Pyrimidine derivative as selelctive cox-2 inhibitors

A compound of formula (I)

• or a pharmaceutically acceptable salt thereof in which:
• X is selected from the group consisting of oxygen or NR2;
• R1 is selected from the group consisting of H, C1-6alkyl, C1-2alkyl substituted by one to five fluorine atoms, C3-6alkenyl, C3-6alkynyl, C3-10cycloalkylC0-6alkyl, C4-12bridged cycloalkyl, A(CR5R6)n and B(CR5R6)n;
• R2 is selected from the group consisting of H and C1-6alkyl;
• R3 is C1-2alkyl substituted by one to five fluorine atoms;
• R4 is selected from the group consisting of C1-6alkyl, NH2 and R8CONH;
• R5 and R6 are independently selected from H or C1-6alkyl;
• A is an unsubstituted 5- or 6-membered heteroaryl or an unsubstituted 6-membered aryl, or a 5- or 6-membered heteroaryl or a 6-membered aryl substituted by one or more R7;
• R7 is selected from the group consisting of halogen, C1-6alkyl, C1-6alkyl substituted by one more fluorine atoms, C1-6alkoxy, C1-6alkoxy substituted by one or more F, NH2SO2 and C1-6alkylSO2;
• B is selected from the group consisting of
• defines the point of attachment of the ring;
• R8 is selected from the group consisting of H, C1-6alkyl, C1-6alkoxy, C1-6alkylOC1-6alkyl, phenyl, HO2CC1-6alkyl, C1-6alkylOCOC1-6alkyl, C1-6alkylOCO, H2NC1-6alkyl, C1-6alkylOCONHC1-6alkyl and C1-6alkylCONHC1-6alkyl;
• and
• n is 0 to 4.