The present invention provides compounds as shown in formula I or a tautomer, a mesomer, a racemate, an enantiomer, a diastereomer, a deuterated compound, a prodrug or a mixture thereof, or a pharmaceutically acceptable salt or solvate of the compounds as shown in formula I or a tautomer, a mesomer, a racemate, an enantiomer, a diastereomer, a deuterated compound, a prodrug or a mixture thereof, wherein R1 to R7 are as defined in the description. The present invention also provides a preparation method and a medical use of the compounds, The compounds of the present invention have an activity superior or equivalent to the candidate drug LY283521 9 currently under phase III clinical trial, and some of the compounds exhibit better selectivity. Moreover, the preferred compounds exhibit good absorption and good blood-brain distribution when administered orally. The compounds of the present invention thus show promise for development into novel drugs for the treatment of diseases associated with cell proliferation, particularly brain tumors, providing new options for clinicians and patients.