Piperidine derivatives as hdac1/2 inhibitors

A compound of Formula I:

• or a pharmaceutically acceptable salt thereof,
• wherein,
• X1 is CR7 or N;
• X2 is CH or N;
• wherein at least one of X1 or X2 is N;
• Y is selected from the group consisting of:
• Z is selected from the group consisting of H, C1-C6-alkyl, C6-aryl, C(O)NR4R5, C(O)OR6, C(O)C1-C6-alkyl, C(O)C0-C6-alkyl-C6-aryl, C(O)—C3-C6-cycloalkyl, C(O)—C2-C6-heterocyclyl, and C(O)C0-6-alkyl-heteroaryl, wherein the aryl, heteroaryl, cycloalkyl, and heterocyclyl groups are optionally substituted by 1 or 2 of C1-C6-alkyl, halo, C1-C6-haloalkyl, hydroxy, or C1-C6-alkoxy;
• Ra and Rb are H, or Ra and Rb together form a fused C6-aryl;
• R1 is selected from the group consisting of H and C1-C6-alkyl;
• R2 is selected from the group consisting of H, C1-C6-alkyl, and C6-aryl;
• R3 is selected from the group consisting of H, C1-C6-alkyl, and C6-aryl;
• or R2 and R3 together form a C2-C6-heterocyclyl;
• R4 is selected from the group consisting of H, C1-C6-alkyl, C1-C6-alkyl-OH, and C1-C6—NH2;
• R5 is C1-C6-alkyl;
• or R4 and R5 together form a C2-C6-heterocyclyl, wherein heterocyclyl is optionally substituted by 1 or 2 of C1-C6-alkyl, halo, C1-C6-haloalkyl, hydroxy, or C1-C6-alkoxy;
• R6 is selected from the group consisting of C1-C6-alkyl and C0-6-alkyl-C6-aryl, wherein aryl is optionally substituted by 1 or 2 of C1-C6-alkyl, halo, or hydroxy;
• and
• R7 is selected from the group consisting of H, C1-C6-alkyl, and C3-C6-cycloalkyl.