Quinazoline-4(3H)-one derivatives as negative allosteric modulators of metabotropic glutamate receptor 2

A compound of formula (I), or a pharmaceutically acceptable salt thereof,

• wherein:
• L1 is a C1-6alkylene or C1-6fluoroalkylene, wherein optionally 1 methylene group in the alkylene or fluoroalkylene of L1 is independently replaced with —O—;
• R1 is hydrogen or C1-6alkyl;
• R2 is hydrogen or C1-6alkyl;
• R3 is phenyl or pyrrolyl, wherein R3 is unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of C1-4alkyl, halogen, cyano, C1-2haloalkyl, —OC1-4alkyl, and —OC1-2haloalkyl;
• R4 is phenyl,
• pyridinyl, imidazolyl, thiazolyl, pyrazolyl, or oxazolyl, wherein R4 is unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of C1-4alkyl, halogen, cyano, C1-2haloalkyl, —OC1-4alkyl, and —OC1-2haloalkyl;
• and
• R5 and R6 are each independently hydrogen, C1-4alkyl, halogen, cyano, C1-2haloalkyl, —OC1-4alkyl, or —OC1-2haloalkyl.