Positive allosteric modulators of the muscarinic acetylcholine receptor M4

A compound of formula (I),

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 and R2 are each independently selected from hydrogen, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, heteroalkyl, heterocycle, and —(CRaRb)n—Y;
• or R1 and R2 are taken together with the nitrogen atom to which they are attached to form a heterocycle;
• 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;
• n is 1, 2, 3, 4, 5, 6, 7, or 8;
• Ra and Rb 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;
• wherein each aryl, cycloalkyl, heterocycle, and heteroaryl is independently unsubstituted or substituted with one or more substituents.