Room‐Temperature Accessible Stereospecific Synthesis of Methyl‐( Z )‐2‐(7‐methyl‐3‐oxo‐5 H ‐thiazolo[3,2‐ a ]pyrimidin‐2(3 H )‐ylidene)acetates:Cd 2+ Fluorescence Probe and DU145 Cell Study

Stereospecific synthesis of Methyl‐( Z )‐2‐(7‐methyl‐3‐oxo‐5 H ‐thiazolo[3,2‐ a ]pyrimidin‐2(3 H )‐ylidene)acetates 3 ( a– t ) is designed and explored their application as fluorescent probes for Cd 2+ ions for the first time. These analogs are synthesized via one‐pot reaction of (R/S)‐2‐thioxo‐3,4‐dihydropyrimidine‐5‐carboxanilides (TDHPM‐5‐carboxanilides) with dimethyl acetylenedicarboxylate in MeOH (methanol) as a reusable green solvent at room temperature (RT). Two new C(sp 2 )N, C(sp 2 )S sigma bonds, and one new C‐N π‐bond are formed during this transformation, achieving yields of up to 99%. This protocol demonstrates a low environmental factor (E‐factor) (0.09 to 0.35), high atom economy (94.83%), and carbon efficiency (142.68%), reflecting a significant advancement in green chemistry. Compound 3a is synthesized in 99% yield on a gram scale. Compound 3p proves to be an excellent fluorescent probe for Cd 2+ ions, showing a ninefold increase in fluorescence intensity. The limit of detection and limit of quantification for 3p with Cd 2+ ions are 7.5 and 25 μM, respectively, with an R 2 value of 0.9903. Density functional theory calculations revealed that Cd 2+ ions bind effectively in the cavity of 3p through a ligand‐to‐metal charge transfer mechanism. Cell viability assays and docking studies show that compounds 3g , 3h , 3p , and 3t exhibited potent activity against the DU145 prostate cancer cell line, with binding affinities of −7.7, −6.8, −8.1, and −7.5 kcal mol − 1 .