The invention provides a chemical entity of Formula (I) wherein R1, R2, R3, R4, Y and Z have any of the values described herein, and compositions comprising such chemical entities; methods of making them; and their use in a wide range of methods, including metabolic and reaction kinetic studies, detection and imaging techniques, and radioactive treatments; and therapies, including inhibiting PDE4, enhancing neuronal plasticity, treating neurological disorders, providing neuroprotection, treating a cognitive impairment associated with a CNS disorder, enhancing the efficiency of cognitive and motor training, providing neurorecovery and neurorehabilitation, enhancing the efficiency of non-human animal training protocols, and treating peripheral disorders, including inflammatory and renal disorders.