We report a Pd-catalyzed ring-opening/arylation/cyclization reaction sequence between 2-aminothiazoles and aryl (pseudo)halides that provides modular access to isocytosine analogues. The scope of the reaction is broad with respect to both coupling partners and a robustness test demonstrated the functional group tolerance of the methodology. Visual kinetic analysis revealed that the product may inhibit catalyst turnover for some substrates.