3a-(4-Chlorophenyl)-1-thioxo-2,3,3a,4-tetrahydroimidazo[1,5-a]quinazolin-5(1H)-one

With the aim of producing new heterocycle molecules, the previously reported 2-(aminomethyl)-2-(4-chlorophenyl)-2,3-dihydroquinazolin-4(1H)-one was converted efficiently by reacting with N,N′-dithiocarbonyldiimidazole (DTCI) to produce the substituted imidazolidine-2-thione moiety inserted in a three-fused-ring scaffold of the title compound. The molecular composition was confirmed by a high-resolution MS experiment, and its structure was elucidated by 1H, 13CNMR, and IR analyses. The thioacetamide form of the product was supported by density functional theory (DFT)–NMR analysis where 13C chemical shifts of the thioacetamide form and of its iminothiol tautomer were calculated in chloroform at the BP86/Jgauss-TZP2 level of theory. The very strong linear correlation between 13C chemical shifts from experimental findings and by calculation for the NHC=S form confirmed the structure.