Synthesis and in vitro cytotoxic activity of novel pyrazolo[1,5-a]pyrimidines and related Schiff bases

The reaction of 5-amino-3-(4-methoxyphenylamino)-N-aryl-1H-pyrazole-4-carboxamides 1a--c with ethyl acetoacetate 2 and 2-(4-fluorobenzylidene)malononitrile 6 yielded pyrazolo[1,5-a]pyrimidines 5a--c and 9a--c, respectively. On the other hand, Schiff bases 11a--f were obtained upon treatment of carboxamides 1a--c with some selected aldehydes 10a and b. The newly synthesized compounds were characterized and confirmed by analytical and spectroscopic data (IR, MS, ¹H NMR, and ¹³C NMR). Pyrazolo[1,5-a]pyrimidines 5a--c and 9a--c and Schiff bases 11b--f were investigated for their cytotoxicity against four human cancer cell lines (colon HCT116, lung A549, breast MCF-7, and liver HepG2) according to SRB assay and the structure--activity relationship was discussed.