The invention is directed to a formula (I): or a pharmaceutically acceptable salt thereof, wherein R1, R2a, R2b and R3-R7 are herein. The invention is also directed to compositions containing a compound of formula (I) and to the use of such compounds in the inhibition of mutant IDH proteins having a neomorphic activity. The invention is further directed to the use of a compound of formula (I) in the treatment of diseases or disorders associated with such mutant IDH proteins including, but not limited to, cell-proliferation disorders, such as cancer.