The invention provides compounds and methods of inhibiting a cyclin-dependent kinase, comprising contacting the cyclin-dependent kinase and an effective amount or concentration of a compound of formula (I) wherein variables are as defined herein. Compounds of formula (I) can be highly selective inhibitors of cyclin-dependent kinases such as CDK12/13, relative to other kinases such as casein kinases, such as CK1δ/ε. Compounds can be used in treatment of cancers, such as breast cancer, brain cancer and ovarian cancer.