Substituted 6-membered aryl or heteroaryl allosteric modulators of nicotinic acetylcholine receptors

A compound having the formula I:

• or a pharmaceutically acceptable salt thereof, wherein:
• X is selected from
• Y is 4 substituents, each independently selected from H, (C1-C4)alkyl, halogen, and OH, wherein said alkyl is optionally substituted with one or more halogen or OH;
• A is a 6-membered heteroaryl ring which is substituted with 1 to 4 R groups each independently selected from OH, oxo, amino, amido, carboxyl, keto, cyano, alkoxy, S(O)m-alkyl, halogen, aminoalkyl, hydroxyalkyl, alkyl, cycloalkyl, alkynyl, aryl, heteroaryl, and heterocyclyl, wherein said amino, amido, carboxyl, keto, alkoxy, S(O)m-alkyl, aminoalkyl, hydroxyalkyl, alkyl, cycloalkyl, alkynyl, aryl, heteroaryl and heterocyclyl are optionally substituted with one or more substituents independently selected from halogen, OH, oxo, CF3, OCF3, CN, (C1-C6)alkyl, O(C1-C4)alkyl, S(O)m—(C1-C4)alkyl, C═O(C1-C4)alkyl, (C═O)NR7R8, (C═O)OR7, (C2-C4)alkynyl, (C3-C6)cycloalkyl, O(C3-C6)cycloalkyl, C═O(C3-C6)cycloalkyl, aryl, heteroaryl and heterocyclyl, wherein said alkyl, aryl, heteroaryl and heterocyclyl are optionally independently substituted with one or more halogen, CF3, OH and oxo;
• R1 is H or (C1-C4)alkyl;
• R2 is H or (C1-C4)alkyl;
• R3 is H, halogen, Si(CH3)3 or (C1-C4)alkyl, wherein said alkyl is optionally substituted with one or more halogen;
• R4 is H, halogen or (C1-C4)alkyl, wherein said alkyl is optionally substituted with one or more halogen;
• or, R3 and R4 optionally can come to together to form a cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl ring wherein said ring may be optionally substituted with one or more substituents independently selected from OH, halogen, or (C1-C4)alkyl;
• R5 is H or (C1-C4)alkyl;
• R6 is H or (C1-C4)alkyl;
• R7 and R8 are independently selected from H, (C1-C6)alkyl, cycloalkyl, aryl, heteroaryl and heterocyclyl, wherein said alkyl, cycloalkyl, aryl, heteroaryl and heterocyclyl are optionally substituted with one or more substituents independently selected from halogen, OH, CF3, (C1-C4)alkyl, O(C1-C4)alkyl, cycloalkyl, CN, aryl, heteroaryl, and heterocyclyl, wherein said alkyl, cycloalkyl, aryl, heteroaryl and heterocyclyl are optionally substituted with one or more substituents independently selected from halogen, OH, CF3, (C1-C4)alkyl, O(C1-C4)alkyl, CN;
• Ra is H or (C1-C4)alkyl;
• Rb is H or (C1-C4)alkyl;
• and
• m is 0, 1, or 2.