The invention provides compounds of the formula (I), or salts, tautomers, N-oxides or solvates thereof wherein: R1 is selected from: (a) 2,6-dichlorophenyl; (b) 2,6-difluorophenyl; (c) a 2,3,6-trisubstituted phenyl group wherein the substituents for the phenyl group are selected from fluorine, chlorine, methyl and methoxy; (d) a group RO; (e) a group R a; (f) a group RIb; (g) a group RIc; (h) a group RId; and 0) 2,6-difluorophenylamino; wherein R) 0.upsilon., r R>llaa, T Rj HbD, T R) HcC, r R>Iid.alpha., r R>>2zaa, r R>22bD and RJ are as defined in the claims. The compounds have activity as inhibitors of cdk kinase (such as cdk1 or cdk2) and glycogen synthase kinase-3 activity.