Heteroaryl inhibitors of PDE4

A method for treating or reducing the symptoms of a central nervous system disease in a patient in need thereof, wherein the disease is characterized by expression of PDE4D and degradation of learning and memory ability, the method comprising the administration to the subject a compound of structural Formula XI:

• and/or a salt thereof, wherein:
• Y is C(R2)2;
• X is chosen from CH and N;
• n is an integer chosen from 0, 1 or 2;
• each R2 is independently chosen from hydrogen and lower alkyl;
• R3 is chosen from methyl, ethyl, trifluoromethyl, and cyclopropyl;
• R4 is chosen from hydrogen and ethyl;
• R5 is either benzoxaborole, or is chosen from phenyl and pyridinyl, either of which is para-substituted with a substituent of the form R8—R9—(R10)a(R10)b, and is optionally substituted with a substituent R13;
• R8 is chosen from a bond and lower alkyl;
• R9 is chosen from halogen, lower alkyl, lower haloalkyl, lower hydroxyalkyl, lower alkoxy, lower haloalkoxy, cyano, —C(O)N—, S(O)2—, B(OH)2, 5-6 membered monocyclic heterocycloalkyl, and 5-6 membered monocyclic heteroaryl;
• (R10)a and (R10)b are each independently chosen from null, hydrogen, halogen, trifluoromethyl, trifluoromethoxy, hydroxyl, lower hydroxyalkyl, cyano, oxo, lower alkyl, C(O)OH, and C(O)O lower alkyl;
• R13 is chosen from halogen, hydroxy, lower alkyl, trifluoromethyl, lower alkoxy, trifluoromethoxy, NH2, and cyano;
• R6 is chosen from 3-chlorophenyl, 5-chloro-2-thienyl, cyclopentyl optionally substituted with one or two R14, and cyclopentoxy optionally substituted with one or two R14;
• and
• each R14 is independently chosen from halogen, hydroxy, lower alkyl, trifluoromethyl, lower alkoxy, trifluoromethoxy, NH2, and cyano.