A compound represented by structural Formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is selected from carbocyclyl, heterocyclyl, aryl and heteroaryl, each of which being optionally substituted with up to 4 independently selected substituents; each of R 2 and R 3 is independently selected from hydrogen, halo, -CN and optionally substituted C 1 -C 8 alkyl; R 4 is selected from hydrogen, optionally substituted carbocyclyl, optionally substituted heterocyclyl, and -C(R 6)(R 7)(R 8); each R 5 is independently selected from hydrogen and C 1 -C 4 alkyl; R 6 is selected from hydrogen and -C 1 -C 4 alkyl, R 7 is selected from hydrogen, halo, -CN, and optionally substituted C 1 -C 8 alkyl; and R 8 is selected from hydrogen, halo, -C 1 -C 4 alkyl, -(C 0 -C 4 alkylene)-carbocyclyl, -(C 0 -C 4 alkylene)-heterocyclyl, -(C 0 -C 4 alkylene)-aryl, and -(C 0 -C 4 alkylene)-heteroaryl, wherein any carbocyclyl, heterocyclyl, aryl, heteroaryl, or alkyl portion of R 8 is optionally substituted; provided that the compound is other than or a pharmaceutically acceptable salt thereof, wherein the substituents for an optionally substituted alkyl, carbocyclyl, heterocyclyl, aryl group and heteroaryl group as defined above are selected from halogen, =O, -CN, ORc, NRaRb, S iRc, NRdS 2Rc, S 2NReRf, C(=O)ORc, OC(=O)ORc,-OC(=O)Rc, -OC(=S)ORc, C(=S)ORc, O(C=S)Rc, C(=O)NReRf, NRdC(=O)Rc, C(=S)NReRf, NRdC(=S)Rc, NRd(C=O)ORc, O(C=O)NReRf, NRd(C=S)ORc, O(C=S)NReRf, NRd(C=O)NReRf, NRd(C=S)NReRf, C(=S)Rc, C(=O)Rc, (C1-C6)alkyl, cycloalkyl, - 1-4-cycloalkyl, heterocyclyl,- 1-4-heterocyclyl, aryl, - 1-4-aryl, heteroaryl and - 1-4-heteroaryl, wherein each of the (C1-C6)alkyl, cycloalkyl, - 1-4-cycloalkyl, heterocyclyl,- 1-4-heterocyclyl, aryl, - 1-4-aryl, heteroaryl and - 1-4-heteroaryl are optionally substituted with halogen, ORc, NO2, CN, NRdC(=O)Rc, NRgRh, S iRc, C(=O)ORc, C(=O)NReRf, C(=O)Rc, (C1-C3)alkyl, halo(C1-C3)alkyl, (C1-C3)alkoxy(C1-C3)alkyl, (C1-C3)alkoxy, and halo(C1-C3)alkoxy; R a and R b are each independently selected from -H and (C 1 -C 6)alkyl optionally substituted with 1 to 3 substituents independently selected from halogen, hydroxy, COOH, -NR g R h, and (C 1 -C 3)alkoxy; R c is -H or (C 1 -C 6)alkyl optionally substituted with 1 to 3 substituents independently selected from halogen, -NR g R h, hydroxyl, and (C 1 -C 3)alkoxy; R d is -H or (C 1 -C 6)alkyl optionally substituted with 1 to 3 substituents independently selected from halogen, -NR g R h, hydroxyl, and (C 1 -C 3)alkoxy; R e and R f are each independently selected from -H and (C 1 -C 6)alkyl optionally substituted with 1 to 3 substituents independently selected from halogen, -NR g R h, hydroxyl, and (C 1 -C 3)alkoxy; or R e and R f, together with the nitrogen to which they are attached, form a 3-8 membered ring optionally substituted with 1 to 3 substituents independently selected from halogen, -NR g R h, -CN, (C 1 -C 6)alkyl, halo(C 1 -C 6)alkyl, (C 1 -C 3)alkoxy, halo(C 1 -C 3)alkoxy, and (C 1 -C 3)alkoxy(C 1 -C 6)alkyl; R g and R h are each independently selected from -H, (C 1 -C 6)alkyl, halo(C 1 -C 6)alkyl, hydroxy(C 1 -C 6)alkyl, and (C 1 -C 3)alkoxy(C 1 -C 6)alkyl; and i is 0, 1 or 2. R 1 is selected from carbocyclyl, heterocyclyl, aryl and heteroaryl, each of which being optionally substituted with up to 4 independently selected substituents; each of R 2 and R 3 is independently selected from hydrogen, halo, -CN and optionally substituted C 1 -C 8 alkyl; R 4 is selected from hydrogen, optionally substituted carbocyclyl, optionally substituted heterocyclyl, and -C(R 6)(R 7)(R 8); each R 5 is independently selected from hydrogen and C 1 -C 4 alkyl; R 6 is selected from hydrogen and -C 1 -C 4 alkyl, R 7 is selected from hydrogen, halo, -CN, and optionally substituted C 1 -C 8 alkyl; and R 8 is selected from hydrogen, halo, -C 1 -C 4 alkyl, -(C 0 -C 4 alkylene)-carbocyclyl, -(C 0 -C 4 alkylene)-heterocyclyl, -(C 0 -C 4 alkylene)-aryl, and -(C 0 -C 4 alkylene)-heteroaryl, wherein any carbocyclyl, heterocyclyl, aryl, heteroaryl, or alkyl portion of R 8 is optionally substituted; R a and R b are each independently selected from -H and (C 1 -C 6)alkyl optionally substituted with 1 to 3 substituents independently selected from halogen, hydroxy, COOH, -NR g R h, and (C 1 -C 3)alkoxy; R c is -H or (C 1 -C 6)alkyl optionally substituted with 1 to 3 substituents independently selected from halogen, -NR g R h, hydroxyl, and (C 1 -C 3)alkoxy; R d is -H or (C 1 -C 6)alkyl optionally substituted with 1 to 3 substituents independently selected from halogen, -NR g R h, hydroxyl, and (C 1 -C 3)alkoxy; R e and R f are each independently selected from -H and (C 1 -C 6)alkyl optionally substituted with 1 to 3 substituents independently selected from halogen, -NR g R h, hydroxyl, and (C 1 -C 3)alkoxy; or R e and R f, together with the nitrogen to which they are attached, form a 3-8 membered ring optionally substituted with 1 to 3 substituents independently selected from halogen, -NR g R h, -CN, (C 1 -C 6)alkyl, halo(C 1 -C 6)alkyl, (C 1 -C 3)alkoxy, halo(C 1 -C 3)alkoxy, and (C 1 -C 3)alkoxy(C 1 -C 6)alkyl; R g and R h are each independently selected from -H, (C 1 -C 6)alkyl, halo(C 1 -C 6)alkyl, hydroxy(C 1 -C 6)alkyl, and (C 1 -C 3)alkoxy(C 1 -C 6)alkyl; and i is 0, 1 or 2.