleha, Shawn Branum, Kenneth Wells, Derek Beauchamp, Raymond Patch, Hui Huang, Mark Player, and William Murray Janssen Research & Development L.L.C., Welsh and McKean Roads, P.O. Box 776, Spring House, Pennsylvania 19477, United States ABSTRACT: The development of a reproducible process for multihundred gram production of (Z)-5-((1-(4-chloro-2(trifluoromethyl)benzyl)-1H-indazol-5-yl)methylene)-3-((3R,4R)-3-fluoro-1-methylpiperidin-4-yl)thiazolidine-2,4-dione (26), a potent and selective inhibitor of estrogen-related receptor 1 (ERR1), is described. This multihundred gram synthesis was achieved via magnesium perchlorate-catalyzed regioselective epoxide ring-opening of tert-butyl 7-oxa-3-azabicyclo[4.1.0]heptane3-carboxylate (9) with thiazolidine-2,4-dione (6, TZD) to form a diastereomeric mixture tert-butyl 4-(2,4-dioxothiazolidin-3-yl)3-hydroxypiperidine-1-carboxylate (17), of which the 3-hydroxyl group was functionally transformed to 3-fluoro derivative 19 after treatment with Deoxo-Fluor. Chiral separation of 19 provided the desired diastereomer (3R,4R)-21 that was converted to the secondary amine 23 TFA salt. Reductive amination of 23 produced the key intermediate N-methyl 24. Knoevenagel condensation of 24 with 1-(4-chloro-2-(trifluoromethyl)benzyl)-1H-indazole-5-carbaldehyde (5) produced the final product 26 in 10% overall yield (99.7% HPLC area% with ≥99.5% de) after a convergent eight synthetic steps with the only column purification being the chiral HPLC separation of 3R,4R-21 from 3S,4S-22.

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INTRODUCTION The Janssen Pharmaceutical R&D medicinal chemists discovered a highly potent and selective inhibitor of estrogen-related receptor 1 (ERR1), (Z)-5-((1-(4-chloro-2-(trifluoromethyl)benzyl)-1H-indazol-5-yl)methylene)-3-((3R,4R)-3-fluoro-1methylpiperidin-4-yl)thiazolidine-2,4-dione (26), for the treatment of hyperglycemia in patients with type 2 diabetes mellitus. In a TR-FRET based assay, compound 26 competitively displaces a coactivator peptide with an EC50 of 23 nM, whereas in a cellular two-hybrid luciferase reporter assay, it reduces the constitutive activity of the receptor with an apparent ED50 of 0.7 μM.1 Initially 50 g of 26 was requested for the rat tolerability study, which was later followed by an additional request for 500 g of 26 for monkey tolerability and cardiovascular toxic studies. The original discovery preparation of 26, as shown in Scheme 1, was an eight-step synthesis with overall yield of 4.7%. Some improvement areas for scale-up of 26 were noted: for example, (1) a selective N1-alkylation process to produce the key intermediate aldehyde 5; (2) nonmicrowave epoxide ring-opening of compound 9 by thiazolidine-2,4-dione (6, TZD); (3) improvement of the isomer mixture of 17/18 to >1:1; (4) removal of the silica gel column purifications for intermediates 19, 12, 14, 16 and the final product 26; and (5) remove or move the formaldehyde Nmethylation step. Herein, we report our results for the initial 50-g synthesis of 26 as well as the improved scalable process for multihundred grams of 26.

discover a nonmicrowave epoxide ring-opening method for intermediate 9, and (3) to reduce or eliminate the normal phase chromatographic purification. The direct alkylation of commercially available 1H-indazole5-carbaldehyde (1) with 4-chloro-2-(trifluoromethyl)benzyl bromide (3), as reported2 resulted in a N1/N2 mixture of 5/ 5d (∼1:1). The desired N1 product 5 was very difficult to separate from the N2 side product 5d by column chromatography (Scheme 2). The pure N1 alkylated 5 was alternatively prepared by a modified three-step regioselective method. In practice, bromination of 1 using NBS in MeCN afforded 82% isolated yield of 3-bromo compound 2 with ≥95% chemical purity.3 Compound 2 was contaminated with a small amount (∼3−5%) of 1 due to the fast formation of solid 2 that trapped unreacted 1. Selective N1 alkylation of 2 with 3 in the presence of K2CO3 (1.2 equiv) resulted in a crude material that contained ∼88−91% of the desired N1 product 4 and ∼6−8% of the undesired N2 side product 4a, which was completely removed by crystallization in EtOAc/heptanes and afforded pure 4 (>99%, HPLC area%). The hydrodebromination of 4 using 5−20% Pd/C as the catalyst resulted in a mixture of 5/5a/5b/5c, and the ratio of 5/ 5a/5b/5c changed notably under different reaction conditions. It was very important to identify a set of conditions that would afford the highest yield of 5 vs the three side products 5a/5b/ 5c, especially deschloro-5b. The presence of 5b in 5 would originate the side product 27 (Figure 1) after going through the necessary steps in Scheme 3 or Scheme 5, and the side product 27 is also difficult to remove from the final compound 26. A number of variables (such as catalyst, reaction time, temper-

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RESULTS AND DISCUSSION By working together with medicinal chemistry, our goals for the 50-g campaign of 26 were: (1) to quickly develop a N1-selective and scalable process for intermediate aldehyde 5, (2) to © XXXX American Chemical Society

Received: November 14, 2013

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Scheme 1. Original discovery route

Scheme 2. Preparation of compound 5

EtOAc and EtOH (1:1, vol/vol) at 20 °C for 4 h. The water content in Pd/C catalyst was identified as the most important factor that governs the ratio of 5/5a/5b/5c with a 5% Pd/C catalyst containing 35.6% of H2O producing the most acceptable mixture (typically, in a ratio of ∼90%/∼1%/∼9%/

ature, hydrogen pressure, etc.) that would impact the ratio 5/ 5a/5b/5c were investigated extensively (Table 1). The best reaction conditions for this hydrodebromination was found to be 5% Pd/C under low hydrogen pressure (5 psi) in the presence of DIPEA (3.1 equiv) with the mixed solvents of B

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with NaHSO3 to remove excess m-CPBA and other peroxide byproducts, followed by a 10% NaOH wash to remove 2chlorobenzoic acid. Addition of 10% excess m-CPBA or extending the reaction time to 26 h did not push the reaction to 100% conversion. Epoxide 9 was used without further purification in next step after drying, since the presence of small amount of 8 in 9 did not impact epoxide-ring-opening with TZD derivative 7. Other alternative reagents/conditions for stereoselective epoxidation of 8 were not investigated.5e In order to develop a more regioselective and scalable epoxide-opening condition of 9 to replace the original microwave promoted conditions, a number of Lewis acidcatalyzed conditions were studied (Table 2). In general, all Lewis acid-catalyzed conditions produced the desired 3-OH 10 preferably over the undesired 4-OH 11. Mg(ClO4)2 in DMF produced the best results and afforded a mixture of 10/11 in a ratio of 3.2−4.0/1. The solvent DMF was optimum as there was only a small amount (≤3 HPLC area%) of products 10/11 when the reaction was conducted in either refluxing MeCN, DCE, dioxane, isopropyl acetate, or MeTHF. Other regioselective epoxide ring-opening conditions6 were not investigated. After the compatibility of Mg(ClO4)2 in DMF as well as the thermal stability of the mixture of epoxide 9 and Mg(ClO4)2 in DMF were checked by TGA that indicated no unexpected exothermal decompositions. The conditions of Mg(ClO4)2 in DMF were chosen for scale-up on the strength of the short reaction time, high ratio of product/regioisomer, and easy workup. The DMF was removed from the 10/11 mixture by diluting with water that resulted in >100% mass recovered of crude 10/11. Since it was difficult to separate 10 from 11 by normal-phase column chromatography, the mixture was used “as is” for the conversion of hydroxyl groups to the corresponding fluoro

Figure 1.

∼1%) as monitored by HPLC and LC/MS. Compound 5 was isolated in 77% yield with 95−97% of 5 (plus 3−5% of 5b) after crystallization of the mixture in EtOAc/heptanes that completely removed 5a and 5c (97% chemical purity and 99.5% de, which was used in the next step without further purification. For the reductive N-methylation, the (3R,4R)-23 TFA salt was treated in situ with 1.23 equiv of Na2CO3 to give free base 23, which was subsequently treated with HCHO/H2O and NaHB(OAc)3 (both reduced from 2.0 equiv to 1.35 equiv) to afford 83−89% isolated yield of (3R,4R)-1-methyl 24 with 98% chemical purity and diastereomeric purity of 99.2% de. Knoevenagel condensation of (3R,4R)-24 was performed in the dark with an equal equivalent of 5 (98.8% wt% with 1.2% deschloro side product 5b) in the presence of 0.53 equiv of piperidine in toluene at 110−112 °C over 72−86 h. The resulting desired 26 free base was obtained in 82−91% isolated yield with 99.5% wt% and 99.7% de simply after collecting the solid 26 from the cold reaction mixture and washing with hexanes. The photoisomerization of (Z)-26 to E-byproduct was minimized from previously ∼3.0% to ≤0.3% as determined by both RP-HPLC and chiral HPLC. Finally, 26 free base in THF was converted to its HCl salt after treatment with 2.0 equiv of 1.0 M HCl in Et2O to afford 26 HCl salt in 97% isolated yield with 99.7% wt% and 99.7% de as an amorphous solid.

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CONCLUSIONS

In summary, a reproducible process was developed for largescale production of 26, which afforded 800 g of 26 HCl salt was prepared in 9% overall yield with 99.7% chemical purity and ≥99.5% de over eight synthetic steps, with only one chiral chromatography required for the separation of (3R,4R)-21 from (3S,4S)-22. The 500-g route is improved as compared to the initial campaign in that: (1) formaldehyde is now introduced earlier in the process, (2) the required amount of costly aldehyde 5 is reduced by six, and (3) the 500-g route results in much less (≤0.3%) of the undesired E-isomer. This process has been repeated successfully at the same scale.

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EXPERIMENTAL SECTION The purity/impurity ratio of compound 9 was determined on an Agilent 6890 series GC System with 7639 series injector and a HP-5 5% phenyl methyl siloxane column (dimensions = capillary 30.0 m × 320 μm × 0.25 μm nominal), oven temperature = 50 to 210 °C, ramp = 10 °C/min, detector heater = 250 °C; H2 flow = 40 mL/min, air flow = 450 mL/ min, N2 flow = 25 mL/min. The purity/impurity ratios of all compounds were determined on an Agilent series 1100 system at 254 nm (UVmax) and with specified columns and conditions as described below. A Phenomenex Luna C18 (2) column (4.6 mm ID × 50 mm, 5.0 μm) was used for analyzing compounds 2, 4, 5, and 26 (as well as 26·HCl salt) at 35 °C with using solvents: A = H2O + 0.1% TFA, B = CH3CN + 0.1%TFA at flow rates of 1.0 mL/ min. The run times for compounds 2, 4, and 5 were 10.0 min with Gradient: B 15%/0.0 min, B 50%/1.0 min, B 85%/4.0 min, B 85%/8.0 min, B 15%/10.0 min. The run times for compound 26 were 12.0 min with Gradient: B 15%/0.0 min, B 50%/1.0 min, B 85%/4.0 min, B 85%/10.0 min, B 15%/12.0 min. The run times for compound 24 were 20 min with solvents: A = H2O, B = CH3CN and Gradient: B 30%/0.0 min, B 70%/6.0 min, B 90%/12.0 min, B 90%/18.0 min, B 30%/20.0 min. A Zorbax Eclipse XDB-phenyl column (4.6 mm ID × 50 mm, 3.5 μm) was used for analyzing compounds 17, 19, 21, and 23 TFA salt at 35 °C with solvents: A = H2O + 0.1% TFA, B = CH3CN + 0.1%TFA at flow rate of 1.0 mL/min. The run times for compound 17 were 26.0 min with Gradient: B 6% /0.0 min, B 20%/20.0 min, B 90%/25.0 min, B 6%/26 min. The run times for compounds 19, 21, and 23 TFA salt were 20.0 min with Gradient: B 6%/0.0 min, B 30%/8.0 min, B 90%/18.0 min, B 6%/20 min. An analytical ChiraPack AD column (4.6 mm ID × 250 mm, 3.5 μm) was used to determine the optical purity of compounds 17, 19, and 21 at 25 °C with solvents: A = EtOH + 0.05% DEA, B = heptanes (A/B = 7/3). The run time was 30.0 min with an isocratic flow rate of 0.6 mL/min. An analytical ChiraPack AD-H column (4.6 mm ID × 250 mm, 3.5 μm) was used to determine the optical purity of compounds 23 and 24 at 25 °C with solvents: A = EtOH + 0.1% DEA, B = heptanes (A/B = 9/1). The run time was 30.0 min with an isocratic flow rate of 1.0 mL/min, whereas for compound 26 and 26·HCl salt it was with solvents: A = EtOH + 0.05% DEA, B = heptanes (A/B = 6/4). The run time was 50.0 min with an isocratic flow rate of 0.6 mL/min. 3-Bromo-1H-indazole (2). 1H-Indazole-5-carbaldehyde (1) (250.0 g, 1.71 mol) and acetonitrile (5.00 L) were stirred for 40 min at 20 °C until it became a clear solution. NF

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containing 35.6% of water) was introduced. The flask was set at 5 psi at 20 °C for 3 h and the progress of the reaction was monitored by HPLC and LC/MS (until the starting 4 was ≤1%). The catalyst was removed by filtering through a Celite 545 pad, which was washed with EtOAc (120 mL × 3). The combined filtrate was concentrated at 66 °C under house vacuum to give the crude material (96.3 g that contained DIPEA+Br− salt) which was redissolved in EtOAc (660 mL) and washed with D.I. H2O (360 mL × 2). The organic phase was separated and concentrated at 66 °C at 10 mmHg to give 56.1 g (97% isolated yield, 89% of 5, 1.6% of 4, a total 9.4% of reduced alcohol 5a and des-chloro 5b, and