4-(4-{3-[4-chloro-3-(trifluoromethyl)phenyl]ureido}phenoxy)-Λ/²-methylpyridine-2- carboxamide is commonly known as sorafenib (I). Sorafenib is prepared as its tosylate salt. Sorafenib blocks the enzyme RAF kinase, a critical component of the RAF/MEK/ERK signaling pathway that controls cell division and proliferation; in addition, sorafenib inhibits the VEGFR-2/PDGFR-beta signaling cascade, thereby blocking tumor angiogenesis.

Sorafenib, marketed as Nexavar by Bayer, is a drug approved for the treatment of advanced renal cell carcinoma (primary kidney cancer). It has also received “Fast Track” designation by the FDA for the treatment of advanced hepatocellular carcinoma (primary liver cancer). It is a small molecular inhibitor of Raf kinase, PDGF (platelet-derived growth factor), VEGF receptor 2 & 3 kinases and c Kit the receptor for Stem cell factor.

Sorafenib and pharmaceutically acceptable salts thereof is disclosed in WO0042012. Sorafenib is also disclosed in WO0041698. Both these patents disclose processes for the preparation of sorafenib.

WO0042012 and WO0041698 describe the process as given in scheme I which comprises reacting picolinic acid (II) with thionyl chloride in dimethyl formamide (DMF) to form acid chloride salt (III). This salt is then reacted with methylamine dissolved in tetrahydrofuran (THF) to give carboxamide (IV). This carboxamide when further reacted with 4- aminophenol in anhydrous DMF and potassium tert-butoxide 4-(2-(N-methylcarbamoyl)-4- pyridyloxy)aniline (V) is formed. Subsequent reaction of this aniline with 4-chloro-3- (trifluoromethyl) phenyl isocyanate (Vl) in methylene chloride yields sorafenib (I). The reaction is represented by Scheme I as given below.

Scheme I

Picolini

Sorafenib (I)

WO2006034796 also discloses a process for the preparation of sorafenib and its tosylate salt. The process comprises reacting 2-picolinic acid (II) with thionyl chloride in a solvent inert toward thionyl chloride without using dimethyl formamide to form acid chloride salt (III). This acid salt on further reaction with aqueous solution methylamine or gaseous methylamine gives compound (IV). Compound (IV) is then reacted with 4-aminophenol with addition of a carbonate salt in the presence of a base to yield compound (V).

Compound (V) can also be obtained by reacting compound (IV) with 4-aminophenol in the presence of water with addition of a phase transfer catalyst. Compound (V) when reacted with 4-chloro-3-(trifluoromethyl) phenyl isocyanate (Vl) in a non-chlorinated organic solvent, inert towards isocyanate gives sorafenib (I). Sorafenib by admixing with p- toluenesulfonic acid in a polar solvent gives sorafenib tosylate (VII). The reaction is represented by Scheme Il as given below.

Scheme Il

P

A key step in the synthesis of sorafenib is the formation of the urea bond. The processes disclosed in the prior art involve reactions of an isocyanate with an amine. These isocyanate compounds though commercially available are very expensive. Further synthesis of isocyanate is very difficult which requires careful and skillful handling of reagents.

Isocyanate is prepared by reaction of an amine with phosgene or a phosgene equivalent, such as bis(trichloromethyl) carbonate (triphosgene) or trichloromethyl chloroformate (diphosgene). Isocyanate can also be prepared by using a hazardous reagent such as an azide. Also, the process for preparation of an isocyanate requires harsh reaction conditions such as strong acid, higher temperature etc. Further, this isocyanate is reacted with an amine to give urea.

Reactions of isocyanates suffer from one or more disadvantages. For example phosgene or phosgene equivalents are hazardous and dangerous to use and handle on a large scale. These reagents are also not environment friendly. Isocyanates themselves are thermally unstable compounds and undergo decomposition on storage and they are incompatible with a number of organic compounds. Thus, the use of isocyanate is not well suited for industrial scale application.

Sorafenib and its pharmaceutically acceptable salts and solvates are reported for the first time in WO0041698 (corresponding US 03139605) by Bayer. In the literature only one route is disclosed for the preparation of sorafenib. According to this route (Scheme-I), picolinic acid of formula III is reacted with thionyl chloride to give the 4-chloro derivative which on treatment

VII

Scheme-I with methanol gave the methyl ester of formula V. Compound of formula V is reacted with methylamine to get the corresponding amide of formula VL Compound of formula VI is reacted with 4-aminophenol to get the ether derivative of formula VII. Compound of formula VII is reacted with 4-chloro-3-trifluoromethylphenylisocyante to get sorafenib base of formula I. Overall yield of sorafenib in this process is 10% from commercially available 2-picolinic acid of formula II. Main drawback in this process is chromatographic purification of the intermediates involved in the process and low yield at every step.

Donald Bankston’s (Org. Proc. Res. Dev., 2002, 6, 777-781) development of an improved synthesis of the above basic route afforded sorafenib in an overall yield of 63% without involving any chromatographic purification. Process improvements like reduction of time in thionyl chloride reaction; avoid the isolation of intermediates of formulae IV and V₅ reduction of base quantity in p-aminophenol reaction, etc lead to the simplification of process and improvement in yield of final compound of formula I.

Above mentioned improvements could not reduce the number of steps in making sorafenib of formula-I. In the first step all the raw materials are charged and heated to target temperature (72°C). Such a process on commercial scale will lead to sudden evolution of gas emissions such as sulfur dioxide and hydrogen chloride. Also, in the aminophenol reaction two bases (potassium carbonate and potassium t-butoxide) were used in large excess to accomplish the required transformation.

A scalable process for the preparation of sorafenib is disclosed in WO2006034796. In this process also above mentioned chemistry is used in making sorafenib of formula I. In the first step, catalytic quantity. of DMF used in the prior art process is replaced with reagents like hydrogen bromide, thionyl bromide and sodium bromide. Yield of required product remained same without any advantages from newly introduced corrosive reagents. Process improvements like change of solvents, reagents, etc were applied in subsequent steps making the process scalable. Overall yield of sorafenib is increased to 74% from the prior art 63% yield. Purity of sorafenib is only 95% and was obtained as light brown colored solid.

Main drawbacks in this process are production of low quality sorafenib and requirement of corrosive and difficult to handle reagents such as thionyl bromide and hydrogen bromide. Also, there is no major improvement in the yield of sorafenib.

Sorafenib tosylate ( Brand name: Nexavar ®, BAY 43-9006 other name, Chinese name: Nexavar, sorafenib, Leisha Wa) was Approved by U.S. FDA for the treatment of advanced kidney cancer in 2005 and liver cancer in 2007 .

Sorafenib, co-Developed and co-marketed by Germany-based Bayer AG and South San Francisco-based Onyx Pharmaceuticals , is an Oral Multi-kinase inhibitor for VEGFR1, VEGFR2, VEGFR3, PDGFRbeta, Kit, RET and Raf-1.

In March 2012 Indian drugmaker Natco Pharma received the first compulsory license ever from Indian Patent Office to make a generic Version of Bayer’s Nexavar despite the FACT that Nexavar is still on Patent. This Decision was based on the Bayer Drug being too expensive to most patients. The Nexavar price is expected to drop from $ 5,500 per person each month to $ 175, a 97 percent decline. The drug generated $ 934 million in global sales in 2010, according to India’s Patent Office.

Sorafenib tosylate

Chemical Name: 4-Methyl-3-((4 – (3-pyridinyl)-2-pyrimidinyl) amino)-N-(5 – (4-methyl-1H-imidazol-1-yl) -3 – (trifluoromethyl) phenyl) benzamide monomethanesulfonate, Sorafenib tosylate

CAS Number 475207-59-1 (Sorafenib tosylate ) , 284461-73-0 (Sorafenib)

References for the Preparation of Sorafenib References

1) Bernd Riedl, Jacques Dumas, Uday Khire, Timothy B. Lowinger, William J. Scott, Roger A. Smith, Jill E. Wood, Mary-Katherine Monahan, Reina Natero, Joel Renick, Robert N. Sibley; Omega-carboxyaryl Substituted diphenyl Ureas as RAF kinase inhibitors ; U.S. Patent numberUS7235576
2) Rossetto, Pierluigi; Macdonald, Peter, Lindsay; Canavesi, Augusto; Process for preparation of sorafenib and Intermediates thereof , PCT Int. Appl., WO2009111061
3) Lögers, Michael; gehring, Reinhold; Kuhn, Oliver; Matthäus, Mike; Mohrs, Klaus; müller-gliemann, Matthias; Stiehl, jürgen; berwe, Mathias; Lenz, Jana; Heilmann, Werner; Process for the preparation of 4 – {4 – [( {[4-chloro-3-(TRIFLUOROMETHYL) phenyl] amino} carbonyl) amino] phenoxy}-N-methylpyridine-2-carboxamide , PCT Int. Appl., WO2006034796
4) Shikai Xiang, Liu Qingwei, Xieyou Rong, sorafenib preparation methods, invention patent application Publication No. CN102311384 , Application No. CN201010212039
5) Zhao multiply there, Chenlin Jie, Xu Xu, MASS MEDIA Ji Yafei; sorafenib tosylate synthesis ,Chinese Journal of Pharmaceuticals , 2007 (9): 614 -616

Preparation of Sorafenib Tosylate (Nexavar) Nexavar, sorafenib Preparation of methyl sulfonate

Sorafenib (Sorafenib) chemical name 4 – {4 – [({[4 – chloro -3 – (trifluoromethyl) phenyl] amino} carbonyl) amino] phenoxy}-N-methyl-pyridine -2 – formamide by Bayer (Bayer) research and development, in 2005 the U.S. Food and Drug Administration (FDA) approval. Trade name Nexavar (Nexavar). This product is an oral multi-kinase inhibitor, for the treatment of liver cancer and kidney cancer.

Indian Patent Office in March this year for Bayer’s Nexavar in liver and kidney cancer drugs (Nexavar) has released a landmark “compulsory licensing” (compulsory license). Indian Patent Office that due to the high price Nexavar in India, the vast majority of patients can not afford the drug locally, thus requiring local Indian pharmaceutical company Natco cheap Nexavar sales. Nexavar in 2017 before patent expiry, Natco pay only Bayer’s pharmaceutical sales to 6% royalties. The move to make Nexavar patent drug prices, the supply price from $ 5,500 per month dropped to $ 175, the price reduction of 97%. Compulsory licensing in India for other life-saving drugs and patent medicines overpriced open a road, the Indian Patent Office through this decision made it clear that the patent monopoly does not guarantee that the price is too high. Nexavar is a fight against advanced renal cell carcinoma, liver cancer cure. In China, a box of 60 capsules of Nexavar price of more than 25,000 yuan. In accordance with the recommended dose, which barely enough to eat half of patients with advanced cancer. In September this year India a patent court rejected Bayer Group in India cheap drugmaker emergency appeal. Indian government to refuse patent medicine overpriced undo “compulsory licensing rules,” allowing the production of generic drugs Nexavar.

Sorafenat by Natco – Sorafenib – Nexavar – India natco Nexavar

Chemical Synthesis of  Sorafenib Tosylate (Nexavar)

Sorafenib tosylate (brand name :Nexavar®, other name BAY 43-9006, was approved by US FDA for the treatment of kidney cancer in 2005 and advanced liver cancer in 2007.

US Patent US7235576, WO2006034796, WO2009111061 and Faming Zhuanli Shenqing(CN102311384) disclosed processes for preparation of sorafenib base and its salt sorafenib tosylate.

References

1)Bernd Riedl, Jacques Dumas, Uday Khire, Timothy B. Lowinger, William J. Scott, Roger A. Smith, Jill E. Wood, Mary-Katherine Monahan, Reina Natero, Joel Renick, Robert N. Sibley; Omega-carboxyaryl substituted diphenyl ureas as raf kinase inhibitors; US patent numberUS7235576
2)Rossetto, pierluigi; Macdonald, peter, lindsay; Canavesi, augusto; Process for preparation of sorafenib and intermediates thereof, PCT Int. Appl., WO2009111061
3)Lögers, michael; gehring, reinhold; kuhn, oliver; matthäus, mike; mohrs, klaus; müller-gliemann, matthias; stiehl, jürgen; berwe, mathias; lenz, jana; heilmann, werner; Process for the preparation of 4-{4-[({[4-chloro-3-(trifluoromethyl)phenyl]amino}carbonyl)amino]phenoxy}-n-methylpyridine-2-carboxamide, PCT Int. Appl., WO2006034796CN102311384, CN201010212039

Full Experimental Details for the preparation of Sorafenib Tosylate (Nexavar) 

Synthesis of 4-(2-(N-methylcarbamoyl)-4-pyridyloxy)aniline.

A solution of 4-aminophenol (9.60 g, 88.0 mmol) in anh. DMF (150 mL) was treated with potassium tert-butoxide (10.29 g, 91.7 mmol), and the reddish-brown mixture was stirred at room temp. for 2 h. The contents were treated with 4-chloro- N -methyl-2-pyridinecarboxamide (15.0 g, 87.9mmol) and K2CO3 (6.50 g, 47.0 mmol) and then heated at 80°C. for 8 h. The mixture was cooled to room temp. and separated between EtOAc (500 mL) and a saturated NaCl solution (500 mL). The aqueous phase was back-extracted with EtOAc (300 mL). The combined organic layers were washed with a saturated NaCl solution (4×1000 mL), dried (Na2SO4) and concentrated under reduced pressure. The resulting solids were dried under reduced pressure at 35°C. for 3 h to afford 4-(2-(N-methylcarbamoyl)-4-pyridyloxy)aniline as a light-brown solid 17.9 g, 84%):. 1H-NMR (DMSO-d6) δ 2.77 (d, J = 4.8 Hz, 3H), 5.17 (br s, 2H), 6.64, 6.86 (AA’BB’ quartet, J = 8.4 Hz, 4H), 7.06 (dd, J = 5.5, 2.5 Hz, 1H), 7.33 (d, J = 2.5 Hz, 1H), 8.44 (d, J = 5.5 Hz; 1H), 8.73 (br d, 1H); HPLC ES-MS m/z 244 ((M+H)+).

Synthesis of 4-{4-[({[4-Chloro-3-(trifluoromethyl)phenyl]amino}carbonyl)amino]phenoxy}-N-methylpyridine-2-carboxamide (sorafenib)

4-(4-Aminophenoxy)-N-methyl-2-pyridinecarboxamide (52.3 kg, 215 mol) is suspended in ethyl acetate (146 kg) and the suspension is heated to approx. 40° C. 4-Chloro-3-trifluoromethylphenyl isocyanate (50 kg, 226 mol), dissolved in ethyl acetate (58 kg), is then added to such a degree that the temperature is kept below 60° C. After cooling to 20° C. within 1 h, the mixture is stirred for a further 30 min and the product is filtered off. After washing with ethyl acetate (30 kg), the product is dried under reduced pressure (50° C., 80 mbar). 93 kg (93% of theory) of the title compound are obtained as colorless to slightly brownish crystals. m.p. 206-208° C. 1H-NMR (DMSO-d6, 500 MHz): δ =2.79 (d, J=4.4 Hz, 3H, NCH3); 7.16 (dd, J=2.5, 5.6 Hz, 1H, 5-H); 7.18 (d, J=8.8 Hz, 2H, 3′-H, 5′-H); 7.38 (d, J=2.4 Hz, 1H, 3-H); 7.60-7.68 (m, 4H, 2′-H, 6′-H, 5″-H, 6″-H); 8.13 (d, J=1.9 Hz, 1H, 2″-H); 8.51 (d, J=5.6 Hz, 1H, 6-H); 8.81 (d, J=4.5 Hz, 1H, NHCH3); 9.05 (br. s, 1H, NHCO); 9.25 (br. s, 1H, NHCO) MS (ESI, CH3CN/H2O): m/e=465 [M+H]+.

Synthesis of Sorafenib Tosylate (Nexavar)

4-(4-{3-[4-chloro-3-(trifluoromethyl)phenyl]ureido}phenoxy)-N2-methylpyridine-2-carboxamide (sorafenib) (50g, 0.1076 mol) is suspended in ethyl acetate (500 g) and water (10g). The mixture is heated to 69°C within 0.5 h, and a filtered solution of p-toluenesulfonic acid monohydrate (3.26 g, 0.017 mol) in a mixture of water (0.65 g) and ethyl acetate (7.2 g) is added. After filtration a filtered solution of p-toluenesulfonic acid monohydrate (22g, 0.11 mol) in a mixture of ethyl acetate (48 g) and water (4.34 g) is added. The mixture is cooled to 23°C within 2 h. The product is filtered off, washed twice with ethyl acetate (92.5 g each time) and dried under reduced pressure. The sorafenib tosylate (65.5 g, 96% of theory) is obtained as colorless to slightly brownish crystals.

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http://www.google.com/patents/EP2195286A2?cl=en

Example 22: Synthesis of Sorafenib

Phenyl 4-chloro-3-(trifluoromethyl)phenylcarbamate (100 g, 0.3174 mol) and 4-(4- aminophenoxy)-N-methylpicolinamide (77.14 g, 0.3174 mol) were dissolved in N₁N- dimethyl formamide (300 ml) to obtain a clear reaction mass. The reaction mass was agitated at 40-45⁰C for 2-3 hours, cooled to room temperature and diluted with ethyl acetate (1000 ml). The organic layer was washed with water (250 ml) followed by 1N HCI (250ml) and finally with brine (250 ml). The organic layer was separated, dried over sodium sulfate and degassed to obtain solid. This solid was stripped with ethyl acetate and finally slurried in ethyl acetate (1000 ml) at room temperature. It was then filtered and vacuum dried to give (118 g) of 4-(4-(3-(4-chloro-3- (trifluoromethyl)phenyl)ureido)phenoxy)-N-methylpicolinamide (sorafenib base).

Example 23: Synthesis of 1-(4-chloro-3-(trifluoromethyl)phenyl)urea (Compound 4)

Sodium cyanate (1.7 g, 0.02mol) was dissolved in water (17ml) at room temperature to obtain a clear solution. This solution was then charged drop wise to the clear solution of 3- trifluoromethyl-4-chloroaniline (5 g, 0.025 mol) in acetic acid (25 ml) at 40°C-45°C within 1- 2 hours. The reaction mass was agitated for whole day and cooled gradually to room temperature. The obtained solid was filtered washed with water and vacuum dried at 50⁰C to afford the desired product (5.8 g) i.e. 1-(4-chloro-3-(trifluoromethyl)phenyl)urea.

Example 24: Synthesis of Sorafenib

1-(4-chloro-3-(trifluoromethyl) phenyl)urea (15 g, 0.0628 mol), 1 ,8- diazabicyclo[5.4.0]undec-7-ene (11.75 ml, 0.078 mol) and 4-(4-aminophenoxy)-N- methylpicolinamide (15.27 g, 0.0628 mol) were mixed with dimethyl sulfoxide (45 ml) and the reaction mass was then heated to 110-120⁰C for 12-18 hours. The reaction mass was cooled to room temperature and quenched in water (250 ml). The quenched mass was extracted repeatedly with ethyl acetate and the combined ethyl acetate layer was then back washed with water. It was dried over sodium sulfate and evaporated under vacuum to obtain solid. The obtained solid was slurried in acetonitrile (150 ml) at ambient temperature and filtered to give 4-(4-(3-(4-chloro-3-(trifluoromethyl) phenyl) ureido) phenoxy)-N-methylpicolinamide (sorafenib base) (17.5 g).

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http://www.google.com/patents/WO2009054004A2?cl=en

http://worldwide.espacenet.com/publicationDetails/biblio?CC=WO&NR=2009054004A2&KC=A2&FT=D&date=20090430&DB=EPODOC&locale=en_gb

EXAMPLES

Example 1

Preparation of l-(4-chloro-3-(trifluoromethyl)phenyI)-3-(4-hydroxyphenyl)urea Into a 250 ml, four-necked RB flask was charged 1O g of 4-aminophenol and 100 ml of toluene. A solution of 4-chloro-3-(trifluoromethyl)phenyl isocyante (20.4 g) in toluene (50 ml) was added to the reaction mass at 25-30⁰C. The reaction mass was stirred at room temperature for 16 h. The reaction mass was filtered and washed the. solid with 50 ml of toluene. The wet material was dried in the oven at 50-60°C to get 29.8 g of title compound as white solid. M.P. is 218-222°C. IR (KBr): 3306, 1673, 1625, 1590, 1560, 1517, 1482, 1435, 1404, 1328, 1261, 1182, 1160, 1146, 1125, 1095, 1032, 884, 849, 832, 812, 766, 746, 724, 683, 539 and 434 cm^“1.

Example 2 Preparation of sorafenib tosylate

Into a 100 ml, three-necked RB flask was charged 2.0 g of l-(4-chloro-3- (trifluoromethyl)-phenyl)-3-(4-hydroxyphenyl)urea and 10 ml of DMF. Potassium tert- butoxide (2.3 g) was added to the reaction mass and stirred for 45 min at RT. 4-Chlro-N- methylpicolinamide (1.14 g) and potassium carbonate (0.42 g) were added to the reaction mass and heated to 80°C. The reaction mass was maintained at 80-85°C for 8 h and cooled to 30°C. The reaction mass was poured into water and extracted with ethyl acetate. Ethyl acetate layer was washed with water, brine and dried over sodium sulphate. Solvent was distilled of under reduced pressure.

The crude compound (4.7 g) was dissolved in 10 ml of IPA and added 1.9 g of p- toluenesulfonic acid. The reaction mass was stirred at RT for 15 h and filtered. The wet solid was washed with 10 ml of IPA and dried at 50-60°C to get 3.4 g of title compound as off-white crystalline solid.

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A Scaleable Synthesis of BAY 43-9006:  A Potent Raf Kinase Inhibitor for the Treatment of Cancer

http://pubs.acs.org/doi/abs/10.1021/op020205n

Urea 3 (BAY 43–9006), a potent Raf kinase inhibitor, was prepared in four steps with an overall yield of 63%. Significant process research enabled isolation of each intermediate and target without chromatographic purification, and overall yield increases >50% were observed compared to those from previous methods. This report focuses on improved synthetic strategies for production of scaled quantities of 3 for preclinical, toxicological studies. These improvements may be useful to assemble other urea targets as potential therapeutic agents to combat cancer.

References

External links

• Nexavar.com – Manufacturer’s website
• Prescribing Information – includes data from the key studies justifying the use of sorafenib for the treatment of kidney cancer (particularly clear cell renal cell carcinoma, which is associated with the von Hippel-Lindau gene)
• Patient Information from FDA
• Sorafenib in Treating Patients With Soft Tissue Sarcomas
• Sorafenib Sunitinib differences – diagram
• ClinicalTrials.gov NCT00217399  – Sorafenib and Anastrozole in Treating Postmenopausal Women With Metastatic Breast Cancer
• Cipla launches Nexavar generic at 1/10 of Bayer’s price