Ethynyl derivatives

A compound of formula I

• wherein
• Y is C—R1′;
• R1′ is hydrogen, F or Cl;
• R1 is F or Cl;
• R2 is hydrogen or lower alkyl;
• R3 is phenyl, pyridinyl or isothiazolyl, wherein the N atom in the pyridinyl group may be in different positions, optionally substituted by one or two halogen atoms;
• R4 is hydrogen or lower alkyl;
• Het is a 5-membered heteroaryl group, containing two or three heteroatoms, selected from N,O or S, optionally substituted by lower alkyl, cycloalkyl, lower alkoxyalkyl, heterocycloalkyl, wherein the hetero-atom is O, or lower alkyl substituted by hydroxy, or is a bicyclic heteroaromatic ring, containing two or three N-heteroatoms selected from the groups
• or a pharmaceutically acceptable salt or acid addition salt, a racemic mixture, or its corresponding enantiomer and/or optical isomer and/or stereoisomer thereof.