Histone deacetylase inhibitors

A compound of the formula (I):

• wherein
• Ar/Het is selected from the group consisting of pyrazolyl, thiazolyl, oxazolyl, imidazolyl, thienyl, furanyl, isoxazolyl, isothiazolyl, thiadiazolyl, oxadiazolyl, and 1,2,4-triazolyl;
• Y is bond, CRc═CRd, O, NRe, or S(O)m;
• a is 1-3;
• b is 0-3;
• m is 0-2;
• each occurrence of Ra and Rb is independently selected from H, F, OH, C1-C6 alkyl, C3-C6 cycloalkyl, NH2, OCO—(C1-C6 alkyl), OCO—(C3-C6 cycloalkyl), C1-C6 alkoxy, C1-C6 fluoroalkoxy, and cyano;
• each of Rc and Rd is, independently, selected from H, F, OH, C1-C6 alkyl, C3-C5 cycloalkyl, NH2, OCO—(C1-C6 alkyl), OCO—(C3-C5 cycloalkyl), C1-C6 alkoxy, C1-C6 fluoroalkoxy, and cyano;
• each occurrence of Re is independently selected from H, C1-C6 alkyl, —C(═O)H, —C(═O)Rh, C(═O)O(C1-C6 alkyl), C(═O)N(Ri)2, SO2—Rh, wherein Rh is selected from C1-C6 alkyl, CH2-(heteroaryl having 5-10 ring atoms), CH2—(C6-C10 aryl), and C6-C10 aryl;
• and each occurrence of Ri is independently selected from H, C1-C6 alkyl, CH2-(heteroaryl having 5-10 ring atoms), CH2—(C6-C10 aryl), and C6-C10 aryl and the aryl or heteroaryl portion in Rh and Ri can be optionally substituted with one or more independently selected substituents selected from the group consisting of F, C1-C6 alkyl, fluoro C1-C6 alkyl, C3-C6 cycloalkyl, C1-C6 alkoxy, C1-C6 fluoroalkoxy, and cyano;
• each of R4 and R5 is, independently, selected from H, C1-C6 alkyl and F;
• R1 is:
• (i) hydrogen;
• or
• (ii) C6-C10 aryl, which is optionally substituted with from 1-3 Ro;
• or
• (iii) monocyclic or bicyclic heteroaryl having from 5-10 ring atoms, which is optionally substituted with from 1-3 Ro;
• wherein from 1-4 of the ring atoms is/are a heteroatom independently selected from O, N, N—H, N—Ro, and S;
• or
• (iv) heterocyclyl having from 4-10 ring atoms, which is optionally substituted with from 1-3 Ro;
• wherein from 1-4 of the ring atoms is/are a heteroatom independently selected from O, N, N—H, N—Ro, and S;
• and
• each occurrence of Ro is independently selected from the group consisting of:
• halogen;
• C1-C6 alkyl;
• fluoro(C1-C6alkyl);
• hydroxyl;
• hydroxy(C1-C4alkyl);
• C1-C6 alkoxy;
• fluoro(C1-C6alkoxy);
• (C1-C6 alkyl)C(O)—;
• (C1-C6 alkyl)NH—;
• (C1-C6 alkyl)2N—;
• formyl;
• formyl(C1-C4alkyl);
• cyano;
• cyano(C1-C4alkyl);
• benzyl;
• benzyloxy;
• SO2—(C1-C6alkyl);
• SO—(C1-C6alkyl);
• and nitro;
• R2 is selected from H, F, Cl, CF3, CF2CF3, CH2CF3, OCF3, OCHF2, phenyl;
• phenyl substituted with from 1-3 substituents independently selected from F, OH, C1-C6 alkyl, fluoro(C1-C6 alkyl) C3-C6 cycloalkyl, NH2, C1-C6 alkoxy, C1-C6 fluoroalkoxy, and cyano;
• thienyl;
• thiazolyl;
• and pyrazol-1-yl;
• and
• R3 is H, F, or Cl;
• or a pharmaceutically acceptable salt thereof.