Design, Synthesis, and Biological Evaluation of Aryl-Substituted Pyrrolo[2,1-f] [1,2,4] triazine Derivatives as PI3Kα Inhibitors

Phosphoinositide 3-kinase α (PI3Kα) is a clinically validated oncology target, but the development of chemically differentiated inhibitors remains an active medicinal-chemistry challenge because of the close structural relationship among class I PI3K isoforms and the dose-limiting effects associated with pathway inhibition. In the present study, PI3K-IN-38 (compound 123), a reported tricyclic PI3K inhibitor, was used as a reference chemical precedent for a scaffold-redesign strategy rather than as the direct structural parent of the new series. A pyrrolo[2,1-f][1,2,4]triazine core bearing a thiomorpholine 1,1-dioxide vector was selected, and the peripheral aryl region was diversified to generate compounds 5a–5g. The series comprised 3-hydroxyphenyl (5a), 3-methoxyphenyl (5b), 3-fluorophenyl (5c), 3-cyanophenyl (5d), 3-trifluoromethylphenyl (5e), 3-aminophenyl (5f), and pyridin-3-yl (5g) analogues according to the supplied structures and experimental record. The compounds were obtained through nucleophilic substitution of 2,4-dichloropyrrolo[2,1-f][1,2,4]triazine followed by Suzuki cross-coupling. PI3Kα biochemical activity was evaluated using a recombinant p110α/p85α ADP-Glo kinase assay, while MDA-MB-231 cells were used for cell-based evaluation in the supplied study. The chemistry provides a compact SAR platform in which hydrogen-bonding, electron-withdrawing, and heteroaryl substituents can be compared around a common scaffold. The available experimental record supports the feasibility of the scaffold and establishes a basis for further PI3Kα optimization, although the individual 5a–5g biochemical and cellular potency values should be inserted from the original assay dataset before final submission.