2,3,4-trisubstituted thiazoles 3a–i, having a methyl group in position four, were synthesized by the reaction of 1,4-disubstituted thiosemicarbazides with chloroacetone in ethyl acetate/Et₃N at room temperature or in ethanol under reflux. The structures of new compounds were determined using NMR spectroscopy, mass spectrometry, and elemental analyses. Moreover, the structure of compound 3a was unambiguously confirmed with X-ray analysis. The cell viability assay of 3a–i at 50 µM was greater than 87%, and none of the tested substances were cytotoxic. Compounds 3a–i demonstrated good antiproliferative activity, with GI₅₀ values ranging from 37 to 86 nM against the four tested human cancer cell lines, compared to the reference erlotinib, which had a GI₅₀ value of 33 nM. The most potent derivatives were found to be compounds 3a, 3c, 3d, and 3f, with GI₅₀ values ranging from 37 nM to 54 nM. The EGFR-TK and BRAF^V600E inhibitory assays’ results matched the antiproliferative assay’s results, with the most potent derivatives, as antiproliferative agents, also being the most potent EGFR and BRAF^V600E inhibitors. The docking computations were employed to investigate the docking modes and scores of compounds 3a, 3c, 3d, and 3f toward BRAF^V600E and EGFR. Docking computations demonstrated the good affinity of compound 3f against BRAF^V600E and EGFR, with values of −8.7 and −8.5 kcal/mol, respectively.

A mild and versatile method based on Cu-catalyzed [2+3] cycloaddition (Huisgen-Meldal-Sharpless reaction) was developed to tether 3,3’-((4-(prop-2-yn-1-yloxy)phenyl)methylene)bis(4-hydroxyquinolin-2(1H)-ones) with 4-azido-2-quinolones in good yields. This methodology allowed attaching three quinolone molecules via a triazole linker with the proposed mechanism. The products are interesting precursors for their anti-proliferative activity. Compound 8g was the most active one, achieving IC₅₀ = 1.2 ± 0.2 µM and 1.4 ± 0.2 µM against MCF-7 and Panc-1 cell lines, respectively. Moreover, cell cycle analysis of cells MCF-7 treated with 8g showed cell cycle arrest at the G2/M phase (supported by Caspase-3,8,9, Cytochrome C, BAX, and Bcl-2 studies). Additionally, significant pro-apoptotic activity is indicated by annexin V-FITC staining.

The reaction of 4-azido-quinolin-2(1H)-ones 1a–e with the active methylene compounds pentane-2,4-dione (2a), 1,3-diphenylpropane-1,3-dione (2b), and K₂CO₃ was investigated in this study. This approach afforded 4-(1,2,3-triazol-1-yl)quinolin-2(1H)-ones 3a–j in high yields and purity. All newly synthesized products’ structures were identified. Compounds 3a–j were tested for antiproliferative activity against a panel of four cancer cell lines. In comparison to the reference erlotinib (GI₅₀ = 33), compounds 3f–j were the most potent derivatives, with GI₅₀ values ranging from 22 nM to 31 nM. The most effective antiproliferative derivatives, 3f–j, were subsequently investigated as possible multi-target inhibitors of EGFR, BRAF^V600E, and EGFR^T790M. Compound 3h was the most potent inhibitor of the studied molecular targets, with IC₅₀ values of 57 nM, 68 nM, and 9.70 nM, respectively. The apoptotic assay results demonstrated that compounds 3g and 3h function as caspase-3, 8, and Bax activators as well as down-regulators of the antiapoptotic Bcl2, and hence can be classified as apoptotic inducers. Finally, compounds 3g and 3h displayed promising antioxidant activity at 10 µM, with DPPH radical scavenging of 70.6% and 73.5%, respectively, compared to Trolox (77.6%).

Our investigation includes the synthesis of new naphthalene-bis-triazole-bis-quinolin-2(1H)-ones 4a–e and 7a–e via Cu-catalyzed [3 + 2] cycloadditions of 4-azidoquinolin-2(1H)-ones 3a–e with 1,5-/or 1,8-bis(prop-2-yn-1-yloxy)naphthalene (2) or (6). All structures of the obtained products have been confirmed with different spectroscopic analyses. Additionally, a mild and versatile method based on copper-catalyzed [3 + 2] cycloaddition (Meldal–Sharpless reaction) was developed to tether quinolinones to O-atoms of 1,5- or 1,8-dinaphthols. The triazolo linkers could be considered as anti and syn products, which are interesting precursors for functionalized epidermal growth factor receptor (EGFR) inhibitors with potential apoptotic antiproliferative action. The antiproliferative activities of the 4a–e and 7a–e were evaluated. Compounds 4a–e and 7a–e demonstrated strong antiproliferative activity against the four tested cancer cell lines, with mean GI₅₀ ranging from 34 nM to 134 nM compared to the reference erlotinib, which had a GI₅₀ of 33 nM. The most potent derivatives as antiproliferative agents, compounds 4a, 4b, and 7d, were investigated for their efficacy as EGFR inhibitors, with IC₅₀ values ranging from 64 nM to 97 nM. Compounds 4a, 4b, and 7d demonstrated potent apoptotic effects via their effects on caspases 3, 8, 9, Cytochrome C, Bax, and Bcl2. Finally, docking studies show the relevance of the free amino group of the quinoline moiety for antiproliferative action via hydrogen bond formation with essential amino acids.