A compound represented by structural formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is linked to the pyrimidinone via an atom other than carbon and is selected from the group consisting of halo, -OR, O(CH 2) 1-3 OR, O(CH 2) 1-3 N 2, O(CH 2) n C 2 OR, O-(CH 2) n C 4-10 heterocyclyl, O-(CH 2) 1-3 OC 6-10 aryl, O-C 6-10 aryl, N(R X) 2, -NRC 5-10 heterocyclyl, -NRC 6-10 aryl,-NRC 3-10 cycloalkyl, SR, said alkyl, cycloalkyl, heterocyclyl and aryl optionally substituted with one to three groups of R a; R 1a represents H, or C 1-6 alkyl, said alkyl optionally substituted with OH or halo, R 2 and R 3 are independently selected from the group consisting of hydrogen, C 1-6 alkyl, (CH 2) n CN, C R, C OR, CF 3, -C 3-10 cycloalkyl, C 6-10 aryl, C 5-10 heteroaryl, said alkyl, cycloalkyl, aryl and heteroaryl optionally substituted with one to three groups of R b; R 2 and R 3 can combine with the carbon atom to which they are attached to form a C 3-6 cycloalkyl, said cycloalkyl optionally interrupted with 1-2 heteroatoms selected from O, S, or N and optionally substituted with one to three groups of R b R 4 represents hydrogen, halo, or C 1-6 alkyl; or alternatively, R 2 and R 3 along with the carbon atom to which they are attached and the R 4 on the phenyl ring can combine to form a C6-10 bicyclic ring which includes the phenyl ring, said bicyclic ring optionally interrupted with 1-2 heteroatoms selected from O, S, and N and optionally substituted with one to three groups of R b; R represents H, or C 1-6 alkyl; R a is selected from the group consisting of H, halo, CN, C 1-6 alkyl, (CH 2) n OR, p C 1-4 haloalkyl, S s CF 3, S s R, SF 5, C 3-10 cycloalkyl, said alkyl and cycloalkyl optionally substituted with one to three groups of R b; R b is selected from the group consisting of H, halo, C 1-6 alkyl, SO 2 C 1-6 alkyl, and C 1-4 haloalkyl; each occurring R X independently represents H, or C 1-6 alkyl, or two adjacent R X groups can combined together with the nitrogen atom to which they are attached to form a C 4-10 heterocyclyl optionally substituted with one to three groups of R b; n represents 0, 1, 2, 3, or 4; s represents 0, 1, or 2; and p represents 0 or 1. R 1 is linked to the pyrimidinone via an atom other than carbon and is selected from the group consisting of halo, -OR, O(CH 2) 1-3 OR, O(CH 2) 1-3 N 2, O(CH 2) n C 2 OR, O-(CH 2) n C 4-10 heterocyclyl, O-(CH 2) 1-3 OC 6-10 aryl, O-C 6-10 aryl, N(R X) 2, -NRC 5-10 heterocyclyl, -NRC 6-10 aryl,-NRC 3-10 cycloalkyl, SR, said alkyl, cycloalkyl, heterocyclyl and aryl optionally substituted with one to three groups of R a; R 1a represents H, or C 1-6 alkyl, said alkyl optionally substituted with OH or halo, R 2 and R 3 are independently selected from the group consisting of hydrogen, C 1-6 alkyl, (CH 2) n CN, C R, C OR, CF 3, -C 3-10 cycloalkyl, C 6-10 aryl, C 5-10 heteroaryl, said alkyl, cycloalkyl, aryl and heteroaryl optionally substituted with one to three groups of R b; R 2 and R 3 can combine with the carbon atom to which they are attached to form a C 3-6 cycloalkyl, said cycloalkyl optionally interrupted with 1-2 heteroatoms selected from O, S, or N and optionally substituted with one to three groups of R b R 4 represents hydrogen, halo, or C 1-6 alkyl; or alternatively, R 2 and R 3 along with the carbon atom to which they are attached and the R 4 on the phenyl ring can combine to form a C6-10 bicyclic ring which includes the phenyl ring, said bicyclic ring optionally interrupted with 1-2 heteroatoms selected from O, S, and N and optionally substituted with one to three groups of R b; R represents H, or C 1-6 alkyl; R a is selected from the group consisting of H, halo, CN, C 1-6 alkyl, (CH 2) n OR, p C 1-4 haloalkyl, S s CF 3, S s R, SF 5, C 3-10 cycloalkyl, said alkyl and cycloalkyl optionally substituted with one to three groups of R b; R b is selected from the group consisting of H, halo, C 1-6 alkyl, SO 2 C 1-6 alkyl, and C 1-4 haloalkyl; each occurring R X independently represents H, or C 1-6 alkyl, or two adjacent R X groups can combined together with the nitrogen atom to which they are attached to form a C 4-10 heterocyclyl optionally substituted with one to three groups of R b; n represents 0, 1, 2, 3, or 4; s represents 0, 1, or 2; and p represents 0 or 1.