The present invention relates to compounds of formula I: in which R1, R2, R3 and R4 are as defined in the Summary of the Invention. Compounds of formula I are capable of disrupting the BCL-2 interations with proteins containing a BH3 domain. Disrupting this interaction can restore the anti-apoptotic function of BCL-2 in cancer cells and tumor tissue expressing BCL-2. The invention further provides a process for the preparation of compounds of the invention, pharmaceutical preparations comprising such compounds and methods of using such compounds in the treatment of cancerous diseases.