A compound of formula: or pharmaceutically acceptable salts thereof, wherein R 1 is selected from the group consisting of C 1 -C 6 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 haloalkyl, C 1 -C 6 haloalkoxy, C 1 -C 6 alkyl-N(R N) 2, phenyl, benzyl, 4 to 8 membered heterocyclyl and 5 to 6 membered heteroaryl; wherein R 1 is bound to the adjacent carbonyl by a carbon atom, and wherein R 1 is optionally substituted by one or two substituents selected from the group consisting of F, Cl, Br, C 1 -C 6 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 haloalkyl, C 1 -C 6 haloalkoxy, C 1 -C 6 alkyl-N(R N) 2, hydroxyl, hydroxymethyl, cyano, cyanomethyl, cyanoethyl, C C 1 -C 6 alkyl, phenyl, benzyl, CH 2 -(C 3 -C 6 cycloalkyl), 5 to 6 membered heteroaryl, and CH 2 -(5 to 6 membered heteroaryl); each R N is independently selected from the group consisting of H, C 1 -C 6 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 6 alkoxy, and C 1 -C 6 haloalkyl; or two R N may together with the adjacent N form a 4-6 membered ring; R 2 is selected from the group consisting of phenyl, pyrazolyl and pyridinyl, each of which may be unsubstituted or substituted by 1 to 3 substituents selected from the group consisting of halogen, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, and cyano; R 3a and R 3b are each independenly hydrogen or halo; and wherein the compound is selected from: cyclopropyl(7-fluoro-5-(5-fluoropyridin-3-yl)-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl)methanone; (2,2-dimethyl-3-oxabicyclo[3.1.0]hexan-1-yl)-[rac-(5S,7S)-7-fluoro-5-phenyl-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl]methanone; 3-hydroxy-2,2-dimethyl-1-[rac-(5S,7S)-7-fluoro-5-phenyl-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl]propan-1-one; 3-(difluoromethoxy)-2,2-dimethyl-1-[rac-(5S,7S)-7-fluoro-5-phenyl-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl]propan-1-one; 1-[rac-(5S,7S)-7-fluoro-5-(1-methylpyrazol-4-yl)-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl]propan-1-one; 1-(3-((5S,7S)-7-fluoro-5-phenyl-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazole-2-carbonyl)azetidin-1-yl)ethan-1-one; 3-[rac-(5S,7S)-2-(cyclopropanecarbonyl)-7-fluoro-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-5-yl]benzonitrile; cyclopropyl-[rac-(5S,7S)-5-(3-chlorophenyl)-7-fluoro-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl]methanone; cyclopropyl-[rac- -7-phenyl-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl]methanone; cyclopropyl((5S,7S)-7-fluoro-5-(5-fluoropyridin-3-yl)-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl)methanone; and cyclopropyl((5R,7R)-7-fluoro-5-(5-fluoropyridin-3-yl)-6,7-dihydro-5H-pyrrolo[1,2-b][1,2,4]triazol-2-yl)methanone. R 1 is selected from the group consisting of C 1 -C 6 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 haloalkyl, C 1 -C 6 haloalkoxy, C 1 -C 6 alkyl-N(R N) 2, phenyl, benzyl, 4 to 8 membered heterocyclyl and 5 to 6 membered heteroaryl; wherein R 1 is bound to the adjacent carbonyl by a carbon atom, and wherein R 1 is optionally substituted by one or two substituents selected from the group consisting of F, Cl, Br, C 1 -C 6 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 6 alkoxy, C 1 -C 6 haloalkyl, C 1 -C 6 haloalkoxy, C 1 -C 6 alkyl-N(R N) 2, hydroxyl, hydroxymethyl, cyano, cyanomethyl, cyanoethyl, C C 1 -C 6 alkyl, phenyl, benzyl, CH 2 -(C 3 -C 6 cycloalkyl), 5 to 6 membered heteroaryl, and CH 2 -(5 to 6 membered heteroaryl); each R N is independently selected from the group consisting of H, C 1 -C 6 alkyl, C 3 -C 6 cycloalkyl, C 1 -C 6 alkoxy, and C 1 -C 6 haloalkyl; or two R N may together with the adjacent N form a 4-6 membered ring; R 2 is selected from the group consisting of phenyl, pyrazolyl and pyridinyl, each of which may be unsubstituted or substituted by 1 to 3 substituents selected from the group consisting of halogen, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, and cyano; R 3a and R 3b are each independenly hydrogen or halo; and