# Patent

## Title
Carbostyril derivatives and pharmaceutical composition containing the

## Abstract

This invention relates to compounds useful in treating 5-HT.sub.4 and/or 5-HT.sub.3 mediated conditions of the formula ##STR1## or a pharmaceutically acceptable salt thereof wherein R.sub.1 and R.sub.2 are independently selected from the group consisting of hydrogen, alkoxy, halogen, amino, monoalkylamino, dialkylamino, acylamino and alkylsulfonylamino; R.sub.3 is selected from the group consisting of H, alkyl and cycloalkyl; X is NH or O; and Z is selected from the group consisting of ##STR2## pharmaceutical compositions including the compounds and a method for treating serotonin mediated conditions with the compositions which act as 5-HT.sub.4 agonists or antagonists and/or 5-HT.sub.3 antagonists.

## Background
The present invention relates to pharmaceutical agents (compounds) which act as 5-HT.sub.4 agonists or antagonists and/or 5-HT.sub.3 antagonists in mammals. As 5-HT.sub.4 agonists these agents are useful in the treatment of hypomotility disorders of the gastrointestinal (GI) tract including reflux esophagitis, non-ulcer dyspepsia, gastroparesis, ileus, irritable bowel syndrome (constipation predominant) and constipation. Additionally, 5HT.sub.4 agonists are useful for the treatment of learning and memory disorders and as cardiovascular inotropic agents. As 5-HT.sub.4 antagonists these compounds are useful in the treatment of motility disorders of the GI tract such as diarrhea and irritable bowel syndrome (diarrhea predominant). As 5-HT.sub.3 antagonists these compounds are useful for treating emesis (caused by cancer chemotherapy or post-operative), anxiety, cognitive disorders, drug abuse (either cravings or withdrawal syndrome) and irritable bowel syndrome (diarrhea predominant).

Serotonin (5-hydroxytryptamine; 5-HT) functions as a neurotransmitter in the mammalian central nervous system (CNS) and in the periphery. Serotonergic neurons regulate a wide variety of sensory, motor and cortical functions. Additionally serotonin regulates enteric reflexes, mediates contraction of the vascular smooth muscle and platelet shape change and aggregation and as such effects such diverse systems as the cardiovascular system and gastrointestinal system, in addition to the central nervous system.

Pharmacological and physiological studies show that the activity of serotonin is mediated by several distinct cell surface receptor subtypes. These receptor subtypes either transduce extracellular signals by activating GTP-binding proteins (G-protein-coupled receptor subtypes) or activate the opening of nonselective cation channels to promote fast, depolarizing responses in neurons (ligand-gated ion channel receptor subtypes). 5-HT.sub.4 belongs to the former category while 5-HT.sub.3 belongs to the latter. Agents which interact with these receptors thereby modulate a variety of ion channels and intracellular messenger signaling pathways thereby extending the flexibility of serotonin's activity and eliciting a multitude of cellular and physiological responses. P. Bonate, Clinical Neuropharmacology, Vol. 14, No. 1, pp. 1-16 (1991).

European Patent application 309,423 discloses azabicyclo substituted benzimidazoline-2-oxo-1-carboxylic acid derivatives which are useful as 5-HT receptor antagonists.

Dumuis et al., Nauyn-Schmiedeberg's Arch Pharmacol, (1991) 343: 245-251 disclose azabicycloalkyl benzimidazolone derivatives as potent agonists at the 5-HT.sub.4 receptor.

In Pharmacological Research, Vol. 22, Supplement 2, (1990) Schiantarelli et al. disclose two benzimidazolone compounds useful as 5-HT.sub.3 antagonists and 5-HT.sub.4 agonists.

There is a need in the area of serotonin regulation for agents with broad clinical usefulness. Serotonin is one of the newer neurotransmitters to be recognized for physiological importance and agents which interact with 5-HT receptors are currently the focus of much research. P. Bonate, Clinical Neuropharmacology, Vol. 14, No. 1, pp. 1-6 (1991).

Accordingly, it is the object of this invention to produce compounds for use as pharmaceutical agents which will exhibit 5-HT.sub.4 agonist or antagonist and/or 5-HT.sub.3 antagonist activity in mammals. The compounds of the present invention meet the need for an agent which has broad clinical usefulness for treating serotonin mediated conditions in mammals by administering a therapeutically effective amount of the compounds to act as 5-HT.sub.4 agonists or antagonists and/or 5-HT.sub.3 antagonists.

This invention relates to compounds of the Formula I ##STR3## or a pharmaceutically acceptable salt thereof wherein R.sub.1 and R.sub.2 are independently selected from the group consisting of hydrogen, alkoxy, halogen, amino, monoalkylamino, dialkylamino, acylamino and alkylsulfonylamino;

R.sub.3 is selected from the group consisting of H, alkyl and cycloalkyl;

X is NH or O; and

Z is selected from the group consisting of ##STR4##

The present invention also provides pharmaceutical compositions comprised of a therapeutically effective amount of the compounds of Formula I in combination with a pharmaceutically acceptable carrier and a method for treating serotonin mediated conditions with said compositions which act as 5-HT.sub.4 agonists or antagonists and/or 5-HT.sub.3 antagonists.

This invention encompasses compounds of the Formula I as previously described.

Within the class of compounds defined by Formula I, there is a sub-class of preferred compounds represented by Formula II: ##STR5## or a pharmaceutically acceptable salt thereof

wherein R.sub.1 and R.sub.2 are independently selected from the group consisting of hydrogen, alkoxy, halogen, amino, monoalkylamino, dialkylamino, acylamino and alkylsulfonylamino;

R.sub.3 is selected from the group consisting of H, alkyl and cycloalkyl; and

Z is selected from the group consisting of ##STR6##

Included within the preferred subclass of compounds of the Formula II is: -1H-benzimidazole-1-carboxamide.

Included within the classes and subclasses of compounds embraced by Formulas I-II are isomeric forms of the described compounds including diastereoisomers and enantiomers and tautomeric forms of the described compounds. Pharmaceutically acceptable salts of such compounds are also included as well as pharmaceutically acceptable salts of such isomers and tautomers.

In the structures herein a bond drawn across a bond in a ring indicates that the bond can be to any available atom of the ring structure.

The term "pharmaceutically acceptable salt," as used herein, refers to conventionally accepted pharmaceutical salts prepared by processes which are well known to those of ordinary skill in the art. [See for example, S. M. Berge, et al., "Pharmaceutical Salts," J. Pharm. Sci., 66: 1-19 (1977)].

The term "composition" as used herein means a product which results from the mixing or combining of more than one element or ingredient.

The term "pharmaceutically acceptable carrier" as used herein means a pharmaceutically-acceptable material, composition or vehicle, such as a liquid or solid filler, diluent, excipient, solvent or encapsulating material, involved in carrying or transporting a chemical agent from one organ or portion of the body to another organ or portion of the body.

The term "therapeutically effective amount" shall mean that amount of drug or pharmaceutical agent that will elicit the biological or medical response of a tissue, system or animal that is being sought by a researcher or clinician.

The term "alkyl" as used herein means a univalent hydrocarbon radical having from one to twelve carbon atoms, more preferably from one to six carbon atoms and derived by the removal of a single hydrogen atom from a straight or branched chain saturated hydrocarbon. Representative of such radicals are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-octyl, 2,4-dimethylpentyl and the like.

The term "alkoxy" as used herein means an alkyl radical, as defined above having one or more oxygen atoms attached thereto. Representative alkoxy groups include methoxy, ethoxy, propoxy, tert-butoxy and the like.

The term halogen as used herein means a fluoro, chloro, bromo or iodo radical.

The term "monoalkylamino" as used herein is represented by the radical --NHR.sub.4 wherein R.sub.4 is an alkyl group as previously described.

The term "dialkylamino" as used herein is represented by the radical --NR.sub.4 R.sub.5 wherein R.sub.4 and R.sub.5 are the same or different alkyl groups, as defined above.

The term "acylamino" as used herein is represented by the radical ##STR7## wherein R.sub.4 is an alkyl group as described above.

The terms "alkylsulfonylamino" as used herein is represented by the radical R.sub.4 --SO.sub.2 --NH--wherein R.sub.4 is an alkyl group as defined above.

The term "cycloalkyl" as used herein means an alicyclic radical with from 3 to 6 carbon atoms. Examples of suitable cycloalkyl radicals includes cyclopropyl, cyclopropenyl, cyclobutyl, cyclohexyl, 2-cyclohexen-1-yl and the like.

The compounds herein exhibit 5-HT.sub.4 agonism or antagonism and/or 5-HT.sub.3 antagonism. The 5-HT.sub.3 activity possessed by the compounds of this invention was determined by the radioligand receptor binding assay as described herein and in the in vivo Bezold-Jarisch reflex procedure. 5-HT.sub.4 agonist activity was determined in the in vitro rat tunica muscularis mucosae (TMM) assay. (Baxter et al., Naunyn Schmied Arch. Pharmacol, 1991, 343, 439). The 5-HT.sub.4 agonist or antagonist and/or 5-HT.sub.3 antagonist activity of the compounds of the invention can be determined by these assays described herein, without undue experimentation.

By virtue of their activity as 5-HT.sub.4 agonists or antagonists and/or 5-HT.sub.3 antagonists the compounds of Formula I and II are useful in treating serotonin mediated conditions such as gastrointestinal motility disorders, emesis, anxiety, cognitive disorders and other CNS disorders. As used herein 5-HT.sub.4 agonist mediated conditions of the gastrointestinal tract include reflux esophagitis, non-ulcer dyspepsia, gastroparesis, ileus, irritable bowel syndrome (constipation predominant), constipation, and the like. As used herein 5-HT.sub.4 antagonist mediated conditions of the GI tract include diarrhea, irritable bowel syndrome (diarrhea predominant) and the like. Additionally, 5-HT.sub.4 agonists find utility in the treatment of cognitive disorders and as positive inotropic agents. As used herein 5-HT.sub.3 antagonist mediated conditions include emesis due to either cancer chemotherapy or post-operative, anxiety, cognitive disorders, drug abuse (either cravings or withdrawal syndrome), irritable bowel syndrome (diarrhea predominant) and the like. A physician or veterinarian of ordinary skill can readily determine whether a subject exhibits such a serotonin mediated condition.

The compounds of the present invention can be administered in such oral dosage forms as tablets, capsules, softgels, pills, powders, granules, elixirs or syrups. The compounds can also be administered intravascularly, intraperitoneally, subcutaneously, intramuscularly or topically using forms known to the pharmaceutical art. In general the preferred form of administration is oral.

For the orally administered pharmaceutical compositions and methods of the present invention, the foregoing active ingredients will typically be administered in admixture with suitable pharmaceutical diluents, excipients or carriers (collectively referred to hereinafter as "carrier" materials). Such carrier materials are suitably selected with respect to the intended form of administration and consistent with conventional pharmaceutical practices.

For example, for oral administration in the form of tablets or capsules, a therapeutically effective amount of one or more compounds of the present invention can be combined with any oral pharmaceutically acceptable inert carrier such as lactose, starch, sucrose, cellulose, magnesium stearate, calcium sulfate and the like or various combinations thereof. For oral administration in liquid forms, such as in softgels, elixirs, syrups and the like, a therapeutically effective amount of the active drug components can be combined with any oral pharmaceutically acceptable inert carrier such as water, ethanol, polyethylene glycol, vegetable oils, propylene glycol, benzylalcohol and the like or various combinations thereof.

When desired or necessary, suitable binders, lubricants, disintegrating agents, preservatives, and coloring or flavoring agents can also be incorporated into the mixture. Suitable binders include starch, gelatin, natural sugars, corn sweeteners, natural and synthetic gums and waxes and the like, or combinations thereof. Lubricants can include boric acid, sodium benzoate, sodium acetate, sodium chloride and the like, or combinations thereof. Disintegrators include without limitation starch, methylcellulose, agar, bentonite, guar gum and the like, or combinations thereof.

For intravascular, intraperitoneal, subcutaneous or intramuscular administration, one or more compounds of the present invention can be combined with a suitable carrier such as water, saline, aqueous dextrose and the like. For topical administration therapeutically effective amounts of one or more compounds of the present invention can be combined with pharmaceutically acceptable creams, oils, waxes, gels and the like.

Regardless of the route of administration selected, a therapeutically effective amount of the compounds of the present invention are formulated into pharmaceutically acceptable dosage forms by conventional methods known to those skilled in the art. The dosages for preventing or treating serotonin mediated conditions with the compounds of the present invention is determined in accordance with a variety of factors, including the type, age, weight, sex and medical condition of patient, the severity of the condition, the route of administration and the particular compound employed in the treatment. A physician or veterinarian of ordinary skill can readily determine and prescribe the effective amount of drug required to prevent or arrest progress of the condition. In so proceeding, the physician or veterinarian could employ relatively low doses at first and subsequently increase the dose until a maximum response is obtained. The daily doses of the compounds of the invention are ordinarily in the range of about 1 to 1000 mg, more preferably in the range of about 10 to 500 mg.

The compounds of this invention are generally prepared according to reaction schemes I and II. ##STR8##

As shown in reaction Scheme I the 3-unsubstituted benzimidazolones A are reacted with a base (preferably sodium hydride) in an inert etheral solvent (preferably tetrahydrofuran) to generate the sodium salt, which is reacted with phosgene to produce the 3-carbamoylchloride substituted benzimidazolone B. This intermediate is reacted with the appropriate amine (Z-NH.sub.2, as defined above) in an inert solvent (preferably tetrahydrofuran) in the presence of a base (preferably triethylamine) to afford the desired compounds of formulae II.

Alternatively, as shown in reaction Scheme II, intermediate B is reacted with the appropriate alcohol (Z--OH, as defined above) or its metal salt (preferably Na, K, or Cs; formed by reaction with, by illustration, sodium hydride, potassium hydride, cesium carbonate) in an inert solvent (preferably tetrahydrofuran or dimethylformamide) at either ambient or elevated temperature (50.degree. C. to 110.degree. C.) to afford desired compounds of formulae I, wherein X=O.

The following examples illustrate the methods used to prepare the compounds of this invention. These examples are given by way of illustration only and are not meant to be construed as limiting the invention in spirit or scope, as many modifications in materials and methods will be apparent from this disclosure to one having ordinary skill in the art. ##STR9##

5-chloro-2-nitroaniline (8.6 g; 0.05 mole), 2,2-dimethoxypropane (10.0 ml; 0.09 mole) and trifluoroacetic acid [TFA] (4.0 ml; 0.005 moles) were dissolved in toluene (100 ml) and stirred for 1 hr. A boron/pyridine complex (hereinafter BH.sub.3 * pyridine) (5.0 ml; 0.05 moles) was added in 1.0 ml increments. The reaction was exothermic, and the reaction progress was monitored by tlc (40% EtOAc/hexane). Additional TFA, BH.sub.3 * pyridine, and 2,2-dimethoxypropane were added until the tlc indicated that the 5-chloro-2-nitroaniline was consumed. The reaction mixture was placed on a bed of silica and eluted with toluene. The product was the first major component to elute, which produced 6.6 g (61%) of a Yellow crystalline solid. C.sub.9 H.sub.10 ClN.sub.2 O.sub.2 M.W. 213.63 Elements         Calc   Found ______________________________________ Carbon           50.36  50.27 Hydrogen         5.17   5.17 Nitrogen         13.05  12.97 Chlorine         16.52  15.92 ______________________________________ ##STR10##

N-isopropyl-5-chloro-2-nitroaniline (6.5 g; 0.03 mole) was dissolved in MeOH (330 ml) and hydrogenated at room temperature, at 5.0 psi over Ra-Ni for 1. 5 hr. at which time the theoretical hydrogen uptake had been achieved. The reaction mixture was filtered and the filtrate was concentrated. The residue was dissolved in CH.sub.2 Cl.sub.2 (250 ml) and triphosgene (3.06 g; 0.01 mole) dissolved in 25 ml of CH.sub.2 Cl.sub.2 was added. The reaction was exothermic. The reaction mixture was stirred for 1 hr. and then concentrated. The residue was placed on a bed of silica and eluted with EtOH/CH.sub.2 Cl.sub.2 using a gradient from 5% .fwdarw.40% EtOH. The fractions containing the product were combined and concentrated to yield 2.7 g (43%) of a purple-white solid. C.sub.10 H.sub.11 ClN.sub.2 O M.W. 210.65 Elements         Calc   Found ______________________________________ Carbon           57.01  56.61 Hydrogen         5.26   5.29 Nitrogen         13.30  13.19 Chlorine         16.83  17.20 ______________________________________ ##STR11##

4-chloro-2-nitroaniline (8.6 g; 0.05 mole), 2,2-dimethoxypropane (10.0 ml; 0.9 mole) and trifluoroacetic acid [TFA] (4.0 ml; 0.005 moles) were dissolved in toluene (100 ml) and stirred for 1 hr. BH.sub.3 * pyridine (5.0 ml; 0.05 moles) was added in 1.0 ml increments. The reaction was exothermic, and the reaction progress was monitored by tlc 40% EtOAc/Hexane. Additional TFA, BH.sub.3 * pyridine and 2,2-dimethoxypropane were added until the tlc indicated that the 4-chloro-2-nitroaniline was consumed. The reaction mixture was placed on a bed of silica and eluted with toluene. The product was the first major component to elute, which produced 8.4 g (78%) of a yellow crystalline solid. C.sub.9 H.sub.10 ClN.sub.2 O.sub.2 M.W. 213.63 Elements         Calc   Found ______________________________________ Carbon           50.36  50.44 Hydrogen         5.17   5.26 Nitrogen         13.05  12.96 Chlorine         16.52  16.22 ______________________________________ ##STR12##

N-isopropyl-4-chloro-2-nitroaniline (8.3 g; 0.0389 mole) was dissolved in MeOH (330 ml) and hydrogenated at room temperature, at 5.0 psi over Ra--Ni for 1.5 hr. at which time the theoretical hydrogen uptake had been achieved. The reaction mixture was filtered and the filtrate was concentrated. The residue was dissolved in CH.sub.2 Cl.sub.2 (250 ml) and triphosgene (3.9 g; 0.014 mole) dissolved in 25 ml of CH.sub.2 Cl.sub.2 was added. The reaction was exothermic. The reaction mixture was stirred for 1 hr. then concentrated. The solid was triturated with water and filtered, washed with Et.sub.2 O and suction dried which produced 5.7 g (69.5%) of a purple-white solid. C.sub.10 H.sub.11 ClN.sub.2 O M.W. 210.65 Elements         Calc   Found ______________________________________ Carbon           57.01  56.89 Hydrogen         5.26   5.28 Nitrogen         13.30  13.29 Chlorine         16.83  16.54 ______________________________________ ##STR13##

5-chloro-2-nitroaniline (17.2 g; 0.1 mole), acetal aldehyde diethyl acetal (Acetal) (21.1 ml; 0.15 mole) and TFA (7.7 ml; 0.1 moles) were dissolved in toluene (500 ml) and stirred for 1 hr. BH.sub.3 * pyridine (10.0 ml; 0.1 moles) was added in 1.0 ml increments. The reaction was exothermic, and the reaction progress was monitored by tlc 40% EtOAc/Hexane. Additional TFA, BH.sub.3 * pyridine and acetal were added until the tlc indicated that the 5-chloro-2-nitroaniline was consumed. The reaction mixture was washed 2X with water and placed on a bed of silica and eluted with toluene. The product was the first major component to elute. The product was crystallized from MeOH which produced 17.6 g (88%) of a yellow crystalline solid. C.sub.8 H.sub.9 ClN.sub.2 O.sub.2 M.W. 200.63 Elements         Calc   Found ______________________________________ Carbon           47.89  47.69 Hydrogen         4.52   4.36 Nitrogen         13.96  13.92 Chlorine         17.67  17.71 ______________________________________ ##STR14##

N-ethyl-5-chloro-2-nitroaniline (17.6 g; 0.0877 mole) was dissolved in MeOH (1.0 l) and hydrogenated at room temperature, at 5.0 psi over Ra--Ni for 1.9 hr. at which time the theoretical hydrogen uptake had been achieved. The reaction mixture was filtered and the filtrate was concentrated. The residue was dissolved in CH.sub.2 Cl.sub.2 (500 ml) and triphosgene (8.6 g; 0.029 mole) dissolved in 50 ml of CH.sub.2 Cl.sub.2 was added. The reaction was exothermic. The reaction mixture was stirred for 1 hr. and then concentrated. The solid was triturated with water and filtered, washed with Et.sub.2 O and suction dried which produced 7.9 g (46%) of a blue-white solid. C.sub.9 H.sub.9 ClN.sub.2 O M.W. 196.64 Elements         Calc   Found ______________________________________ Carbon           52.57  52.18 Hydrogen         4.90   4.68 Nitrogen         13.62  13.68 Chlorine         17.24  17.17 ______________________________________ ##STR15##

4-chloro-2-nitroaniline (8.6 g; 0.05 mole), acetaldehyde (5.5 ml; 0.05 mole) and HOAc (4.0 ml; 0.1 moles) were dissolved in toluene (100 ml) and stirred for 1 hr. BH.sub.3 * pyridine (5.0 ml; 0.01 moles) was added in 1.0 ml increments. The reaction was exothermic, and the reaction progress was monitored by tlc (40%EtOAc/Hexane). Additional TFA, BH.sub.3 * pyridine and acetaldehyde were added until the tlc indicated that the 4-chloro-2-nitroaniline was consumed. The reaction mixture was washed 2X with water and placed on a bed of silica and eluted with 20% EtOAc/Hexane. The product was the first major component to elute. The product was crystallized from MeOH which produced 5.0 g (50%) of a yellow crystalline solid. C.sub.8 H.sub.9 ClN.sub.2 O.sub.2 M.W. 200.63 Elements         Calc   Found ______________________________________ Carbon           47.89  47.57 Hydrogen         4.52   4.41 Nitrogen         13.96  14.07 Chlorine         17.67  17.77 ______________________________________ ##STR16##

15 N-ethyl-4-chloro-2-nitroaniline (8.7 g; 0.0436 mole) was dissolved in MeOH (330 ml) and hydrogenated at room temperature, at 5.0 psi over Ra--Ni for 3.1 hr. at which time the theoretical hydrogen uptake had been achieved. The reaction mixture was filtered and the filtrate was concentrated. The residue was dissolved in CH.sub.2 Cl.sub.2 (200 ml) and triphosgene (4.3 g; 0.0145 mole) dissolved in 25 ml of CH.sub.2 Cl.sub.2 was added. The reaction was exothermic. The reaction mixture was stirred for 1 hr. then concentrated. The solid was triturated with water and filtered, washed with Et2O and suction dried which produced 5.5 g (64%) of a blue-white solid. C.sub.9 H.sub.9 ClN.sub.2 O M.W. 196.64 Elements         Calc   Found ______________________________________ Carbon           52.57  52.83 Hydrogen         4.90   4.90 Nitrogen         13.62  13.74 Chlorine         17.24  17.21 ______________________________________ ##STR17##

4-Cyanoquinuclidine (610 mg, 4.4 mmol; H. P. Fischer and G. A. Grob, Helvitica Chemica Acta (1968), 51, 153) was dissolved in tetrahydrofuran (THF) (5 mL), and lithium aluminum hydride (10 mL, 10 mmol; 1.0M solution in THF) was added. The solution was heated to reflux for 1.5 h. The solution was cooled to 0.degree. C. and quenched according to Fieser and Fieser work-up (Fieser and Fieser, Reagents for Organic Synthesis, John Wiley and Sons, Inc. (New York) 1967, p. 584). Concentration in vacuo afforded the title compound as a yellow oil, 549 mg (88%).

.sup.1 HNMR (CDC13): 1.36 ppm (t, 6H); 2.42 (s, 2H): 2.89 (t, 6H).

.sup.13 CMR: 28.75 ppm, 28.56; 47.41, 51.67. ##STR18##

60% NaH/Mineral oil (80 mg; 0.002) was washed with hexane and suspended in THF. 1-isopropyl-2-benzimidazolone (176 mg; 0.001 mole) was added to the suspension. This mixture was stirred 15 minutes before adding to a mixture of 2.5 ml (0.004 mole) 20% phosgene in toluene/2.5 ml THF. The resulting mixture was filtered through celite and concentrated. The residue was dissolved in THF (50 ml) and the compound of Example 9 (70 mg; 0.0005 mole) was added with 0.5 ml of Et.sub.3 N. This mixture was stirred 1 hr., filtered and the filtrate concentrated. The residue was chromatographed on a prep tlc plate, eluting with 20% MeOH/CHCl.sub.3. The product was washed from the silica with 5% NH.sub.4 OH/MeOH. The filtrate was concentrated and the residue was dissolved in CHCl.sub.3 and filtered through celite and concentrated. 144 mg (87%) of product was isolated. The product was converted to the HCl salt by dissolving 37.2 .mu.l of acetyl chloride in 5.0 ml of MeOH and adding this solution to the product, then concentrating to dryness. C.sub.10 H.sub.26 N.sub.4 O.sub.2 * 1.2 HCl * 0.5 H.sub.2 O M.W. 395.20. Elements         Calc   Found ______________________________________ Carbon           57.75  57.4 Hydrogen         7.19   7.12 Nitrogen         14.18  14.04 Chlorine         10.76  10.57 ______________________________________ ##STR19##

4-fluoro-2-nitroaniline (15.6 g; 0.1 mole), 2,2-dimethoxypropane (24.6 ml; 0.2 mole) and trifluoroacetic acid [TFA] (23.1 ml; 0.005 moles) were dissolved in toluene (500 ml) and stirred for 1 hr. BH.sub.3 * pyridine (10.0 ml; 0.1 moles) was added in 1.0 ml increments. The reaction was exothermic, and the reaction progress was monitored by tlc 40% EtOAc/Hexane. Additional TFA, BH.sub.3 * pyridine and 2,2-dimethoxypropane were added until the tlc indicated that the 4-fluoro-2-nitroaniline was consumed. The reaction mixture was placed on a bed of silica and eluted with 10% methyl-t-butylether/hexane. The product was the first major component to elute, which produced 11.2 g (58%) of a yellow oil. Elements         Calc   Found ______________________________________ Carbon           54.54  55.09 Hydrogen         5.59   5.63 Nitrogen         14.13  14.00 ______________________________________ ##STR20##

4-fluoro-N-isopropyl-2-nitroaniline (11.1 g; 0.0564 mole) was dissolved in MeOH (330 ml) and hydrogenated at room temperature, at 5.0 psi over Ra--Ni for 1.5 hr. at which time the theoretical hydrogen uptake had been achieved. The reaction mixture was filtered and the filtrate was concentrated. The residue was dissolved in CH.sub.2 Cl.sub.2 (200 ml) and triphosgene (5.6 g; 0.0566 mole) dissolved in 25 ml CH.sub.2 Cl.sub.2 was added. The reaction was exothermic. The reaction mixture was stirred for 1 hr. and then concentrated. The solid was triturated with water and filtered, washed with Et.sub.2 O and suction dried. 5.2 g (47.5%) of a purple-white solid. C.sub.10 H.sub.11 FN.sub.2 O * 0.1 H.sub.2 O M.W. 197.8. Elements         Calc   Found ______________________________________ Carbon           61.28  61.06 Hydrogen         5.76   5.52 Nitrogen         14.29  14.22 ______________________________________ ##STR21##

4-methoxy-2-nitroaniline (16.8 g; 0.1 mole), 2,2-dimethoxypropane (24.6 ml; 0.2 mole) and trifluoroacetic acid [TFA] (23.1 ml; 0.005 moles) were dissolved in toluene (500 ml) and stirred for 1 hr. BH.sub.3 * pyridine (10.0 ml; 0.1 moles) was added in 1.0 ml increments. The reaction was exothermic, and the reaction progress was monitored by tlc 40% EtOAc/Hexane. Additional TFA, BH.sub.3 * pyridine and 2,2-dimethoxypropane were added until the tlc indicated that the 4-fluoro-2-nitroaniline was consumed. The reaction mixture was placed on a bed of silica and eluted with 10% methyl-t-butylether/hexane. The product was the first major component to elute, which produced 13.2 g (62%) of a yellow solid. C.sub.10 H.sub.14 N.sub.2 O.sub.3 M.W. 210.22. Elements         Calc   Found ______________________________________ Carbon           57.13  57.15 Hydrogen         6.71   6.78 Nitrogen         13.32  13.33 ______________________________________ ##STR22##

N-isopropyl-4-methoxy-2-nitroaniline (13.1 g; 0.0627 mole) was dissolved in MeOH (330 ml) and hydrogenated at room temperature, at 5.0 psi over Ra--Ni for 1.5 hr. at which time the theoretical hydrogen uptake had been achieved. The reaction mixture was filtered and the filtrate was concentrated. The residue was dissolved in CH.sub.2 Cl.sub.2 (250 ml) and triphosgene (6.3 g; 0.06447 mole) dissolved in 25 ml CH.sub.2 Cl.sub.2 was added. The reaction was exothermic. The reaction mixture was stirred for 1 hr. then concentrated. The solid was triturated with water and filtered, washed with Et.sub.2 O and suction dried. 9.9 g (76%) of a purple-white solid. C.sub.11 H.sub.14 N.sub.2 O.sub.2 * 0.1 H.sub.2 O M.W. 208.05. Elements         Calc   Found ______________________________________ Carbon           63.51  63.31 Hydrogen         6.88   6.93 Nitrogen         13.46  13.42 ______________________________________

The benzimidazolone compounds of Examples 12 and 14 can be used to prepare the compounds of the claimed invention in a manner similar to that of Example 10.

Procedure

GR65630 binds to the 5-HT.sub.3 receptor. Brain cortices were obtained from male rats and a membrane fraction prepared by standard techniques. 0.04 mg of membrane prep was incubated with 0.2 nM [.sup.3 H]-GR656630 for 60 minutes at 22.degree. C. Non-specific binding g was estimated in the presence of 1 uM ICS 205-930. Membranes were filtered and washed 3 times and the filters were counted to determine [3H]-GR65630 specifically bound. (Kilpatrick G. J., Jones B. J. and Tyers M. B. Identification and distribution of 5-HT.sub.3 receptors in rat brain using radioligand binding. Nature, 330: 746-748, 1987).

Results Effect of Reference Compounds on [H]-GR65630 Bound (0.2 nM) Compound IC.sub.50   Ki          Hill Coefficient ______________________________________ Quipazine 0.5     nM      0.18  nM    0.86 ICS 205-930 2.2     nM      0.51  nM    1.0 5-HT     122     nM      0.39  uM    1.0 RU24969  320     nM      1.85  uM    1.0 Zacopride 0.55    nM      0.18  nM    0.86 Example 10 8.6     nM      4.3   nM    1.0 ______________________________________

The compound to be evaluated was administered i.p. (mg/kg) to a group of 3 mice. Thirty minutes later, a 5-HT (0.25 mg/kg i.v.)-induced bradycardia was recorded in pentobarbital anesthetized animals. A greater than 50 percent (>50) reduction in the bradycardic response relative to vehicle-treated control mice was considered significant. This method has been described by Saxena, P. R. and Lawang, A., Arch. Int. Pharmacodyn., 277: 235-252, 1985.

The assay results for the compounds of the present invention and their Minimum Effective Dose (MED) and the reference compounds and their MEDs are recorded in Table II. ______________________________________ Minimum Effective Dose COMPOUND     (MED) mg/kg ______________________________________ Example 10   0.03 BRL-43694    0.05 cisapride    5 cyproheptadine 5 domperidone  >10 GR-38032     0.5 ketanserin   >10 mecamylamine 2.5 methylsergide >10 metoclopramide 5 scopolamine  2.5 ______________________________________

Serotonin 5-HT.sub.4 agonism was measured in the rat esophagus in vitro preparation as reported by Baxter et al (Naunyn. Schmied. Arch. Pharmacol. 1991, 343, 439). Agonist activity was determined utilizing relaxation of carbachol-contracted rat tunica muscularis mucosae. One 2 cm segment of intrathoracic esophagus proximal to the diaphragm was removed from male rats, weighing approximately 300 gm, and the outer muscle layers removed. The inner tunica muscularis mucosa was mounted under 0.2-0.3 g of tension in a tissue bath containing oxygenated Tyrode's solution at 37.degree. C. Cortisterone acetate (30 .mu.M) and fluoxetine (1 .mu.M) were included in the buffer to prevent uptake of serotonin, as well as pargyline (10 .mu.M) to inhibit monoamine oxidase. Following a 30 min equilibrium period, tissues were isometrically contracted with carbachol (3 .mu.M) to obtain a tonic contraction. A stable plateau was obtained within 20 min when test compound was added cumulatively to relax the muscle strip. EC50 values were obtained for each agonist in tissues from 5 rats. EC50 values for agonists at this 5-HT.sub.4 receptor are indicated in Table III. ______________________________________ 5-HT.sub.4 Agonism (Rat TMM) In Compound   Vitro Assay: EC50 Values ______________________________________ Serotonin          9      nM Example 10         125    nM ______________________________________

Although this invention has been described with respect to specific embodiments, the details of these embodiments are not to be construed as limitations. Various equivalents, changes and modifications may be made without departing from the spirit and scope of this invention, and it is understood that such equivalent embodiments are part of this invention.

## Claims

1. A compound of the formula ##STR23## or a pharmaceutically acceptable salt thereof wherein R.sub.1 and R.sub.2 are independently selected from the group consisting of hydrogen, alkoxy, halogen, amino, monoalkylamino, dialkylamino, acylamino and alkylsulfonylamino; ##STR24##

2. A compound according to claim 1 wherein Z is ##STR25##

3. A compound according to claim 2 wherein X is NH.

4. A compound according to claim 3 which is N-(1-azabicyclo[2.2.2]octan-4-ylmethyl)-2,3-dihydro-3-(1-methylethyl)-2-ox o-1H-benzimidazole-1-carboxamide.

5. A compound according to claim 1 wherein Z is ##STR26##

6. A compound according to claim 5 wherein X is NH.

7. A compound according to claim 1 wherein Z is ##STR27##

8. A compound according to claim 7 wherein X is NH.

9. A pharmaceutical composition comprising a therapeutically effective amount of a compound of the formula ##STR28## or a pharmaceutically acceptable salt thereof wherein R.sub.1 and R.sub.2 are independently selected from the group consisting of hydrogen, alkoxy, halogen, amino, monoalkylamino, dialkylamino, acylamino and alkylsulfonylamino; ##STR29## ; and a pharmaceutically acceptable carrier.

10. A pharmaceutical composition according to claim 9 wherein the compound is N-(1-azabicyclo[2.2.2]octan-4-ylmethyl)-2,3-dihydro-3-(1-methylethyl)-2-ox o-1H-benzimidazole-1-carboxamide.

11. A method of treating 5-HT.sub.4 and 5-HT.sub.3 mediated conditions comprising administering to a subject in need of such treatment a therapeutically effective amount of a compound of the formula ##STR30## or a pharmaceutically acceptable salt thereof, wherein R.sub.1 and R.sub.2 are independently selected from the group consisting of hydrogen, alkoxy, halogen, amino, monoalkylamino, dialkylamino, acylamino, and alkylsulfonylamino; ##STR31##

12. A method of treating gastrointestinal motility disorders, anxiety, cognitive disorders, cardiac hypocontractility and CNS disorders comprising administering to a subject in need of such treatment a therapeutically effective amount of a compound of the formula ##STR32## or a pharmaceutically acceptable salt thereof, wherein R.sub.1 and R.sub.2 are independently selected from the group consisting of hydrogen, alkoxy, halogen, amino, monoalkylamino, dialkylamino, acylamino, and alkylsulfonylamino; ##STR33##