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Showing posts with label FLIBANSERIN. Show all posts
Showing posts with label FLIBANSERIN. Show all posts

Friday 14 February 2014

'Female Viagra' Flibanserin

Flibanserin, girosa
167933-07-5
 cas no
147359-76-0 (monoHCl)
Flibanserin, BIMT-17-BS, BIMT-17
1 - [2 - [4 - [3 - (Trifluoromethyl) phenyl] piperazin-1-yl] ethyl] -2,3-dihydro-1H-benzimidazol-2-one
1-[2-(4-(3-trifluoromethyl-phenyl)piperazin-1-yl)ethyl]-2,3-dihydro-1H-benzimidazol-2-one

C20-H21-F3-N4-O, 390.412, Boehringer Ingelheim (Originator)
  • Bimt 17
  • BIMT 17 BS
  • Bimt-17
  • Flibanserin
  • Girosa
  • UNII-37JK4STR6Z
Boehringer Ingelheim (Originator)

Antidepressants, Disorders of Sexual Function and Reproduction, Treatment of, ENDOCRINE DRUGS, Mood Disorders, Treatment of, PSYCHOPHARMACOLOGIC DRUGS, Treatment of Female Sexual Dysfunction, 5-HT1A Receptor Agonists, 5-HT2A Antagonists

Patents
EP 526434, JP 94509575, US 5576318, WO 9303016.
 WO2010/128516 , US2007/265276

Papers
Pharmaceutical Research, 2002 ,  vol. 19,  3,   pg. 345 - 349
Naunyn-Schmiedeberg's Archives of Pharmacology, 1995 ,  vol. 352, 3  pg. 283 - 290
Journal of Pharmaceutical and Biomedical Analysis, v.57, 2012 Jan 5, p.104(5)

FLIBANSERIN
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FEBRUARY 11, 2014
Women with low libido in the US will have to wait even longer for approval of the first ever treatment for the condition after regulators requested more data on the forerunner flibanserin, delaying its submission until later this year.
The US Food and Drug Administration has asked manufacturer Sprout Pharmaceuticals for data on how flibanserin interacts with other medicines and also how it affects driving ability, after around 10% of patients experienced sleepiness while on the drug
Read more at: http://www.pharmatimes.com/Article/14-02-11/Female_Viagra_now_on_track_for_Q3_filing_in_USA.aspx#ixzz2tAWxwzRD
............................
December 11, 2013 – Sprout Pharmaceuticals today announced that it has received and appealed the Food and Drug Administration’s (FDA) Complete Response Letter (CRL) for flibanserin through the Formal Dispute Resolution process.
Flibanserin is an investigational, once-daily treatment for Hypoactive Sexual Desire Disorder, or HSDD, in premenopausal women. HSDD is the most commonly reported form of female sexual dysfunction
read all here picture    animation
A new drug being developed by Boehringer Ingelheim could give a boost to the sex drive of women with low libido. The drug, known as flibanserin, has been shown in clinical trials to increase their sexual desire when taken once a day at bedtime.
The results from four pivotal Phase III clinical trials on women with hypoactive sexual desire disorder (HSDD) were presented this week at the European Society for Sexual Medicine's congress in Lyon, France. The trials showed that participants taking flibanserin had a significant improvement in their sexual desire compared to those given a placebo. They also experienced less of the distress associated with sexual dysfunction.
The drug was initially being investigated as a treatment for depression, and acts on the serotonin receptors in the brain - it is both a 5-HT1A receptor agonist and a 5-HT2A receptor antagonist. It is also a partial agonist at the dopamine D4 receptor.
Neurotransmitters such as serotonin are believed to be involved in sexual function, and antidepressants are commonly associated with a loss of libido, so this was an obvious side-effect to look out for during clinical trials in depression. But far from suppressing the libido in women, it appeared to have the opposite effect, so trials in women with HSDD were initiated.
Hormone replacement can improve the libido of women who have had their ovaries removed, but there is no available drug to treat those who have not. There have been accusations that pharma companies invent new diseases like HSDD in order to sell more medicines, but according to Kathleen Segraves, an assistant professor at Case Western Reserve University in the US who has worked in the field of sexual functioning for many years, this is not the case here. HSDD is a very real disorder, she says, and the potential for a treatment for these women is very exciting.
Mona Lisa Painting animation
Flibanserin (code name BIMT-17; proposed trade name Girosa) is a drug that was investigated by Boehringer Ingelheim as a novel, non-hormonal treatment for pre-menopausal women with Hypoactive Sexual Desire Disorder (HSDD).[1][2] Development was terminated in October 2010 following a negative report by the U.S. Food and Drug Administration.[3]
HSDD is the most commonly reported female sexual complaint and characterized by a decrease in sexual desire that causes marked personal distress and/or personal difficulties. According to prevalence studies about 1 in 10 women reported low sexual desire with associated distress, which may be HSDD.[4] The neurobiological pathway of female sexual desire involves interactions among multiple neurotransmitters, sex hormones and various psychosocial factors. Sexual desire is modulated in distinct brain areas by a balance between inhibitory and excitatory neurotransmitters, serotonin acting as an inhibitor while dopamine and norepinephrine act as a stimulator of sexual desire.[5][6]Flibanserin is a 5-HT1A receptor agonist and 5-HT2A receptor antagonist that had initially been investigated as an antidepressant. Preclinical evidence suggested that flibanserin targets these receptors preferentially in selective brain areas and helps to restore a balance between these inhibitory and excitatory effects.[6] HSDD has been recognized as a distinct sexual function disorder for more than 30 years.
The proposed mechanism of action refers back to the Kinsey dual control model. Several sex steroids, neurotransmitters, and hormones have important excitatory or inhibitory effects on the sexual response. Among the neurotransmitters, the excitatory activity is driven by dopamine and norepinephrine, while the inhibitory activity is driven by serotonin. The balance between these systems is relevant for a healthy sexual response. By modulating these neurotransmitters in selective brain areas, flibanserin, a 5-HT1A receptoragonist and 5-HT2A receptor antagonist, is likely to restore the balance between these neurotransmitter systems.[6]

Several large pivotal Phase III studies with Flibanserin were conducted in the USA, Canada and Europe. They involved more than 5,000 pre-menopausal women with generalized acquired Hypoactive Sexual Desire Disorder (HSDD). The results of the Phase III North American Trials demonstrated that
Although the two North American trials that used the flibanserin 100 mg qhs dose showed a statistically significant difference between flibanserin and placebo for the endpoint of [satisfying sexual events], they both failed to demonstrate a statistically significant improvement on the co-primary endpoint of sexual desire. Therefore, neither study met the agreed-upon criteria for success in establishing the efficacy of flibanserin for the treatment of [Hypoactive Sexual Desire Disorder].
These data were first presented on November 16, 2009 at the congress of the European Society for Sexual Medicine in Lyon, France. The women receiving Flibanserin reported that the average number of times they had “satisfying sexual events” rose from 2.8 to 4.5 times a month. However, women receiving placebo reported also an increase of “satisfying sexual events” from 2.7 to 3.7 times a month.
Evaluation of the overall improvement of their condition and whether the benefit was meaningful to the women, showed a significantly higher rate of a meaningful benefit in the flibanserin-treated patient group versus the placebo group.The onset of the Flibanserin effect was seen from the first timepoint measured after 4 weeks of treatment and maintained throughout the treatment period.
The overall incidence of adverse events among women taking flibanserin was low, the majority of adverse events being mild to moderate and resolved during the treatment. The most commonly reported adverse events included dizziness, nausea, fatigue, somnolence and insomnia.

On June 18, 2010, a federal advisory panel to the U.S. Food and Drug Administration (FDA) unanimously voted against recommending approval of Flibanserin.
Earlier in the week, a FDA staff report also recommended non-approval of the drug. While the FDA still might approve Flibanserin, in the past, negative panel votes tended to cause the FDA not to approve.

On October 8, 2010, Boehringer Ingelheim announced that it would discontinue its development of flibanserin in light of the FDA advisory panel's recommendation.

On June 27, 2013, Sprout Pharmaceuticals confirmed they had resubmitted flibanserin for FDA approval.
Flibanserin, chemically 1 -[2-(4-(3-trifluoromethylphenyl)piperazin-1 - yl)ethyl]-2,3-dihydro-1 H-benzimidazole-2-one was disclosed in form of its hydrochloride in European Patent No. 526,434 ('434) and has the following chemical structure:
Figure imgf000002_0001
Process for preparation of flibanserin were disclosed in European Patent No. '434, U.S. Application Publication No. 2007/0032655 and Drugs of the future 1998, 23(1): 9-16.
According to European Patent No. '434 flibanserin is prepared by condensing 1-(2-chloroethyl)-2,3-dihydro-1 H-benzimidazol-one with m- trifluoromethyl phenyl piperazine. According to U.S. Application Publication No. 2007/0032655 flibanserin is prepared by condensing 1-[(3-trifluoromethyl)phenyl]-4-(2- chloroethyl)piperazine with 1 -(2-propenyl)-1 ,3-dihydro-benzimidazol-2H-one.
According to Drugs of the future 1998, 23(1): 9-16 flibanserin is prepared by reacting 1-(2-chloroethyl)-2,3-dihydro-1 H-benzimidazol-one with m- trifluoromethylphenylpiperazine.
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1-[2-(4-(3-trifluoromethyl-phenyl)piperazin-1-yl)ethyl]-2,3-dihydro-1H-benzimidazol-2-one
Compound 3
    • Hydrochloride salt (isopropanol) M.p. 230-231°C
Analysis
  • Figure imgb0022
    ¹H NMR (DMSO-d₆/CDCL₃ 5:2) 11.09 (b, 1H), 11.04 (s, 1H), 7.5-6.9 (8H), 4.36 (t, 2H), 4.1-3.1 (10H)
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 drawing   animation

The compound 1-[2-(4-(3-trifluoromethyl-phenyl)piperazin-1-yl)ethyl]-2,3-dihydro-1 H- benzimidazol-2-one (flibanserin) is disclosed in form of its hydrochlorid in European Patent Application EP-A-526434 and has the following chemical structure:
Figure imgf000003_0001
Flibanserin shows affinity for the 5-HTιA and 5-HT2-receptor. It is therefore a promising therapeutic agent for the treatment of a variety of diseases, for instance depression, schizophrenia, Parkinson, anxiety, sleep disturbances, sexual and mental disorders and age associated memory impairment.
EXAMPLE......... EP1518858A1
375 kg of 1-[(3-trifluoromethyl)phenyl]-4-(2-cloroethyl)piperazin are charged in a reactor with 2500 kg of water and 200 kg of aqueous Sodium Hydroxide 45%. Under stirring 169.2 kg of 1-(2-propenyl)-1,3-dihydro-benzimidazol-2H-one, 780 kg of isopropanol, 2000 kg of water and 220 kg of aqueous Sodium Hydroxide 45% are added. The reaction mixture is heated to 75-85° C. and 160 kg of concentrated hydrochloric acid and 200 kg of water are added.
The reaction mixture is stirred at constant temperature for about 45 minutes. After distillation of a mixture of water and Isopropanol (about 3000 kg) the remaining residue is cooled to about 65-75° C. and the pH is adjusted to 6.5-7.5 by addition of 125 kg of aqueous Sodium Hydroxide 45%. After cooling to a temperature of 45-50° C., the pH value is adjusted to 8-9 by addition of about 4 kg of aqueous Sodium Hydroxide 45%. Subsequently the mixture is cooled to 30-35° C. and centrifuged. The residue thus obtained is washed with 340 l of water and 126 l of isopropanol and then with water until chlorides elimination.
The wet product is dried under vacuum at a temperature of about 45-55° C. which leads to 358 kg of crude flibanserin polymorph A. The crude product thus obtained is loaded in a reactor with 1750 kg of Acetone and the resulting mixture is heated under stirring until reflux. The obtained solution is filtered and the filtrate is concentrated by distillation. The temperature is maintained for about 1 hour 0-5° C., then the precipitate solid is isolated by filtration and dried at 55° C. for at least 12 hours.
The final yield is 280 kg of pure flibanserin polymorph A.
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Flibanserin may be prepared by reacting 1-(phenylvinyl)-2,3-dihydro-1H-benzimidazol-2-one (I) with 1,2-dichloroethane (II) in the presence of NaH in warm dimethylformamide. The resulting 1-(2-chloroethyl)-2,3-dihydro-1H-benzimidazol-one (III) is in turn coupled with commercially available m-trifluoromethylphenylpiperazine hydrochloride (IV) in the presence of sodium carbonate and catalytic potassium iodide in refluxing ethanol. The crude flibanserin hydrochloride (V) is then dissolved in aqueous ethanol and the pure base is precipitated upon addition of sodium hydroxide.
PICK UP INTERMEDIATES FROM CHEM24H.COM
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A process for the preparation of a compound of formula X or a salt thereof:
Figure imgf000026_0001
wherein R2 is hydrogen or an amino protecting group which comprises reacting the compound of formula VII
Figure imgf000026_0002
wherein R2 is as defined in formula X; with a compound of formula Xl:
Figure imgf000026_0003
According to another aspect of the present invention there is provided a novel compound or a salt thereof selected from the compounds of formula I, IV and VII:
Figure imgf000014_0001
Figure imgf000014_0002
Wherein R is hydrogen or an amino protecting group.
Preferable the amino protecting groups are selected from butyl, 1 ,1- diphenylmethyl, methoxymethyl, benzyloxymethyl, trichloroethoxymethyl, pyrrolidinomethyl, cyanomethyl, pivaloyloxymethyl, allyl, 2-propenyl, t- butyldimethylsilyl, methoxy, thiomethyl, phenylvinyl, 4-methoxyphenyl, benzyl, A- methoxybenzyl, 2,4-dimethoxybenzyl, 2-nitrobenzyl, t-butoxycarbonyl, benzyloxycarbonyl, phenoxycarbonyl, 4-chlorophenoxycarbonyl, A- nitrophenoxycarbonyl, methoxycarbonyl and ethoxycarbonyl. Still more preferable protecting groups are selected from t- butoxycarbonyl, ethoxycarbonyl, methoxycarbonyl, benzyloxycarbonyl, phenoxycarbonyl, phenylvinyl and 2-propenyl.
R1 is independently selected from chlorine, bromine, iodine, methanesulphonate, trifluoromethanesulphonate, paratoluenesulphonate or benzenesulphonate. Preferable R1 is independently selected from chlorine, bromine or iodine and more preferable R1 is chlorine.
Wherein R2 is hydrogen or an amino protecting group.
The amino protecting group may be any of the groups commonly used to protect the amino function such as alkyl, substituted alkyl, hetero substituted alkyl, substituted or unsubstituted unsaturated alkyl, alkyl substituted hetero atoms, substituted or unsubstituted phenyl, substituted or unsubstituted benzyl, alkyoxy carbonyl groups and aryloxy carbonyl groups.
Preferable the amino protecting groups are selected from butyl, 1 ,1 - diphenylmethyl, methoxymethyl, benzyloxymethyl, trichloroethoxymethyl, pyrrolidinomethyl, cyanomethyl, pivaloyloxymethyl, allyl, 2-propenyl, t- butyldimethylsilyl, methoxy, thiomethyl, phenylvinyl, 4-methoxyphenyl, benzyl, A- methoxybenzyl, 2,4-dimethoxybenzyl, 2-nitrobenzyl, t-butoxycarbonyl, benzyloxycarbonyl, phenoxycarbonyl, 4-chlorophenoxycarbonyl, A- nitrophenoxycarbonyl, methoxycarbonyl and ethoxycarbonyl. Still more preferable protecting groups are selected from t- butoxycarbonyl, ethoxycarbonyl, methoxycarbonyl, benzyloxycarbonyl, phenoxycarbonyl, phenylvinyl and 2-propenyl. The following examples are given for the purpose of illustrating the present invention and should not be considered as limitations on the scope and spirit of the invention.
EXAMPLES Example 1
A mixture of sodium hydroxide (47 gm) and i-(α-methylvinyl) benzimidazol-2-one (100 gm) in dimethylformamide (400 ml) was .stirred for 1 hour at room temperature. Dibromoethane (217 gm) was slowly added to the mixture and stirred at 1 hour 30 minutes. The resulting solution after addition water (500 ml) was extracted with ethyl acetate. The combined ethyl acetate extract washed with water. After drying the solvent was removed under vacuum to yield 132 gm of 1 ,3-dihydro-1-(2-bromoethyl)-3-isopropenyl-2H-benzimidazol- 2-one as a yellow oily liquid.
Example 2 A mixture of 1 ,3-dihydro-1-(2-bromoethyl)-3-isopropenyl-2H- benzimidazol-2-one (100 gm), diethanolamine (175 ml), sodium carbonate (40 gm) and potassium iodide (10 gm) was heated to 90 to 95 deg C and stirred for 2 hours. The reaction mass was cooled to room temperature and added water (500 ml). The resulting mixture extracted into ethyl acetate and the organic layer washed with water. After drying the solvent was removed under vacuum to yield 105 gm of 1 ,3-dihydro-1-[2-[N-bis-(2-hydroxyethyl)amino]ethyl]-3-isopropenyl- 2H-benzimidazol-2-one as a thick yellow oily liquid.
Example 3
To the mixture of 1 ,3-dihydro-1-[2-[N-bis-(2-hydroxyethyl)amino]ethyl]-3- isopropenyl-2H-benzimidazol-2-one (100 gm) obtained as in example 2 and chloroform (300 ml), thionyl chloride (95 ml) was slowly added. The mixture was heated to reflux and stirred for 2 hours. The excess thionyl chloride and chloroform was distilled off to yield 98 gm of 1 ,3-dihydro-1-[2-[N-[bis-(2- chloroethyl)amino]ethyl]-3-isopropenyl-2H-benzimidazol-2-one as a brown coloured sticky residue.
Example 4
1 ,3-dihydro-1-[2-[N-[bis-(2-chloroethyl)amino]ethyl]-3-isopropenyl-2H- benzimidazol-2-one (98 gm) obtained as in example 3 was added to water (500 ml) and concentrated hydrochloric acid (200 ml) mixture. The mixture was heated to 60 to 65 deg C and stirred for 1 hour. The contents of the flask cooled to room temperature and pH of the solution adjusted to 9 - 10 with 10% sodium hydroxide solution. The resulting solution extracted with ethyl acetate and washed the organic layer with water. Evaporate the solvent under reduced pressure to yield 82 gm of 1 ,3-dihydro-1-[2-[N-bis-(2-chloroethyl)amino]ethyl]- 2H-benzimidazol-2-one as a dark brown coloured oily liquid
Example 5
A mixture of 1 ,3-dihydro-1-[2-[N-bis-(2-chloroethyl)amino]ethyl]-1,2-H- benzimidazol-2-one (82 gm) obtained as in example 4, xylene (300 ml) and m- trifluoromethyl aniline (58 gm) was refluxed for 64 hours. The reaction mass was cooled to room temperature and filtered to obtain 1-[2-(4-(3- thfluoromethylphenyl)piperazin-1-yl)ethyl]-2,3-dihydro-1 H-benzimidazole-2-one hydrochloride (Flibanserin hydrochloride) as a light brown coloured solid.
The crude flibanserin hydrochloride was purified in isopropyl alcohol to give 85 gm of pure flibanserin hydrochloride as off white solid.
Example 6
Piperazine (12 gm), toluene(60 ml) and tetra butyl ammonium bromide (1 gm) mixture was heated to 60 deg C, added 1 ,3-dihydro-1-(2-bromoethyl)-3- isopropenyl-2H-benzimidazol-2-one (10 gm) and stirred for 4 hours at 90 to 95 deg C. The mixture was cooled to 60 deg C and added water (50 ml). The separated toluene layer distilled under vacuum to give 8.5 gm of 1 ,3-dihydro-1- (2-piperazinyl)ethyl-3-isopropenyl-2H-benzimidazol-2-one as a white solid.
Example 7
To the mixture of concentrated hydrochloric acid (20 ml) and water (100 ml) was added 1 ,3-dihydro-1-(2-piperazinylethyl)-3-isopropenyl-2H- benzimidazol-2-one (10 gm) obtained as in example 6 and heated to 60 to 65 deg C 1 hour. The mixture was cooled to room temperature and pH of the solution was adjusted to 9 - 10 with 10% sodium hydroxide solution, extracted with ethyl acetate and the organic layer was washed with water. After drying the solvent was removed under vacuum to yield 8.5 gm of 1 ,3-dihydro-1-(2- piperazinyl ethyl)-2H-benzimidazol-2-one as a white solid.
Example 8
3-trifluoromethylaniline (40 gm) and hydrobromic acid (85 ml; 48- 50%w/w) mixture was cooled to 0 to 5 deg C. To this mixture added sodium nitrite solution (18.5 gm in 25 ml of water) at 5 to 10 deg C and copper powder (1 gm). The temperature was slowly raised to 50 to 55 deg C and stirred for 30 minutes. Added water (200 ml) to reaction mass and applied steam distillation, collected m-trifluoromethylbromobenzene as oily liquid. The oily liquid washed with sulfuric acid for two times (2 X 10 ml) followed by washed with water (2 X 20 ml) and dried the liquid with sodium sulphate to give 22 gm of m- trifluoromethylbromobenzene.
Example 9
To a mixture of 1 ,3-dihydro-1-(2-piperazinyl ethyl)-2H-benzimidazol-2- one (10 gm) obtained as in example 7, m-trifluoromethylbromobenzene (9 gm) obtained as in example 8, sodium tert-butoxide (5.5 gm), palladium acetate (4.5 mg) and xylene (80 ml) was added tri-tert.-butylphosphine (0.2 ml). The mixture was heated to 120 deg C and stirred for 3 hours. The reaction mass was cooled, added water (100 ml) and extracted with ethyl acetate and the organic layer was washed with water. After drying the solvent was removed under vacuum to yield
10 gm of 1-[2-(4-(3-trifluoromethylphenyl)piperazin-1-yl)ethyl]-2,3-dihydro-1 H- benzimidazole-2-one (Flibanserin).
Example 10
To a mixture of 1 ,3-dihydro-1-[2-[N-bis-(2-hydroxyethyl)amino]ethyl]-3- isopropenyl-2H-benzimidazol-2-one (100 gm) obtained as in example 3, cyclohexane (400 ml) and sodium carbonate (35 gm) was added benzene sulfonyl chloride (116 gm) at room temperature. The mixture was heated to 80 to
85 deg C and stirred for 8 hours . The contents were cooled to room temperature and added water (500 ml). Distilled the organic layer to give 182 gm of 1 ,3-dihydro-1-[2-[N-[bis-(2-benzenesulfonyloxy)- ethyl]amino]ethyl]-3- isopropenyl- 2H-benzimidazol-2-one.
Example 11
1 ,3-dihydro-1 -[2-[N-[bis-(2-benzenesulfonyloxy)- ethyl]amino]ethyl]-3- isopropenyl- 2H-benzitηidazol-2-one (100 gm) obtained as in example 10, dimethylformamide (500 ml) and sodium corbonate (18 gm) was mixed and heated to 70 deg C. To the mixture was added m-trifluoromethyl aniline (27 gm) and heated to 80 to 85 deg C, stirred for 5 hours. The reaction mass was cooled and added water (2000 ml), filtered the solid to yield 1 ,3-dihydro-1-[2-[4-(3- trifluoromethylphenyl)piperazinyl]ethyl]-3-isopropenyl-2H benzimidazol-2-one. Example 12
1 ,3-dihydro-1-[2-[N-[bis-(2-benzenesulfonyloxy)- ethyl]amino]ethyl]-3- isopropenyl- 2H-benzimidazol-2-one (100 gm) obtained as in example 11 added to the mixture of water (500 ml) and concentrated hydrochloric acid (200 ml), heated to 65 deg C and stirred for 1 hour. The reaction mass was cooled to room temperature and pH adjusted to 10 to 10-5 with 10% sodium hydroxide solution. The resulting mixture was extracted with ethyl acetate and the organic
 layer was washed with water. After drying the solvent was removed under vacuum to yield 87 gm of 1-[2-(4-(3-trifluoromethylphenyl)piperazin-1-yl)ethyl]- 2,3-dihydro-1 H-benzimidazole -2-one (Flibanserin).
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Paper
Journal of Pharmaceutical and Biomedical Analysis, v.57, 2012 Jan 5, p.104(5)
Isolation and structural elucidation of flibanserin as an adulterant in a health supplement used for female sexual performance enhancement
Low, Min-Yong et al
Full-size image (5 K)
This proposed formula and structure was further confirmed by 1H and 13C NMR data which indicated the presence of 20 carbon atoms and 21 protons.
1H NMR








13C NMR





 




1D and 2DNMR data were used to assign the protons and carbon atoms.

In the1H NMR spectrum , a sharp singlet at 10.00 ppm integrating for one
proton is a typical proton attached to nitrogen. HMBC correlated this proton to C-2, C-4, and C-9 suggesting that it was H-3.
Complex signals were observedbetween 7.00 to 7.31 ppm, integrating for eight protons. A triplet at 7.31 ppm,integrating for a proton has a coupling constant of 8.0 Hz. HMBC correlated thisproton with C-16, C-19, and C-21 suggesting that it was H-20.
A double-doubletsplitting pattern at chemical shift 7.11 ppm, integrating for a proton, has couplingconstants of 6.3 Hz and 1.6 Hz.
HMBC correlated this proton to C-6, C-7, and C-9 showing that it was H-8. Overlapped signals were observed from 7.04 ppm to7.10 ppm, integrating for five protons. A double-doublet splitting pattern at 7.01ppm with coupling constant 8.0 Hz and 2.0 Hz, integrating for a proton was
observed.
HMBC correlated this proton to C-17 suggesting that it was either H-19or H-21. Four triplet signals were also observed from 2.73 ppm to 4.08 ppm,integrating for a total of twelve protons.
Two of these triplet signals at 2.74 ppmand 3.22 ppm integrated for four protons each, suggesting overlapping signals ofmethylene protons. This was further confirmed by 13C and DEPT NMR.
13C and DEPT NMR data showed the signals of four methylene, eight methineand six quaternary carbon atoms. The DEPT signals at 53.1 ppm and 48.6 ppmhave intensities which were double of those from the rest of the methylene carbonsignals, suggesting two methylene carbon atoms each contributing to the signal at 53.1 ppm and 48.6 ppm.
DEPT

HMQC results further indicated that these two methylene carbon signals at 53.1 ppm and 48.6 ppm were correlated to the protons signal at 2.73 ppm and 4.08 ppm respectively, which corresponded to four protons each. The finding confirmed overlapping methylene carbon signals (at 53.1 ppm and 48.6 ppm) and methylene proton signals (at 2.73 ppm and 4.08 ppm). Hence, the unknown compound has six methylene carbon atoms with a total of twelve methylene protons.
The chemical shifts of the twelve methylene protons suggested that they were attached to relatively electronegative atoms. It was speculated that the six methylene groups were attached to the nitrogen atoms and the electron withdrawing effect of these electronegative nitrogen atoms resulted in the deshielding of the protons. HMBC and COSY correlations were used to assign the rest of the protons
The 13C NMR data  showed that there were two quaternary carbon at
155.6 ppm and 151.3 ppm. The carbon with chemical shift 155.6 ppm was C-2. Inthe structure of imidazolone, carbonyl carbon C-2 was attached to two nitrogenatoms which helped to withdraw electrons from oxygen to C-2. Hence, C-2 wasless deshielded as compared to a normal carbonyl carbon which has chemical shiftabove 170 ppm.
Eight methine carbons and two quaternary carbons with chemicalshifts above 108 ppm suggested the presence of two aromatic rings. Thequaternary carbon with chemical shift 125.4 ppm was C-22 which was attached tothree fluorine atoms. Due to the strong electron withdrawing effect of the fluorineatoms, C-22 was highly deshielded and had a high chemical shift.
The IR spectrum of the isolated compound showed absorption bands of amide (νC=O 1685 cm-1, νN-H (stretch) 3180 cm-1, νN-H (bending) 1610 cm-1), alkyl fluoride (νC-F1077 cm-1, 1112 cm-1, 1158 cm-1), aromatic ring (ν Ar-H 3028 cm-1, 3078 cm-1 andνC=C 1401 cm-1, 1446 cm-1, 1453 cm-1, 1468 cm-1, 1487 cm-1) and alkane (νC-H2891 cm-1, 2930 cm-1 2948 cm-).




 





COSY





 mass

 
 
 


 HMBC
 

HMQC

 

 
NMR PREDICT
H EXPLODED

1H NMR PREDICT1H NMR DB GRAPH 1H NMR DB VAL CHEMDDODLE


13C NMR PREDICT
fliban chemspider image
13C NMR DB GRAPH 13C NMR DB VAL fliban chemspider image

COSY PREDICT
COSY NMR prediction (27)

NMR PREDICT FROM MOLBASE
1H NMR MOLBASE GRAPH1H NMR MOLBASE VAL 13C NMR MOLBASE GRAPH13C NMR MOLBASE VAL


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US5576318, 1996
1 H NMR (DMSO-d6 /CDCL3 5:2) 11.09 (b, 1H), 11.04 (s, 1H), 7.5-6.9 (SH), 4.36 (t, 2H), 4.1-3.1 (10 H)
UPDATES............

A Facile Route of Synthesis for Making Flibanserin

 CAS Key Laboratory for Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
 University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China
§ Topharman Shanghai Co., Ltd., 1088 Chuansha Road, Shanghai 201209, China
Org. Process Res. Dev., Article ASAP
DOI: 10.1021/acs.oprd.6b00108
*For Y.H.: phone, +86 21 20231000-2409; e-mail: heyang@simm.ac.cn., *For J.S.: phone, +86 21 20231962; e-mail:jsshen@mail.shcnc.ac.cn.
Abstract Image





REFERENCES
  1.  Borsini F, Evans K, Jason K, Rohde F, Alexander B, Pollentier S (summer 2002). "Pharmacology of flibanserin". CNS Drug Rev. 8 (2): 117–142. doi:10.1111/j.1527-3458.2002.tb00219.xPMID 12177684.
  2.  Jolly E, Clayton A, Thorp J, Lewis-D’Agostino D, Wunderlich G, Lesko L (April 2008). "Design of Phase III pivotal trials of flibanserin in female Hypoactive Sexual Desire Disorder (HSDD)". Sexologies 17 (Suppl 1): S133–4. doi:10.1016/S1158-1360(08)72886-X.
  3.  Spiegel online: Pharmakonzern stoppt Lustpille für die Frau, 8 October 2010 (in German)
  4.  Nygaard I (November 2008). "Sexual dysfunction prevalence rates: marketing or real?". Obstet Gynecol 112 (5): 968–9.doi:10.1097/01.AOG.0000335775.68187.b2PMID 18978094.
  5.  Clayton AH (July 2010). "The pathophysiology of hypoactive sexual desire disorder in women"Int J Gynaecol Obstet 110 (1): 7–11.doi:10.1016/j.ijgo.2010.02.014PMID 20434725.
  6.  Pfaus JG (June 2009). "Pathways of sexual desire". J Sex Med 6 (6): 1506–33. doi:10.1111/j.1743-6109.2009.01309.x.PMID 19453889.
EP0200322A1 *Mar 18, 1986Nov 5, 1986H. Lundbeck A/SHeterocyclic compounds
BE904945A1 *Title not available
GB2023594A *Title not available
US3472854 *May 29, 1967Oct 14, 1969Sterling Drug Inc1-((benzimidazolyl)-lower-alkyl)-4-substituted-piperazines
US4954503 *Sep 11, 1989Sep 4, 1990Hoechst-Roussel Pharmaceuticals, Inc.3-(1-substituted-4-piperazinyl)-1H-indazoles

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str1

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1-(2-(4-(3-(Trifluoromethyl)phenyl)piperazin-1-yl)ethyl)-1H-benzo[d]imidazol-2(3H)-one (1)
1H NMR (400 MHz, DMSO-d6) δ 11.27 (s, 1H), 11.08 (s, 1H), 7.48 (t, J = 7.9 Hz, 1H), 7.40–7.34 (m, 1H), 7.31 (d, J = 8.8 Hz, 2H), 7.16 (d, J = 7.6 Hz, 1H), 7.09–7.01 (m, 3H), 4.32 (t, J = 6.6 Hz, 2H), 4.01 (d, J = 9.9 Hz, 2H), 3.75 (d, J = 8.6 Hz, 2H), 3.48 (d, J = 4.0 Hz, 2H), 3.33–3.15 (m, 4H).
ESI-MS (m/z): 391.1 [M + H]+.
HPLC: retention time of 9.1 min, 99.8% purity.
Pure compound 1 as a white solid (540 g, 70%) was produced via recrystallization in isopropanol (1.2 L). 1H NMR (400 MHz, DMSO-d6) δ 10.83 (s, 1H), 7.40 (t, J = 8.0 Hz, 1H), 7.20 (dd, J = 8.4 Hz, 2.4 Hz, 1H), 7.127.17 (m, 2H), 7.05 (d, J = 7.6 Hz, 1H), 6.947.02 (m, 3H), 3.94 (t, J = 6.6 Hz, 2H), 3.17 (brt, 4H), 2.58–2.65 (m, 6H); ESI-MS (m/z): 391.6 [M + H]+; HPLC: retention time of 9.1 min, 99.9% purity.

Abstract Image
A novel and efficient route of synthesis for making flibanserin via 2-ethoxy-1H-benzo[d]imidazole (12) was described with excellent yield. This protocol provided a more facile approach toflibanserin.

A Facile Route of Synthesis for Making Flibanserin

 CAS Key Laboratory for Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
 University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China
§ Topharman Shanghai Co., Ltd., 1088 Chuansha Road, Shanghai 201209, China
Org. Process Res. Dev.201620 (9), pp 1576–1580
DOI: 10.1021/acs.oprd.6b00108
*For Y.H.: phone, +86 21 20231000-2409; e-mail: heyang@simm.ac.cn., *For J.S.: phone, +86 21 20231962; e-mail:jsshen@mail.shcnc.ac.cn.
Figure
Original Route of Synthesis for Making Flibanserina
aReagents and conditions: (a) ethyl benzoylacetate, 200 °C; (b) dichloroethane, NaH, DMF; (c) conc HCl (aq); (d) 1-(3-(trifluoromethyl)phenyl)piperazine hydrochloride, Na2CO3, KI, EtOH; (e)
  • 3.BiettiG.BorsiniF.TurconiM.GiraldoE.BignottiM. For treatment of central nervous system disorders. U.S. Patent 5,576,318, 1996.
  • 4.Mohan RaoD.Krishna ReddyP.Venkat ReddyB. Preparing benzoimidazol-2-one compound, useful to prepare flibanserin, comprises reacting benzoimidazol-2-one compound with 2-(2-hydroxy-ethylamino)-ethanol to give (bis-(hydroxy-ethyl)-amino)-ethyl-benzoimidazol-2-one compound. PCT. Int.WO2,010,128,516, 2010.5.
  • 5.VerninG.DomlogH.SivC.MetzgerJ.El-ShafeiA. K.Synthesis of 1-alkyl and 1, 3-dialkyl-2-benzimidazolones from 1-alkenyl-2-benzimidazolones using phase-transfer catalysis technique J. Heterocycl. Chem. 19811885– 89DOI: 10.1002/jhet.5570180118
Figure
aReagents and conditions: (a) ethyl acetoacetate, KOH, EtOH, xylene, reflux, 56%; (b) 1,2-dibromoethane, K2CO3, DMF, 50 °C, 50%; (c) K2CO3, CH3CN, 70 °C, 80%; (d) conc. HCl (aq), isopropanol, 70 °C; (e) NaOH (aq), rt, 72% over two steps.

Figure
aReagents and conditions: (a) tetraethyl orthocarbonate, AcOH, 70 °C, 94%; (b) 1-bromo-2-chloroethane, K2CO3, acetone, reflux, 75%; (c) K2CO3, NaI, H2O, reflux, 92%; (d) conc. HCl (aq), isopropanol, 70 °C; (e) NaOH (aq), 68% over two steps.




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Route to Benzimidazol-2-ones via Decarbonylative Ring Contraction of Quinoxalinediones: Application to the Synthesis of Flibanserin, A Drug for Treating Hypoactive Sexual Desire Disorder in Women and Marine Natural Product Hunanamycin Analogue
 Division of Organic Chemistry, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
 Academy of Scientific and Innovative Research (AcSIR), New Delhi 110 025, India
ACS Omega, 2017, 2 (8), pp 5137–5141
DOI: 10.1021/acsomega.7b00819
 
*E-mail: ds.reddy@ncl.res.in. Phone: +91-20-2590 2445 (D.S.R.).
 
ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
INTRODUCTION
Benzimidazol-2-ones 1 are an important class of heterocycles and a privileged scaffold in medicinal chemistry. They consist of cyclic urea fused with the aromatic backbone, which can potentially interact in a biological system by various noncovalent interactions such as hydrogen bonding and π stacking. Benzimidazolone derivatives exhibit a wide range of biological activities, and they are useful in treating various diseases including cancer, type II diabetes, central nervous system disorders, pain management, and infectious disease.1 Selected compounds embedded with a benzimidazol-2-one moiety along with their use are captured in Figure 1. It is worth mentioning that oxatomide drug with a benzimidazol-2-one core was approved for marketing a few years ago.2a Very recently, US Food and Drug Administration approved a new drug called flibanserin for the treatment of hypoactive sexual desire disorder (HSDD) in females, which contains benzimidazol-2- one motif.2b
CONCLUSIONS
We have developed a mild and new protocol for the synthesis of benzimidazol-2-ones from quinoxalinediones through decarbonylation. The present methodology can be an addition to the toolbox to prepare benzimidazolones, and it will be useful in medicinal chemistry, particularly, late-stage functionalization of natural products, drug scaffolds, or an intermediate containing quinoxaline-2,3-diones. As direct application of this method, we have successfully developed a new route for the synthesis of recently approved drug flibanserin and a urea analogue of antibiotic natural product hunanamycin A. Later application demonstrates the utility of the present method in late-stage functionalization

Synthesis of 1-(2-(4-(3-(trifluoromethyl)phenyl)piperazin-1-yl)ethyl)-1,3-dihydro-2Hbenzo[d]imidazol-2-one (Flibanserin)
Flibanserin hydrochloride as white solid.
1H NMR (400MHz ,DMSO-d6)  11.06 (s, 1 H), 10.93 (br. s., 1 H), 7.54 - 7.41 (t, J = 7.9 Hz, 1 H), 7.36 - 7.22 (m, 3 H), 7.15 (d, J = 7.6 Hz, 1 H), 7.09 – 7.01 (m, 3 H), 4.30 (t, J = 6.7 Hz, 2 H), 4.01 (d, J = 11.6 Hz, 2 H), 3.75 (d, J = 10.4 Hz, 2 H), 3.54 - 3.43 (d, J = 4.2 Hz 2 H), 3.31 - 3.10 (m, 4 H);
HRMS (ESI): m/z calculated for C20H22ON4F3[M+H]+ 391.1740 found 391.1743;
str0STR1
Figure
Scheme 4. Synthesis of Flibanserin through Ring Contraction
The same methodology was applied for the synthesis of flibanserin, also known as “female viagra”, which is the first approved medication for treating HSDD in women and is classified as a multifunctional serotonin agonist antagonist.(14, 15) Our synthesis of flibanserin commenced with 1-benzyl-1,4-dihydroquinoxaline-2,3-dione 36,(16) which was reacted with known chloride 37(17) under the basic condition in DMF to give the desired product 38 in good yield. Compound 38 was subjected for the decarbonylative cyclization under the optimized condition to afford the product 39 in 59% yield. Finally, the benzyl group was deprotected using trifluoromethanesulfonic acid in toluene under microwave irradiation,(8b, 18) which gave flibanserin in excellent yield (Scheme 4). The final product was isolated as HCl salt, and all of the spectral data are in agreement with the published data.(15c)
Image result for Rahul D. Shingare
Rahul D. Shingare completed his M.Sc  (Chemistry) from Fergusson College,  Pune  in 2008. He worked as a research associate in Ranbaxy and Lupin New drug discovery center, Gurgaon and Pune respectively until 2012 and currently pursuing his doctoral research in NCL - Pune from 2012.
Current Research Interests: Antibacterial Natural Product Hunanamycin A: Total Synthesis, SAR and Related Chemistry.
e-mail: rd.shingare@ncl.res.in







Akshay Kulkarni completed his M.Sc. from Ferguson College, Pune University in the year 2015 and joined our group as a Project Assistant in the month of October, 2015.
Current research interest: Synthesis of silicon incorporated biologically active antimalerial compounds.
e-mail : as.kulkarni@ncl.res.in
Image result for Rahul D. Shingare

Dr.D. Srinivasa Reddy
Organic Chemistry Division
CSIR-National Chemical Laboratory
  1. 14.
    StahlS. M. Mechanism of action of Flibanserin, A multifunctional serotonin agonist and antagonist (MSAA), in hypoactive sexual desire disorder CNS Spectrums 2015201 DOI: 10.1017/s1092852914000832
  2. 15.
    See, previous synthesis of Flibanserin:
    (a) BiettiG.BorsiniF.TurconiM.GiraldoE.BignottiM. For treatment of central nervous system disorders. U.S. Patent 5,576,318, 1996.
    (b) MohanR. D.ReddyP. K.;ReddyB. V. Process for the preparation of Flibanserin involving novel intermediates. WO2010128516 A2,2010.
    (c) YangF.WuC.LiZ.TianG.WuJ.ZhuF.ZhangJ.HeY.ShenJ. A Facile route of synthesis for making Flibanserin Org. Process Res. Dev. 2016201576 DOI: 10.1021/acs.oprd.6b00108
  3. 16.
    JarrarA. A.FataftahZ. A. Photolysis of some quinoxaline-1,4-dioxides Tetrahedron 1977332127 DOI: 10.1016/0040-4020(77)80326-8
  4. 17.
    XueongX. Preparation method of Flibanserin. CN104926734 A, 2015.
  5. 18.
    RomboutsF.FrankenD.Martínez-LamencaC.BraekenM.ZavattaroC.ChenJ.TrabancoA. A.Microwave-assisted N-debenzylation of amides with triflic acid Tetrahedron Lett. 2010514815 DOI: 10.1016/j.tetlet.2010.07.022

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