2-spiro-5- and 6-hydroxamic acid indanes as HDAC inhibitors

A compound of the Formula I:

• or a pharmaceutically acceptable salt thereof, wherein:
• X1, X2, X3, X4, X5, and X6 are each independently, at each occurrence, —CR1R2—, —NR3—, —O—, —C(O)—, —S(O)2—, —S(O)—, or —S—;
• Y1, Y2, Y3 and Y4 are each independently, at each occurrence, N or CR1, wherein —C(O)NHOH is attached at Y2 or Y3, and Y2 or Y3 is a carbon atom when attached to —C(O)NHOH;
• L is a bond, —(CR1R2)p—, —C(O)NR3—, —S(O)2—, —S(O)2NR3—, —S(O)—, —S(O)NR3—, —C(O)(CR1R2)pO—, or —C(O)(CR1R2)p—;
• R is —H, —C1-C6alkyl, —C2-C6alkenyl, —C4-C8cycloalkenyl, —C2-C6alkynyl, —C3-C8cycloalkyl, —C5-C12spirocycloalkyl, heterocyclyl, spiroheterocyclyl, aryl, or heteroaryl containing 1-5 heteroatoms selected from the group consisting of N, S, P, or O, wherein each alkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkyl, spirocycloalkyl, heterocyclyl, spiroheterocyclyl, aryl, or heteroaryl is optionally substituted with one or more —OH, halogen, oxo, —NO2, —CN, —R1, —R2, —SR3, —OR3, —NHR3, —NR3R4, —S(O)2NR3R4, —S(O)2R1, —C(O)R1, —CO2R1, —NR3S(O)2R1, —S(O)R1, —S(O)NR3R4, —NR3S(O)R1, heterocyclyl, aryl, or heteroaryl;
• R1 and R2 are independently, at each occurrence, —H, —R3, —R4, —C1-C6alkyl, —C2-C6alkenyl, —C4-C8cycloalkenyl, —C2-C6alkynyl, —C3-C8cycloalkyl, heterocyclyl, aryl, heteroaryl containing 1-5 heteroatoms selected from the group consisting of N, S, P and O, —OH, halogen, —NO2, —CN, —NH(C1-C6alkyl), —N(C1-C6alkyl)2, —S(O)2N(C1-C6alkyl)2, —N(C1-C6alkyl)S(O)2R5, —S(O)2(C1-C6alkyl), —(C1-C6alkyl)S(O)2R5, —C(O)C1-C6alkyl, —CO2C1-C6alkyl, —N(C1-C6alkyl)S(O)2(C1-C6alkyl), or —(CHR5)pNR3R4, wherein each alkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl is optionally substituted with one or more —OH, halogen, —NO2, oxo, —CN, —R5, —OR3, —NHR3, —NR3R4, —S(O)2N(R3)2—, —S(O)2R5, —C(O)R5, —CO2R5, —NR3S(O)2R5, —S(O)R5, —S(O)NR3R4, —NR3S(O)R5, heterocyclyl, aryl, or heteroaryl;
• or R1 and R2, when on the same atom, can combine with the carbon atom to which they are both attached to form a cycloalkyl, heterocyclyl, spirocycloalkyl, spiroheterocyclyl, or spirocycloalkenyl;
• or R1 and R2, when on adjacent or non-adjacent atoms, can combine to form a heterocyclyl, cycloalkyl, aryl, heteroaryl containing 1-5 heteroatoms selected from the group consisting of N, S, P and O, or cycloalkenyl;
• R3 and R4 are independently, at each occurrence, —H, —C1-C6alkyl, —C2-C6alkenyl, —C4-C8cycloalkenyl, —C2-C6alkynyl, —C3-C8cycloalkyl, heterocyclyl, aryl, heteroaryl containing 1-5 heteroatoms selected from N, S, P, and O, —S(O)2N(C1-C6alkyl)2, —S(O)2(C1-C6alkyl), —(C1-C6alkyl)S(O)2R5, —C(O)C1-C6alkyl, —CO2C1-C6alkyl, or —(CHR5)pN(C1-C6alkyl)2, wherein each alkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more substituents selected from —OH, halogen, —NO2, oxo, —CN, —R5, —O(C1-C6)alkyl, —NH(C1-C6alkyl), —N(C1-C6alkyl)2, —S(O)2N(C1-C6alkyl)2, —S(O)2NH(C1-C6alkyl), —C(O)C1-C6alkyl, —CO2C1-C6alkyl, —N(C1-C6alkyl)S(O)2(C1-C6alkyl), —S(O)R5, —S(O)N(C1-C6alkyl)2, —N(C1-C6alkyl)S(O)R5, heterocyclyl, aryl, or heteroaryl;
• R5 is independently, at each occurrence, —H, —C1-C6alkyl, —C2-C6alkenyl, —C4-C8cycloalkenyl, —C2-C6alkynyl, —C3-C8cycloalkyl, heterocyclyl, aryl, heteroaryl containing 1-5 heteroatoms selected from N, S, P and O, —OH, halogen, —NO2, —CN, —NHC1-C6(alkyl), —N(C1-C6alkyl)2, —S(O)2NH(C1-C6alkyl), —S(O)2N(C1-C6alkyl)2, —S(O)2(C1-C6alkyl), —C(O)C1-C6alkyl, —CO2C1-C6alkyl, —N(C1-C6alkyl)S(O)2(C1-C6alkyl), —S(O)(C1-C6alkyl), —S(O)N(C1-C6alkyl)2, —N(C1-C6alkyl)S(O)(C1-C6alkyl) or —(CH2)pN(C1-C6alkyl)2;
• p is 0, 1, 2, 3, 4, 5, or 6;
• n is 0, 1, 2, 3, or 4;
• m is 0, 1, or 2;
• and
• wherein the sum m+n is 4.