5,6,7,8-tetrahydro-derivatives [1,2-a] pyrazine as P2X7 modulators

A compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein: A is hydrogen, C1-4alkyl, C3-6cycloalkyl, C1-3 alkoxy, (C1-3 alkoxy) - (C1-4 alkyl) , C1-2 fluoroalkyl, halogen, NR6R7, Het, or phenyl wherein the phenyl is optionally substituted with 1, 2 or 3 substituents sonindependientemente fluoro, chloro, C1-3alkyl, OH, methoxy or deuterium; wherein Het is: i) a monocyclic 6-membered heteroaromatic containing 1, 2 or 3 nitrogen atoms in elanillo, or ii) a monocyclic 5-membered heteroaromatic containing 1, 2 or 3 ring heteroatoms queson independently N, O or S, wherein no more than one of the heteroatoms in the ring of 5 miembroses O or S; iii) a bicyclic heteroaromatic ring 9 or 10 membered ring containing 1, 2 or 3 nitrogen atoms in elanillo; and wherein Het is optionally substituted with 1 or 2 substituents independently C1-3 alkyl, fluorine, chlorine, OH including a tautomer thereof, methoxy or deuterium; and wherein: R1 is hydrogen, chlorine, fluorine, bromine, C1 fluoroalkyl, cyano or C1-3 alkyl; R2 is hydrogen, fluorine, chlorine, bromine, C 1 fluoroalkyl, cyano or C1-3 alkyl; R3 is hydrogen, fluorine, chlorine or C1-3 alkyl, R4 is hydrogen; R5 is hydrogen, fluorine, chlorine or methyl; R6 and R7 are independently hydrogen or C1-3 alkyl; or R6 and R7 are taken together and are - (CH2) 2-O- (CH2) 2-, - (CH2) 2-O- (CH2) 3-, or - (CH2) n1 wherein n1 is 3, 4, 5 or 6; and R14 is hydrogen, C1-6 alkyl, C1-2 fluoroalkyl, C3-6 cycloalkyl, halogen, or phenyl wherein the phenyl estaopcionalmente substituted with 1 or 2 substituents independently fluorine, chlorine, methyl, -CF3 or methoxy; in wherein when A is hydrogen, C1-4 alkyl, or C1-3 alkyl, C1-3 alkoxy, (C1-3 alkoxy) - (C1-4 alkyl), C1-2 fluoroalkyl, halogen or NR6R7, then R1 is chloro , fluorine, bromine, C1 fluoroalkyl, cyano or C1-3alkyl, and at least one of R2 and R3 is other than hydrogen; and when A is Het or optionally substituted phenyl, then R1 is hydrogen, chlorine, fluorine, bromine, C1 fluoroalkyl, cyano or C1-3 alkyl, at least one of R1, R2 and R3 is other than hydrogen, and R14 is hydrogen, C1-6 alkyl, C1-2 fluoroalkyl, C3-6 cycloalkyl or halogen; ~ and wherein when R5 is fluoro, chloro or methyl, then R1 is chlorine, fluorine, fluoroalkyl C1 or methyl and R2 eshidrogeno.