Fused bicyclic-substituted amines as histamine-3 receptor ligands

1. A method of treating a condition or disorder affecting or cognition in a mammal in need thereof, wherein the condition or disorder is attention-deficit hyperactivity disorder, bipolar disorder, depression, mild cognitive impairment, migraine, mood and attention alteration, obsessive compulsive disorder, seizure, and wakefulness, comprising administering an effective amount of a compound of the formula:

or a pharmaceutically acceptable salt, ester, amide, or prodrug thereof, wherein:

X is S

Y, and Y′ are each independently CH or CF;

Z is N;

one of R 1 and R 2 is heteroaryl or heterocycle;

the other of R 1 and R 2 is selected from the group consisting of hydrogen, alkyl, alkoxy, aryl, cycloalkyl, halo, cyano, and thioalkoxy;

R 3 is absent;

R 4 and R 5 taken together with the nitrogen atom to which each is attached form a non-aromatic ring of the structure (a):

R 7 , R 8 , R 9 , and R 10 are each independently selected from the group consisting of hydrogen, hydroxyalkyl, fluoroalkyl, and alkyl;

R 11 and R 12 are each independently selected from the group consisting of hydrogen, hydroxy, hydroxyalkyl, alkyl, and fluoro;

R 13 and R 14 at each occurrence are independently selected from the group consisting of hydrogen, alkyl, and fluoro;

L is —[C(R 15 )(R 16 )] n —;

R 15 and R 16 at each occurrence are independently selected from the group consisting of hydrogen, alkyl, alkoxy, and fluoro;

m is 1; and

n is an integer from 2-3.

2. The method according to claim 1 , wherein R 1 is heteroaryl.

3. The method according to claim 1 , wherein R 1 and R 2 are each independently selected from the group consisting of furyl, imidazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, oxazolyl, nicotinyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridazinonyl, pyridinyl, pyrimidinyl, pyrrolyl, tetrazolyl, thiadiazolyl, thiazolyl, thienyl, triazinyl, triazolyl, azepanyl, azetidinyl, aziridinyl, azocanyl morpholinyl, piperazinyl, piperidinyl, pyrrolidinyl, pyrrolinyl, thiomorpholinyl, tetrahydrofuryl, tetrahydropyranyl, benzothienyl, isoquinolyl, indolyl, indolizin-2-yl, indazolyl, imidazo[1,2-a]pyridin-2-yl, pyrazolo[1,5-a)pyridin-2-yl, 3-oxo-2H-pyridazin-2-yl, quinolyl, and 2-oxo-1H-pyridin-1-yl.

4. The method according to claim 1 , wherein

R 1 is heteroaryl;

R 2 is hydrogen;

L is —CH 2 CH 2 —; and

R 4 and R 5 are taken together to form a pyrrolidinyl ring of formula (a),

wherein one of R 7 , R 8 , R 9 , and R 10 is methyl and the remaining three substituents are hydrogen.

5. The method according to claim 4 , wherein R 1 is substituted pyridine or unsubstituted pyridine.

6. The method according to claim 1 , wherein the compound of formula (I) is 6-(2,6-dimethyl-pyridin-3-yl)-2-[2-(2(R)-methyl-pyrrolidin-1-yl)-ethyl]-benzothiazole or a salt thereof.

7. The method according to claim 1 , wherein the condition or disorder is attention-deficit hyperactivity disorder.