Rilpivirine

500287-72-9  cas no

4-{[4-({4-[(E)-2-cyanovinyl]-2,6-dimethylphenyl}amino)pyrimidin-2-yl]amino}benzonitrile

Rilpivirine (TMC278, trade name Edurant) is a pharmaceutical drug, developed byTibotec, for the treatment of HIV infection.^[1][2] It is a second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) with higher potency, longer half-life and reducedside-effect profile compared with older NNRTIs, such as efavirenz.^[3][4]

Rilpivirine entered phase III clinical trials in April 2008,^[5][6] and was approved for use in the United States in May 2011.^[7] A fixed-dose drug combining rilpivirine with emtricitabine andtenofovir, was approved by the U.S. Food and Drug Administration in August 2011 under the brand name Complera.^[8]

Like etravirine, a second-generation NNRTI approved in 2008, rilpivirine is a diarylpyrimidine(DAPY). Rilpivirine in combination with emtricitabine and tenofovir has been shown to have higher rates of virologic failure than Atripla in patients with baseline HIV viral loads greater than 100,000 copies.

• Rilpivirine bound to proteins in the PDB

EDURANT (rilpivirine, Janssen Therapeutics) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) of human immunodeficiency virus type 1 (HIV-1). EDURANT is available as a white to off-white, film-coated, round, biconvex, 6.4 mm tablet for oral administration. Each tablet contains 27.5 mg of rilpivirine hydrochloride, which is equivalent to 25 mg of rilpivirine.

The chemical name for rilpivirine hydrochloride is 4-[[4-[[4-[(E)-2-cyanoethenyl]-2,6-dimethylphenyl]amino]2-pyrimidinyl]amino]benzonitrile monohydrochloride. Its molecular formula is C₂₂H₁₈N₆ • HCl and its molecular weight is 402.88. Rilpivirine hydrochloride has the following structural formula:

Rilpivirine hydrochloride is a white to almost white powder. Rilpivirine hydrochloride is practically insoluble in water over a wide pH range.

Each EDURANT tablet also contains the inactive ingredients croscarmellose sodium, lactose monohydrate, magnesium stearate, polysorbate 20, povidone K30 and silicified microcrystalline cellulose. The tablet coating contains hypromellose 2910 6 mPa.s, lactose monohydrate, PEG 3000, titanium dioxide and triacetin.

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papers

Sun, et al.: J. Med. Chem., 41, 4648 (1998),

Kashiwada, et al.: Bioorg. Med. Chem. Lett., 11, 183 (2001)

Journal of Medicinal Chemistry, 2005 ,  vol. 48,  6  , pg. 2072 – 2079

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patents

WO201356003, WO200635067,

WO2013038425 

The following PCT Publications describe the synthesis of Rilpivirine:

WO03016306, WO2005021001, WO2006024667, WO2006024668, W02994916581, WO2009007441, WO2006125809, and WO2005123662. [0006] Crystalline Rilpivirine base Forms I and II are described in the US Patent

Publication: US2010189796. Crystalline Rilpivirine HC1, Forms A, B, C, and D, are described in the US Patent Publications: US2009/012108, and US2011/0008434. Rilpivirine fumarate and a synthesis thereof are disclosed in WO2006024667.

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Rilpivirine and its hydrochloride salt were disclosed in U.S. patent no. 7,125,879.Process for the preparation of rilpivirine was disclosed in U.S. patent no. 7,399,856 (’856 patent). According to the ’856 patent, rilpivirine can be prepared by reacting the (E)-3-(4-amino-3,5-dimethylphenyI)acrylonitrile hydrochloride of formula II with 4-(4-chloropyrimidin-2-ylamino)benzonitrile of formula III-a in the presence of potassium carbonate and acetonitrile under reflux for 69 hours. The synthetic procedure is illustrated in scheme I, below: Scheme 1 Process for the preparation of rilpivirine was disclosed in U.S. patent no. 7,705,148 (Ί48 patent). According to the Ί48 patent, rilpivirine can be prepared by reacting the 4-[[4-[[4-bromo-2,6-dimethylphenyl]amino]-2- pyrimidinyl]amino]benzonitrile with acrylonitrile in the presence of palladium acetate, Ν,Ν-diethylethanamine and tris(2-methylphenyl)phosphine in acetonitrile. According to the Ί48 patent, rilpivirine can be prepared by reacting the compound of formula IV with 4-(4-chloropyrimidin-2-ylamino)benzonitrile formula Ill-a in the presence of hydrochloric acid and n-propanol to obtain a compound of formula Vll, and then the compound was treated with acetonitrile and potassium carbonate under reflux for 69 hours. The synthetic procedure is illustrated in scheme II, below: Rilpivirine Scheme II U.S. patent no. 7,563,922 disclosed a process for the preparation of (E)-3-(4- amino-3,5-dimethylphenyl)acrylonitrile hydrochloride. According to the patent, (E)-3-(4- amino-3,5-dimethylphenyl)acrylonitrile hydrochloride can be prepared by reacting the 4- iodo-2,6-dimethyl-benzenamine in Ν,Ν-dimethylacetamide with acrylonitrile in the presence of sodium acetate and toluene, and then the solid thus obtained was reacted with hydrochloric acid in 2-propanol in the presence of ethanol and diisopropyl ether. U.S. patent no. 7,956,063 described a polymorphic Form A, Form B, Form C and Form D of rilpivirine hydrochloride. An unpublished application, IN 1415/CHE/201 1 assigned to Hetero Research Foundation discloses a process for the preparation of rilpivirine. According to the application, rilpivirine can be prepared by reacting the 4-(4-chloropyrimidin-2- ylamino)benzonitrile with (E)-3-(4-amino-3,5-dimethylphenyl)acrylonitrile hydrochloride in the presence of p-toluene sulfonic acid monohydrate and 1 ,4-dioxane. It has been found that the rilpivirine produced according to the prior art procedures results in low yields.

The synthesis is as follows:

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Rilpivirine, which is chemically known as 4-{[4-({4-[(lE)-2-cyanoethenyl]-2,6- dimethylphenyl} amino) pyrimidin-2-yl]amino}benzonitrile, is a non-nucleoside reverse transcriptase inhibitor (NNRTI) and exhibits human immunodeficiency virus (HIV) replication inhibiting properties. Rilpivirine is used as its hydrochloride salt in the anti-HIV formulations.

Conventionally, various processes followed for the synthesis of Rilpivirine hydrochloride (I), generally involve preparation of the key intermediate, (E)-4-(2- cyanoemenyl)-2,6-dimethylphenylamine hydrochloride of formula (II).

(E)-4-(2-cyanoethenyl)-2,6-dimethylphenylamine hydrochloride (II)

WO 03/016306 first disclosed the synthesis of Rilpivirine involving different routes for synthesis of 4-(2-cyanoethenyl)-2,6-dimethylphenylamine. The first route involved protection of the amino group of 4-bromo-2,6-dimemylphenylarnine by converting to Ν,Ν-dimethylmethanimidamide, followed by formylation involving n- butyl lithium and dimethylformamide. The resulting formyl derivative was treated with diethyl(cyanomethyl) phosphonate to give the cyanoethenyl compound which was deprotected using zinc chloride to yield the cyanoethenylphenylamine intermediate having an undisclosed E/Z ratio. This route involved an elaborate sequence of synthesis comprising protection of amine by its conversion into imide, use of a highly moisture sensitive and pyrophoric base such as butyl lithium and a low yielding formylation reaction. All these factors made the process highly unviable on industrial scale.

The second route disclosed in WO 03/016306 employed 4-iodo-2,6- dimethylphenylamine as a starting material for synthesis of cyanoemenylphenylamine intermediate, which involved reaction of the dimethylphenylamine derivative with acrylonitrile for atleast 12 hours at 130 C in presence of sodium acetate and a heterogeneous catalyst such as palladium on carbon. Isolation of the desired compound involved solvent treatment with multiple solvents followed by evaporation. This route also does not give any details of the E/Z ratio of the unsaturated intermediate product. Although this route avoids use of phosphine ligands but lengthy reaction time and problem of availability of pure halo-phenylamine derivatives coupled with moderate yields hampers the commercial usefulness of this route.

The third route disclosed in WO 03/016306 involved reaction of 4-bromo-2,6- dimethylphenylamine with acrylamide in presence of palladium acetate, tris(2- methylphenyl)phosphine and N,N-diethylethanamine. The resulting amide was dehydrated using phosphoryl chloride to give 4-(2-cyanoethenyi)-2,6- dimethylphenylamine in a moderate yield of 67% without mentioning the E/Z ratio. Although the E/Z isomer ratio for the cyanoethenyl derivative obtained from these routes is not specifically disclosed in the patent, however, reproducibility of the abovementioned reactions were found to provide an E/Z ratio between 70/30 and 80/20. Various other methods have also been reported in the literature for introduction of the ‘ cyanoethenyl group in Rilpivirine. The Journal of Medicinal Chemistry (2005), 48, 2072-79 discloses Wittig or Wadsworth-Emmons reaction of the corresponding aldehyde with cyanomethyl triphenylphosphonium chloride to provide a product having an E/Z isomer ratio of 80/20. An alternate method of Heck reaction comprising reaction of aryl bromide with acrylonitrile in presence of tri-o- tolylphosphine and palladium acetate gave the same compound with a higher E/Z isomer ratio of 90/10. The method required further purification in view of the presence of a significant proportion of the Z isomer in the unsaturated intermediate. A similar method was disclosed in Organic Process Research and Development (2008), 12, 530-536. However, the E/Z ratio of 4-(2-cyanoethenyl)-2,6- dimethylphenylamine was found to be 80/20, which was found to improve to 98/2 (E/Z) after the compound was converted to its hydrochloride salt utilizing ethanol and isopropanol mixture.

It would be evident from the foregoing that prior art methods are associated with the following drawbacks:

a) High proportion of Z isomer, which requires elaborate purification by utilizing column chromatographic techniques, crystallization, or successive treatment with multiple solvents, which decreases the overall yield,

b) Introduction of cyanoethenyl group to the formylated benzenamine derivatives involves a moisture sensitive reagent like n-butyl lithium, which is not preferred on industrial scale. Further, the method utilizes cyanomethyl phosphonate esters and is silent about the proportion of the Z isomer and the higher percentage of impurities which requires elaborate purification and ultimately lowers the yield,

c) Prior art routes involve use of phosphine ligands which are expensive, environmentally toxic for large scale operations,

d) Prior art methods utilize phase transfer catalysts such as tetrabutyl ammonium bromide in stoichiometric amounts and the reactions are carried out at very high temperatures of upto 140-150°C.

Thus, there is a need to develop an improved, convenient and cost effective process for preparation of (E)-4-(2-cyanoethenyl)-2,6-dimethylphenylamine hydrochloride of formula (II) having Z-isomer less than 0.5%, without involving any purification and does not involve use of phosphine reagent and which subsequently provides Rilpivirine hydrochloride (I) conforming to regulatory specifications.

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http://www.google.com/patents/EP2643294A2?cl=en

The present inventors have developed a process for stereoselective synthesis of the key Rilpivirine intermediate, (E)-4-(2-cyanoethenyl)-2,6-dimemylphenylarnine hydrochloride (II), comprising diazotization of 2,6-dimethyl-4-amino-l- carboxybenzyl phenylamine followed by treatment with alkali tetrafluoroborate to provide the tetrafluoroborate salt of the diazonium ion which is followed by reaction with acrylonitrile in presence of palladium (II) acetate and subsequent deprotection of the amino group with an acid followed by treatment with hydrochloric acid to give the desired E isomer of compound (II) having Z isomer content less than 0.5% and with a yield of 75-80%. The compound (II) was subsequently converted to Rilpivirine hydrochloride of formula (I) with Z isomer content less than 0.1%.

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Chemical structures of selected NNRTIs

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http://pubs.acs.org/doi/full/10.1021/jm040840e