Energy properties and structure of 2- and 8-allylthioquinoline complexes with iodine

The study focuses on the energy and quantum topological properties of substituted 2- and 8-allylthioquinoline complexes with iodine, which are assumed to correspond to prereaction states in the iodocyclization reaction leading to the formation of thiazolo- and tiazinoquinoline systems. The structures of the complexes and the corresponding atomic interactions are modeled considering the different conformational states of allyl-substituted quinolinethiols (thioquinolines). The energy values are analyzed for the interactions between the iodine molecule and different donor centers of the substituted quinoline system: the nitrogen heteroatom, sulfur, and π-system of the allyl group. It is shown that the formation of stable complexes with the nitrogen of the quinoline ring is complicated by steric hindrances posed by the S-allyl group at positions 2 and 8 of the quinoline system, which in turn contributes to the convergence of the cyclization centers.