Attempted Synthesis and Theoretical Calculations of the Elusive Polycyclic Arene Episulfides

Synthesis and Characterization of Thermodynamically Unstable Polycyclic Aromatic Hydrocarbon Episulfides and Episulfoxides

“…Significantly, the 1 H NMR (CDCl 3 ) of H 3 and H 4 in 3 (3.77 and 4.64, J 3,4 = 6.6 Hz) is in full accord with that reported for the corresponding H 3 and H 4 in 1a (3.92 and 4.98 J 3,4 = 6.5 Hz) . It was previously found experimentally 4,5 and theoretically, via molecular orbital calculations, , that K-region PAH-episulfides are, thermodynamically, more stable toward sulfur extrusion than their bay-region isomers. This, together with the relatively higher thermodynamic stability of the episulfides with the higher aromatic character of the ring system, is in accord with the instability of 3 .…”

“…Polycyclic arene epoxides have been established as the primary metabolites of the carcinogenic polycyclic aromatic hydrocarbons (PAHs), − leading, eventually, to the ultimate carcinogenic PAH-diol epoxides (DEs). The first sulfur analogues 1a , b and 2c , d of the parent epoxides and DEs (saturated A-ring) have been just recently prepared, , while the syntheses of selected polycyclic arene episulfides have been previously attempted and their thermodynamic stability theoretically studied. , These episulfides were found to be, thermodynamically, significantly less stable than the corresponding epoxides toward elimination of sulfur and oxygen, respectively. Their relative stability can be deduced from the degree of the aromatic character of the rings that do not carry the heteroatom …”