# Patent

## Title
Substituted 6-(1-piperazinyl)-pyridazines as 5-HT6 receptor antagonists

## Abstract

The present invention is concerned with novel substituted 6-(1-piperazinyl)-pyridazines of Formula (I)




wherein R1, R2, R3 and X have the meaning defined in the claims, having 5-HT6-antagonistic properties. The invention further relates to processes for preparing such novel compounds, pharmaceutical compositions comprising said novel compound as an active ingredient as well as the use of said compounds as a medicine.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority from and is the national stage of PCT Application No. PCT/EP2009/004745, filed Jul. 1, 2009, the entire disclosure of which is hereby incorporated by reference in its entirety, which claims priority from European Patent Application No. 08159591.0, filed Jul. 3, 2008.
FIELD OF THE INVENTION
The present invention is concerned with novel substituted 6-(1-piperazinyl)-pyridazines having 5-HT6-antagonistic properties. The invention further relates to processes for preparing such novel compounds, pharmaceutical compositions comprising said novel compound as an active ingredient as well as the use of said compounds as a medicine.
BACKGROUND PRIOR ART
WO-2003/066604 relates amongst others to 3-aryl-6-piperazin-1-ylpyridazines with histamine H3 receptor activity which can be used in the treatment of narcolepsy.


DESCRIPTION OF THE INVENTION
The 5-hydroxytryptamine receptor 6 (5-HT6) receptor belongs to the G-protein-coupled receptor family and is coupled to the Gs-family of G proteins, including the 5-HT4 and 5-HT7 receptor, that stimulate adenylate cyclase activity. The 5-HT6 receptor also appears to regulate glutaminergic and cholinergic neuronal activity. 5-HT6 receptors are selectively found in the brain areas involved in cognitive processes. The blockade of serotonin 5-HT6 may be beneficial in higher cognitive processes such as memory and when negative symptoms associated with schizophrenia are considered.
Indeed, numerous preclinical data have shown that 5-HT6 receptor antagonism has positive effects on cognitive processes in rodents (Mitchell and Neumaier (2005) 5-HT6 receptors: a novel target for cognitive enhancement. Pharmacology & Therapeutics 108:320-333). The 5-HT6 receptor has little or no expression in peripheral tissues, which may result in selectivity in drug targeting with fewer side effects.
More in general, compounds with 5-HT6 receptor affinity may further be useful for the treatment of a variety of disorders of the Central Nervous System, anxiety, depression, attention deficit hyperactivity disorder, Alzheimer's disease, epilepsy, and schizophrenia.
In addition, 5-HT6 antagonism has also been linked to appetite and food intake suppression. The prevalence of food ingestion disorders, like for example obesity, makes this a leading public health problem in all age groups. Food ingestion disorders predispose to various serious diseases such as diabetes, disorders of the gastrointestinal tracts, cardiovascular diseases, sleep apnea and osteoarthritis. The 5-HT6 receptor has generated an enormous interest as a molecular target for the development of a new generation of safe and more effective anti-obesity drugs.
It is the object of the present invention to provide novel compounds that are selective 5-HT6 receptor antagonists which have negligible interactions with other receptors resulting in fewer side-effects. The invention further relates to methods for their preparation and pharmaceutical compositions comprising them. The invention also relates to the use of these derivatives for the manufacture of a medicament for the treatment or prophylaxis of cognitive impairment and food related disorders.
The present invention concerns novel compounds according to Formula (I):




    
    
        and stereoisomeric forms thereof, wherein
        Rl is chloro, trifluoromethyl or cyano;
        R2 is phenyl or phenyl substituted with halo;
        R3 is hydrogen, C1-4-alkyl or pyridinylmethyl;
        X is —O—, —NH—, —CH2—, —CH(OH)—, —SO2—, —CO—, —NH—CH2—, —O—CH2—,
        1,2-ethenediyl or ethynediyl;

and the pharmaceutically acceptable addition salts, and solvates thereof.

    
    


The present invention will now be further described. In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.
For example, the invention relates to compounds of Formula (I) and stereoisomeric forms thereof, wherein

    
    
        Rl is trifluoromethyl;
        R2 is phenyl or phenyl substituted with halo; preferably R2 is phenyl substituted with halo;
        R3 is hydrogen, C1-4-alkyl or pyridinylmethyl; preferably R3 is hydrogen, methyl or pyridinylmethyl;
        X is —O—, —NH—, —CH2—, —CH(OH)—, —SO2—, —CO—, —NH—CH2—, —O—CH2—,
        1,2-ethenediyl or ethynediyl;

and the pharmaceutically acceptable addition salts, and solvates thereof.

    
    


The invention relates in particular to compounds of Formula (I) and stereoisomeric forms thereof, wherein

    
    
        Rl is trifluoromethyl;
        R2 is phenyl or phenyl substituted with fluoro;
        R3 is hydrogen, methyl or pyridinylmethyl;
        X is —O—, —NH—, —CH2—, —CH(OH)—, —SO2—, —CO—, —NH—CH2—, —O—CH2—,
        1,2-ethenediyl or ethynediyl;

and the pharmaceutically acceptable addition salts and solvates thereof.

    
    


In a further embodiment, the invention relates to compounds according to any of the other embodiments, wherein R2 is phenyl or phenyl substituted with one or more substituents selected from the group consisting of halo.
In a further embodiment, the invention relates to compounds according to any of the other embodiments, wherein R2 is phenyl or phenyl substituted with one, two or three substituents selected from the group consisting of halo.
In a further embodiment, the invention relates to compounds according to any of the other embodiments, wherein R2 is phenyl or phenyl substituted with one halo.
In a further embodiment, the invention relates to compounds according to any of the other embodiments, wherein halo is fluoro.
Amongst the compounds of Formula (I) and the stereoisomeric forms thereof, the most interesting are, for example,

    4-(4-fluorophenoxy)-6-(1-piperazinyl)-3-(trifluoromethyl)-pyridazine,
    N-(4-fluorophenyl)-6-(1-piperazinyl)-3-(trifluoromethyl)-4-pyridazinamine,
    4-(phenylmethyl)-6-(1-piperazinyl)-3-(trifluoromethyl)-pyridazine,
    phenyl[6-(1-piperazinyl)-3-(trifluoromethyl)-4-pyridazinyl]-methanone,
    alpha-phenyl-6-(1-piperazinyl)-3-(trifluoromethyl)-4-pyridazinemethanol,
    4-(phenylsulfonyl)-6-(1-piperazinyl)-3-(trifluoromethyl)-pyridazine,
    4-[(Z)-2-(4-fluorophenyl)ethenyl]-6-(1-piperazinyl)-3-(trifluoromethyl)-pyridazine,
    4-[(E)-2-(4-fluorophenyl)ethenyl]-6-(1-piperazinyl)-3-(trifluoromethyl)-pyridazine,
    4-[(4-fluorophenyl)ethynyl]-6-(1-piperazinyl)-3-(trifluoromethyl)-pyridazine,
    6-(4-methyl-1-piperazinyl)-4-[(E)-2-phenylethenyl]-3-(trifluoromethyl)-pyridazine,
    [6-(4-methyl-1-piperazinyl)-3-(trifluoromethyl)-4-pyridazinyl]phenyl-methanone,
    N-[(4-fluorophenyl)methyl]-6-(1-piperazinyl)-3-(trifluoromethyl)-4-pyridazinamine,
    4-[(4-fluorophenyl)methoxy]-6-(1-piperazinyl)-3-(trifluoromethyl)-pyridazine,
    4-[(E)-2-phenylethenyl]-6-(1-piperazinyl)-3-(trifluoromethyl)-pyridazine,
    N-(4-fluorophenyl)-6-(1-piperazinyl)-3-(trifluoromethyl)-4-pyridazinamine.2.5HCl .0.5H2O,
    4-[(E)-2-phenylethenyl]-6-[4-(4-pyridinylmethyl)-1-piperazinyl]-3-(trifluoromethyl)-pyridazine,
    4-[(E)-2-phenylethenyl]-6-[4-(2-pyridinylmethyl)-1-piperazinyl]-3-(trifluoromethyl)-pyridazine,

and the pharmaceutically acceptable addition salts and solvates thereof.



The chemical names of the compounds of the present invention were generated according to the nomenclature rules agreed upon by the Chemical Abstracts Service (CAS). In case of tautomeric forms, the name of the depicted tautomeric form of the structure was generated. However it should be clear that the other non-depicted tautomeric form is also included within the scope of the present invention.
Whenever the term “substituted” is used in the present invention, it is meant to indicate that one or more hydrogens, preferably from 1 to 3 hydrogens, more preferably 1 hydrogen, on the atom indicated in the expression using “substituted” are replaced with a selection from the indicated group, provided that the indicated atom's normal valency is not exceeded, and that the substitution results in a chemically stable compound, i.e. a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation into a therapeutic agent. For example, when phenyl is substituted with halo, this means that said phenyl is substituted with one or more substituents selected from halo.
Throughout this application, the term “C1-4alkyl” defines straight or branched chain saturated hydrocarbon radicals having from 1 to 4 carbon atoms such as methyl, ethyl, propyl, 1-methylethyl, butyl, 1,1-dimethylethyl. The term halo as a group or part of a group is generic to fluoro, chloro, bromo, and iodo unless otherwise is indicated or is clear from the context.
When any variable occurs more than one time in any constituent, each definition is independent.
The pharmaceutically acceptable salts are defined to comprise the therapeutically active non-toxic acid addition salts forms that the compounds according to Formula (I) are able to form. Said salts can be obtained by treating the base form of the compounds according to Formula (I) with appropriate acids, for example inorganic acids, for example hydrohalic acid, in particular hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid and phosphoric acid; organic acids, for example acetic acid, hydroxyacetic acid, propanoic acid, lactic acid, pyruvic acid, oxalic acid, malonic acid, succinic acid, maleic acid, mandelic acid, fumaric acid, malic acid, tartaric acid, citric acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, cyclamic acid, salicylic acid, p-aminosalicylic acid, pamoic acid and mandelic acid. Conversely, said salts forms can be converted into the free forms by treatment with an appropriate base. The compounds of Formula (I) containing an acidic proton may also be converted into their non-toxic metal or amine addition salt forms by treatment with appropriate organic and inorganic bases. Appropriate base salt forms comprise, for example, the ammonium salts, the alkali and earth alkaline metal salts, e.g. the lithium, sodium, potassium, magnesium, calcium salts and the like, salts with organic bases, e.g. primary, secondary and tertiary aliphatic and aromatic amines such as methylamine, ethylamine, propylamine, isopropylamine, the four butylamine isomers, dimethylamine, diethylamine, diethanolamine, dipropylamine, diisopropyl-amine, di-n-butylamine, pyrrolidine, piperidine, morpholine, trimethylamine, triethyl-amine, tripropylamine, quinuclidine, pyridine, quinoline and isoquinoline; the benzathine, N-methyl-D-glucamine, hydrabamine salts, and salts with amino acids such as, for example, arginine, lysine and the like. Conversely the salt form can be converted by treatment with acid into the free acid form.
The term solvate comprises the hydrates and solvent addition forms which the compounds of formula (I) are able to form, as well as the salts thereof. Examples of such forms are e.g. hydrates, alcoholates and the like.
It will be appreciated that some of the compounds of Formula (I) and their pharmaceutically acceptable addition salts and stereoisomeric forms may contain one or more centers of chirality and exist as stereoisomeric forms.
The term “stereoisomeric forms” as used hereinbefore defines all the possible isomeric forms that the compounds of Formula (I) may possess. Unless otherwise mentioned or indicated, the chemical designation of compounds denotes the mixture of all possible stereoisomeric forms, said mixtures containing all diastereomers and enantiomers of the basic molecular structure. More in particular, stereogenic centers may have the R- or S-configuration; substituents on bivalent cyclic (partially) saturated radicals may have either the cis- or trans-configuration. Compounds encompassing double bonds can have an E or Z-stereochemistry at said double bond. Stereoisomeric forms of the compounds of Formula (I) are embraced within the scope of this invention.
When a specific stereoisomeric form is indicated, this means that said form is substantially free, i.e. associated with less than 50%, preferably less than 20%, more preferably less than 10%, even more preferably less than 5%, further preferably less than 2% and most preferably less than 1% of the other isomer(s).
For therapeutic use, salts of the compounds of Formula (I) are those wherein the counterion is pharmaceutically acceptable. However, salts of acids and bases which are non-pharmaceutically acceptable may also find use, for example, in the preparation or purification of a pharmaceutically acceptable compound. All salts, whether pharmaceutically acceptable or not are included within the ambit of the present invention.
The compounds of Formula (I) as prepared in the processes described below may be synthesized in the form of racemic mixtures of enantiomers that can be separated from one another following art-known resolution procedures. The racemic compounds of Formula (I) may be converted into the corresponding diastereomeric salt forms by reaction with a suitable chiral acid. Said diastereomeric salt forms are subsequently separated, for example, by selective or fractional crystallization and the enantiomers are liberated therefrom by alkali. An alternative manner of separating the enantiomeric forms of the compounds of Formula (I) involves liquid chromatography using a chiral stationary phase. Said pure stereoisomeric forms may also be derived from the corresponding pure stereoisomeric forms of the appropriate starting materials, provided that the reaction occurs stereospecifically. Preferably if a specific stereoisomer is desired, said compound would be synthesized by stereospecific methods of preparation. These methods will advantageously employ enantiomerically pure starting materials.
In the framework of this application, a compound according to the invention is inherently intended to comprise all isotopic combinations of its chemical elements. In the framework of this application, a chemical element, in particular when mentioned in relation to a compound according to Formula (I), comprises all isotopes and isotopic mixtures of this element. In particular, when hydrogen is mentioned, it is understood to refer to 1H, 2H, 3H and mixtures thereof.
A compound according to the invention therefore inherently comprises a compound with one or more isotopes of one or more elements, and mixtures thereof, including a radioactive compound, also called radiolabelled compound, wherein one or more non-radioactive atoms has been replaced by one of its radioactive isotopes. By the term “radiolabelled compound” is meant any compound according to formula (I), or a pharmaceutically acceptable salt thereof, which contains at least one radioactive atom. For example, a compound can be labelled with positron or with gamma emitting radioactive isotopes. For radioligand-binding techniques, the 3H-atom or the 125I-atom is the atom of choice to be replaced. For imaging, the most commonly used positron emitting (PET) radioactive isotopes are 11C, 18F, 15O and 13N all of which are accelerator produced and have half-lives of 20, 100, 2 and 10 minutes (min) respectively. Since the half-lives of these radioactive isotopes are so short, it is only feasible to use them at institutions which have an accelerator on site for their production, thus limiting their use. The most widely used of these are 18F, 99mTc, 201Tl and 123I. The handling of these radioactive isotopes, their production, isolation and incorporation in a molecule are known to the skilled person.
In particular, the radioactive atom is selected from the group of hydrogen, carbon, nitrogen, sulfur, oxygen and halogen. In particular, the radioactive isotope is selected from the group of 3H, 11C, 18F, 122I, 123I, 125I, 131I, 75Br, 76Br, 77Br and 82Br.
As used in the specification and the appended claims, the singular forms “a”, “an,” and “the” also include plural referents unless the context clearly dictates otherwise. For example, “a compound” means 1 compound or more than 1 compound.
The terms described above and others used in the specification are well understood to those in the art.
Pharmacology
In order to find compounds active for the treatment of cognitive impairment and food related disorders, we have screened for compounds selectively interacting with the serotonin 5-HT6 receptor. The compounds within the scope of this invention, were found to have a clean profile, this is to have low affinity for the tested receptors, with the exception of the serotonin 5-HT6 receptor.
Compounds of the present invention may further be expected to be active in the ‘Reversal of subchronic PCP-induced attentional set shifting in rats’ test (J. S. Rodefer et al., Neurospychopharmacology (2007), 1-10).
In view of the aforementioned pharmacology of the compounds of Formula (I), it follows that they are suitable for use as a medicine.
More especially a medicine in the treatment or prevention of conditions wherein cognition is impaired; Alzheimer's disease, Parkinson's disease, Schizophrenia, Huntingdon's disease, Lewy Body Dementia, dementia due to HIV disease, dementia due to Creutzfeldt-Jakob disease; amnestic disorders; mild cognitive impairment; and age-related cognitive decline; for the treatment and/or prevention of feeding disorders and diseases, for the regulation of appetite; for the maintenance, increase or reduction of body weight; anorexia, bulimia, obesity, cachexia, type II diabetes (non insulin dependent diabetes mellitus), type II diabetes caused by obesity; for the treatment and/or prevention of stroke; migraine; head trauma; epilepsy; irritable colon syndrome; irritable bowl syndrome; for the treatment of disorders of the central nervous system; schizophreniform disorder, schizoaffective disorder, delusional disorder, brief psychotic disorder, shared psychotic disorder, psychotic disorder due to a general medical condition, substance-induced psychotic disorder, psychotic disorder not otherwise specified; psychosis associated with dementia; major depressive disorder, dysthymic disorder, premenstrual dysphoric disorder, depressive disorder not otherwise specified, Bipolar I disorder, bipolar II disorder, cyclothymic disorder, bipolar disorder not otherwise specified, mood disorder due to a general medical condition, substance-induced mood disorder, mood disorder not otherwise specified; generalized anxiety disorder, obsessive-compulsive disorder, panic disorder, acute stress disorder, post-traumatic stress disorder; mental retardation; pervasive developmental disorders; attention deficit disorders, attention-deficit/hyperactivity disorder, disruptive behaviour disorders; personality disorder of the paranoid type, personality disorder of the schizoid type, personality disorder of the schizotypical type; tic disorders, Tourette's syndrome; trichotillomania; convulsive disorder; seizure; substance dependence; substance abuse; substance withdrawal; for the treatment and/or prevention of drug addiction and/or withdrawal; for the treatment and/or prevention of nicotine addiction and/or withdrawal; for the treatment and/or prevention of alcohol addiction and/or withdrawal.
To optimize treatment of patients suffering from a disorder as mentioned in the foregoing paragraph, the compounds of Formula (I) may be administered together with other psychotropic compounds.
The present invention also provides a method of treating warm-blooded animals suffering from such disorders, said method comprising the systemic administration of a therapeutic amount of a compound of Formula (I) effective in treating the above described disorders.
The present invention also relates to the use of compounds of Formula (I) as defined hereinabove for the manufacture of a medicament, more especially a medicine in the treatment and/or prevention of conditions wherein cognition is impaired; Alzheimer's disease, Parkinson's disease, Schizophrenia, Huntingdon's disease, Lewy Body Dementia, dementia due to HIV disease, dementia due to Creutzfeldt-Jakob disease; amnestic disorders; mild cognitive impairment; and age-related cognitive decline; for the treatment and/or prevention of feeding disorders and diseases, for the regulation of appetite; for the maintenance, increase or reduction of body weight; anorexia, bulimia, obesity, cachexia, type II diabetes (non insulin dependent diabetes mellitus), type II diabetes caused by obesity; for the treatment and/or prevention of stroke; migraine; head trauma; epilepsy; irritable colon syndrome; irritable bowl syndrome; for the treatment of disorders of the central nervous system; schizophreniform disorder, schizoaffective disorder, delusional disorder, brief psychotic disorder, shared psychotic disorder, psychotic disorder due to a general medical condition, substance-induced psychotic disorder, psychotic disorder not otherwise specified; psychosis associated with dementia; major depressive disorder, dysthymic disorder, premenstrual dysphoric disorder, depressive disorder not otherwise specified, Bipolar I disorder, bipolar II disorder, cyclothymic disorder, bipolar disorder not otherwise specified, mood disorder due to a general medical condition, substance-induced mood disorder, mood disorder not otherwise specified; generalized anxiety disorder, obsessive-compulsive disorder, panic disorder, acute stress disorder, post-traumatic stress disorder; mental retardation; pervasive developmental disorders; attention deficit disorders, attention-deficit/hyperactivity disorder, disruptive behaviour disorders; personality disorder of the paranoid type, personality disorder of the schizoid type, personality disorder of the schizotypical type; tic disorders, Tourette's syndrome; trichotillomania; convulsive disorder; seizure; substance dependence; substance abuse; substance withdrawal; for the treatment and/or prevention of drug addiction and/or withdrawal; for the treatment and/or prevention of nicotine addiction and/or withdrawal; for the treatment and/or prevention of alcohol addiction and/or withdrawal.
In an embodiment, said conditions are selected from the treatment and/or prevention of drug addiction and/or withdrawal; the treatment and/or prevention of nicotine addiction and/or withdrawal; the treatment and/or prevention of alcohol addiction and/or withdrawal.
In an embodiment, said diseases or conditions are selected from conditions wherein cognition is impaired, disorders of the central nervous system, anxiety, depression, attention deficit hyperactivity disorder, Alzheimer's disease, epilepsy, schizophrenia, feeding disorders and diseases.
In an embodiment, said diseases or conditions are selected from conditions wherein cognition is impaired, disorders of the central nervous system, anxiety, depression, attention deficit hyperactivity disorder, Alzheimer's disease, epilepsy, and schizophrenia.
In an embodiment, said diseases or conditions are selected from conditions wherein cognition is impaired, anxiety, Alzheimer's disease, and schizophrenia.
In an embodiment, said diseases or conditions are selected from anxiety, Alzheimer's disease, and schizophrenia.
In an embodiment, said disease is schizophrenia.
In an embodiment, said disease is Alzheimer's disease.
In an embodiment, said condition is a condition wherein cognition is impaired.
The present invention also relates to the use of compounds of Formula (I) as defined hereinabove for the manufacture of a medicament, more especially a medicine in the treatment of said diseases or conditions.
The present invention also relates to compounds of Formula (I) for use in treating or preventing the diseases or conditions mentioned hereinbefore.
The present invention also relates to compounds of Formula (I) for use in treating the diseases or conditions mentioned hereinbefore.
The present invention also relates to compounds of Formula (I) for treating or preventing the diseases or conditions mentioned hereinbefore.
The present invention also relates to compounds of Formula (I) for treating the diseases or conditions mentioned hereinbefore.
Those of skill in the treatment of such diseases could determine the effective therapeutic daily amount from the test results presented hereinafter. An effective therapeutic daily amount would be from about 0.01 mg/kg to about 10 mg/kg body weight, more preferably from about 0.05 mg/kg to about 1 mg/kg body weight.
The invention also relates to a pharmaceutical composition comprising a pharmaceutically acceptable carrier and, as active ingredient, a therapeutically effective amount of a compound according to Formula (I).
For ease of administration, the subject compounds may be formulated into various pharmaceutical forms for administration purposes. The compounds according to the invention, in particular the compounds according to Formula (I), a pharmaceutically acceptable acid or base addition salt thereof, a stereoisomeric form thereof, or any subgroup or combination thereof may be formulated into various pharmaceutical forms for administration purposes. As appropriate compositions there may be cited all compositions usually employed for systemically administering drugs. To prepare the pharmaceutical compositions of this invention, an effective amount of the particular compound, optionally in addition salt form, as the active ingredient is combined in intimate admixture with a pharmaceutically acceptable carrier, which carrier may take a wide variety of forms depending on the form of preparation desired for administration. These pharmaceutical compositions are desirable in unitary dosage form suitable, in particular, for administration orally, rectally, percutaneously, by parenteral injection or by inhalation. For example, in preparing the compositions in oral dosage form, any of the usual pharmaceutical media may be employed such as, for example, water, glycols, oils, alcohols and the like in the case of oral liquid preparations such as suspensions, syrups, elixirs, emulsions and solutions; or solid carriers such as starches, sugars, kaolin, diluents, lubricants, binders, disintegrating agents and the like in the case of powders, pills, capsules and tablets. Because of their ease in administration, tablets and capsules represent the most advantageous oral dosage unit forms in which case solid pharmaceutical carriers are obviously employed. For parenteral compositions, the carrier will usually comprise sterile water, at least in large part, though other ingredients, for example, to aid solubility, may be included. Injectable solutions, for example, may be prepared in which the carrier comprises saline solution, glucose solution or a mixture of saline and glucose solution. Injectable solutions, for example, may be prepared in which the carrier comprises saline solution, glucose solution or a mixture of saline and glucose solution. Injectable solutions containing compounds of Formula (I) may be formulated in an oil for prolonged action. Appropriate oils for this purpose are, for example, peanut oil, sesame oil, cottonseed oil, corn oil, soybean oil, synthetic glycerol esters of long chain fatty acids and mixtures of these and other oils. Injectable suspensions may also be prepared in which case appropriate liquid carriers, suspending agents and the like may be employed. Also included are solid form preparations that are intended to be converted, shortly before use, to liquid form preparations. In the compositions suitable for percutaneous administration, the carrier optionally comprises a penetration enhancing agent and/or a suitable wetting agent, optionally combined with suitable additives of any nature in minor proportions, which additives do not introduce a significant deleterious effect on the skin. Said additives may facilitate the administration to the skin and/or may be helpful for preparing the desired compositions. These compositions may be administered in various ways, e.g., as a transdermal patch, as a spot-on, as an ointment. Acid or base addition salts of compounds of Formula (I) due to their increased water solubility over the corresponding base or acid form, are more suitable in the preparation of aqueous compositions.
It is especially advantageous to formulate the aforementioned pharmaceutical compositions in unit dosage form for ease of administration and uniformity of dosage. Unit dosage form as used herein refers to physically discrete units suitable as unitary dosages, each unit containing a predetermined quantity of active ingredient calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. Examples of such unit dosage forms are tablets (including scored or coated tablets), capsules, pills, powder packets, wafers, suppositories, injectable solutions or suspensions and the like, and segregated multiples thereof.
Since the compounds according to the invention are potent orally administrable compounds, pharmaceutical compositions comprising said compounds for administration orally are especially advantageous.
In order to enhance the solubility and/or the stability of the compounds of Formula (I) in pharmaceutical compositions, it can be advantageous to employ α-, β- or γ-cyclodextrins or their derivatives, in particular hydroxyalkyl substituted cyclodextrins, e.g. 2-hydroxypropyl-β-cyclodextrin. Also co-solvents such as alcohols may improve the solubility and/or the stability of the compounds according to the invention in pharmaceutical compositions.
Depending on the mode of administration, the pharmaceutical composition will preferably comprise from 0.05 to 99% by weight, more preferably from 0.1 to 70% by weight, even more preferably from 0.1 to 50% by weight of the compound of formula (I), and, from 1 to 99.95% by weight, more preferably from 30 to 99.9% by weight, even more preferably from 50 to 99.9% by weight of a pharmaceutically acceptable carrier, all percentages being based on the total weight of the composition.
Preparation
Compounds of Formula (I-a),




wherein Rl is chloro, trifluoromethyl or cyano, R3a is C1-4alkyl or pyridinylmethyl and where R2 and X are defined as mentioned before, can be prepared by reacting a compound of Formula (I-b)





wherein Rl, X and R2 are defined as mentioned before, with a C1-4-aldehyde (such as e.g. formaldehyde or acetaldehyde) or pyridinecarboxaldehyde in the presence of a base such as Et3N, a reducing agent such as NaBH(OAc)3, Pt/C (not suitable for R1a=Cl) or Raney Nickel (not suitable for R1a=CN) and a suitable reaction solvent such as dichloromethane (DCM), methanol or ethanol.

Compounds of Formula (I-b)





wherein the substituents are defined as mentioned before, may be prepared by deprotection of the protecting group in an intermediate of Formula (II),





wherein L represents a suitable protecting group, such as tert-butyloxycarbonyl, and R1, R2 and X are defined as mentioned before, under suitable conditions, such as in the presence of trifluoroacetic acid (TFA) in DCM, or an acid cation-exchange resin of the sulphonated polystyrene type (e.g. AMBERLITETM acid) in methanol (MeOH), or HCl in a solvent as dioxane.

Intermediates of Formula (II′)





wherein L represents a suitable protecting group, such as tert-butyloxycarbonyl, and R2 and X are defined as mentioned before, may be prepared by reacting the chloro derivative (II′′) with Zn(CN)2 in the presence of a palladium catalyst such as tetrakis(triphenylphosphine)palladium in a suitable solvent such as for example DMF.

Intermediates of Formula (II-a)





wherein R1a is chloro or trifluoromethyl and the other substituents are defined as hereabove, are generally prepared in a N,N-dimethylglycine-promoted Ullmann coupling reaction between an intermediate of Formula (III)





wherein R1a and L are as defined hereabove, with a commercially available Rx-phenol, wherein Rx is hydrogen or halo. This type of reaction typically can be performed under copper or nickel catalysed conditions (for example using copper or nickel salts such as for example Cu2O, CuI or Ni(OAc)2) and a base like Cs2CO3, K3PO4 or K2CO3 at an elevated temperature (70-100° C.) in an appropriate inert solvent such as dioxane or toluene.

Intermediates of Formula (II-b)





wherein R1a, R2 and L are defined as hereabove, are generally prepared by reaction of an intermediate of Formula (III) with a commercially available Rx-benzenamine, wherein Rx is hydrogen or halo, typically in the presence of a ligand such as (1S)-[1,1′-Binaphthalene]-2,2′-diylbis[diphenylphosphine] ((S)-BINAP), and a base like Cs2CO3, K3PO4, K2CO3 or sodium tert-butoxide (tert-BuONa) at an elevated temperature (70-100° C.) in an appropriate inert solvent such as dioxane or toluene.

Intermediates of Formula (II-c)





wherein R1a, R2 and L are defined as hereabove, are generally prepared by the CuI/L-proline catalysed coupling reaction of an intermediate of Formula (III) with a Rx-benzenesulfinic acid sodium salt, wherein Rx is hydrogen or halo, in the presence of a base like Cs2CO3, K3PO4 or K2CO3 at an elevated temperature (70-100° C.) in an appropriate solvent such as dimethyl sulfoxide (DMSO).

Intermediates of Formula (II-d)





wherein R1a, R2 and L are defined as hereabove and where X′ is 1,2-ethenediyl or ethynediyl are generally prepared by coupling of an intermediate of Formula (III) to [(Rx-phenyl)ethenyl)]-boronic acid or (Rx-phenyl)ethynyl), wherein Rx is hydrogen or halo, in the presence of a catalyst as tetrakis(triphenylphosphine)palladium (Pd(PPh3)4), a base like Cs2CO3, K3PO4 or K2CO3 and optionally copper or nickel salts such as, for example, Cu2O, CuI or Ni(OAc)2 optionally in the presence a suitable solvent such as dioxane or N,N-dimethylformamide (DMF), under suitable reaction conditions, such as a convenient temperature, either by conventional heating or under microwave irradiation for a period of time to ensure the completion of the reaction.

Intermediates of Formula (II-e)





wherein R1a, R2 and L are defined as hereabove and wherein X′′ is —NH—CH2— or —O—CH2—, are generally prepared by coupling of an intermediate of Formula (III) to an Rx-benzenemethanamine or an Rx-benzenemethanol, wherein Rx is hydrogen or halo, in the presence of a base like NaH in a suitable solvent such as THF or DMF, under suitable reaction conditions, such as a convenient temperature for a period of time to ensure the completion of the reaction.

Intermediates of Formula (II-f)





wherein R1a and L are defined as hereabove, may be prepared by the reduction of an intermediate of Formula (II-g)





wherein R1a and L are defined as hereabove, with a Pd/C catalyst under H2 atmosphere in an appropriate solvents such as EtOH or MeOH at room temperature.

Intermediates of Formula (II-h)





wherein R1a and L are defined as hereabove, may be prepared by the oxidation of an intermediate of Formula (II-g) with an oxidizing agent such as MnO2 or 1,1,1-tris(acetyloxy)-3H-1,2-benziodoxo1-3-one (Dess Martin's reagent) in a suitable solvent such as DCM or ethyl acetate (EtOAc) at low temperatures, typically at 0° C.

Intermediates of Formula (II-g) may be prepared by reacting a compound of Formula (IV)





wherein R1a and L are defined as hereabove, with benzaldehyde in the presence of a suitable base such as a mixture of butyllithium and 2,2,6,6-tetramethylpiperidine in a suitable inert solvent such as tetrahydrofuran (THF) at low temperatures, typically ranging from −78° C. to 0° C.

Intermediates of Formula (III) may be prepared by reacting an intermediate of Formula (IV) with iodine in the presence of a suitable base such as a mixture of butyllithium and 2,2,6,6-tetramethylpiperidine in a suitable inert solvent such as THF at low temperatures, typically ranging from −78° C. to 0° C.
Intermediates of Formula (IV′)




may be prepared by reacting 6-chloro-3-trifluoromethylpyridazine (prepared by following the procedure described in Goodman, A. J.; Stanforth, S. P; Tarbit B. Tetrahedron 1999, 55, 15067-15070) with tent-butyl 1-piperazinecarboxylate in the presence of a suitable base such as diisopropylethylamine (DIPEA) in a suitable solvent such as CH3CN at a convenient temperature, either by conventional heating or under microwave irradiation for a period of time to ensure the completion of the reaction.

The following examples illustrate the present invention.

Experimental Part

Hereinafter, the term “DCM” means dichloromethane, “MeOH” means methanol, “THF” means tetrahydrofuran, “LCMS” means Liquid Chromatography/Mass spectrometry, “q.s.” means quantum sufficit, “HPLC” means high-performance liquid chromatography, “r.t.” means room temperature, “Pd(OAc)2” means palladium acetate, “DIPEA” means diisopropylethylamine, “min.” means minutes, “h.” means hours, “(S)-BINAP” means (1S)-[1,1′-Binaphthalene]-2,2′-diylbis[diphenylphosphine], “EtOAc” means ethyl acetate, “Et3N” means triethylamine, “EtOH” means ethanol, “r.m.” means reaction mixture, “DMSO” means dimethyl sulfoxide, “TFA” means trifluoroacetic acid, “Pd(PPh3)4” means tetrakis(triphenylphosphine)palladium, and “NaBH(OAc)3” means sodium triacetoxyborohydride.
Microwave assisted reactions were performed in a single-mode reactor: EmrysTM Optimizer microwave reactor (Personal Chemistry A.B., currently Biotage).
1H NMR spectra were recorded either on a Bruker DPX-400 or on a Bruker AV-500 spectrometer with standard pulse sequences, operating at 400 MHz and 500 MHz respectively, using CDCl3 and DMSO-d6 as solvents. Chemical shifts (δ) are reported in parts per million (ppm) downfield from tetramethylsilane (TMS), which was used as internal standard.
A. Preparation of the Intermediates
EXAMPLE A1
a) Preparation of Intermediate 1




A mixture of 6-chloro-3-trifluoromethylpyridazine (0.666 g, 5.09 mmol) (prepared by following the procedure described in Goodman, A. J.; Stanforth, S. P; Tarbit B. Tetrahedron 1999, 55, 15067-15070), tert-butyl 1-piperazinecarboxylate (1.138 g, 6.11 mmol) and DIPEA (1.95 ml, 1.12 mmol) in CH3CN (10 ml) was stirred at 180° C. for 30 min. under microwave irradiation. The solvent was evaporated in vacuo and the residue was purified by column chromatography (silica gel; hexane/EtOAc) to yield intermediate 1 (1.67 g, 99%) as a light yellow solid. C14H19F3N4O2 requires 332; Found 333 (MH+).
b) Preparation of Intermediate 2




2,2,6,6-Tetramethylpiperidine (3.808 ml, 22.56 mmol) was added to a mixture of butyllithium (2.5 M in hexanes) (6.31 ml, 15.79 mmol) in THF (125 ml) at 0° C. The r.m. was stirred at r.t. for 1 h. The mixture was cooled to −78° C. and then a solution of intermediate 1 (2.5 g, 7.52 mmol) in THF (20 ml) was added. The mixture was stirred for 1 h. at −78° C. before adding a solution of iodine (2.29 g, 9.024 mmol) in THF (10 ml). The mixture was stirred at −78° C. for 1 h. and then diluted with a 10% solution of acetic acid in THF. Subsequently, the mixture was allowed to reach r.t. and the solvent was evaporated in vacuo. The residue was diluted with DCM and extracted with water. The organic layer was separated, dried (MgSO4), filtered and the solvent was evaporated in vacuo. The residue was precipitated from diethyl ether to yield intermediate 2 (2.81 g, 82%) as a light yellow solid. C14H18F3IN4O2 requires 458; Found 459 (MH+).
Intermediate 5




was prepared according to an analogous protocol as intermediate 2, but benzaldehyde was used instead of iodine. Yield: 84%.

c-1) Preparation of Intermediate 3




A mixture of intermediate 2 (0.490 g, 1.069 mmol), 4-fluorophenol (0.215 g, 1.92 mmol), N,N-dimethylglycine (0.107 mmol), CuI (0.0061 g, 0.032 mmol) and Cs2CO3 (0.697 g, 2.14 mmol) in dioxane (5 ml) was flushed with N2 and heated at 100° C. for 16 hours. Subsequently, the mixture was cooled and DCM, H2O and a concentrated NH4OH solution was added. The mixture was extracted and the separated organic layers were filtered over cotton. The solvent was evaporated and the residue was purified by flash column chromatography over silica gel (eluent: DCM/EtOAc 0-1-2-5%). The desired fractions were collected and the solvent was evaporated to yield 0.435 g (92%) of intermediate 3 as a white solid.
c-2) Preparation of Intermediate 4




A mixture of intermediate 2 (0.15 g, 0.327 mmol), 4-fluorobenzenamine (0.034 ml, 0.3 mmol), (S)-BINAP (0.0061 g, 0.009 mmol), Pd(OAc)2 (0.002 g, 0.009 mmol), Cs2CO3 (0.533 g, 1.63 mmol) and Et3N (0.002 ml, 0.02 mmol) in toluene (2 ml) was stirred and heated at 100° C. for 24 h. Subsequently, the mixture was cooled, filtered through diatomaceous earth (CELITETM) and the organic layer was evaporated. The residue was purified by flash column chromatography over silica gel ((eluent: DCM/EtOAc 100/0-97/3-95/5). The desired fractions were collected and the solvent was evaporated yielding 0.117 g (81%) of intermediate 4 as a yellow solid.
c-3) Preparation of Intermediate 7




A solution of intermediate 2 (0.200 g, 0.0004 mol) in DMSO (1.5 ml; dry) was flushed with N2 for a few min. Then a mixture of benzenesulfinic acid sodium salt (0.143 g, 0.0009 mol), L-proline (0.020 g, 0.0002 mol), CuI (0.08 g) and K3PO4 (0.093 g, 0.0004 mol) were added to the solution and the r.m. was heated at 85° C. for 18 h. Subsequently, the mixture was diluted with DCM and the resulting mixture was washed with an aqueous solution of ammonia. The organic layer was separated, dried (MgSO4), filtered and the filtrate was evaporated. The residue was purified by flash chromatography (eluent: DCM/(NH3 7N solution in MeOH) first 100/0 then 90/10). The desired fractions were collected and the solvent was evaporated. Yield: 0.148 g of intermediate 7 (72%) as a pale yellow solid.
c-4) Preparation of Intermediate 8




A mixture of intermediate 2 (0.2 g, 0.00043 mol), [2-(4-fluorophenyl)vinyl]boronic acid (0.092 g, 0.00055 mol), Pd(PPh3)4 (0.015 g, 0.0000086 mol), K2CO3 (0.118 g, 0.000129 mol), dioxane (2 ml) and DMF (0.5 ml) was irradiated at 160° C. for 1 h under microwave irradiation. Then the solvent was evaporated and the residue was purified by flash column chromatography over silica gel (eluent: DCM/(NH3 7N solution in MeOH) 97/3). The desired fractions were collected and the solvent was evaporated. Yield: 0.179 g of intermediate 8 (92%; mixture of E/Z) as a yellow oil.
Intermediate 10




was prepared according to an analogous protocol as was used for the synthesis of intermediate 8, but (E)-(2-phenylvinyl)boronic acid was used as the starting material instead of [2-(4-fluorophenyl)vinyl]boronic acid.

c-5) Preparation of Intermediate 9




A mixture of intermediate 2 (0.2 g, 0.43 mmol), 1-ethynyl-4-fluorobenzene (0.067 g, 0.55 mmol), Pd(PPh3)4 (0.010 g, 0.0086 mmol), CuI (0.002 g, 0.129 mmol) and Et3N (2 ml) was stirred at 55° C. for 3 h. Then, the mixture was cooled, filtered through diatomaceous earth (CELITETM) and the filtrate was evaporated. The residue was purified by flash column chromatography over silicagel (eluent: DCM/(NH3 7N solution in MeOH) 97/3). The desired fractions were collected and the solvent was evaporated. Yield: 0.132 g of intermediate 9 (68%).
c-6) Preparation of Intermediate 12




A mixture of intermediate 2 (0.400 g, 0.873 mmol) and 4-fluorobenzenemethanamine (1.2 ml, 10.5 mmol) was stirred for 1 h. at 150° C. Subsequently, water, a saturated NH4Cl solution and DCM were added. The organic layers were separated and were filtered over cotton. The filtrate was evaporated and the residue was purified by flash column chromatography over silica gel (eluent: DCM/EtOAc 100/0-95/5). The desired fractions were collected and the solvent was evaporated. Yield: 0.340 g of intermediate 12 (86%).
c-7) Preparation of Intermediate 13




4-Fluorobenzenemethanol (0.19 ml, 1.74 mmol) was added to a mixture of NaH (0.062 g, 1.55 mmol; 60% in oil) and DMF (4 ml; anhydrous). This mixture was stirred for 10 min. and then intermediate 2 (0.400 g, 0.873 mmol) in DMF (2 ml; anhydrous) was added. The r.m. was stirred for 1 h. at r.t. Subsequently, a saturated NH4Cl solution, water and DCM were added. The organic layer was separated and was filtered over cotton. The filtrate was evaporated and the residue was purified by flash column chromatography (eluent: DCM/EtOAc 100/0-98/2-96/4). The desired fractions were collected and the solvent was evaporated. Yield: 0.295 g of intermediate 13 (74%).
EXAMPLE 2
Preparation of Intermediate 6




Intermediate 5 (0.06 g, 0.0001 mol) was dissolved in EtOH (5 ml) and Pd/C (0.005 g) was added to this solution. The r.m. was stirred at r.t. and atmospheric pressure under H2 atmosphere for 2 days. Then the mixture was filtered through a pad of diatomaceous earth (CELITETM) and the filtrate was evaporated. The residue was purified by column chromatography (eluent: DCM). The desired fractions were collected and the solvent was evaporated. Yield: 0.050 g of intermediate 6 (86%).
EXAMPLE A3
a) Preparation of Intermediate 11




Intermediate 5 (0.08 g, 0.00018 mol) was dissolved in DCM (2 ml) and the solution was cooled down to 0° C. 1,1,1-Tris(acetyloxy)-3H-1,2-benziodoxol-3-one (Dess Martin's reagent) (0.12 g, 0.00027 mol) was added to this solution and the r.m. was stirred at 0° C. for 1 h. Subsequently, water was added and the layers were separated. The organic layer was dried (Na2SO4), filtered and the solvent was evaporated. Yield: Intermediate 11 (crude, used as such in the next reaction step).
b) Preparation of Intermediate 11 (Alternative Reaction Procedure)
MnO2 (5 g, 0.058 mol) was added to a mixture of intermediate 5 (3 g, 0.007 mol) in EtOAc (60 ml). The r.m. was stirred overnight at r.t. Then the mixture was filtered and the solvent was evaporated to yield 2.5 g of intermediate 11 (83%; crude, used as such in the next reaction step).
B. Preparation of the Compounds
EXAMPLE B1
Preparation of Compound 1




A mixture of intermediate 3 (0.435 g, 0.983 mmol) in TFA (2 ml) and DCM (18 ml) was stirred for 3 hours at r.t. Then DCM, a saturated Na2CO3 solution and H2O were added and the mixture was extracted. The separated organic layers were filtered over cotton, the solvent was evaporated and the residue was purified by flash column chromatography over silica gel (DCM/(NH3 7 N solution in MeOH) 100/0-98/2). The desired fractions were collected and the solvent was evaporated to yield 0.316 g (94%) of compound 1.
1H NMR (400 MHz, CDCl) δ ppm: 2.86-3.06 (m, 4 H) 3.57-3.64 (m, 4 H) 5.96 (s, 1 H) 7.08-7.25 (m, 4 H).
EXAMPLE B2
a-1) Preparation of Compound 2




A mixture of intermediate 4 (0.117 g, 0.33 mmol) and an acid cation-exchange resin of the sulphonated polystyrene type (AMBERLITETM acid) (q.s.) in MeOH (8 ml) was shaken for 24 h. The resin was filtered off and the organic layer was discarded. Subsequently, the resin was washed with MeOH and stirred for 30 min. in a NH3 7N solution in MeOH. The resin was filtered off and the obtained organic layer was concentrated in vacuo. The residue was purified by flash column chromatography over silica gel (DCM/MeOH 70/30). The desired fractions were collected and the solvent was evaporated to yield a yellow solid. This solid was repurified by HPLC to yield 0.048 g (53%) of a white solid. The amorphous solid was recrystallized from ethyl ether to yield 0.015 g of compound 2 (free base) as a crystalline white solid.
1H NMR (400 MHz, DMSO-d6) ppm 2.81-2.93 (m, 4 H) 3.47-3.53 (m, 4 H) 6.15 (s, 1 H) 7.26 (t, J=8.81 Hz, 2 H) 7.30-7.39 (m, 2 H) 8.13 (s, 1 H).
a-2) Preparation of Compound 16




A mixture of intermediate 4 (0.425 g, 0.963 mmol), DCM (18 ml) and TFA (2 ml) was stirred for 3 h. at r.t. Then DCM, saturated Na2CO3 and H2O were added and the mixture was extracted. The separated organic layers were filtered over cotton and the solvent was evaporated. The residue was purified by flash chromatography over silica gel (eluent: DCM/(NH3 7N solution in MeOH) from 100/0 till 97/3). The desired fractions were collected and the solvent was evaporated. The residue was dissolved in EtOAc/DIPE and a HCl solution in 2-propanol (5-6 N) was added. Subsequently, the major part of the solvent was evaporated. Extra EtOAc was added to the concentrate and sonication in an ultrasonic bath was applied to the mixture. The precipitate was filtered off and dried. Yield: 0.388 g of compound 16 (97%; .2.5HCl.0.5H2O).
1H NMR (400 MHz, DMSO-d6) δ ppm 3.14 (br. s., 4 H) 3.71-3.79 (m, 4 H) 6.28 (s, 1 H) 7.28 (t, J=8.79 Hz, 2 H) 7.32-7.42 (m, 2 H) 8.47 (s, 1 H) 9.43 (br. s., 2 H).
b) Preparation of Compounds 7 and 8




Compound 7 (Z-isomer) and compound 8 (E-isomer) were prepared according to an analogous protocol as was used for the synthesis of compound 2, but intermediate 8 (mixture of E/Z) was used as the starting material instead of intermediate 4. After the HPLC purification, two pure isomers were obtained.
Compound 7:
1H NMR (400 MHz, DMSO-d6) δ ppm: 2.59-2.82 (m, 4 H) 3.45-3.57 (m, 4 H) 6.59 (br. d, J=12.4 Hz, 1 H) 6.91 (s, 1 H) 6.96 (d, J=12.4 Hz, 1 H) 7.04-7.25 (m, 4 H).
Compound 8:
1H NMR (400 MHz, DMSO-d6) δ ppm 2.75-2.88 (m, 4 H) 3.65-3.77 (m, 4 H) 7.05 (dd, J=16.17, 1.87 Hz, 1 H) 7.24-7.34 (m, 2 H) 7.53 (s, 0 H) 7.64-7.76 (m, 3 H).
c) Preparation of Compound 9




Compound 9 was prepared according to an analogous protocol as was used for the synthesis of compound 2, but intermediate 9 was used as the starting material instead of intermediate 4. Yield: Compound 9 as a yellow solid (80%).
1H NMR (400 MHz, DMSO-d6) δ ppm: 2.72-2.86 (m, 4 H) 3.63-3.75 (m, 4 H) 7.31 -7.41 (m, 2 H) 7.60 (s, 1 H) 7.62-7.69 (m, 2 H).
EXAMPLE B3
a) Preparation of Compound 3




Intermediate 6 (0.05 g, 0.0001 mol) was dissolved in HCl 4M in dioxane (1 ml). The solution was stirred for 1 h. at r.t. The solvent was evaporated and the residue was dissolved in DCM. This solution was washed with a saturated NaHCO3 solution, dried (Na2SO4) and filtered. The compound was purified by normal phase column chromatography (eluent: DCM/(NH3 7N solution in MeOH)). The desired fractions were collected and the solvent was evaporated yielding 0.035 g of compound 3 (90%).
1H NMR (500 MHz, CDCl3) δ ppm 2.82-2.89 (m, 4 H) 3.42-3.61 (m, 4 H) 3.98 (s, 2 H) 6.32 (s, 1 H) 7.09 (d, J=7.51 Hz, 2 H) 7.20-7.26 (m, 1 H) 7.29 (t, J=7.37 Hz, 2 H).
b) Preparation of Compound 5




A solution of intermediate 5 (0.054 g, 0.109 mmol) and a 4M HCl solution in dioxane was stirred at r.t. for 16 h. The solvent was evaporated and the residue was treated with ethyl ether to yield a light yellow precipitate that was filtered off. Yield: 0.0426 g of compound 5 (92%; HCl-salt).
1H NMR (400 MHz, DMSO-d6) δ ppm: 3.18-3.32 (m, 4 H) 3.82-4.20 (m, 4 H) 5.87 (s, 1 H) 7.14-7.43 (m, 5 H) 7.65 (s, 1H) 9.07 (br. s., 2H).
EXAMPLE 4
a) Preparation of Compound 4 and Compound 12




Intermediate 11 (crude; the residue that was obtained in example A3.a was dissolved in a 4M HCl solution in dioxane (2 ml) and the mixture was stirred at r.t. for 1 h. The solvent was evaporated and the residue was treated with a saturated NaHCO3 solution, extracted with DCM and purified by column chromatography (eluent: DCM/EtOAc 7/3. The desired fractions were collected and the solvent was evaporated. Yield: 0.030 g of compound 4 (50%).
The HCl-salt of compound 4, compound 12, was obtained by dissolving intermediate 11 (0.5 g, 0.001145 mol) in a HCl solution in MeOH (15 ml). The r.m. was stirred for 4 h. at r.t. Then the solvent was evaporated to yield 0.350 g of compound 12 (81.9%; HCl-salt form).
b) Preparation of Compound 13




A mixture of compound 12 (0.080 g, 0.215 mmol), formaldehyde (0.050 g, 0.47 mmol), NaBH(OAc)3 (0.100 g, 0.47 mmol) and Et3N (0.1 g, 1 mmol) in DCM (5 ml) was stirred overnight at r.t. Subsequently, the mixture was washed with a saturated NaHCO3 solution. The separated organic layer was dried (Na2SO4), filtered and the solvent was evaporated in vacuo. The residue was purified by preparative TLC (eluent: DCM/MeOH 20/1). Yield: Compound 13 (42%).
EXAMPLE B5
a) Preparation of Compound 6




TFA (1 ml) was added to a solution of intermediate 7 (0.145 g, 0.0003 mol) in DCM (4 ml) and the r.m. was stirred for 2 h. at r.t. Subsequently, the solvent was evaporated and the residue was dissolved in DCM. This organic solution was washed with a saturated Na2CO3 solution. The organic layer was separated, dried (MgSO4), filtered and the filtrate was evaporated. The product was purified by flash column chromatography (eluent: DCM/(NH3 7N solution in MeOH) first 100/0 then 95/5). The desired fractions were collected and the solvent was evaporated, to yield 0.103 g of a pale yellow solid. This solid was further purified by HPLC to yield 0.0513 g of compound 6 (45%) as a pale yellow solid.
1H NMR (400 MHz, CDCl3) δ ppm 2.96-3.08 (m, 4 H) 3.80-3.89 (m, 4 H) 7.45 -7.54 (m, 2 H) 7.58-7.64 (m, 1 H) 7.66 (s, 1 H) 7.79 (d, J=7.88 Hz, 2 H).
b) Preparation of Compound 14




A mixture of intermediate 12 (0.340 g, 0.7465 mmol), TFA (1 ml) and DCM (9 ml) was stirred for 3 h. at r.t. Then a saturated Na2CO3 solution, water and DCM were added. The organic layer was separated and filtered over cotton. The solvent was evaporated and the residue was purified by flash column chromatography over silica gel (eluent: DCM/(NH3 7N solution in MeOH) first 100/0, then 99/1, then 98/2). The desired fractions were collected and the solvent was evaporated. The sticky product was treated with 5-6 N HCl in 2-propanol (0.5 ml). The solvent was evaporated and EtOAc was added to the residue. Sonication in an ultrasonic bath was applied to the mixture and subsequently the compound was filtered off and dried. Yield: 0.275 g of compound 14 (86%; . 2.5HCl.0.5H2O).
1H NMR (400 MHz, DMSO-d6) δ ppm 3.17 (br. s., 4 H) 3.80-3.92 (m, 4 H) 4.59 (d, J=6.01 Hz, 2 H) 6.36 (s, 1 H) 7.18 (t, J=8.79 Hz, 2 H) 7.44 (dd, J=8.67, 5.66 Hz, 2 H) 7.85 (br. s., 1 H) 9.51 (br. s., 2 H).
c) Preparation of Compound 15




Compound 15 was prepared according to an analogous protocol as was used for the synthesis of compound 6, but intermediate 13 was used as the starting material instead of intermediate 7. Yield: Compound 15 (88%).
1H NMR (400 MHz, CDCl3) δ ppm: 2.93-3.04 (m, 4 H) 3.62-3.76 (m, 4 H) 5.15 (s, 2 H) 6.23 (s, 1 H) 7.10 (t, J=8.67 Hz, 2 H) 7.38 (dd, J=8.55, 5.32 Hz, 2 H).
EXAMPLE B6
a) Preparation of Compound 10




A mixture of intermediate 10 (5.5 g, 0.0127 mol) and a HCl solution in MeOH (110 ml) was stirred for 4 h. at r.t. Subsequently, the solvent was evaporated to yield 4.5 g of compound 10 (95%; HCl-salt).
b) Preparation of Compound 11




A mixture of compound 10 (0.080 g, 0.22 mmol), formaldehyde (0.25 mmol), NaBH(OAc)3 (q.s.) and Et3N (0.101 g, 1 mmol) in DCM (5 ml) was stirred overnight at r.t. Then the solvent was evaporated and the residue was purified by preparative TLC (eluent: DCM/MeOH 20/1) to yield compound 11.
The following compounds of formula (I), as depicted in Table 1, were prepared by analogy to the above examples (Ex. No.). Some compounds were obtained as salt forms. In case the exact stoichiometry was determined, the result is shown in the column ‘Salt forms’, for example see Co. No. 14 and 16. In case the exact stoichiometry was not determined, only the type of salt form of the compound is indicated, for example see Co. No. 5.







TABLE 1







(I)








 












Co. No.
Ex. No.
- - - -X- - - -
- - - -R2
- - - -R3
Salt forms















1
B1












free base


 


2
B2.a-1












free base


 


3
B3.a












free base


 


4
B4.a












free base


 


5
B3.b












HCl-salt


 


6
B5












free base


 


7
B2.b












free base


 


8
B2.b












free base


 


9
B2.c












free base


 


10
B6.a












HCl-salt


 


11
B6.b












free base


 


12
B4.a












HCl-salt


 


13
B4.b












free base


 


14
B5.b












•2.5HCl •0.5H2O


 


15
B5.c












free base


 


16
B2.a-2












•2.5HCl •0.5H2O


 


17
B6.b












trifluoroacetate


 


18
B6.b












free base









C. Analytical Part

LCMS

General Procedure A

The HPLC measurement was performed using a Shimadzu 2010 LCMS-system comprising a pump, photo diode array detector (PDA) (wavelength used 220 nm), a column oven and a column as specified in the respective methods below. Flow from the column was split to a Shimadzu 2010 MSD detector. MS detector was configured with API-ES (atmospheric pressure electrospray ionization). Mass spectra were acquired by scanning from 100 to 1000. The interface voltage was 4500 V for positive ionization mode. The nebulizing gas flow was 1.5 l/min. The CDL (Curved Desolvation Line with heated capillary) temperature was 250° C. and the CDL voltage was 30 V. The heat block temperature was 200° C. The detector voltage was 1500 V.
General Procedure B
The LC measurement was performed using an Acquity Ultra Performance Liquid Chromatography (UPLC) (Waters) system comprising a binary pump, a sample organizer, a column heater (set at 55° C.), a diode-array detector (DAD) and a column as specified in the respective methods below. Flow from the column was split to a MS spectrometer. The MS detector was configured with an electrospray ionization source. Mass spectra were acquired by scanning from 100 to 1000 in 0.18 seconds using a dwell time of 0.02 seconds. The capillary needle voltage was 3.5 kV and the source temperature was maintained at 140° C. Nitrogen was used as the nebulizer gas. Data acquisition was performed with a Waters-Micromass MassLynx-Openlynx data system.
LCMS Method 1
In addition to general procedure A: Reversed phase HPLC was carried out on a YMC-Pack ODS-AQ, 50×2.0 mm 7 μm column with a flow rate of 1.0 ml/min. Two mobile phases (mobile phase A: water with 0.1% TFA; mobile phase B: CH3CN with 0.05% TFA) were used to run a gradient from 99% A and 1% B to 90% A and 10% B in 0.01 min. Subsequently, a gradient was applied to 20% A and 80% B at 2.2 min. and this was hold for 0.28 min. Typical injection volumes of 1 μl were used. Oven temperature was 50° C. (MS polarity: positive)
LCMS Method 2
In addition to general procedure B: Reversed phase UPLC was carried out on a bridged ethylsiloxane/silica hybrid (BEH) C18 column (1.7 μm, 2.1×50 mm; Waters Acquity) with a flow rate of 0.8 ml/min. Two mobile phases (mobile phase A: 0.1% formic acid in H2O/MeOH 95/5; mobile phase B: MeOH) were used to run a gradient condition from 95% A and 5% B to 5% A and 95% B in 1.3 min. and hold for 0.2 min. An injection volume of 0.5 μl was used. Cone voltage was 10 V for positive ionization mode and 20 V for negative ionization mode.
Melting Points
For a number of compounds, melting points were determined in open capillary tubes on a Mettler FP62 apparatus. Melting points were measured with a temperature gradient of 3 or 10° C./minute. Maximum temperature was 300° C. The melting point was read from a digital display.







TABLE 2







Retention time (Rt) in min., MH+ (also [M + H]+) peak


(protonated molecule), LCMS method and m.p. (melting point in ° C.).


‘n.d.’ means not determined.











Co. No.
Rt
MH+
LCMS Method
m.p. (° C.)














1
0.93
343
2
132.5


2
0.75
342
2
n.d.


3
0.94
323
2
133.8


4
0.85
337
2
289.5


5
0.82
339
2
199.7


6
0.83
373
2
180.3


7
0.96
353
2
n.d.


8
1.05
353
2
180.6


9
1.05
351
2
251.6


10
1.73
335
1
n.d.


11
1.03
349
2
135.8


12
0.85
337
2
n.d.


13
0.85
351
2
136.3


14
0.82
356
2
n.d.


15
0.99
357
2
142.1


16
0.75
342
2
>300  


17
1.14
426
2
163.9


18
1.20
426
2
121.4









D. Pharmacology

In vitro Binding Affinity for Human 5-HT6 Receptor

Frozen membranes of human Serotonin 5-HT6 receptor-transfected HEK cells were thawed, briefly homogenized using an Ultra-Turrax T25 homogeniser and diluted in 50 mM Tris-HCl assay buffer containing 10 mM MgCl2, 1 mM EDTA and 10 μM Pargyline (adjusted to pH 7.4 with HCl) to an appropriate protein concentration optimized for specific and non-specific binding. Radioligand [3H]Lysergic acid diethylamide (Perkin Elmer, specific activity  ̃80 Ci/mmol) was diluted in assay buffer at a concentration of 20 nM. Radioligand (20 μl), along with 40 μl of either the 10% DMSO control, Methiothepine (10−5M final concentration for measurement of non specific binding), or compound of interest, was then incubated with 70 μl of the prepared membrane solution and 70 μl of WGA (wheat germ agglutinin) coated PVT (polyvinyltoluidene) beads (0.25 mg/well final concentration). The final concentration of radioligand per well was 2 nM. After shaking for 24 h. at RT, plates were counted in a TopcountTM scintillation counter. Percentage specific binding and competition binding curves were calculated using S-Plus software (Insightful).







TABLE 3







pIC50 Values (5-HT6)










Co. No.
pIC50














1
6.6



2
7.2



3
6.9



4
6.9



5
6.2



6
6.6



7
6.8



8
7.2



9
5.8



10
n.d.



11
6.4



12
n.d.



13
6.8



14
6.2



15
6.4



16
n.d.



17
5.9



18
5.2










In vitro Binding Assay for Human H3 Receptor

Binding of compounds to the cloned human H3 receptor, stably expressed in SK-N-MC cells, was performed as described earlier (Lovenberg T W, Pyati J, Chang H, Wilson S J, Erlander M G. Cloning of rat histamine H3 receptor reveals distinct species pharmacological profiles. J Pharmacol Expt Ther 2000;293:771-778). Briefly, cell pellets from SK-N-MC cells expressing the human H3 receptor were homogenized in 50 mM Tris-HCl/5 mM EDTA and recentrifuged at 30000 g for 30 min. Pellets were rehomogenized in 50 mM Tris/5 mM EDTA (pH 7.4). Membranes were incubated for 1 h at 25° C. with 125I-iodoproxyfan diluted with cold iodoproxifan in 50 mM Tris-HCl/5 mM EDTA. The final total iodoproxifan concentration in the reactions is 1 nM. The cold iodoproxifan is included at 0.975 nM and the 125I-iodoproxyfan is included at 0.025 nM final concentration. The reactions were terminated by filtration thru GF/B plates (pretreated with 0.3% polyethylenimine) on the cell harvester. The plates were washed 5 times with buffer. Nonspecific binding was defined in the presence of 100 μM histamine Inhibitory concentration (responsible for 50% inhibition of maximal effect, IC50) values were determined by a single site curve-fitting program (GraphPad, San Diego, Calif.) and converted to Ki values based on a 125I-iodoproxyfan dissociation constant (Kd) of 1 nM.







TABLE 4







Ki Values(H3)








Co.



No.
Ki (nM)











1
5000


2
>10000


3
>10000


4
>10000


5
>10000


6
>10000


7
>10000


8
>10000


9
>10000


10
n.d.


11
>10000


12
n.d.


13
>10000


14
>10000


15
>10000


16
>10000


17
>10000


18
>10000









E. COMPOSITION EXAMPLES
“Active ingredient” (A.I.) as used throughout these examples relates to a compound of Formula (I), the pharmaceutically acceptable acid or base addition salts thereof, and the stereoisomeric forms thereof
Example E.1
Oral Drops
500 Grams of the A.I. was dissolved in 0.5 1 of 2-hydroxypropanoic acid and 1.5 l of the polyethylene glycol at 60 ̃80° C. After cooling to 30 ̃40° C. there were added 35 l of polyethylene glycol and the mixture was stirred well. Then there was added a solution of 1750 grams of sodium saccharin in 2.5 l of purified water and while stirring there were added 2.5 l of cocoa flavor and polyethylene glycol q.s. to a volume of 50 l, providing an oral drop solution comprising 10 mg/ml of A.I. The resulting solution was filled into suitable containers.
Example E.2
Oral Solution
9 Grams of methyl 4-hydroxybenzoate and 1 gram of propyl 4-hydroxybenzoate were dissolved in 41 of boiling purified water. In 3 l of this solution were dissolved first 10 grams of 2,3-dihydroxybutanedioic acid and thereafter 20 grams of the A.I. The latter solution was combined with the remaining part of the former solution and 12 l 1,2,3-propanetriol and 3 l of sorbitol 70% solution were added thereto. 40 Grams of sodium saccharin were dissolved in 0.5 l of water and 2 ml of raspberry and 2 ml of gooseberry essence were added. The latter solution was combined with the former, water was added q.s. to a volume of 20 l providing an oral solution comprising 5 mg of the active ingredient per teaspoonful (5 ml). The resulting solution was filled in suitable containers.
Example E.3
Film-Coated Tablets
Preparation of Tablet Core
A mixture of 100 grams of the A.I., 570 grams lactose and 200 grams starch was mixed well and thereafter humidified with a solution of 5 grams sodium dodecyl sulfate and 10 grams polyvinylpyrrolidone in about 200 ml of water. The wet powder mixture was sieved, dried and sieved again. Then there was added 100 grams microcrystalline cellulose and 15 grams hydrogenated vegetable oil. The whole was mixed well and compressed into tablets, giving 10.000 tablets, each containing 10 mg of the active ingredient.
Coating
To a solution of 10 grams methyl cellulose in 75 ml of denaturated ethanol there was added a solution of 5 grams of ethyl cellulose in 150 ml of dichloromethane. Then there were added 75 ml of dichloromethane and 2.5 ml 1,2,3-propanetriol. 10 Grams of polyethylene glycol was molten and dissolved in 75 ml of dichloromethane. The latter solution was added to the former and then there were added 2.5 grams of magnesium octadecanoate, 5 grams of polyvinylpyrrolidone and 30 ml of concentrated colour suspension and the whole was homogenated. The tablet cores were coated with the thus obtained mixture in a coating apparatus.
Example E.4
Injectable Solution
1.8 Grams methyl 4-hydroxybenzoate and 0.2 grams propyl 4-hydroxybenzoate were dissolved in about 0.5 l of boiling water for injection. After cooling to about 50° C. there were added while stirring 4 grams lactic acid, 0.05 grams propylene glycol and 4 grams of the A.I. The solution was cooled to room temperature and supplemented with water for injection q.s. ad 1 l, giving a solution comprising 4 mg/ml of A.I. The solution was sterilized by filtration and filled in sterile containers.

## Claims

1. A compound of formula (I)



or a stereoisomeric form thereof, wherein
R1 is chloro, trifluoromethyl or cyano;
R2 is phenyl or phenyl substituted with halo;
R3 is hydrogen, C1-4-alkyl or pyridinylmethyl;
X is —O—, —NH—, —CH2—, —CH(OH)—, —SO2—, —CO—, —NH—CH2—, —O—CH2—,
1,2-ethenediyl or ethynediyl;
or a pharmaceutically acceptable addition salt thereof.

2. The compound according to claim 1 wherein
R1 is trifluoromethyl;
R2 is phenyl or phenyl substituted with fluoro;
R3 is hydrogen, methyl or pyridinylmethyl;
X is —O—, —NH—, —CH2—, —CH(OH)—, —SO2—, —CO—, —NH—CH2—, —O—CH2—,
1,2-ethenediyl or ethynediyl;
or a pharmaceutically acceptable addition salt thereof.

3. The compound according to claim 1 wherein
R2 is phenyl or phenyl substituted with one fluoro.

4. The compound according to claim 1 wherein the compound is N-(4-fluorophenyl)-6-(1-piperazinyl)-3-(trifluoromethyl)-4-pyridazinamine.

5. The compound N-(4-fluorophenyl)-6-(1-piperazinyl)-3-(trifluoromethyl)-4-pyridazinamine.2.5 HCl 0.5 H2O.

6. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and, as active ingredient, a therapeutically effective amount of a compound as defined in claim 1.

7. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and, as active ingredient, a therapeutically effective amount of a compound as defined in claim 2.

8. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and, as active ingredient, a therapeutically effective amount of a compound as defined in claim 3.

9. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and, as active ingredient, a therapeutically effective amount of a compound as defined in claim 4.

10. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and, as active ingredient, a therapeutically effective amount of a compound as defined claim 5.