A quantum-chemical study of cyclization of bis(3-thioxo-1-propenyl) sulfide in the ground and excited states

10.1007/s11176-008-2019-5

“…The relative population of rotamers depends on many factors, including regioselectivity of synthesis, nature of inner-sphere surrounding, type and degree of external effects, etc. The probability of rearrangements depends primarily on the nature of the starting rotational state [3,4]. Thermal or luminous stimulus induces in sulfide systems intramolecular rearrangements involving formation of mono-or polycyclic structures [2].…”

“…The lowest triplet state can generate, along with the thiabicyclic structure, thiophene (II) and thiirane (IV) biradical forms [4] whose formation and accumulation in chemically significant amounts in the ground state is impossible due to high activation barriers and low stability of symmetrically suitable rotamers [4]. The lowest triplet state can generate, along with the thiabicyclic structure, thiophene (II) and thiirane (IV) biradical forms [4] whose formation and accumulation in chemically significant amounts in the ground state is impossible due to high activation barriers and low stability of symmetrically suitable rotamers [4].…”

“…The disrotatory formation of the thiophene cycle in the lowest triplet state can lead to an equally probable accumulation of the cis (IIa) or trans (IIb) isomers with respect to R 1 (the activation barriers differ by 7 kJ mol 31 ) [4].…”