Substituted 1,2,3,4,5,6-hexahydroazepino[4,5-b]indoles for treating brain disorders

A compound having the following structure (Ia):

• or a pharmaceutically acceptable salt or stereoisomer thereof, wherein:
• R1 is H;
• R3a is C1-6 alkyl;
• R3c is H;
• R4 is H;
• R5 is H, halogen, CN, NO2, C1-6 alkyl, C1-6 haloalkyl, C1-6 aminoalkyl, C3-14 alkylene-cycloalkyl, C4-16 alkylene-heterocycloalkyl, C7-18 alkylene-aryl, C4-16 alkylene-heteroaryl, C2-6 alkenyl, C2-6 alkynyl, C(O)R8b, C(O)C(O)NR8bR8c, C(O)NR8bR8c, C(O)OR8b, NR8bR8c, NR8bC(O)R8c, NR8bC(O)NR8cR8d, NR8bC(O)OR8c, OR8a, OC1-6 haloalkyl, OC(O)R8b, OC(O)NR8bR8c, OC(O)OR8b, S(O)2R8b, S(O)2NR8bR8c, C3-8 cycloalkyl, C4-10 heterocycloalkyl, C6-12 aryl, or C5-10 heteroaryl;
• R6 is F, CH3, CF3, N(CH3)2, NHC(O)CH3, N(CH3)C(O)CH3, OH, OCH3, OCH(CH3)2, or OCF3;
• or
• R5 and R6, together with the carbon atoms to which they are attached form a divalent C3-6 heterocycloalkyl;
• R7 is H;
• R8a is H or C1-6 alkyl;
• R8b is H or C1-6 alkyl;
• R8c is H or C1-6 alkyl;
• R8d is H or C1-6 alkyl;
• and
• n is 2,
• with the provisos that:
• (1) if R3a is CH2CH3, then R6 is not OCH3;
• (2) if R6 is F, then R5 is not H;
• and
• (3) if R6 is F, CH3, or OCH3, then R3a is CH3.