A compound of formula III': or a pharmaceutically acceptable salt thereof, wherein: A' is phenyl, an 8-10 membered bicyclic aryl ring, a 5-6membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen and sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen and sulfur, wherein A' is optionally substituted with one or more R 1' substituents; each R 1' is independently selected from the group consisting of halogen, -NO 2, -CN, -OR a, -SR a, -N(R a) 2, -N 3, or -L 1 -R; L 1 is a covalent bond or an optionally substituted bivalent C 1-6 hydrocarbon chain, wherein one or more methylene units of L 1 is optionally and independently replaced by -Cy-, -O-, -S-, -N(R a)-, -C -, -C -, -C N(R a)-, -N(R a)C N(R a)-, -N(R a)C -, -N(R a)C O-, -OC N(R a)-, -S -, -S 2 -, -S 2 N(R a)-, -N(R a)S 2 -, -OC -, or -C O-; -Cy- is an optionally substituted bivalent ring selected from a 3-7 membered saturated or partially unsaturated cycloalkylene ring, a 4-7 membered saturated or partially unsaturated heterocycloalkylene ring having 1-4 heteroatoms independently selected from nitrogen, oxygen and sulfur, phenylene, a 5-6 membered monocyclic heteroarylene having 1-3 heteroatoms independently selected from nitrogen, oxygen and sulfur, an 8-10 membered bicyclic arylene, or an 8-10 membered bicyclic heteroarylene having 1-4 heteroatoms independently selected from nitrogen, oxygen and sulfur; each R a is independently -H, -R or -C R; each R is independently optionally substituted C 1-8 alkyl; C 2-8 alkenyl; C 2-8 alkynyl; haloalkyl; phenyl; a 3-7 membered saturated or partially unsaturated cycloalkyl ring; an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring; a 4-7 membered saturated or partially unsaturated heterocycloalkyl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur; a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, and sulfur; or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur; or: two R on the same nitrogen are taken together with their intervening atoms to form a 4-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen and sulfur; and R 3' is -CH 2 -(5-6 membered monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen and sulfur). A' is phenyl, an 8-10 membered bicyclic aryl ring, a 5-6membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen and sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen and sulfur, wherein A' is optionally substituted with one or more R 1' substituents; each R 1' is independently selected from the group consisting of halogen, -NO 2, -CN, -OR a, -SR a, -N(R a) 2, -N 3, or -L 1 -R; L 1 is a covalent bond or an optionally substituted bivalent C 1-6 hydrocarbon chain, wherein one or more methylene units of L 1 is optionally and independently replaced by -Cy-, -O-, -S-, -N(R a)-, -C -, -C -, -C N(R a)-, -N(R a)C N(R a)-, -N(R a)C -, -N(R a)C O-, -OC N(R a)-, -S -, -S 2 -, -S 2 N(R a)-, -N(R a)S 2 -, -OC -, or -C O-; -Cy- is an optionally substituted bivalent ring selected from a 3-7 membered saturated or partially unsaturated cycloalkylene ring, a 4-7 membered saturated or partially unsaturated heterocycloalkylene ring having 1-4 heteroatoms independently selected from nitrogen, oxygen and sulfur, phenylene, a 5-6 membered monocyclic heteroarylene having 1-3 heteroatoms independently selected from nitrogen, oxygen and sulfur, an 8-10 membered bicyclic arylene, or an 8-10 membered bicyclic heteroarylene having 1-4 heteroatoms independently selected from nitrogen, oxygen and sulfur; each R a is independently -H, -R or -C R; each R is independently optionally substituted C 1-8 alkyl; C 2-8 alkenyl; C 2-8 alkynyl; haloalkyl; phenyl; a 3-7 membered saturated or partially unsaturated cycloalkyl ring; an 8-10 membered bicyclic saturated, partially unsaturated or aryl carbocyclic ring; a 4-7 membered saturated or partially unsaturated heterocycloalkyl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur; a 5-6 membered monocyclic heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, and sulfur; or an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur; or: two R on the same nitrogen are taken together with their intervening atoms to form a 4-7 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen and sulfur; and R 3' is -CH 2 -(5-6 membered monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen and sulfur).