Bicyclic [4,6,0] hydroxamic acids as HDAC inhibitors

A compound of Formula IA-2:

• or a pharmaceutically acceptable salt thereof, wherein
• Y1, Y3, and Y4 are each independently N or CR1;
• L is a bond, —(CR1R2)n—, —C(O)—, —C(O)O—, —C(O)NR3—, —S(O)2—, —S(O)2NR3—, —S(O)—, —S(O)NR3—, —C(O)(CR1R2)nO—, or —C(O)(CR1R2)n—;
• R is independently, and at each occurrence, —H, —C1-C6alkyl, —C2-C6alkenyl, —C4-C8cycloalkenyl, —C2-C6alkynyl, —C3-C8cycloalkyl, —C5-C12spirocycle, heterocyclyl, spiroheterocyclyl, aryl, or heteroaryl containing 1-5 heteroatoms selected from N, S, P, or O, wherein each alkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkyl, spirocycle, heterocyclyl, spiroheterocyclyl, aryl, or heteroaryl is optionally substituted with one or more —OH, halogen, oxo, —NO2, —CN, —R1, —R2, —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, heterocycle, aryl, or heteroaryl, with the proviso that when L is —C(O)— the spiroheterocyclyl is not bound to L via a nitrogen atom;
• R1 and R2 are independently, and 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 N, S, P, or O, —OH, halogen, —NO2, —CN, —NHC1-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)2C1-C6alkyl, or (CHR5)nNR3R4, wherein each alkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl is optionally substituted with one or more substituents selected from —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, heterocycle, aryl, or heteroaryl containing 1-5 heteroatoms selected from N, S, P, or O;
• R3 and R4 are independently, and at each occurrence, —H, —C2-C6alkenyl, —C4-C8cycloalkenyl, —C2-C6alkynyl, —C3-C8cycloalkyl, heterocyclyl, aryl, heteroaryl containing 1-5 heteroatoms selected from N, S, P, or 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)nN(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-C6)alkyl, —N(C1-C6alkyl)2, —S(O)2N(C1-C6alkyl)2, —S(O)2NHC1-C6alkyl, —C(O)C1-C6alkyl, —CO2C1-C6alkyl, —N(C1-C6alkyl)S(O)2C1-C6alkyl, —S(O)R5, —S(O)N(C1-C6alkyl)2, —N(C1-C6alkyl)S(O)R5, heterocycle, aryl, or heteroaryl containing 1-5 heteroatoms selected from N, S, P, or O;
• R5 is independently, and at each occurrence, —H, —C2-C6alkenyl, —C3-C8cycloalkenyl, —C2-C6alkynyl, —C3-C8cycloalkyl, heterocyclyl, aryl, heteroaryl, —OH, halogen, —NO2, —CN, —NHC1-C6alkyl, —N(C1-C6alkyl)2, —S(O)2NH(C1-C6alkyl), —S(O)2N(C1-C6alkyl)2, —S(O)2C1-C6alkyl, —C(O)C1-C6alkyl, —CO2C1-C6alkyl, —N(C1-C6alkyl)SO2C1-C6alkyl, —S(O)(C1-C6alkyl), —S(O)N(C1-C6alkyl)2, —N(C1-C6alkyl)S(O)(C1-C6alkyl), or —(CH2)nN(C1-C6alkyl)2;
• and
• n is independently, and at each occurrence, an integer from 0 to 6.