A compound according to formula wherein: R 1 is R 2 or R 2 -NHC -; R 2 is phenyl optionally substituted with one or two substituents each independently selected from the group consisting of: halo, OH, CN, NO 2, C 1-6 alkyl, C 1-6 alkoxy, C 1-6 haloalkyl, C R a, COOR a, NR a R b, NHC R a, and C NR a R b; or R 2 is a 5 membered heteroaryl having one to four heteroatoms selected from the group consisting of N, O, and S, or R 2 is a 6 membered heteroaryl having one or two N, said 5 and 6 membered heteroaryl rings being optionally substituted with one to three substituents each independently selected from the group consisting of: halo, oxo, OH, CN, NO 2, C 1-6 alkyl, C 1-6 alkoxy, C 1-6 haloalkyl, C R a, COOR a, NR a R b, NHC R a, and C NR a R b; or R 2 is an 8-10 membered bicyclic heteroaryl having 3 or 4 heteroatoms selected from the group consisting of N, O, and S, said 8-10 membered heteroaryl being optionally substituted with one to three substituents each independently selected from the group consisting of: (a) halo, (b) oxo, (c) OH, (d) CN, (e) NO 2, (f) C 1-6 alkyl optionally substituted with one hydroxy or one C 1-6 alkoxy, (g) C 1-6 alkoxy, (h) C 1-6 haloalkyl, (i) C R a, (j) COOR a, (k) NR a R b, (l) NHC R a, and (m) C NR a R b; R 3 is H and R 4 is phenyl optionally substituted with one to three substituents each independently selected from the group consisting of: halo, OH, CN, NO 2, C 1-6 alkyl, C 1-6 alkoxy, C 1-6 haloalkyl, C R a, COOR a, NR a R b, NHC R a, and C NR a R b; or R 3 and R 4 together with the atoms to which they are attached form optionally substituted indan-1-one, said indan-1-one is attached to the piperidine ring of formula through spiro carbon 4 and is optionally substituted with one to three substituents each independently selected from the group consisting of: halo and C 1-6 alkoxy; R a is H or C 1-6 alkyl; R b is H or C 1-6 alkyl; and n is 1 or 2; or a pharmaceutically acceptable salt thereof. R 1 is R 2 or R 2 -NHC -; R 2 is phenyl optionally substituted with one or two substituents each independently selected from the group consisting of: halo, OH, CN, NO 2, C 1-6 alkyl, C 1-6 alkoxy, C 1-6 haloalkyl, C R a, COOR a, NR a R b, NHC R a, and C NR a R b; or R 2 is a 5 membered heteroaryl having one to four heteroatoms selected from the group consisting of N, O, and S, or R 2 is a 6 membered heteroaryl having one or two N, said 5 and 6 membered heteroaryl rings being optionally substituted with one to three substituents each independently selected from the group consisting of: halo, oxo, OH, CN, NO 2, C 1-6 alkyl, C 1-6 alkoxy, C 1-6 haloalkyl, C R a, COOR a, NR a R b, NHC R a, and C NR a R b; or R 2 is an 8-10 membered bicyclic heteroaryl having 3 or 4 heteroatoms selected from the group consisting of N, O, and S, said 8-10 membered heteroaryl being optionally substituted with one to three substituents each independently selected from the group consisting of: (a) halo, (b) oxo, (c) OH, (d) CN, (e) NO 2, (f) C 1-6 alkyl optionally substituted with one hydroxy or one C 1-6 alkoxy, (g) C 1-6 alkoxy, (h) C 1-6 haloalkyl, (i) C R a, (j) COOR a, (k) NR a R b, (l) NHC R a, and (m) C NR a R b; (a) halo, (b) oxo, (c) OH, (d) CN, (e) NO 2, (f) C 1-6 alkyl optionally substituted with one hydroxy or one C 1-6 alkoxy, (g) C 1-6 alkoxy, (h) C 1-6 haloalkyl, (i) C R a, (j) COOR a, (k) NR a R b, (l) NHC R a, and (m) C NR a R b; R 3 is H and R 4 is phenyl optionally substituted with one to three substituents each independently selected from the group consisting of: halo, OH, CN, NO 2, C 1-6 alkyl, C 1-6 alkoxy, C 1-6 haloalkyl, C R a, COOR a, NR a R b, NHC R a, and C NR a R b; or R 3 and R 4 together with the atoms to which they are attached form optionally substituted indan-1-one, said indan-1-one is attached to the piperidine ring of formula through spiro carbon 4 and is optionally substituted with one to three substituents each independently selected from the group consisting of: halo and C 1-6 alkoxy; R a is H or C 1-6 alkyl; R b is H or C 1-6 alkyl; and n is 1 or 2; or a pharmaceutically acceptable salt thereof.