Compounds for treating disorders mediated by metabotropic glutamate receptor 5, and methods of use thereof

A compound of formula I:

• wherein.
• R1 is hydrogen, lower alkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, alkylcycloalkyl, alkylheterocycloalkyl, alkylaryl, alkylheteroaryl, aryl or heteroaryl, each of which is optionally substituted;
• R2 is hydrogen, lower alkyl, lower alkenyl, heteroalkyl, cycloalkyl, heterocycloalkyl, alkylcycloalkyl, alkylheterocycloalkyl, alkylaryl, alkylheteroaryl, aryl, heteroaryl, —C(O)OR12, or —CO—NR12, each of which is optionally substituted;
• R3 is hydrogen, lower alkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, alkylcycloalkyl, alkylheterocycloalkyl, alkylaryl, alkylheteroaryl, aryl or heteroaryl, each of which is optionally substituted;
• or
• R2 and R3 are optionally joined, together with the atoms to which they are attached, to form a mono or bicyclic ring that is carbocyclic or heterocyclic, each of which is optionally substituted;
• G is CHR2 or NR2 when b and c are both single bonds, or G is CR2 or N when one of b and c is a double bond;
• Q is NH or CH2 when d and e are single bonds, or N or CH when one of d or e is a double bond, or;
• X is CH or N when f is a single bond, or C when f is a double bond;
• Z is CH2, C═O, C═S or a bond when b is a single bond, or CH or N when b is a double bond;
• b, c, d, e, and f are each independently a single bond or a double bond, provided that when b is a double bond, c is a single bond;
• when c is a double bond, b and d are single bonds;
• when d is a double bond, c and e are single bonds;
• when e is a double bond, d and f are single bonds;
• and when f is a double bond, e is a single bond;
• Y1, Y2 and Y3 are each independently CH, C-halogen, C-lower alkyl, or N, provided that no more than one of Y2 and Y3 is N;
• L1 is —C≡C—, —HC═CH—, -(lower alkyl)C═C(lower alkyl)-, —CH2—CH2—, —CO—CH2—, —CH(OH)—CH2, —CH2—CO—, —C0-6alkyl-O—C0-6alkyl-, —NR12SO—, —SONR12—, —NR12SO2—, —SO2NR12—, —NR12—CO—, —CO—NR12—,
• R12 is hydrogen or lower alkyl;
• W1 and W2 are each independently N or CH;
• W3 is O, S or NR4;
• and
• R4 is hydrogen or lower alkyl;
• or a pharmaceutically acceptable salt thereof;
• provided that at least one of c and d is a double bond.