Compounds for treating proliferative diseases

A method of treating cancer in a subject in need thereof, the method comprising administering to the subject an effective amount of a compound of Formula (I):

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is substituted or unsubstituted alkyl, substituted or unsubstituted carbocyclyl, or substituted or unsubstituted heterocyclyl;
• R2 is substituted or unsubstituted heteroaryl, —ORA, —N(RB)2,
• RA is substituted or unsubstituted heterocyclyl;
• RA2 is —N(RC)2, wherein each instance of RC is independently substituted or unsubstituted alkyl, or substituted or unsubstituted heterocyclyl;
• RA3 is —N(RA4)2, wherein each instance of RA4 is independently substituted or unsubstituted alkyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;
• or two instances of RA4 are joined to form a substituted or unsubstituted, heterocyclic ring, or substituted or unsubstituted, heteroaryl ring;
• each occurrence of RB is independently substituted or unsubstituted alkyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl;
• or a nitrogen protecting group;
• or
• two instances of RB are joined to form a substituted or unsubstituted, heterocyclic ring, or substituted or unsubstituted, heteroaryl ring;
• R3 is hydrogen, substituted or unsubstituted C1-6 alkyl, or a nitrogen protecting group;
• and
• R4 is hydrogen, substituted or unsubstituted C1-6 alkyl, or a nitrogen protecting group.