Novel thiazole, pyrimidine and benzylidene derivatives derived from quinazoline scaffold have been synthesized. The antitumor evaluation of the newly synthesized products against three cancer cell lines namely breast adenocarcinoma (MCF-7), non-small cell lung cancer (NCI-H460), and CNS cancer (SF-268) showed that the benzylidene–quinazoline derivative 12a showed remarkable activity against all three cell lines. The thiazolo-quinazoline derivative 10 showed greater activity than the control against breast adenocarcinoma (MCF-7) with a concentration of 0.01 lM. Moreover, the antileishmanial activity of the newly synthesized products tested on Leishmania donovani amastigotes showed that compounds 4, 14, and 18 had very promising activity.