Positive allosteric modulators of the muscarinic acetylcholine receptor M4

A compound of formula (I),

• or a pharmaceutically acceptable salt thereof, wherein:
• B is O or S;
• X is N;
• Z is N or CR3;
• R2 is selected from hydrogen, C1-C4-alkyl, C1-C4-haloalkyl, C1-C4-hydroxyalkyl, C1-C4 acetoxyalkyl, halo, and —ORb;
• R3 is selected from hydrogen and C1-C4-alkyl;
• R4 and R5 are each independently selected from hydrogen, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, heteroalkyl, heterocycle, and —(CRcRd)n—Y, each of which may be optionally substituted;
• or R4 and R5 are taken together with the nitrogen atom to which they are attached to form an optionally substituted heterocyclic ring;
• R6 is selected from hydrogen and C1-C4-alkyl;
• each Y is independently selected from halo, —OR, —SR, —C(O)R, —C(O)OR, —S(O)R, —SO2R, —NR2, —C(O)NR2, —NRC(O)R, —S(O)2NR2, —NRS(O)2R, aryl, heteroaryl, cycloalkyl, and heterocycle, each of which may be optionally substituted;
• n is 1, 2, 3, 4, 5, 6, 7, or 8;
• Rb is selected from hydrogen, C1-C4-alkyl, C1-C4-haloalkyl, aryl, heteroaryl, cycloalkyl, and heterocycle;
• Rc and Rd are each independently selected from hydrogen, C1-C4-alkyl, C1-C4-haloalkyl, and halo;
• and
• each R is independently selected from hydrogen, alkyl, aryl, arylalkyl, cycloalkyl, cycloalkylalkyl, heterocycle, heterocyclealkyl, heteroaryl, heteroarylalkyl, and heteroalkyl, each of which may be optionally substituted.