A compound of formula I: or a pharmaceutically acceptable salt thereof, wherein: R' is a 5-membered heterocyclic or heteroaryl ring having 1-3 heteroatoms selected from N, NH, O, SO, and SO 2; wherein the 5-membered heterocyclic or heteroaryl ring has 0-3 substituents selected independently from J; R is H, halogen or (C1-C12)-aliphatic-, wherein said (C1-C12)-aliphatic group is substituted with 0-3 substituents independently selected from J; A and B are each independently selected from: (C6-C10)-aryl-, (C5-C10)-heteroaryl-, and (C3-C10)-heterocyclo-; wherein A and B are each independently substituted with 0-5 substituents independently selected from J; each J is independently selected from: halogen, -OR 3, -NO 2, -CN, -CF 3, -OCF 3, -R 3, oxo, thioxo, 1,2-methylenedioxy, 1,2-ethylenedioxy, =N(R 3), =N(OR 3), -N(R 3) 2, -SR 3, -SOR 3, -SO 2 R 3, -SO 2 N(R 3) 2, -SO 3 R 3, -C R 3, -C C R 3, -C CH 2 C R 3, -C R 3, -C OR 3, -C OR 3, -C C OR 3, -C C N(R 3) 2, -OC R 3, -C N(R 3) 2, -OC N(R 3) 2, -C N(R 3) 2, -(CH 2) 0-2 NHC R 3, -N(R 3)N(R 3)COR 3, -N(R 3)N(R 3)C OR 3, -N(R 3)N(R 3)CON(R 3) 2, -N(R 3)SO 2 R 3, -N(R 3)SO 2N (R 3) 2, -N(R 3)C OR 3, -N(R 3)C R 3, -N(R 3)C R 3, -N(R 3)C N(R 3) 2, -N(R 3)C N(R 3) 2, -N(COR 3)COR 3, -N(OR 3)R 3, -C(=NH)N(R 3) 2, -C N(OR 3)R 3, -C(=NOR 3)R 3, -OP (OR 3) 2, -P (R 3) 2, -P (OR 3) 2, and -P (OR 3); each R 3 is independently selected from: H-, (C1-C12)-aliphatic-, (C3-C10)-cycloalkyl-, (C3-C10)-cycloalkenyl-, [(C3-C10)-cycloalkyl]-(C1-C12)-aliphatic-, [(C3-C10)- cycloalkenyl]-(C1-C12)-aliphatic-, (C6-C10)-aryl-, (C6-C10)-aryl-(C1-C12)aliphatic-, (C3-C10)-heterocyclyl-, (C6-C10)-heterocyclyl-(C1-C12)aliphatic-, (C5-C10)-heteroaryl-, and (C5-C10)-heteroaryl-(C1-C12)-aliphatic-; or two R 3 groups bound to the same atom may be taken together with the atom to which they are bound to form a 3- to 10-membered aromatic or non-aromatic ring having 1-3 heteroatoms independently selected from N, O, S, SO, and SO 2, wherein said ring is optionally fused to a (C6-C10)aryl, (C5-C10)heteroaryl, (C3-C10)cycloalkyl, or a (C3-C10)heterocyclyl; provided that said compound of formula I is not: R' is a 5-membered heterocyclic or heteroaryl ring having 1-3 heteroatoms selected from N, NH, O, SO, and SO 2; wherein the 5-membered heterocyclic or heteroaryl ring has 0-3 substituents selected independently from J; R is H, halogen or (C1-C12)-aliphatic-, wherein said (C1-C12)-aliphatic group is substituted with 0-3 substituents independently selected from J; A and B are each independently selected from: (C6-C10)-aryl-, (C5-C10)-heteroaryl-, and (C3-C10)-heterocyclo-; (C6-C10)-aryl-, (C5-C10)-heteroaryl-, and (C3-C10)-heterocyclo-; halogen, -OR 3, -NO 2, -CN, -CF 3, -OCF 3, -R 3, oxo, thioxo, 1,2-methylenedioxy, 1,2-ethylenedioxy, =N(R 3), =N(OR 3), -N(R 3) 2, -SR 3, -SOR 3, -SO 2 R 3, -SO 2 N(R 3) 2, -SO 3 R 3, -C R 3, -C C R 3, -C CH 2 C R 3, -C R 3, -C OR 3, -C OR 3, -C C OR 3, -C C N(R 3) 2, -OC R 3, -C N(R 3) 2, -OC N(R 3) 2, -C N(R 3) 2, -(CH 2) 0-2 NHC R 3, -N(R 3)N(R 3)COR 3, -N(R 3)N(R 3)C OR 3, -N(R 3)N(R 3)CON(R 3) 2, -N(R 3)SO 2 R 3, -N(R 3)SO 2N (R 3) 2, -N(R 3)C OR 3, -N(R 3)C R 3, -N(R 3)C R 3, -N(R 3)C N(R 3) 2, -N(R 3)C N(R 3) 2, -N(COR 3)COR 3, -N(OR 3)R 3, -C(=NH)N(R 3) 2, -C N(OR 3)R 3, -C(=NOR 3)R 3, -OP (OR 3) 2, -P (R 3) 2, -P (OR 3) 2, and -P (OR 3); H-, (C1-C12)-aliphatic-, (C3-C10)-cycloalkyl-, (C3-C10)-cycloalkenyl-, [(C3-C10)-cycloalkyl]-(C1-C12)-aliphatic-, [(C3-C10)- cycloalkenyl]-(C1-C12)-aliphatic-, (C6-C10)-aryl-, (C6-C10)-aryl-(C1-C12)aliphatic-, (C3-C10)-heterocyclyl-, (C6-C10)-heterocyclyl-(C1-C12)aliphatic-, (C5-C10)-heteroaryl-, and (C5-C10)-heteroaryl-(C1-C12)-aliphatic-; or two R 3 groups bound to the same atom may be taken together with the atom to which they are bound to form a 3- to 10-membered aromatic or non-aromatic ring having 1-3 heteroatoms independently selected from N, O, S, SO, and SO 2, wherein said ring is optionally fused to a (C6-C10)aryl, (C5-C10)heteroaryl, (C3-C10)cycloalkyl, or a (C3-C10)heterocyclyl;