4,6-Disubstituted pyrazolo[3,4-d]pyrimidine derivatives were explored as irreversible Bruton's tyrosine kinase (BTK) inhibitors. The structure–activity relationship was established with over 20 synthesized to determine initial hit compounds, based on activities against BTK enzyme and TMD8 cells. It turned out that introducing 1-acrylamido-4-aminopiperdine (1b) at the C4 position of pyrazolopyri...