Heterocyclylmethylidene derivatives and their use as modulators of mGluR5 receptors

A compound of formula IA:

• or an enantiomer, diastereomer, N-oxide, or a pharmaceutically acceptable salt or combinations thereof, wherein:
• R1 is an optionally substituted monocyclic 6-membered aryl group or an optionally substituted monocyclic 6-membered heteroaryl group containing 1 or 2 nitrogen atoms;
• A is a carbon-carbon triple bond;
• R2 and R3 each represent an alkyl;
• n is 0 or 1 and m is 1;
• R4 is a carbonyl, a thiocarbonyl or a sulphonyl group, or a bond;
• B is an oxygen or sulphur atom, a nitrogen atom optionally substituted by a C1-C5 alkyl group or a methoxy group, or B is absent;
• R5 is an optionally substituted mono-, bi- or tricyclic C6-C14 aryl group, an optionally substituted mono-, bi- or tricyclic C1-C13 heterocyclic group containing from 1 to 5 heteroatoms selected from N, O and S, an optionally substituted C3-C6 cycloalkyl group, an optionally substituted C3-C6 cycloalkenyl group or an optionally substituted C1-C6 alkyl group;
• and R6 is a hydrogen atom, an optionally substituted C1-C4 alkyl group or a fluorine atom,
• wherein the optional substituents are each independently selected from the group consisting of halogen atoms and C1-C6 alkyl, C1-C6 alkoxy, hydroxy, mercapto, nitro, cyano, oxo, halo(C1-C6)alkyl, halo(C1-C6)alkoxy, C1-C6 alkylthio, C1-C6 alkylsulphonyl, C1-C6 alkylcarbonyl, sulphamoyl, C1-C6 alkylsulphamoyl, di(C1-C6)alkylsulphamoyl, (C1-C6)alkoxycarbonyl and (C1-C6)alkylcarbonyl(C1-C6)alkyl groups, and from groups of the formulae —NR*R*, —C(═O)—NR*R*, -A, —O-A, —C(═O)-A, —(CH2)q-A, —NR**-A, —C(═O)NR **-A, —NR **C(═O)-A and —O—C(═O)-A wherein each R* independently represents a hydrogen atom or a C1-C6 alkyl, C1-C6 alkoxy, C1-C6 alkylcarbonyl, phenyl or benzyl group, R** represents a hydrogen atom or a C1-C6 alkyl group, q is an integer from 1 to 6 and A represents a phenyl group or a C1-C8 heterocyclic group containing from 1 to 3 heteroatoms selected from N, O and S;
• a C1-C6 cycloalkyl group;
• each group A being optionally substituted with from 1 to 3 groups independently selected from halo, hydroxy, cyano, nitro and C1-C6 alkyl.