Copper‐Catalyzed C─N and C─S Bonds Formation Approach Toward the Synthesis of <i>1H</i> , <i>6H</i> ‐Benzo[ <i>d</i> ]pyrimido[2,1‐ <i>b</i> ][1,3]thiazin‐1‐ones: Evaluation of Their Cytotoxic Activities Against Cancer Cell Lines

Abstract A copper(I)‐catalyzed regioselective strategy has been put forth toward the effective synthesis of 1 H ,6 H ‐benzo[ d ]pyrimido[2,1‐ b ][1,3]thiazin‐1‐ones 4 via the cascade intermolecular S ‐benzylation and intramolecular N ‐arylation processes. The developed method has been accomplished by the reaction between 2‐iodobenzyl bromides 1 and 2‐thioxo‐2,3‐dihydropyrimidin‐4(1 H )‐ones as the easily available substrates under the influence of Cu(I)‐catalyst to afford the corresponding product 4 in yields up to 89%. The resulting N ‐heterocyclic moieties were examined for cytotoxic activities against cancer cell lines. It was investigated that the molecule 4a was effective against Leukemia (K562) cell lines with acceptable IC 50 value of 10.0 ± 2.9 µM; molecules 4d , 4j , 4q , and 4r were moderately active against MCF‐7 breast cancer cell lines and compounds 4a , 4d , 4n , 4q , and 4r were also found to exhibit moderate activities against MDA‐MB‐231 breast cancer cell lines. Further modifications of these bioactive molecules may lead to effective anticancer drug candidates.