Oxazole tyrosine kinase inhibitors

A compound which is an amide having the formula (3a):

• or a salt, N-oxide or tautomer thereof;
• wherein
• Ar1 is a monocyclic or bicyclic 5- to 10-membered aryl or heteroaryl group containing up to 4 heteroatoms selected from O, N and S, and being optionally substituted by one or more substituents R1;
• Ar2 is a monocyclic or bicyclic 5- to 10-membered aryl or heteroaryl group containing up to 4 heteroatoms selected from O, N and S and being optionally substituted by one or more substituents R2;
• R1 is halogen;
• cyano;
• nitro;
• a group Ra-Rb;
• or a 3 to 8-membered carbocyclic or heterocyclic ring containing up to 4 heteroatoms selected from O, N and S and being optionally substituted by one or more substituents R3;
• Ra is a bond, O, CO, X1C(X2), C(X2)X1, X1C(X2)X1, S, SO, SO2, NRc, SO2NRc or NRcSO2;
• Rb is:
• hydrogen;
• or
• a 3 to 8-membered carbocyclic or heterocyclic ring containing up to 4 heteroatoms selected from O, N and S and being optionally substituted by one or more substituents R3;
• or
• a C1-12 acyclic hydrocarbon group optionally substituted by one or more substituents selected from hydroxy;
• oxo;
• halogen;
• cyano;
• nitro;
• carboxy;
• amino;
• N(Rc)2;
• and 3 to 8-membered carbocyclic or heterocyclic rings containing up to 4 heteroatoms selected from O, N and S and being optionally substituted by one or more substituents R3;
• wherein one to three but not all of the carbon atoms of the C1-12 acyclic hydrocarbon group may optionally be replaced by O, CO, X1C(X2), C(X2)X1, X1C(X2)X1, S, SO, SO2, NRc, SO2NR or NRcSO2;
• Rc is hydrogen or a C1-4 hydrocarbon group;
• X1 is O, S or NRc;
• X2 is ═O, ═S or ═NRc;
• R2 is halogen;
• cyano;
• nitro;
• or a group Ra-Rd;
• Rd is hydrogen;
• a C1-4 alkyl group optionally substituted by one or more fluorine atoms;
• or a benzyl group wherein the benzene ring of the benzyl group is optionally substituted with one to three substituents selected from halogen, cyano, C1-4 alkyl and C1-4 alkoxy, and wherein the C1-4 alkyl and C1-4 alkoxy substituents on the benzene ring are each optionally substituted with one or more fluorine atoms;
• R3 is X2;
• halogen;
• cyano;
• nitro;
• a group Ra-Re;
• or a 3 to 7-membered carbocyclic or heterocyclic ring containing up to 4 heteroatoms selected from O, N and S and being optionally substituted by a group R4;
• Re is:
• hydrogen;
• or
• a C1-6 acyclic hydrocarbon group optionally substituted by one or more substituents selected from hydroxy;
• oxo;
• halogen;
• cyano;
• nitro;
• carboxy;
• amino;
• and N(R)2;
• wherein one to three but not all of the carbon atoms of the C1-6 acyclic hydrocarbon group may optionally be replaced by O, S, SO, SO2, NRc, X1C(X2), C(X2)X1 or X1C(X2)X1;
• or
• a benzyl group wherein the benzene ring of the benzyl group is optionally substituted with one to three substituents selected from halogen, cyano, C1-4 alkyl and C1-4 alkoxy, and wherein the C1-4 alkyl and C1-4 alkoxy groups are each optionally substituted with one or more fluorine atoms;
• and
• R4 is selected from halogen, cyano, nitro and a group Ra-Rd;
• provided that Ar1—(NH)a— does not form an optionally substituted quinoxalin-4-ylamino group;
• and that Ar2 is other than a bicyclic group containing a pyrrole or pyrazole ring fused to a non-aromatic six-membered carbocyclic ring wherein the point of attachment of Ar2 is a nitrogen atom of the pyrrole or pyrazole ring.